mirror of
https://github.com/edk2-porting/linux-next.git
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Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into locking/kcsan
Pull the KCSAN subsystem from Paul E. McKenney:
"This pull request contains base kernel concurrency sanitizer
(KCSAN) enablement for x86, courtesy of Marco Elver. KCSAN is a
sampling watchpoint-based data-race detector, and is documented in
Documentation/dev-tools/kcsan.rst. KCSAN was announced in September,
and much feedback has since been incorporated:
http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@mail.gmail.com
The data races located thus far have resulted in a number of fixes:
https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan
Additional information may be found here:
https://lore.kernel.org/lkml/20191114180303.66955-1-elver@google.com/
"
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
commit
8e1d58ae0c
@ -21,6 +21,7 @@ whole; patches welcome!
|
||||
kasan
|
||||
ubsan
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kmemleak
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kcsan
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gdb-kernel-debugging
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kgdb
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kselftest
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256
Documentation/dev-tools/kcsan.rst
Normal file
256
Documentation/dev-tools/kcsan.rst
Normal file
@ -0,0 +1,256 @@
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The Kernel Concurrency Sanitizer (KCSAN)
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========================================
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Overview
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--------
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*Kernel Concurrency Sanitizer (KCSAN)* is a dynamic data race detector for
|
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kernel space. KCSAN is a sampling watchpoint-based data race detector. Key
|
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priorities in KCSAN's design are lack of false positives, scalability, and
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simplicity. More details can be found in `Implementation Details`_.
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KCSAN uses compile-time instrumentation to instrument memory accesses. KCSAN is
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supported in both GCC and Clang. With GCC it requires version 7.3.0 or later.
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With Clang it requires version 7.0.0 or later.
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Usage
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-----
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To enable KCSAN configure kernel with::
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CONFIG_KCSAN = y
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KCSAN provides several other configuration options to customize behaviour (see
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their respective help text for more info).
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Error reports
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~~~~~~~~~~~~~
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A typical data race report looks like this::
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==================================================================
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BUG: KCSAN: data-race in generic_permission / kernfs_refresh_inode
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write to 0xffff8fee4c40700c of 4 bytes by task 175 on cpu 4:
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kernfs_refresh_inode+0x70/0x170
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kernfs_iop_permission+0x4f/0x90
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inode_permission+0x190/0x200
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link_path_walk.part.0+0x503/0x8e0
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path_lookupat.isra.0+0x69/0x4d0
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filename_lookup+0x136/0x280
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user_path_at_empty+0x47/0x60
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vfs_statx+0x9b/0x130
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__do_sys_newlstat+0x50/0xb0
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__x64_sys_newlstat+0x37/0x50
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do_syscall_64+0x85/0x260
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entry_SYSCALL_64_after_hwframe+0x44/0xa9
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read to 0xffff8fee4c40700c of 4 bytes by task 166 on cpu 6:
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generic_permission+0x5b/0x2a0
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kernfs_iop_permission+0x66/0x90
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inode_permission+0x190/0x200
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link_path_walk.part.0+0x503/0x8e0
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path_lookupat.isra.0+0x69/0x4d0
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filename_lookup+0x136/0x280
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user_path_at_empty+0x47/0x60
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do_faccessat+0x11a/0x390
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__x64_sys_access+0x3c/0x50
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do_syscall_64+0x85/0x260
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entry_SYSCALL_64_after_hwframe+0x44/0xa9
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Reported by Kernel Concurrency Sanitizer on:
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CPU: 6 PID: 166 Comm: systemd-journal Not tainted 5.3.0-rc7+ #1
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Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
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==================================================================
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The header of the report provides a short summary of the functions involved in
|
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the race. It is followed by the access types and stack traces of the 2 threads
|
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involved in the data race.
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The other less common type of data race report looks like this::
|
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|
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==================================================================
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BUG: KCSAN: data-race in e1000_clean_rx_irq+0x551/0xb10
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race at unknown origin, with read to 0xffff933db8a2ae6c of 1 bytes by interrupt on cpu 0:
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e1000_clean_rx_irq+0x551/0xb10
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e1000_clean+0x533/0xda0
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net_rx_action+0x329/0x900
|
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__do_softirq+0xdb/0x2db
|
||||
irq_exit+0x9b/0xa0
|
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do_IRQ+0x9c/0xf0
|
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ret_from_intr+0x0/0x18
|
||||
default_idle+0x3f/0x220
|
||||
arch_cpu_idle+0x21/0x30
|
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do_idle+0x1df/0x230
|
||||
cpu_startup_entry+0x14/0x20
|
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rest_init+0xc5/0xcb
|
||||
arch_call_rest_init+0x13/0x2b
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start_kernel+0x6db/0x700
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|
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Reported by Kernel Concurrency Sanitizer on:
|
||||
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.3.0-rc7+ #2
|
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Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
|
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==================================================================
|
||||
|
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This report is generated where it was not possible to determine the other
|
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racing thread, but a race was inferred due to the data value of the watched
|
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memory location having changed. These can occur either due to missing
|
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instrumentation or e.g. DMA accesses.
|
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|
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Selective analysis
|
||||
~~~~~~~~~~~~~~~~~~
|
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|
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To disable KCSAN data race detection for an entire subsystem, add to the
|
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respective ``Makefile``::
|
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|
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KCSAN_SANITIZE := n
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|
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To disable KCSAN on a per-file basis, add to the ``Makefile``::
|
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|
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KCSAN_SANITIZE_file.o := n
|
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|
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KCSAN also understands the ``data_race(expr)`` annotation, which tells KCSAN
|
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that any data races due to accesses in ``expr`` should be ignored and resulting
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behaviour when encountering a data race is deemed safe.
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debugfs
|
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~~~~~~~
|
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* The file ``/sys/kernel/debug/kcsan`` can be read to get stats.
|
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|
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* KCSAN can be turned on or off by writing ``on`` or ``off`` to
|
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``/sys/kernel/debug/kcsan``.
|
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|
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* Writing ``!some_func_name`` to ``/sys/kernel/debug/kcsan`` adds
|
||||
``some_func_name`` to the report filter list, which (by default) blacklists
|
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reporting data races where either one of the top stackframes are a function
|
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in the list.
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|
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* Writing either ``blacklist`` or ``whitelist`` to ``/sys/kernel/debug/kcsan``
|
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changes the report filtering behaviour. For example, the blacklist feature
|
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can be used to silence frequently occurring data races; the whitelist feature
|
||||
can help with reproduction and testing of fixes.
|
||||
|
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Data Races
|
||||
----------
|
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|
||||
Informally, two operations *conflict* if they access the same memory location,
|
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and at least one of them is a write operation. In an execution, two memory
|
||||
operations from different threads form a **data race** if they *conflict*, at
|
||||
least one of them is a *plain access* (non-atomic), and they are *unordered* in
|
||||
the "happens-before" order according to the `LKMM
|
||||
<../../tools/memory-model/Documentation/explanation.txt>`_.
|
||||
|
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Relationship with the Linux Kernel Memory Model (LKMM)
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
The LKMM defines the propagation and ordering rules of various memory
|
||||
operations, which gives developers the ability to reason about concurrent code.
|
||||
Ultimately this allows to determine the possible executions of concurrent code,
|
||||
and if that code is free from data races.
|
||||
|
||||
KCSAN is aware of *atomic* accesses (``READ_ONCE``, ``WRITE_ONCE``,
|
||||
``atomic_*``, etc.), but is oblivious of any ordering guarantees. In other
|
||||
words, KCSAN assumes that as long as a plain access is not observed to race
|
||||
with another conflicting access, memory operations are correctly ordered.
|
||||
|
||||
This means that KCSAN will not report *potential* data races due to missing
|
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memory ordering. If, however, missing memory ordering (that is observable with
|
||||
a particular compiler and architecture) leads to an observable data race (e.g.
|
||||
entering a critical section erroneously), KCSAN would report the resulting
|
||||
data race.
|
||||
|
||||
Race conditions vs. data races
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Race conditions are logic bugs, where unexpected interleaving of racing
|
||||
concurrent operations result in an erroneous state.
|
||||
|
||||
Data races on the other hand are defined at the *memory model/language level*.
|
||||
Many data races are also harmful race conditions, which a tool like KCSAN
|
||||
reports! However, not all data races are race conditions and vice-versa.
|
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KCSAN's intent is to report data races according to the LKMM. A data race
|
||||
detector can only work at the memory model/language level.
|
||||
|
||||
Deeper analysis, to find high-level race conditions only, requires conveying
|
||||
the intended kernel logic to a tool. This requires (1) the developer writing a
|
||||
specification or model of their code, and then (2) the tool verifying that the
|
||||
implementation matches. This has been done for small bits of code using model
|
||||
checkers and other formal methods, but does not scale to the level of what can
|
||||
be covered with a dynamic analysis based data race detector such as KCSAN.
|
||||
|
||||
For reasons outlined in this `article <https://lwn.net/Articles/793253/>`_,
|
||||
data races can be much more subtle, but can cause no less harm than high-level
|
||||
race conditions.
|
||||
|
||||
Implementation Details
|
||||
----------------------
|
||||
|
||||
The general approach is inspired by `DataCollider
|
||||
<http://usenix.org/legacy/events/osdi10/tech/full_papers/Erickson.pdf>`_.
|
||||
Unlike DataCollider, KCSAN does not use hardware watchpoints, but instead
|
||||
relies on compiler instrumentation. Watchpoints are implemented using an
|
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efficient encoding that stores access type, size, and address in a long; the
|
||||
benefits of using "soft watchpoints" are portability and greater flexibility in
|
||||
limiting which accesses trigger a watchpoint.
|
||||
|
||||
More specifically, KCSAN requires instrumenting plain (unmarked, non-atomic)
|
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memory operations; for each instrumented plain access:
|
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|
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1. Check if a matching watchpoint exists; if yes, and at least one access is a
|
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write, then we encountered a racing access.
|
||||
|
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2. Periodically, if no matching watchpoint exists, set up a watchpoint and
|
||||
stall for a small delay.
|
||||
|
||||
3. Also check the data value before the delay, and re-check the data value
|
||||
after delay; if the values mismatch, we infer a race of unknown origin.
|
||||
|
||||
To detect data races between plain and atomic memory operations, KCSAN also
|
||||
annotates atomic accesses, but only to check if a watchpoint exists
|
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(``kcsan_check_atomic_*``); i.e. KCSAN never sets up a watchpoint on atomic
|
||||
accesses.
|
||||
|
||||
Key Properties
|
||||
~~~~~~~~~~~~~~
|
||||
|
||||
1. **Memory Overhead:** The current implementation uses a small array of longs
|
||||
to encode watchpoint information, which is negligible.
|
||||
|
||||
2. **Performance Overhead:** KCSAN's runtime aims to be minimal, using an
|
||||
efficient watchpoint encoding that does not require acquiring any shared
|
||||
locks in the fast-path. For kernel boot on a system with 8 CPUs:
|
||||
|
||||
- 5.0x slow-down with the default KCSAN config;
|
||||
- 2.8x slow-down from runtime fast-path overhead only (set very large
|
||||
``KCSAN_SKIP_WATCH`` and unset ``KCSAN_SKIP_WATCH_RANDOMIZE``).
|
||||
|
||||
3. **Annotation Overheads:** Minimal annotations are required outside the KCSAN
|
||||
runtime. As a result, maintenance overheads are minimal as the kernel
|
||||
evolves.
|
||||
|
||||
4. **Detects Racy Writes from Devices:** Due to checking data values upon
|
||||
setting up watchpoints, racy writes from devices can also be detected.
|
||||
|
||||
5. **Memory Ordering:** KCSAN is *not* explicitly aware of the LKMM's ordering
|
||||
rules; this may result in missed data races (false negatives).
|
||||
|
||||
6. **Analysis Accuracy:** For observed executions, due to using a sampling
|
||||
strategy, the analysis is *unsound* (false negatives possible), but aims to
|
||||
be complete (no false positives).
|
||||
|
||||
Alternatives Considered
|
||||
-----------------------
|
||||
|
||||
An alternative data race detection approach for the kernel can be found in
|
||||
`Kernel Thread Sanitizer (KTSAN) <https://github.com/google/ktsan/wiki>`_.
|
||||
KTSAN is a happens-before data race detector, which explicitly establishes the
|
||||
happens-before order between memory operations, which can then be used to
|
||||
determine data races as defined in `Data Races`_. To build a correct
|
||||
happens-before relation, KTSAN must be aware of all ordering rules of the LKMM
|
||||
and synchronization primitives. Unfortunately, any omission leads to false
|
||||
positives, which is especially important in the context of the kernel which
|
||||
includes numerous custom synchronization mechanisms. Furthermore, KTSAN's
|
||||
implementation requires metadata for each memory location (shadow memory);
|
||||
currently, for each page, KTSAN requires 4 pages of shadow memory.
|
||||
11
MAINTAINERS
11
MAINTAINERS
@ -8850,6 +8850,17 @@ F: Documentation/kbuild/kconfig*
|
||||
F: scripts/kconfig/
|
||||
F: scripts/Kconfig.include
|
||||
|
||||
KCSAN
|
||||
M: Marco Elver <elver@google.com>
|
||||
R: Dmitry Vyukov <dvyukov@google.com>
|
||||
L: kasan-dev@googlegroups.com
|
||||
S: Maintained
|
||||
F: Documentation/dev-tools/kcsan.rst
|
||||
F: include/linux/kcsan*.h
|
||||
F: kernel/kcsan/
|
||||
F: lib/Kconfig.kcsan
|
||||
F: scripts/Makefile.kcsan
|
||||
|
||||
KDUMP
|
||||
M: Dave Young <dyoung@redhat.com>
|
||||
M: Baoquan He <bhe@redhat.com>
|
||||
|
||||
3
Makefile
3
Makefile
@ -478,7 +478,7 @@ export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
|
||||
|
||||
export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
|
||||
export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
|
||||
export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN
|
||||
export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN CFLAGS_KCSAN
|
||||
export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
|
||||
export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
|
||||
export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
|
||||
@ -900,6 +900,7 @@ endif
|
||||
include scripts/Makefile.kasan
|
||||
include scripts/Makefile.extrawarn
|
||||
include scripts/Makefile.ubsan
|
||||
include scripts/Makefile.kcsan
|
||||
|
||||
# Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
|
||||
KBUILD_CPPFLAGS += $(KCPPFLAGS)
|
||||
|
||||
@ -226,6 +226,7 @@ config X86
|
||||
select VIRT_TO_BUS
|
||||
select X86_FEATURE_NAMES if PROC_FS
|
||||
select PROC_PID_ARCH_STATUS if PROC_FS
|
||||
select HAVE_ARCH_KCSAN if X86_64
|
||||
|
||||
config INSTRUCTION_DECODER
|
||||
def_bool y
|
||||
|
||||
@ -9,7 +9,9 @@
|
||||
# Changed by many, many contributors over the years.
|
||||
#
|
||||
|
||||
# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
|
||||
KASAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
OBJECT_FILES_NON_STANDARD := y
|
||||
|
||||
# Kernel does not boot with kcov instrumentation here.
|
||||
|
||||
@ -17,7 +17,9 @@
|
||||
# (see scripts/Makefile.lib size_append)
|
||||
# compressed vmlinux.bin.all + u32 size of vmlinux.bin.all
|
||||
|
||||
# Sanitizer runtimes are unavailable and cannot be linked for early boot code.
|
||||
KASAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
OBJECT_FILES_NON_STANDARD := y
|
||||
|
||||
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
|
||||
|
||||
@ -10,8 +10,11 @@ ARCH_REL_TYPE_ABS += R_386_GLOB_DAT|R_386_JMP_SLOT|R_386_RELATIVE
|
||||
include $(srctree)/lib/vdso/Makefile
|
||||
|
||||
KBUILD_CFLAGS += $(DISABLE_LTO)
|
||||
|
||||
# Sanitizer runtimes are unavailable and cannot be linked here.
|
||||
KASAN_SANITIZE := n
|
||||
UBSAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
OBJECT_FILES_NON_STANDARD := y
|
||||
|
||||
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
|
||||
|
||||
@ -201,8 +201,12 @@ arch_test_and_change_bit(long nr, volatile unsigned long *addr)
|
||||
return GEN_BINARY_RMWcc(LOCK_PREFIX __ASM_SIZE(btc), *addr, c, "Ir", nr);
|
||||
}
|
||||
|
||||
static __always_inline bool constant_test_bit(long nr, const volatile unsigned long *addr)
|
||||
static __no_kcsan_or_inline bool constant_test_bit(long nr, const volatile unsigned long *addr)
|
||||
{
|
||||
/*
|
||||
* Because this is a plain access, we need to disable KCSAN here to
|
||||
* avoid double instrumentation via instrumented bitops.
|
||||
*/
|
||||
return ((1UL << (nr & (BITS_PER_LONG-1))) &
|
||||
(addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
|
||||
}
|
||||
|
||||
@ -28,6 +28,10 @@ KASAN_SANITIZE_dumpstack_$(BITS).o := n
|
||||
KASAN_SANITIZE_stacktrace.o := n
|
||||
KASAN_SANITIZE_paravirt.o := n
|
||||
|
||||
# With some compiler versions the generated code results in boot hangs, caused
|
||||
# by several compilation units. To be safe, disable all instrumentation.
|
||||
KCSAN_SANITIZE := n
|
||||
|
||||
OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o := y
|
||||
OBJECT_FILES_NON_STANDARD_test_nx.o := y
|
||||
OBJECT_FILES_NON_STANDARD_paravirt_patch.o := y
|
||||
|
||||
@ -13,6 +13,9 @@ endif
|
||||
KCOV_INSTRUMENT_common.o := n
|
||||
KCOV_INSTRUMENT_perf_event.o := n
|
||||
|
||||
# As above, instrumenting secondary CPU boot code causes boot hangs.
|
||||
KCSAN_SANITIZE_common.o := n
|
||||
|
||||
# Make sure load_percpu_segment has no stackprotector
|
||||
nostackp := $(call cc-option, -fno-stack-protector)
|
||||
CFLAGS_common.o := $(nostackp)
|
||||
|
||||
@ -6,10 +6,14 @@
|
||||
# Produces uninteresting flaky coverage.
|
||||
KCOV_INSTRUMENT_delay.o := n
|
||||
|
||||
# KCSAN uses udelay for introducing watchpoint delay; avoid recursion.
|
||||
KCSAN_SANITIZE_delay.o := n
|
||||
|
||||
# Early boot use of cmdline; don't instrument it
|
||||
ifdef CONFIG_AMD_MEM_ENCRYPT
|
||||
KCOV_INSTRUMENT_cmdline.o := n
|
||||
KASAN_SANITIZE_cmdline.o := n
|
||||
KCSAN_SANITIZE_cmdline.o := n
|
||||
|
||||
ifdef CONFIG_FUNCTION_TRACER
|
||||
CFLAGS_REMOVE_cmdline.o = -pg
|
||||
|
||||
@ -7,6 +7,10 @@ KCOV_INSTRUMENT_mem_encrypt_identity.o := n
|
||||
KASAN_SANITIZE_mem_encrypt.o := n
|
||||
KASAN_SANITIZE_mem_encrypt_identity.o := n
|
||||
|
||||
# Disable KCSAN entirely, because otherwise we get warnings that some functions
|
||||
# reference __initdata sections.
|
||||
KCSAN_SANITIZE := n
|
||||
|
||||
ifdef CONFIG_FUNCTION_TRACER
|
||||
CFLAGS_REMOVE_mem_encrypt.o = -pg
|
||||
CFLAGS_REMOVE_mem_encrypt_identity.o = -pg
|
||||
|
||||
@ -17,7 +17,9 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
|
||||
LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
|
||||
targets += purgatory.ro
|
||||
|
||||
# Sanitizer runtimes are unavailable and cannot be linked here.
|
||||
KASAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
KCOV_INSTRUMENT := n
|
||||
|
||||
# These are adjustments to the compiler flags used for objects that
|
||||
|
||||
@ -6,7 +6,10 @@
|
||||
# for more details.
|
||||
#
|
||||
#
|
||||
|
||||
# Sanitizer runtimes are unavailable and cannot be linked here.
|
||||
KASAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
OBJECT_FILES_NON_STANDARD := y
|
||||
|
||||
subdir- := rm
|
||||
|
||||
@ -6,7 +6,10 @@
|
||||
# for more details.
|
||||
#
|
||||
#
|
||||
|
||||
# Sanitizer runtimes are unavailable and cannot be linked here.
|
||||
KASAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
OBJECT_FILES_NON_STANDARD := y
|
||||
|
||||
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
|
||||
|
||||
@ -31,7 +31,9 @@ KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
|
||||
-D__DISABLE_EXPORTS
|
||||
|
||||
GCOV_PROFILE := n
|
||||
# Sanitizer runtimes are unavailable and cannot be linked here.
|
||||
KASAN_SANITIZE := n
|
||||
KCSAN_SANITIZE := n
|
||||
UBSAN_SANITIZE := n
|
||||
OBJECT_FILES_NON_STANDARD := y
|
||||
|
||||
|
||||
File diff suppressed because it is too large
Load Diff
@ -24,6 +24,15 @@
|
||||
#define __no_sanitize_address
|
||||
#endif
|
||||
|
||||
#if __has_feature(thread_sanitizer)
|
||||
/* emulate gcc's __SANITIZE_THREAD__ flag */
|
||||
#define __SANITIZE_THREAD__
|
||||
#define __no_sanitize_thread \
|
||||
__attribute__((no_sanitize("thread")))
|
||||
#else
|
||||
#define __no_sanitize_thread
|
||||
#endif
|
||||
|
||||
/*
|
||||
* Not all versions of clang implement the the type-generic versions
|
||||
* of the builtin overflow checkers. Fortunately, clang implements
|
||||
|
||||
@ -145,6 +145,13 @@
|
||||
#define __no_sanitize_address
|
||||
#endif
|
||||
|
||||
#if defined(__SANITIZE_THREAD__) && __has_attribute(__no_sanitize_thread__)
|
||||
#define __no_sanitize_thread \
|
||||
__attribute__((__noinline__)) __attribute__((no_sanitize_thread))
|
||||
#else
|
||||
#define __no_sanitize_thread
|
||||
#endif
|
||||
|
||||
#if GCC_VERSION >= 50100
|
||||
#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
|
||||
#endif
|
||||
|
||||
@ -178,6 +178,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
|
||||
#endif
|
||||
|
||||
#include <uapi/linux/types.h>
|
||||
#include <linux/kcsan-checks.h>
|
||||
|
||||
#define __READ_ONCE_SIZE \
|
||||
({ \
|
||||
@ -193,12 +194,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
|
||||
} \
|
||||
})
|
||||
|
||||
static __always_inline
|
||||
void __read_once_size(const volatile void *p, void *res, int size)
|
||||
{
|
||||
__READ_ONCE_SIZE;
|
||||
}
|
||||
|
||||
#ifdef CONFIG_KASAN
|
||||
/*
|
||||
* We can't declare function 'inline' because __no_sanitize_address confilcts
|
||||
@ -207,18 +202,44 @@ void __read_once_size(const volatile void *p, void *res, int size)
|
||||
* '__maybe_unused' allows us to avoid defined-but-not-used warnings.
|
||||
*/
|
||||
# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
|
||||
# define __no_sanitize_or_inline __no_kasan_or_inline
|
||||
#else
|
||||
# define __no_kasan_or_inline __always_inline
|
||||
#endif
|
||||
|
||||
static __no_kasan_or_inline
|
||||
#ifdef __SANITIZE_THREAD__
|
||||
/*
|
||||
* Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
|
||||
* compilation units where instrumentation is disabled.
|
||||
*/
|
||||
# define __no_kcsan_or_inline __no_sanitize_thread notrace __maybe_unused
|
||||
# define __no_sanitize_or_inline __no_kcsan_or_inline
|
||||
#else
|
||||
# define __no_kcsan_or_inline __always_inline
|
||||
#endif
|
||||
|
||||
#ifndef __no_sanitize_or_inline
|
||||
#define __no_sanitize_or_inline __always_inline
|
||||
#endif
|
||||
|
||||
static __no_kcsan_or_inline
|
||||
void __read_once_size(const volatile void *p, void *res, int size)
|
||||
{
|
||||
kcsan_check_atomic_read(p, size);
|
||||
__READ_ONCE_SIZE;
|
||||
}
|
||||
|
||||
static __no_sanitize_or_inline
|
||||
void __read_once_size_nocheck(const volatile void *p, void *res, int size)
|
||||
{
|
||||
__READ_ONCE_SIZE;
|
||||
}
|
||||
|
||||
static __always_inline void __write_once_size(volatile void *p, void *res, int size)
|
||||
static __no_kcsan_or_inline
|
||||
void __write_once_size(volatile void *p, void *res, int size)
|
||||
{
|
||||
kcsan_check_atomic_write(p, size);
|
||||
|
||||
switch (size) {
|
||||
case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
|
||||
case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
|
||||
@ -289,6 +310,26 @@ unsigned long read_word_at_a_time(const void *addr)
|
||||
__u.__val; \
|
||||
})
|
||||
|
||||
#include <linux/kcsan.h>
|
||||
|
||||
/*
|
||||
* data_race: macro to document that accesses in an expression may conflict with
|
||||
* other concurrent accesses resulting in data races, but the resulting
|
||||
* behaviour is deemed safe regardless.
|
||||
*
|
||||
* This macro *does not* affect normal code generation, but is a hint to tooling
|
||||
* that data races here should be ignored.
|
||||
*/
|
||||
#define data_race(expr) \
|
||||
({ \
|
||||
typeof(({ expr; })) __val; \
|
||||
kcsan_nestable_atomic_begin(); \
|
||||
__val = ({ expr; }); \
|
||||
kcsan_nestable_atomic_end(); \
|
||||
__val; \
|
||||
})
|
||||
#else
|
||||
|
||||
#endif /* __KERNEL__ */
|
||||
|
||||
/*
|
||||
|
||||
97
include/linux/kcsan-checks.h
Normal file
97
include/linux/kcsan-checks.h
Normal file
@ -0,0 +1,97 @@
|
||||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
|
||||
#ifndef _LINUX_KCSAN_CHECKS_H
|
||||
#define _LINUX_KCSAN_CHECKS_H
|
||||
|
||||
#include <linux/types.h>
|
||||
|
||||
/*
|
||||
* Access type modifiers.
|
||||
*/
|
||||
#define KCSAN_ACCESS_WRITE 0x1
|
||||
#define KCSAN_ACCESS_ATOMIC 0x2
|
||||
|
||||
/*
|
||||
* __kcsan_*: Always calls into runtime when KCSAN is enabled. This may be used
|
||||
* even in compilation units that selectively disable KCSAN, but must use KCSAN
|
||||
* to validate access to an address. Never use these in header files!
|
||||
*/
|
||||
#ifdef CONFIG_KCSAN
|
||||
/**
|
||||
* __kcsan_check_access - check generic access for data race
|
||||
*
|
||||
* @ptr address of access
|
||||
* @size size of access
|
||||
* @type access type modifier
|
||||
*/
|
||||
void __kcsan_check_access(const volatile void *ptr, size_t size, int type);
|
||||
|
||||
#else
|
||||
static inline void __kcsan_check_access(const volatile void *ptr, size_t size,
|
||||
int type) { }
|
||||
#endif
|
||||
|
||||
/*
|
||||
* kcsan_*: Only calls into runtime when the particular compilation unit has
|
||||
* KCSAN instrumentation enabled. May be used in header files.
|
||||
*/
|
||||
#ifdef __SANITIZE_THREAD__
|
||||
#define kcsan_check_access __kcsan_check_access
|
||||
#else
|
||||
static inline void kcsan_check_access(const volatile void *ptr, size_t size,
|
||||
int type) { }
|
||||
#endif
|
||||
|
||||
/**
|
||||
* __kcsan_check_read - check regular read access for data races
|
||||
*
|
||||
* @ptr address of access
|
||||
* @size size of access
|
||||
*/
|
||||
#define __kcsan_check_read(ptr, size) __kcsan_check_access(ptr, size, 0)
|
||||
|
||||
/**
|
||||
* __kcsan_check_write - check regular write access for data races
|
||||
*
|
||||
* @ptr address of access
|
||||
* @size size of access
|
||||
*/
|
||||
#define __kcsan_check_write(ptr, size) \
|
||||
__kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE)
|
||||
|
||||
/**
|
||||
* kcsan_check_read - check regular read access for data races
|
||||
*
|
||||
* @ptr address of access
|
||||
* @size size of access
|
||||
*/
|
||||
#define kcsan_check_read(ptr, size) kcsan_check_access(ptr, size, 0)
|
||||
|
||||
/**
|
||||
* kcsan_check_write - check regular write access for data races
|
||||
*
|
||||
* @ptr address of access
|
||||
* @size size of access
|
||||
*/
|
||||
#define kcsan_check_write(ptr, size) \
|
||||
kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE)
|
||||
|
||||
/*
|
||||
* Check for atomic accesses: if atomic access are not ignored, this simply
|
||||
* aliases to kcsan_check_access, otherwise becomes a no-op.
|
||||
*/
|
||||
#ifdef CONFIG_KCSAN_IGNORE_ATOMICS
|
||||
#define kcsan_check_atomic_read(...) \
|
||||
do { \
|
||||
} while (0)
|
||||
#define kcsan_check_atomic_write(...) \
|
||||
do { \
|
||||
} while (0)
|
||||
#else
|
||||
#define kcsan_check_atomic_read(ptr, size) \
|
||||
kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC)
|
||||
#define kcsan_check_atomic_write(ptr, size) \
|
||||
kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC | KCSAN_ACCESS_WRITE)
|
||||
#endif
|
||||
|
||||
#endif /* _LINUX_KCSAN_CHECKS_H */
|
||||
115
include/linux/kcsan.h
Normal file
115
include/linux/kcsan.h
Normal file
@ -0,0 +1,115 @@
|
||||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
|
||||
#ifndef _LINUX_KCSAN_H
|
||||
#define _LINUX_KCSAN_H
|
||||
|
||||
#include <linux/kcsan-checks.h>
|
||||
#include <linux/types.h>
|
||||
|
||||
#ifdef CONFIG_KCSAN
|
||||
|
||||
/*
|
||||
* Context for each thread of execution: for tasks, this is stored in
|
||||
* task_struct, and interrupts access internal per-CPU storage.
|
||||
*/
|
||||
struct kcsan_ctx {
|
||||
int disable_count; /* disable counter */
|
||||
int atomic_next; /* number of following atomic ops */
|
||||
|
||||
/*
|
||||
* We distinguish between: (a) nestable atomic regions that may contain
|
||||
* other nestable regions; and (b) flat atomic regions that do not keep
|
||||
* track of nesting. Both (a) and (b) are entirely independent of each
|
||||
* other, and a flat region may be started in a nestable region or
|
||||
* vice-versa.
|
||||
*
|
||||
* This is required because, for example, in the annotations for
|
||||
* seqlocks, we declare seqlock writer critical sections as (a) nestable
|
||||
* atomic regions, but reader critical sections as (b) flat atomic
|
||||
* regions, but have encountered cases where seqlock reader critical
|
||||
* sections are contained within writer critical sections (the opposite
|
||||
* may be possible, too).
|
||||
*
|
||||
* To support these cases, we independently track the depth of nesting
|
||||
* for (a), and whether the leaf level is flat for (b).
|
||||
*/
|
||||
int atomic_nest_count;
|
||||
bool in_flat_atomic;
|
||||
};
|
||||
|
||||
/**
|
||||
* kcsan_init - initialize KCSAN runtime
|
||||
*/
|
||||
void kcsan_init(void);
|
||||
|
||||
/**
|
||||
* kcsan_disable_current - disable KCSAN for the current context
|
||||
*
|
||||
* Supports nesting.
|
||||
*/
|
||||
void kcsan_disable_current(void);
|
||||
|
||||
/**
|
||||
* kcsan_enable_current - re-enable KCSAN for the current context
|
||||
*
|
||||
* Supports nesting.
|
||||
*/
|
||||
void kcsan_enable_current(void);
|
||||
|
||||
/**
|
||||
* kcsan_nestable_atomic_begin - begin nestable atomic region
|
||||
*
|
||||
* Accesses within the atomic region may appear to race with other accesses but
|
||||
* should be considered atomic.
|
||||
*/
|
||||
void kcsan_nestable_atomic_begin(void);
|
||||
|
||||
/**
|
||||
* kcsan_nestable_atomic_end - end nestable atomic region
|
||||
*/
|
||||
void kcsan_nestable_atomic_end(void);
|
||||
|
||||
/**
|
||||
* kcsan_flat_atomic_begin - begin flat atomic region
|
||||
*
|
||||
* Accesses within the atomic region may appear to race with other accesses but
|
||||
* should be considered atomic.
|
||||
*/
|
||||
void kcsan_flat_atomic_begin(void);
|
||||
|
||||
/**
|
||||
* kcsan_flat_atomic_end - end flat atomic region
|
||||
*/
|
||||
void kcsan_flat_atomic_end(void);
|
||||
|
||||
/**
|
||||
* kcsan_atomic_next - consider following accesses as atomic
|
||||
*
|
||||
* Force treating the next n memory accesses for the current context as atomic
|
||||
* operations.
|
||||
*
|
||||
* @n number of following memory accesses to treat as atomic.
|
||||
*/
|
||||
void kcsan_atomic_next(int n);
|
||||
|
||||
#else /* CONFIG_KCSAN */
|
||||
|
||||
static inline void kcsan_init(void) { }
|
||||
|
||||
static inline void kcsan_disable_current(void) { }
|
||||
|
||||
static inline void kcsan_enable_current(void) { }
|
||||
|
||||
static inline void kcsan_nestable_atomic_begin(void) { }
|
||||
|
||||
static inline void kcsan_nestable_atomic_end(void) { }
|
||||
|
||||
static inline void kcsan_flat_atomic_begin(void) { }
|
||||
|
||||
static inline void kcsan_flat_atomic_end(void) { }
|
||||
|
||||
static inline void kcsan_atomic_next(int n) { }
|
||||
|
||||
#endif /* CONFIG_KCSAN */
|
||||
|
||||
#endif /* _LINUX_KCSAN_H */
|
||||
@ -31,6 +31,7 @@
|
||||
#include <linux/task_io_accounting.h>
|
||||
#include <linux/posix-timers.h>
|
||||
#include <linux/rseq.h>
|
||||
#include <linux/kcsan.h>
|
||||
|
||||
/* task_struct member predeclarations (sorted alphabetically): */
|
||||
struct audit_context;
|
||||
@ -1172,6 +1173,9 @@ struct task_struct {
|
||||
#ifdef CONFIG_KASAN
|
||||
unsigned int kasan_depth;
|
||||
#endif
|
||||
#ifdef CONFIG_KCSAN
|
||||
struct kcsan_ctx kcsan_ctx;
|
||||
#endif
|
||||
|
||||
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
||||
/* Index of current stored address in ret_stack: */
|
||||
|
||||
@ -37,8 +37,24 @@
|
||||
#include <linux/preempt.h>
|
||||
#include <linux/lockdep.h>
|
||||
#include <linux/compiler.h>
|
||||
#include <linux/kcsan.h>
|
||||
#include <asm/processor.h>
|
||||
|
||||
/*
|
||||
* The seqlock interface does not prescribe a precise sequence of read
|
||||
* begin/retry/end. For readers, typically there is a call to
|
||||
* read_seqcount_begin() and read_seqcount_retry(), however, there are more
|
||||
* esoteric cases which do not follow this pattern.
|
||||
*
|
||||
* As a consequence, we take the following best-effort approach for raw usage
|
||||
* via seqcount_t under KCSAN: upon beginning a seq-reader critical section,
|
||||
* pessimistically mark then next KCSAN_SEQLOCK_REGION_MAX memory accesses as
|
||||
* atomics; if there is a matching read_seqcount_retry() call, no following
|
||||
* memory operations are considered atomic. Usage of seqlocks via seqlock_t
|
||||
* interface is not affected.
|
||||
*/
|
||||
#define KCSAN_SEQLOCK_REGION_MAX 1000
|
||||
|
||||
/*
|
||||
* Version using sequence counter only.
|
||||
* This can be used when code has its own mutex protecting the
|
||||
@ -115,6 +131,7 @@ repeat:
|
||||
cpu_relax();
|
||||
goto repeat;
|
||||
}
|
||||
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);
|
||||
return ret;
|
||||
}
|
||||
|
||||
@ -131,6 +148,7 @@ static inline unsigned raw_read_seqcount(const seqcount_t *s)
|
||||
{
|
||||
unsigned ret = READ_ONCE(s->sequence);
|
||||
smp_rmb();
|
||||
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);
|
||||
return ret;
|
||||
}
|
||||
|
||||
@ -183,6 +201,7 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s)
|
||||
{
|
||||
unsigned ret = READ_ONCE(s->sequence);
|
||||
smp_rmb();
|
||||
kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);
|
||||
return ret & ~1;
|
||||
}
|
||||
|
||||
@ -202,7 +221,8 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s)
|
||||
*/
|
||||
static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
|
||||
{
|
||||
return unlikely(s->sequence != start);
|
||||
kcsan_atomic_next(0);
|
||||
return unlikely(READ_ONCE(s->sequence) != start);
|
||||
}
|
||||
|
||||
/**
|
||||
@ -225,6 +245,7 @@ static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
|
||||
|
||||
static inline void raw_write_seqcount_begin(seqcount_t *s)
|
||||
{
|
||||
kcsan_nestable_atomic_begin();
|
||||
s->sequence++;
|
||||
smp_wmb();
|
||||
}
|
||||
@ -233,6 +254,7 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
|
||||
{
|
||||
smp_wmb();
|
||||
s->sequence++;
|
||||
kcsan_nestable_atomic_end();
|
||||
}
|
||||
|
||||
/**
|
||||
@ -243,6 +265,13 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
|
||||
* usual consistency guarantee. It is one wmb cheaper, because we can
|
||||
* collapse the two back-to-back wmb()s.
|
||||
*
|
||||
* Note that, writes surrounding the barrier should be declared atomic (e.g.
|
||||
* via WRITE_ONCE): a) to ensure the writes become visible to other threads
|
||||
* atomically, avoiding compiler optimizations; b) to document which writes are
|
||||
* meant to propagate to the reader critical section. This is necessary because
|
||||
* neither writes before and after the barrier are enclosed in a seq-writer
|
||||
* critical section that would ensure readers are aware of ongoing writes.
|
||||
*
|
||||
* seqcount_t seq;
|
||||
* bool X = true, Y = false;
|
||||
*
|
||||
@ -262,18 +291,20 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
|
||||
*
|
||||
* void write(void)
|
||||
* {
|
||||
* Y = true;
|
||||
* WRITE_ONCE(Y, true);
|
||||
*
|
||||
* raw_write_seqcount_barrier(seq);
|
||||
*
|
||||
* X = false;
|
||||
* WRITE_ONCE(X, false);
|
||||
* }
|
||||
*/
|
||||
static inline void raw_write_seqcount_barrier(seqcount_t *s)
|
||||
{
|
||||
kcsan_nestable_atomic_begin();
|
||||
s->sequence++;
|
||||
smp_wmb();
|
||||
s->sequence++;
|
||||
kcsan_nestable_atomic_end();
|
||||
}
|
||||
|
||||
static inline int raw_read_seqcount_latch(seqcount_t *s)
|
||||
@ -398,7 +429,9 @@ static inline void write_seqcount_end(seqcount_t *s)
|
||||
static inline void write_seqcount_invalidate(seqcount_t *s)
|
||||
{
|
||||
smp_wmb();
|
||||
kcsan_nestable_atomic_begin();
|
||||
s->sequence+=2;
|
||||
kcsan_nestable_atomic_end();
|
||||
}
|
||||
|
||||
typedef struct {
|
||||
@ -430,11 +463,21 @@ typedef struct {
|
||||
*/
|
||||
static inline unsigned read_seqbegin(const seqlock_t *sl)
|
||||
{
|
||||
return read_seqcount_begin(&sl->seqcount);
|
||||
unsigned ret = read_seqcount_begin(&sl->seqcount);
|
||||
|
||||
kcsan_atomic_next(0); /* non-raw usage, assume closing read_seqretry */
|
||||
kcsan_flat_atomic_begin();
|
||||
return ret;
|
||||
}
|
||||
|
||||
static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
|
||||
{
|
||||
/*
|
||||
* Assume not nested: read_seqretry may be called multiple times when
|
||||
* completing read critical section.
|
||||
*/
|
||||
kcsan_flat_atomic_end();
|
||||
|
||||
return read_seqcount_retry(&sl->seqcount, start);
|
||||
}
|
||||
|
||||
|
||||
@ -161,6 +161,14 @@ struct task_struct init_task
|
||||
#ifdef CONFIG_KASAN
|
||||
.kasan_depth = 1,
|
||||
#endif
|
||||
#ifdef CONFIG_KCSAN
|
||||
.kcsan_ctx = {
|
||||
.disable_count = 0,
|
||||
.atomic_next = 0,
|
||||
.atomic_nest_count = 0,
|
||||
.in_flat_atomic = false,
|
||||
},
|
||||
#endif
|
||||
#ifdef CONFIG_TRACE_IRQFLAGS
|
||||
.softirqs_enabled = 1,
|
||||
#endif
|
||||
|
||||
@ -93,6 +93,7 @@
|
||||
#include <linux/rodata_test.h>
|
||||
#include <linux/jump_label.h>
|
||||
#include <linux/mem_encrypt.h>
|
||||
#include <linux/kcsan.h>
|
||||
|
||||
#include <asm/io.h>
|
||||
#include <asm/bugs.h>
|
||||
@ -779,6 +780,7 @@ asmlinkage __visible void __init start_kernel(void)
|
||||
acpi_subsystem_init();
|
||||
arch_post_acpi_subsys_init();
|
||||
sfi_init_late();
|
||||
kcsan_init();
|
||||
|
||||
/* Do the rest non-__init'ed, we're now alive */
|
||||
arch_call_rest_init();
|
||||
|
||||
@ -23,6 +23,9 @@ endif
|
||||
# Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip()
|
||||
# in coverage traces.
|
||||
KCOV_INSTRUMENT_softirq.o := n
|
||||
# Avoid KCSAN instrumentation in softirq ("No shared variables, all the data
|
||||
# are CPU local" => assume no data races), to reduce overhead in interrupts.
|
||||
KCSAN_SANITIZE_softirq.o = n
|
||||
# These are called from save_stack_trace() on slub debug path,
|
||||
# and produce insane amounts of uninteresting coverage.
|
||||
KCOV_INSTRUMENT_module.o := n
|
||||
@ -30,6 +33,7 @@ KCOV_INSTRUMENT_extable.o := n
|
||||
# Don't self-instrument.
|
||||
KCOV_INSTRUMENT_kcov.o := n
|
||||
KASAN_SANITIZE_kcov.o := n
|
||||
KCSAN_SANITIZE_kcov.o := n
|
||||
CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
|
||||
|
||||
# cond_syscall is currently not LTO compatible
|
||||
@ -102,6 +106,7 @@ obj-$(CONFIG_TRACEPOINTS) += trace/
|
||||
obj-$(CONFIG_IRQ_WORK) += irq_work.o
|
||||
obj-$(CONFIG_CPU_PM) += cpu_pm.o
|
||||
obj-$(CONFIG_BPF) += bpf/
|
||||
obj-$(CONFIG_KCSAN) += kcsan/
|
||||
|
||||
obj-$(CONFIG_PERF_EVENTS) += events/
|
||||
|
||||
@ -117,6 +122,7 @@ obj-$(CONFIG_RSEQ) += rseq.o
|
||||
|
||||
obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o
|
||||
KASAN_SANITIZE_stackleak.o := n
|
||||
KCSAN_SANITIZE_stackleak.o := n
|
||||
KCOV_INSTRUMENT_stackleak.o := n
|
||||
|
||||
$(obj)/configs.o: $(obj)/config_data.gz
|
||||
|
||||
11
kernel/kcsan/Makefile
Normal file
11
kernel/kcsan/Makefile
Normal file
@ -0,0 +1,11 @@
|
||||
# SPDX-License-Identifier: GPL-2.0
|
||||
KCSAN_SANITIZE := n
|
||||
KCOV_INSTRUMENT := n
|
||||
|
||||
CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE)
|
||||
|
||||
CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) \
|
||||
$(call cc-option,-fno-stack-protector,)
|
||||
|
||||
obj-y := core.o debugfs.o report.o
|
||||
obj-$(CONFIG_KCSAN_SELFTEST) += test.o
|
||||
27
kernel/kcsan/atomic.h
Normal file
27
kernel/kcsan/atomic.h
Normal file
@ -0,0 +1,27 @@
|
||||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
|
||||
#ifndef _KERNEL_KCSAN_ATOMIC_H
|
||||
#define _KERNEL_KCSAN_ATOMIC_H
|
||||
|
||||
#include <linux/jiffies.h>
|
||||
|
||||
/*
|
||||
* Helper that returns true if access to ptr should be considered as an atomic
|
||||
* access, even though it is not explicitly atomic.
|
||||
*
|
||||
* List all volatile globals that have been observed in races, to suppress
|
||||
* data race reports between accesses to these variables.
|
||||
*
|
||||
* For now, we assume that volatile accesses of globals are as strong as atomic
|
||||
* accesses (READ_ONCE, WRITE_ONCE cast to volatile). The situation is still not
|
||||
* entirely clear, as on some architectures (Alpha) READ_ONCE/WRITE_ONCE do more
|
||||
* than cast to volatile. Eventually, we hope to be able to remove this
|
||||
* function.
|
||||
*/
|
||||
static inline bool kcsan_is_atomic(const volatile void *ptr)
|
||||
{
|
||||
/* only jiffies for now */
|
||||
return ptr == &jiffies;
|
||||
}
|
||||
|
||||
#endif /* _KERNEL_KCSAN_ATOMIC_H */
|
||||
626
kernel/kcsan/core.c
Normal file
626
kernel/kcsan/core.c
Normal file
@ -0,0 +1,626 @@
|
||||
// SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
#include <linux/atomic.h>
|
||||
#include <linux/bug.h>
|
||||
#include <linux/delay.h>
|
||||
#include <linux/export.h>
|
||||
#include <linux/init.h>
|
||||
#include <linux/percpu.h>
|
||||
#include <linux/preempt.h>
|
||||
#include <linux/random.h>
|
||||
#include <linux/sched.h>
|
||||
#include <linux/uaccess.h>
|
||||
|
||||
#include "atomic.h"
|
||||
#include "encoding.h"
|
||||
#include "kcsan.h"
|
||||
|
||||
bool kcsan_enabled;
|
||||
|
||||
/* Per-CPU kcsan_ctx for interrupts */
|
||||
static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
|
||||
.disable_count = 0,
|
||||
.atomic_next = 0,
|
||||
.atomic_nest_count = 0,
|
||||
.in_flat_atomic = false,
|
||||
};
|
||||
|
||||
/*
|
||||
* Helper macros to index into adjacent slots slots, starting from address slot
|
||||
* itself, followed by the right and left slots.
|
||||
*
|
||||
* The purpose is 2-fold:
|
||||
*
|
||||
* 1. if during insertion the address slot is already occupied, check if
|
||||
* any adjacent slots are free;
|
||||
* 2. accesses that straddle a slot boundary due to size that exceeds a
|
||||
* slot's range may check adjacent slots if any watchpoint matches.
|
||||
*
|
||||
* Note that accesses with very large size may still miss a watchpoint; however,
|
||||
* given this should be rare, this is a reasonable trade-off to make, since this
|
||||
* will avoid:
|
||||
*
|
||||
* 1. excessive contention between watchpoint checks and setup;
|
||||
* 2. larger number of simultaneous watchpoints without sacrificing
|
||||
* performance.
|
||||
*
|
||||
* Example: SLOT_IDX values for KCSAN_CHECK_ADJACENT=1, where i is [0, 1, 2]:
|
||||
*
|
||||
* slot=0: [ 1, 2, 0]
|
||||
* slot=9: [10, 11, 9]
|
||||
* slot=63: [64, 65, 63]
|
||||
*/
|
||||
#define NUM_SLOTS (1 + 2 * KCSAN_CHECK_ADJACENT)
|
||||
#define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
|
||||
|
||||
/*
|
||||
* SLOT_IDX_FAST is used in fast-path. Not first checking the address's primary
|
||||
* slot (middle) is fine if we assume that data races occur rarely. The set of
|
||||
* indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
|
||||
* {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
|
||||
*/
|
||||
#define SLOT_IDX_FAST(slot, i) (slot + i)
|
||||
|
||||
/*
|
||||
* Watchpoints, with each entry encoded as defined in encoding.h: in order to be
|
||||
* able to safely update and access a watchpoint without introducing locking
|
||||
* overhead, we encode each watchpoint as a single atomic long. The initial
|
||||
* zero-initialized state matches INVALID_WATCHPOINT.
|
||||
*
|
||||
* Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
|
||||
* use more complicated SLOT_IDX_FAST calculation with modulo in fast-path.
|
||||
*/
|
||||
static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS - 1];
|
||||
|
||||
/*
|
||||
* Instructions to skip watching counter, used in should_watch(). We use a
|
||||
* per-CPU counter to avoid excessive contention.
|
||||
*/
|
||||
static DEFINE_PER_CPU(long, kcsan_skip);
|
||||
|
||||
static inline atomic_long_t *find_watchpoint(unsigned long addr, size_t size,
|
||||
bool expect_write,
|
||||
long *encoded_watchpoint)
|
||||
{
|
||||
const int slot = watchpoint_slot(addr);
|
||||
const unsigned long addr_masked = addr & WATCHPOINT_ADDR_MASK;
|
||||
atomic_long_t *watchpoint;
|
||||
unsigned long wp_addr_masked;
|
||||
size_t wp_size;
|
||||
bool is_write;
|
||||
int i;
|
||||
|
||||
BUILD_BUG_ON(CONFIG_KCSAN_NUM_WATCHPOINTS < NUM_SLOTS);
|
||||
|
||||
for (i = 0; i < NUM_SLOTS; ++i) {
|
||||
watchpoint = &watchpoints[SLOT_IDX_FAST(slot, i)];
|
||||
*encoded_watchpoint = atomic_long_read(watchpoint);
|
||||
if (!decode_watchpoint(*encoded_watchpoint, &wp_addr_masked,
|
||||
&wp_size, &is_write))
|
||||
continue;
|
||||
|
||||
if (expect_write && !is_write)
|
||||
continue;
|
||||
|
||||
/* Check if the watchpoint matches the access. */
|
||||
if (matching_access(wp_addr_masked, wp_size, addr_masked, size))
|
||||
return watchpoint;
|
||||
}
|
||||
|
||||
return NULL;
|
||||
}
|
||||
|
||||
static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
|
||||
bool is_write)
|
||||
{
|
||||
const int slot = watchpoint_slot(addr);
|
||||
const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
|
||||
atomic_long_t *watchpoint;
|
||||
int i;
|
||||
|
||||
/* Check slot index logic, ensuring we stay within array bounds. */
|
||||
BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
|
||||
BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT + 1) != 0);
|
||||
BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS - 1,
|
||||
KCSAN_CHECK_ADJACENT) !=
|
||||
ARRAY_SIZE(watchpoints) - 1);
|
||||
BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS - 1,
|
||||
KCSAN_CHECK_ADJACENT + 1) !=
|
||||
ARRAY_SIZE(watchpoints) - NUM_SLOTS);
|
||||
|
||||
for (i = 0; i < NUM_SLOTS; ++i) {
|
||||
long expect_val = INVALID_WATCHPOINT;
|
||||
|
||||
/* Try to acquire this slot. */
|
||||
watchpoint = &watchpoints[SLOT_IDX(slot, i)];
|
||||
if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val,
|
||||
encoded_watchpoint))
|
||||
return watchpoint;
|
||||
}
|
||||
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Return true if watchpoint was successfully consumed, false otherwise.
|
||||
*
|
||||
* This may return false if:
|
||||
*
|
||||
* 1. another thread already consumed the watchpoint;
|
||||
* 2. the thread that set up the watchpoint already removed it;
|
||||
* 3. the watchpoint was removed and then re-used.
|
||||
*/
|
||||
static inline bool try_consume_watchpoint(atomic_long_t *watchpoint,
|
||||
long encoded_watchpoint)
|
||||
{
|
||||
return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint,
|
||||
CONSUMED_WATCHPOINT);
|
||||
}
|
||||
|
||||
/*
|
||||
* Return true if watchpoint was not touched, false if consumed.
|
||||
*/
|
||||
static inline bool remove_watchpoint(atomic_long_t *watchpoint)
|
||||
{
|
||||
return atomic_long_xchg_relaxed(watchpoint, INVALID_WATCHPOINT) !=
|
||||
CONSUMED_WATCHPOINT;
|
||||
}
|
||||
|
||||
static inline struct kcsan_ctx *get_ctx(void)
|
||||
{
|
||||
/*
|
||||
* In interrupt, use raw_cpu_ptr to avoid unnecessary checks, that would
|
||||
* also result in calls that generate warnings in uaccess regions.
|
||||
*/
|
||||
return in_task() ? ¤t->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
|
||||
}
|
||||
|
||||
static inline bool is_atomic(const volatile void *ptr)
|
||||
{
|
||||
struct kcsan_ctx *ctx = get_ctx();
|
||||
|
||||
if (unlikely(ctx->atomic_next > 0)) {
|
||||
/*
|
||||
* Because we do not have separate contexts for nested
|
||||
* interrupts, in case atomic_next is set, we simply assume that
|
||||
* the outer interrupt set atomic_next. In the worst case, we
|
||||
* will conservatively consider operations as atomic. This is a
|
||||
* reasonable trade-off to make, since this case should be
|
||||
* extremely rare; however, even if extremely rare, it could
|
||||
* lead to false positives otherwise.
|
||||
*/
|
||||
if ((hardirq_count() >> HARDIRQ_SHIFT) < 2)
|
||||
--ctx->atomic_next; /* in task, or outer interrupt */
|
||||
return true;
|
||||
}
|
||||
if (unlikely(ctx->atomic_nest_count > 0 || ctx->in_flat_atomic))
|
||||
return true;
|
||||
|
||||
return kcsan_is_atomic(ptr);
|
||||
}
|
||||
|
||||
static inline bool should_watch(const volatile void *ptr, int type)
|
||||
{
|
||||
/*
|
||||
* Never set up watchpoints when memory operations are atomic.
|
||||
*
|
||||
* Need to check this first, before kcsan_skip check below: (1) atomics
|
||||
* should not count towards skipped instructions, and (2) to actually
|
||||
* decrement kcsan_atomic_next for consecutive instruction stream.
|
||||
*/
|
||||
if ((type & KCSAN_ACCESS_ATOMIC) != 0 || is_atomic(ptr))
|
||||
return false;
|
||||
|
||||
if (this_cpu_dec_return(kcsan_skip) >= 0)
|
||||
return false;
|
||||
|
||||
/*
|
||||
* NOTE: If we get here, kcsan_skip must always be reset in slow path
|
||||
* via reset_kcsan_skip() to avoid underflow.
|
||||
*/
|
||||
|
||||
/* this operation should be watched */
|
||||
return true;
|
||||
}
|
||||
|
||||
static inline void reset_kcsan_skip(void)
|
||||
{
|
||||
long skip_count = CONFIG_KCSAN_SKIP_WATCH -
|
||||
(IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
|
||||
prandom_u32_max(CONFIG_KCSAN_SKIP_WATCH) :
|
||||
0);
|
||||
this_cpu_write(kcsan_skip, skip_count);
|
||||
}
|
||||
|
||||
static inline bool kcsan_is_enabled(void)
|
||||
{
|
||||
return READ_ONCE(kcsan_enabled) && get_ctx()->disable_count == 0;
|
||||
}
|
||||
|
||||
static inline unsigned int get_delay(void)
|
||||
{
|
||||
unsigned int delay = in_task() ? CONFIG_KCSAN_UDELAY_TASK :
|
||||
CONFIG_KCSAN_UDELAY_INTERRUPT;
|
||||
return delay - (IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
|
||||
prandom_u32_max(delay) :
|
||||
0);
|
||||
}
|
||||
|
||||
/*
|
||||
* Pull everything together: check_access() below contains the performance
|
||||
* critical operations; the fast-path (including check_access) functions should
|
||||
* all be inlinable by the instrumentation functions.
|
||||
*
|
||||
* The slow-path (kcsan_found_watchpoint, kcsan_setup_watchpoint) are
|
||||
* non-inlinable -- note that, we prefix these with "kcsan_" to ensure they can
|
||||
* be filtered from the stacktrace, as well as give them unique names for the
|
||||
* UACCESS whitelist of objtool. Each function uses user_access_save/restore(),
|
||||
* since they do not access any user memory, but instrumentation is still
|
||||
* emitted in UACCESS regions.
|
||||
*/
|
||||
|
||||
static noinline void kcsan_found_watchpoint(const volatile void *ptr,
|
||||
size_t size, bool is_write,
|
||||
atomic_long_t *watchpoint,
|
||||
long encoded_watchpoint)
|
||||
{
|
||||
unsigned long flags;
|
||||
bool consumed;
|
||||
|
||||
if (!kcsan_is_enabled())
|
||||
return;
|
||||
/*
|
||||
* Consume the watchpoint as soon as possible, to minimize the chances
|
||||
* of !consumed. Consuming the watchpoint must always be guarded by
|
||||
* kcsan_is_enabled() check, as otherwise we might erroneously
|
||||
* triggering reports when disabled.
|
||||
*/
|
||||
consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
|
||||
|
||||
/* keep this after try_consume_watchpoint */
|
||||
flags = user_access_save();
|
||||
|
||||
if (consumed) {
|
||||
kcsan_report(ptr, size, is_write, true, raw_smp_processor_id(),
|
||||
KCSAN_REPORT_CONSUMED_WATCHPOINT);
|
||||
} else {
|
||||
/*
|
||||
* The other thread may not print any diagnostics, as it has
|
||||
* already removed the watchpoint, or another thread consumed
|
||||
* the watchpoint before this thread.
|
||||
*/
|
||||
kcsan_counter_inc(KCSAN_COUNTER_REPORT_RACES);
|
||||
}
|
||||
kcsan_counter_inc(KCSAN_COUNTER_DATA_RACES);
|
||||
|
||||
user_access_restore(flags);
|
||||
}
|
||||
|
||||
static noinline void kcsan_setup_watchpoint(const volatile void *ptr,
|
||||
size_t size, bool is_write)
|
||||
{
|
||||
atomic_long_t *watchpoint;
|
||||
union {
|
||||
u8 _1;
|
||||
u16 _2;
|
||||
u32 _4;
|
||||
u64 _8;
|
||||
} expect_value;
|
||||
bool value_change = false;
|
||||
unsigned long ua_flags = user_access_save();
|
||||
unsigned long irq_flags;
|
||||
|
||||
/*
|
||||
* Always reset kcsan_skip counter in slow-path to avoid underflow; see
|
||||
* should_watch().
|
||||
*/
|
||||
reset_kcsan_skip();
|
||||
|
||||
if (!kcsan_is_enabled())
|
||||
goto out;
|
||||
|
||||
if (!check_encodable((unsigned long)ptr, size)) {
|
||||
kcsan_counter_inc(KCSAN_COUNTER_UNENCODABLE_ACCESSES);
|
||||
goto out;
|
||||
}
|
||||
|
||||
/*
|
||||
* Disable interrupts & preemptions to avoid another thread on the same
|
||||
* CPU accessing memory locations for the set up watchpoint; this is to
|
||||
* avoid reporting races to e.g. CPU-local data.
|
||||
*
|
||||
* An alternative would be adding the source CPU to the watchpoint
|
||||
* encoding, and checking that watchpoint-CPU != this-CPU. There are
|
||||
* several problems with this:
|
||||
* 1. we should avoid stealing more bits from the watchpoint encoding
|
||||
* as it would affect accuracy, as well as increase performance
|
||||
* overhead in the fast-path;
|
||||
* 2. if we are preempted, but there *is* a genuine data race, we
|
||||
* would *not* report it -- since this is the common case (vs.
|
||||
* CPU-local data accesses), it makes more sense (from a data race
|
||||
* detection point of view) to simply disable preemptions to ensure
|
||||
* as many tasks as possible run on other CPUs.
|
||||
*/
|
||||
local_irq_save(irq_flags);
|
||||
|
||||
watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
|
||||
if (watchpoint == NULL) {
|
||||
/*
|
||||
* Out of capacity: the size of `watchpoints`, and the frequency
|
||||
* with which `should_watch()` returns true should be tweaked so
|
||||
* that this case happens very rarely.
|
||||
*/
|
||||
kcsan_counter_inc(KCSAN_COUNTER_NO_CAPACITY);
|
||||
goto out_unlock;
|
||||
}
|
||||
|
||||
kcsan_counter_inc(KCSAN_COUNTER_SETUP_WATCHPOINTS);
|
||||
kcsan_counter_inc(KCSAN_COUNTER_USED_WATCHPOINTS);
|
||||
|
||||
/*
|
||||
* Read the current value, to later check and infer a race if the data
|
||||
* was modified via a non-instrumented access, e.g. from a device.
|
||||
*/
|
||||
switch (size) {
|
||||
case 1:
|
||||
expect_value._1 = READ_ONCE(*(const u8 *)ptr);
|
||||
break;
|
||||
case 2:
|
||||
expect_value._2 = READ_ONCE(*(const u16 *)ptr);
|
||||
break;
|
||||
case 4:
|
||||
expect_value._4 = READ_ONCE(*(const u32 *)ptr);
|
||||
break;
|
||||
case 8:
|
||||
expect_value._8 = READ_ONCE(*(const u64 *)ptr);
|
||||
break;
|
||||
default:
|
||||
break; /* ignore; we do not diff the values */
|
||||
}
|
||||
|
||||
if (IS_ENABLED(CONFIG_KCSAN_DEBUG)) {
|
||||
kcsan_disable_current();
|
||||
pr_err("KCSAN: watching %s, size: %zu, addr: %px [slot: %d, encoded: %lx]\n",
|
||||
is_write ? "write" : "read", size, ptr,
|
||||
watchpoint_slot((unsigned long)ptr),
|
||||
encode_watchpoint((unsigned long)ptr, size, is_write));
|
||||
kcsan_enable_current();
|
||||
}
|
||||
|
||||
/*
|
||||
* Delay this thread, to increase probability of observing a racy
|
||||
* conflicting access.
|
||||
*/
|
||||
udelay(get_delay());
|
||||
|
||||
/*
|
||||
* Re-read value, and check if it is as expected; if not, we infer a
|
||||
* racy access.
|
||||
*/
|
||||
switch (size) {
|
||||
case 1:
|
||||
value_change = expect_value._1 != READ_ONCE(*(const u8 *)ptr);
|
||||
break;
|
||||
case 2:
|
||||
value_change = expect_value._2 != READ_ONCE(*(const u16 *)ptr);
|
||||
break;
|
||||
case 4:
|
||||
value_change = expect_value._4 != READ_ONCE(*(const u32 *)ptr);
|
||||
break;
|
||||
case 8:
|
||||
value_change = expect_value._8 != READ_ONCE(*(const u64 *)ptr);
|
||||
break;
|
||||
default:
|
||||
break; /* ignore; we do not diff the values */
|
||||
}
|
||||
|
||||
/* Check if this access raced with another. */
|
||||
if (!remove_watchpoint(watchpoint)) {
|
||||
/*
|
||||
* No need to increment 'data_races' counter, as the racing
|
||||
* thread already did.
|
||||
*/
|
||||
kcsan_report(ptr, size, is_write, size > 8 || value_change,
|
||||
smp_processor_id(), KCSAN_REPORT_RACE_SIGNAL);
|
||||
} else if (value_change) {
|
||||
/* Inferring a race, since the value should not have changed. */
|
||||
kcsan_counter_inc(KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN);
|
||||
if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
|
||||
kcsan_report(ptr, size, is_write, true,
|
||||
smp_processor_id(),
|
||||
KCSAN_REPORT_RACE_UNKNOWN_ORIGIN);
|
||||
}
|
||||
|
||||
kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
|
||||
out_unlock:
|
||||
local_irq_restore(irq_flags);
|
||||
out:
|
||||
user_access_restore(ua_flags);
|
||||
}
|
||||
|
||||
static __always_inline void check_access(const volatile void *ptr, size_t size,
|
||||
int type)
|
||||
{
|
||||
const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
|
||||
atomic_long_t *watchpoint;
|
||||
long encoded_watchpoint;
|
||||
|
||||
/*
|
||||
* Avoid user_access_save in fast-path: find_watchpoint is safe without
|
||||
* user_access_save, as the address that ptr points to is only used to
|
||||
* check if a watchpoint exists; ptr is never dereferenced.
|
||||
*/
|
||||
watchpoint = find_watchpoint((unsigned long)ptr, size, !is_write,
|
||||
&encoded_watchpoint);
|
||||
/*
|
||||
* It is safe to check kcsan_is_enabled() after find_watchpoint in the
|
||||
* slow-path, as long as no state changes that cause a data race to be
|
||||
* detected and reported have occurred until kcsan_is_enabled() is
|
||||
* checked.
|
||||
*/
|
||||
|
||||
if (unlikely(watchpoint != NULL))
|
||||
kcsan_found_watchpoint(ptr, size, is_write, watchpoint,
|
||||
encoded_watchpoint);
|
||||
else if (unlikely(should_watch(ptr, type)))
|
||||
kcsan_setup_watchpoint(ptr, size, is_write);
|
||||
}
|
||||
|
||||
/* === Public interface ===================================================== */
|
||||
|
||||
void __init kcsan_init(void)
|
||||
{
|
||||
BUG_ON(!in_task());
|
||||
|
||||
kcsan_debugfs_init();
|
||||
|
||||
/*
|
||||
* We are in the init task, and no other tasks should be running;
|
||||
* WRITE_ONCE without memory barrier is sufficient.
|
||||
*/
|
||||
if (IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE))
|
||||
WRITE_ONCE(kcsan_enabled, true);
|
||||
}
|
||||
|
||||
/* === Exported interface =================================================== */
|
||||
|
||||
void kcsan_disable_current(void)
|
||||
{
|
||||
++get_ctx()->disable_count;
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_disable_current);
|
||||
|
||||
void kcsan_enable_current(void)
|
||||
{
|
||||
if (get_ctx()->disable_count-- == 0) {
|
||||
/*
|
||||
* Warn if kcsan_enable_current() calls are unbalanced with
|
||||
* kcsan_disable_current() calls, which causes disable_count to
|
||||
* become negative and should not happen.
|
||||
*/
|
||||
kcsan_disable_current(); /* restore to 0, KCSAN still enabled */
|
||||
kcsan_disable_current(); /* disable to generate warning */
|
||||
WARN(1, "Unbalanced %s()", __func__);
|
||||
kcsan_enable_current();
|
||||
}
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_enable_current);
|
||||
|
||||
void kcsan_nestable_atomic_begin(void)
|
||||
{
|
||||
/*
|
||||
* Do *not* check and warn if we are in a flat atomic region: nestable
|
||||
* and flat atomic regions are independent from each other.
|
||||
* See include/linux/kcsan.h: struct kcsan_ctx comments for more
|
||||
* comments.
|
||||
*/
|
||||
|
||||
++get_ctx()->atomic_nest_count;
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_nestable_atomic_begin);
|
||||
|
||||
void kcsan_nestable_atomic_end(void)
|
||||
{
|
||||
if (get_ctx()->atomic_nest_count-- == 0) {
|
||||
/*
|
||||
* Warn if kcsan_nestable_atomic_end() calls are unbalanced with
|
||||
* kcsan_nestable_atomic_begin() calls, which causes
|
||||
* atomic_nest_count to become negative and should not happen.
|
||||
*/
|
||||
kcsan_nestable_atomic_begin(); /* restore to 0 */
|
||||
kcsan_disable_current(); /* disable to generate warning */
|
||||
WARN(1, "Unbalanced %s()", __func__);
|
||||
kcsan_enable_current();
|
||||
}
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_nestable_atomic_end);
|
||||
|
||||
void kcsan_flat_atomic_begin(void)
|
||||
{
|
||||
get_ctx()->in_flat_atomic = true;
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_flat_atomic_begin);
|
||||
|
||||
void kcsan_flat_atomic_end(void)
|
||||
{
|
||||
get_ctx()->in_flat_atomic = false;
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_flat_atomic_end);
|
||||
|
||||
void kcsan_atomic_next(int n)
|
||||
{
|
||||
get_ctx()->atomic_next = n;
|
||||
}
|
||||
EXPORT_SYMBOL(kcsan_atomic_next);
|
||||
|
||||
void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
|
||||
{
|
||||
check_access(ptr, size, type);
|
||||
}
|
||||
EXPORT_SYMBOL(__kcsan_check_access);
|
||||
|
||||
/*
|
||||
* KCSAN uses the same instrumentation that is emitted by supported compilers
|
||||
* for ThreadSanitizer (TSAN).
|
||||
*
|
||||
* When enabled, the compiler emits instrumentation calls (the functions
|
||||
* prefixed with "__tsan" below) for all loads and stores that it generated;
|
||||
* inline asm is not instrumented.
|
||||
*
|
||||
* Note that, not all supported compiler versions distinguish aligned/unaligned
|
||||
* accesses, but e.g. recent versions of Clang do. We simply alias the unaligned
|
||||
* version to the generic version, which can handle both.
|
||||
*/
|
||||
|
||||
#define DEFINE_TSAN_READ_WRITE(size) \
|
||||
void __tsan_read##size(void *ptr) \
|
||||
{ \
|
||||
check_access(ptr, size, 0); \
|
||||
} \
|
||||
EXPORT_SYMBOL(__tsan_read##size); \
|
||||
void __tsan_unaligned_read##size(void *ptr) \
|
||||
__alias(__tsan_read##size); \
|
||||
EXPORT_SYMBOL(__tsan_unaligned_read##size); \
|
||||
void __tsan_write##size(void *ptr) \
|
||||
{ \
|
||||
check_access(ptr, size, KCSAN_ACCESS_WRITE); \
|
||||
} \
|
||||
EXPORT_SYMBOL(__tsan_write##size); \
|
||||
void __tsan_unaligned_write##size(void *ptr) \
|
||||
__alias(__tsan_write##size); \
|
||||
EXPORT_SYMBOL(__tsan_unaligned_write##size)
|
||||
|
||||
DEFINE_TSAN_READ_WRITE(1);
|
||||
DEFINE_TSAN_READ_WRITE(2);
|
||||
DEFINE_TSAN_READ_WRITE(4);
|
||||
DEFINE_TSAN_READ_WRITE(8);
|
||||
DEFINE_TSAN_READ_WRITE(16);
|
||||
|
||||
void __tsan_read_range(void *ptr, size_t size)
|
||||
{
|
||||
check_access(ptr, size, 0);
|
||||
}
|
||||
EXPORT_SYMBOL(__tsan_read_range);
|
||||
|
||||
void __tsan_write_range(void *ptr, size_t size)
|
||||
{
|
||||
check_access(ptr, size, KCSAN_ACCESS_WRITE);
|
||||
}
|
||||
EXPORT_SYMBOL(__tsan_write_range);
|
||||
|
||||
/*
|
||||
* The below are not required by KCSAN, but can still be emitted by the
|
||||
* compiler.
|
||||
*/
|
||||
void __tsan_func_entry(void *call_pc)
|
||||
{
|
||||
}
|
||||
EXPORT_SYMBOL(__tsan_func_entry);
|
||||
void __tsan_func_exit(void)
|
||||
{
|
||||
}
|
||||
EXPORT_SYMBOL(__tsan_func_exit);
|
||||
void __tsan_init(void)
|
||||
{
|
||||
}
|
||||
EXPORT_SYMBOL(__tsan_init);
|
||||
275
kernel/kcsan/debugfs.c
Normal file
275
kernel/kcsan/debugfs.c
Normal file
@ -0,0 +1,275 @@
|
||||
// SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
#include <linux/atomic.h>
|
||||
#include <linux/bsearch.h>
|
||||
#include <linux/bug.h>
|
||||
#include <linux/debugfs.h>
|
||||
#include <linux/init.h>
|
||||
#include <linux/kallsyms.h>
|
||||
#include <linux/seq_file.h>
|
||||
#include <linux/slab.h>
|
||||
#include <linux/sort.h>
|
||||
#include <linux/string.h>
|
||||
#include <linux/uaccess.h>
|
||||
|
||||
#include "kcsan.h"
|
||||
|
||||
/*
|
||||
* Statistics counters.
|
||||
*/
|
||||
static atomic_long_t counters[KCSAN_COUNTER_COUNT];
|
||||
|
||||
/*
|
||||
* Addresses for filtering functions from reporting. This list can be used as a
|
||||
* whitelist or blacklist.
|
||||
*/
|
||||
static struct {
|
||||
unsigned long *addrs; /* array of addresses */
|
||||
size_t size; /* current size */
|
||||
int used; /* number of elements used */
|
||||
bool sorted; /* if elements are sorted */
|
||||
bool whitelist; /* if list is a blacklist or whitelist */
|
||||
} report_filterlist = {
|
||||
.addrs = NULL,
|
||||
.size = 8, /* small initial size */
|
||||
.used = 0,
|
||||
.sorted = false,
|
||||
.whitelist = false, /* default is blacklist */
|
||||
};
|
||||
static DEFINE_SPINLOCK(report_filterlist_lock);
|
||||
|
||||
static const char *counter_to_name(enum kcsan_counter_id id)
|
||||
{
|
||||
switch (id) {
|
||||
case KCSAN_COUNTER_USED_WATCHPOINTS:
|
||||
return "used_watchpoints";
|
||||
case KCSAN_COUNTER_SETUP_WATCHPOINTS:
|
||||
return "setup_watchpoints";
|
||||
case KCSAN_COUNTER_DATA_RACES:
|
||||
return "data_races";
|
||||
case KCSAN_COUNTER_NO_CAPACITY:
|
||||
return "no_capacity";
|
||||
case KCSAN_COUNTER_REPORT_RACES:
|
||||
return "report_races";
|
||||
case KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN:
|
||||
return "races_unknown_origin";
|
||||
case KCSAN_COUNTER_UNENCODABLE_ACCESSES:
|
||||
return "unencodable_accesses";
|
||||
case KCSAN_COUNTER_ENCODING_FALSE_POSITIVES:
|
||||
return "encoding_false_positives";
|
||||
case KCSAN_COUNTER_COUNT:
|
||||
BUG();
|
||||
}
|
||||
return NULL;
|
||||
}
|
||||
|
||||
void kcsan_counter_inc(enum kcsan_counter_id id)
|
||||
{
|
||||
atomic_long_inc(&counters[id]);
|
||||
}
|
||||
|
||||
void kcsan_counter_dec(enum kcsan_counter_id id)
|
||||
{
|
||||
atomic_long_dec(&counters[id]);
|
||||
}
|
||||
|
||||
/*
|
||||
* The microbenchmark allows benchmarking KCSAN core runtime only. To run
|
||||
* multiple threads, pipe 'microbench=<iters>' from multiple tasks into the
|
||||
* debugfs file.
|
||||
*/
|
||||
static void microbenchmark(unsigned long iters)
|
||||
{
|
||||
cycles_t cycles;
|
||||
|
||||
pr_info("KCSAN: %s begin | iters: %lu\n", __func__, iters);
|
||||
|
||||
cycles = get_cycles();
|
||||
while (iters--) {
|
||||
/*
|
||||
* We can run this benchmark from multiple tasks; this address
|
||||
* calculation increases likelyhood of some accesses overlapping
|
||||
* (they still won't conflict because all are reads).
|
||||
*/
|
||||
unsigned long addr =
|
||||
iters % (CONFIG_KCSAN_NUM_WATCHPOINTS * PAGE_SIZE);
|
||||
__kcsan_check_read((void *)addr, sizeof(long));
|
||||
}
|
||||
cycles = get_cycles() - cycles;
|
||||
|
||||
pr_info("KCSAN: %s end | cycles: %llu\n", __func__, cycles);
|
||||
}
|
||||
|
||||
static int cmp_filterlist_addrs(const void *rhs, const void *lhs)
|
||||
{
|
||||
const unsigned long a = *(const unsigned long *)rhs;
|
||||
const unsigned long b = *(const unsigned long *)lhs;
|
||||
|
||||
return a < b ? -1 : a == b ? 0 : 1;
|
||||
}
|
||||
|
||||
bool kcsan_skip_report_debugfs(unsigned long func_addr)
|
||||
{
|
||||
unsigned long symbolsize, offset;
|
||||
unsigned long flags;
|
||||
bool ret = false;
|
||||
|
||||
if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
|
||||
return false;
|
||||
func_addr -= offset; /* get function start */
|
||||
|
||||
spin_lock_irqsave(&report_filterlist_lock, flags);
|
||||
if (report_filterlist.used == 0)
|
||||
goto out;
|
||||
|
||||
/* Sort array if it is unsorted, and then do a binary search. */
|
||||
if (!report_filterlist.sorted) {
|
||||
sort(report_filterlist.addrs, report_filterlist.used,
|
||||
sizeof(unsigned long), cmp_filterlist_addrs, NULL);
|
||||
report_filterlist.sorted = true;
|
||||
}
|
||||
ret = !!bsearch(&func_addr, report_filterlist.addrs,
|
||||
report_filterlist.used, sizeof(unsigned long),
|
||||
cmp_filterlist_addrs);
|
||||
if (report_filterlist.whitelist)
|
||||
ret = !ret;
|
||||
|
||||
out:
|
||||
spin_unlock_irqrestore(&report_filterlist_lock, flags);
|
||||
return ret;
|
||||
}
|
||||
|
||||
static void set_report_filterlist_whitelist(bool whitelist)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
spin_lock_irqsave(&report_filterlist_lock, flags);
|
||||
report_filterlist.whitelist = whitelist;
|
||||
spin_unlock_irqrestore(&report_filterlist_lock, flags);
|
||||
}
|
||||
|
||||
/* Returns 0 on success, error-code otherwise. */
|
||||
static ssize_t insert_report_filterlist(const char *func)
|
||||
{
|
||||
unsigned long flags;
|
||||
unsigned long addr = kallsyms_lookup_name(func);
|
||||
ssize_t ret = 0;
|
||||
|
||||
if (!addr) {
|
||||
pr_err("KCSAN: could not find function: '%s'\n", func);
|
||||
return -ENOENT;
|
||||
}
|
||||
|
||||
spin_lock_irqsave(&report_filterlist_lock, flags);
|
||||
|
||||
if (report_filterlist.addrs == NULL) {
|
||||
/* initial allocation */
|
||||
report_filterlist.addrs =
|
||||
kmalloc_array(report_filterlist.size,
|
||||
sizeof(unsigned long), GFP_KERNEL);
|
||||
if (report_filterlist.addrs == NULL) {
|
||||
ret = -ENOMEM;
|
||||
goto out;
|
||||
}
|
||||
} else if (report_filterlist.used == report_filterlist.size) {
|
||||
/* resize filterlist */
|
||||
size_t new_size = report_filterlist.size * 2;
|
||||
unsigned long *new_addrs =
|
||||
krealloc(report_filterlist.addrs,
|
||||
new_size * sizeof(unsigned long), GFP_KERNEL);
|
||||
|
||||
if (new_addrs == NULL) {
|
||||
/* leave filterlist itself untouched */
|
||||
ret = -ENOMEM;
|
||||
goto out;
|
||||
}
|
||||
|
||||
report_filterlist.size = new_size;
|
||||
report_filterlist.addrs = new_addrs;
|
||||
}
|
||||
|
||||
/* Note: deduplicating should be done in userspace. */
|
||||
report_filterlist.addrs[report_filterlist.used++] =
|
||||
kallsyms_lookup_name(func);
|
||||
report_filterlist.sorted = false;
|
||||
|
||||
out:
|
||||
spin_unlock_irqrestore(&report_filterlist_lock, flags);
|
||||
return ret;
|
||||
}
|
||||
|
||||
static int show_info(struct seq_file *file, void *v)
|
||||
{
|
||||
int i;
|
||||
unsigned long flags;
|
||||
|
||||
/* show stats */
|
||||
seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled));
|
||||
for (i = 0; i < KCSAN_COUNTER_COUNT; ++i)
|
||||
seq_printf(file, "%s: %ld\n", counter_to_name(i),
|
||||
atomic_long_read(&counters[i]));
|
||||
|
||||
/* show filter functions, and filter type */
|
||||
spin_lock_irqsave(&report_filterlist_lock, flags);
|
||||
seq_printf(file, "\n%s functions: %s\n",
|
||||
report_filterlist.whitelist ? "whitelisted" : "blacklisted",
|
||||
report_filterlist.used == 0 ? "none" : "");
|
||||
for (i = 0; i < report_filterlist.used; ++i)
|
||||
seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]);
|
||||
spin_unlock_irqrestore(&report_filterlist_lock, flags);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int debugfs_open(struct inode *inode, struct file *file)
|
||||
{
|
||||
return single_open(file, show_info, NULL);
|
||||
}
|
||||
|
||||
static ssize_t debugfs_write(struct file *file, const char __user *buf,
|
||||
size_t count, loff_t *off)
|
||||
{
|
||||
char kbuf[KSYM_NAME_LEN];
|
||||
char *arg;
|
||||
int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
|
||||
|
||||
if (copy_from_user(kbuf, buf, read_len))
|
||||
return -EFAULT;
|
||||
kbuf[read_len] = '\0';
|
||||
arg = strstrip(kbuf);
|
||||
|
||||
if (!strcmp(arg, "on")) {
|
||||
WRITE_ONCE(kcsan_enabled, true);
|
||||
} else if (!strcmp(arg, "off")) {
|
||||
WRITE_ONCE(kcsan_enabled, false);
|
||||
} else if (!strncmp(arg, "microbench=", sizeof("microbench=") - 1)) {
|
||||
unsigned long iters;
|
||||
|
||||
if (kstrtoul(&arg[sizeof("microbench=") - 1], 0, &iters))
|
||||
return -EINVAL;
|
||||
microbenchmark(iters);
|
||||
} else if (!strcmp(arg, "whitelist")) {
|
||||
set_report_filterlist_whitelist(true);
|
||||
} else if (!strcmp(arg, "blacklist")) {
|
||||
set_report_filterlist_whitelist(false);
|
||||
} else if (arg[0] == '!') {
|
||||
ssize_t ret = insert_report_filterlist(&arg[1]);
|
||||
|
||||
if (ret < 0)
|
||||
return ret;
|
||||
} else {
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
return count;
|
||||
}
|
||||
|
||||
static const struct file_operations debugfs_ops = { .read = seq_read,
|
||||
.open = debugfs_open,
|
||||
.write = debugfs_write,
|
||||
.release = single_release };
|
||||
|
||||
void __init kcsan_debugfs_init(void)
|
||||
{
|
||||
debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
|
||||
}
|
||||
94
kernel/kcsan/encoding.h
Normal file
94
kernel/kcsan/encoding.h
Normal file
@ -0,0 +1,94 @@
|
||||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
|
||||
#ifndef _KERNEL_KCSAN_ENCODING_H
|
||||
#define _KERNEL_KCSAN_ENCODING_H
|
||||
|
||||
#include <linux/bits.h>
|
||||
#include <linux/log2.h>
|
||||
#include <linux/mm.h>
|
||||
|
||||
#include "kcsan.h"
|
||||
|
||||
#define SLOT_RANGE PAGE_SIZE
|
||||
#define INVALID_WATCHPOINT 0
|
||||
#define CONSUMED_WATCHPOINT 1
|
||||
|
||||
/*
|
||||
* The maximum useful size of accesses for which we set up watchpoints is the
|
||||
* max range of slots we check on an access.
|
||||
*/
|
||||
#define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 + KCSAN_CHECK_ADJACENT))
|
||||
|
||||
/*
|
||||
* Number of bits we use to store size info.
|
||||
*/
|
||||
#define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCODABLE_SIZE)
|
||||
/*
|
||||
* This encoding for addresses discards the upper (1 for is-write + SIZE_BITS);
|
||||
* however, most 64-bit architectures do not use the full 64-bit address space.
|
||||
* Also, in order for a false positive to be observable 2 things need to happen:
|
||||
*
|
||||
* 1. different addresses but with the same encoded address race;
|
||||
* 2. and both map onto the same watchpoint slots;
|
||||
*
|
||||
* Both these are assumed to be very unlikely. However, in case it still happens
|
||||
* happens, the report logic will filter out the false positive (see report.c).
|
||||
*/
|
||||
#define WATCHPOINT_ADDR_BITS (BITS_PER_LONG - 1 - WATCHPOINT_SIZE_BITS)
|
||||
|
||||
/*
|
||||
* Masks to set/retrieve the encoded data.
|
||||
*/
|
||||
#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG - 1)
|
||||
#define WATCHPOINT_SIZE_MASK \
|
||||
GENMASK(BITS_PER_LONG - 2, BITS_PER_LONG - 2 - WATCHPOINT_SIZE_BITS)
|
||||
#define WATCHPOINT_ADDR_MASK \
|
||||
GENMASK(BITS_PER_LONG - 3 - WATCHPOINT_SIZE_BITS, 0)
|
||||
|
||||
static inline bool check_encodable(unsigned long addr, size_t size)
|
||||
{
|
||||
return size <= MAX_ENCODABLE_SIZE;
|
||||
}
|
||||
|
||||
static inline long encode_watchpoint(unsigned long addr, size_t size,
|
||||
bool is_write)
|
||||
{
|
||||
return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) |
|
||||
(size << WATCHPOINT_ADDR_BITS) |
|
||||
(addr & WATCHPOINT_ADDR_MASK));
|
||||
}
|
||||
|
||||
static inline bool decode_watchpoint(long watchpoint,
|
||||
unsigned long *addr_masked, size_t *size,
|
||||
bool *is_write)
|
||||
{
|
||||
if (watchpoint == INVALID_WATCHPOINT ||
|
||||
watchpoint == CONSUMED_WATCHPOINT)
|
||||
return false;
|
||||
|
||||
*addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK;
|
||||
*size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >>
|
||||
WATCHPOINT_ADDR_BITS;
|
||||
*is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK);
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
/*
|
||||
* Return watchpoint slot for an address.
|
||||
*/
|
||||
static inline int watchpoint_slot(unsigned long addr)
|
||||
{
|
||||
return (addr / PAGE_SIZE) % CONFIG_KCSAN_NUM_WATCHPOINTS;
|
||||
}
|
||||
|
||||
static inline bool matching_access(unsigned long addr1, size_t size1,
|
||||
unsigned long addr2, size_t size2)
|
||||
{
|
||||
unsigned long end_range1 = addr1 + size1 - 1;
|
||||
unsigned long end_range2 = addr2 + size2 - 1;
|
||||
|
||||
return addr1 <= end_range2 && addr2 <= end_range1;
|
||||
}
|
||||
|
||||
#endif /* _KERNEL_KCSAN_ENCODING_H */
|
||||
108
kernel/kcsan/kcsan.h
Normal file
108
kernel/kcsan/kcsan.h
Normal file
@ -0,0 +1,108 @@
|
||||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
|
||||
/*
|
||||
* The Kernel Concurrency Sanitizer (KCSAN) infrastructure. For more info please
|
||||
* see Documentation/dev-tools/kcsan.rst.
|
||||
*/
|
||||
|
||||
#ifndef _KERNEL_KCSAN_KCSAN_H
|
||||
#define _KERNEL_KCSAN_KCSAN_H
|
||||
|
||||
#include <linux/kcsan.h>
|
||||
|
||||
/* The number of adjacent watchpoints to check. */
|
||||
#define KCSAN_CHECK_ADJACENT 1
|
||||
|
||||
/*
|
||||
* Globally enable and disable KCSAN.
|
||||
*/
|
||||
extern bool kcsan_enabled;
|
||||
|
||||
/*
|
||||
* Initialize debugfs file.
|
||||
*/
|
||||
void kcsan_debugfs_init(void);
|
||||
|
||||
enum kcsan_counter_id {
|
||||
/*
|
||||
* Number of watchpoints currently in use.
|
||||
*/
|
||||
KCSAN_COUNTER_USED_WATCHPOINTS,
|
||||
|
||||
/*
|
||||
* Total number of watchpoints set up.
|
||||
*/
|
||||
KCSAN_COUNTER_SETUP_WATCHPOINTS,
|
||||
|
||||
/*
|
||||
* Total number of data races.
|
||||
*/
|
||||
KCSAN_COUNTER_DATA_RACES,
|
||||
|
||||
/*
|
||||
* Number of times no watchpoints were available.
|
||||
*/
|
||||
KCSAN_COUNTER_NO_CAPACITY,
|
||||
|
||||
/*
|
||||
* A thread checking a watchpoint raced with another checking thread;
|
||||
* only one will be reported.
|
||||
*/
|
||||
KCSAN_COUNTER_REPORT_RACES,
|
||||
|
||||
/*
|
||||
* Observed data value change, but writer thread unknown.
|
||||
*/
|
||||
KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN,
|
||||
|
||||
/*
|
||||
* The access cannot be encoded to a valid watchpoint.
|
||||
*/
|
||||
KCSAN_COUNTER_UNENCODABLE_ACCESSES,
|
||||
|
||||
/*
|
||||
* Watchpoint encoding caused a watchpoint to fire on mismatching
|
||||
* accesses.
|
||||
*/
|
||||
KCSAN_COUNTER_ENCODING_FALSE_POSITIVES,
|
||||
|
||||
KCSAN_COUNTER_COUNT, /* number of counters */
|
||||
};
|
||||
|
||||
/*
|
||||
* Increment/decrement counter with given id; avoid calling these in fast-path.
|
||||
*/
|
||||
void kcsan_counter_inc(enum kcsan_counter_id id);
|
||||
void kcsan_counter_dec(enum kcsan_counter_id id);
|
||||
|
||||
/*
|
||||
* Returns true if data races in the function symbol that maps to func_addr
|
||||
* (offsets are ignored) should *not* be reported.
|
||||
*/
|
||||
bool kcsan_skip_report_debugfs(unsigned long func_addr);
|
||||
|
||||
enum kcsan_report_type {
|
||||
/*
|
||||
* The thread that set up the watchpoint and briefly stalled was
|
||||
* signalled that another thread triggered the watchpoint.
|
||||
*/
|
||||
KCSAN_REPORT_RACE_SIGNAL,
|
||||
|
||||
/*
|
||||
* A thread found and consumed a matching watchpoint.
|
||||
*/
|
||||
KCSAN_REPORT_CONSUMED_WATCHPOINT,
|
||||
|
||||
/*
|
||||
* No other thread was observed to race with the access, but the data
|
||||
* value before and after the stall differs.
|
||||
*/
|
||||
KCSAN_REPORT_RACE_UNKNOWN_ORIGIN,
|
||||
};
|
||||
/*
|
||||
* Print a race report from thread that encountered the race.
|
||||
*/
|
||||
void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
|
||||
bool value_change, int cpu_id, enum kcsan_report_type type);
|
||||
|
||||
#endif /* _KERNEL_KCSAN_KCSAN_H */
|
||||
320
kernel/kcsan/report.c
Normal file
320
kernel/kcsan/report.c
Normal file
@ -0,0 +1,320 @@
|
||||
// SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/preempt.h>
|
||||
#include <linux/printk.h>
|
||||
#include <linux/sched.h>
|
||||
#include <linux/spinlock.h>
|
||||
#include <linux/stacktrace.h>
|
||||
|
||||
#include "kcsan.h"
|
||||
#include "encoding.h"
|
||||
|
||||
/*
|
||||
* Max. number of stack entries to show in the report.
|
||||
*/
|
||||
#define NUM_STACK_ENTRIES 64
|
||||
|
||||
/*
|
||||
* Other thread info: communicated from other racing thread to thread that set
|
||||
* up the watchpoint, which then prints the complete report atomically. Only
|
||||
* need one struct, as all threads should to be serialized regardless to print
|
||||
* the reports, with reporting being in the slow-path.
|
||||
*/
|
||||
static struct {
|
||||
const volatile void *ptr;
|
||||
size_t size;
|
||||
bool is_write;
|
||||
int task_pid;
|
||||
int cpu_id;
|
||||
unsigned long stack_entries[NUM_STACK_ENTRIES];
|
||||
int num_stack_entries;
|
||||
} other_info = { .ptr = NULL };
|
||||
|
||||
/*
|
||||
* This spinlock protects reporting and other_info, since other_info is usually
|
||||
* required when reporting.
|
||||
*/
|
||||
static DEFINE_SPINLOCK(report_lock);
|
||||
|
||||
/*
|
||||
* Special rules to skip reporting.
|
||||
*/
|
||||
static bool skip_report(bool is_write, bool value_change,
|
||||
unsigned long top_frame)
|
||||
{
|
||||
if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && is_write &&
|
||||
!value_change) {
|
||||
/*
|
||||
* The access is a write, but the data value did not change.
|
||||
*
|
||||
* We opt-out of this filter for certain functions at request of
|
||||
* maintainers.
|
||||
*/
|
||||
char buf[64];
|
||||
|
||||
snprintf(buf, sizeof(buf), "%ps", (void *)top_frame);
|
||||
if (!strnstr(buf, "rcu_", sizeof(buf)) &&
|
||||
!strnstr(buf, "_rcu", sizeof(buf)) &&
|
||||
!strnstr(buf, "_srcu", sizeof(buf)))
|
||||
return true;
|
||||
}
|
||||
|
||||
return kcsan_skip_report_debugfs(top_frame);
|
||||
}
|
||||
|
||||
static inline const char *get_access_type(bool is_write)
|
||||
{
|
||||
return is_write ? "write" : "read";
|
||||
}
|
||||
|
||||
/* Return thread description: in task or interrupt. */
|
||||
static const char *get_thread_desc(int task_id)
|
||||
{
|
||||
if (task_id != -1) {
|
||||
static char buf[32]; /* safe: protected by report_lock */
|
||||
|
||||
snprintf(buf, sizeof(buf), "task %i", task_id);
|
||||
return buf;
|
||||
}
|
||||
return "interrupt";
|
||||
}
|
||||
|
||||
/* Helper to skip KCSAN-related functions in stack-trace. */
|
||||
static int get_stack_skipnr(unsigned long stack_entries[], int num_entries)
|
||||
{
|
||||
char buf[64];
|
||||
int skip = 0;
|
||||
|
||||
for (; skip < num_entries; ++skip) {
|
||||
snprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]);
|
||||
if (!strnstr(buf, "csan_", sizeof(buf)) &&
|
||||
!strnstr(buf, "tsan_", sizeof(buf)) &&
|
||||
!strnstr(buf, "_once_size", sizeof(buf))) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
return skip;
|
||||
}
|
||||
|
||||
/* Compares symbolized strings of addr1 and addr2. */
|
||||
static int sym_strcmp(void *addr1, void *addr2)
|
||||
{
|
||||
char buf1[64];
|
||||
char buf2[64];
|
||||
|
||||
snprintf(buf1, sizeof(buf1), "%pS", addr1);
|
||||
snprintf(buf2, sizeof(buf2), "%pS", addr2);
|
||||
return strncmp(buf1, buf2, sizeof(buf1));
|
||||
}
|
||||
|
||||
/*
|
||||
* Returns true if a report was generated, false otherwise.
|
||||
*/
|
||||
static bool print_report(const volatile void *ptr, size_t size, bool is_write,
|
||||
bool value_change, int cpu_id,
|
||||
enum kcsan_report_type type)
|
||||
{
|
||||
unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 };
|
||||
int num_stack_entries =
|
||||
stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1);
|
||||
int skipnr = get_stack_skipnr(stack_entries, num_stack_entries);
|
||||
int other_skipnr;
|
||||
|
||||
/*
|
||||
* Must check report filter rules before starting to print.
|
||||
*/
|
||||
if (skip_report(is_write, true, stack_entries[skipnr]))
|
||||
return false;
|
||||
|
||||
if (type == KCSAN_REPORT_RACE_SIGNAL) {
|
||||
other_skipnr = get_stack_skipnr(other_info.stack_entries,
|
||||
other_info.num_stack_entries);
|
||||
|
||||
/* value_change is only known for the other thread */
|
||||
if (skip_report(other_info.is_write, value_change,
|
||||
other_info.stack_entries[other_skipnr]))
|
||||
return false;
|
||||
}
|
||||
|
||||
/* Print report header. */
|
||||
pr_err("==================================================================\n");
|
||||
switch (type) {
|
||||
case KCSAN_REPORT_RACE_SIGNAL: {
|
||||
void *this_fn = (void *)stack_entries[skipnr];
|
||||
void *other_fn = (void *)other_info.stack_entries[other_skipnr];
|
||||
int cmp;
|
||||
|
||||
/*
|
||||
* Order functions lexographically for consistent bug titles.
|
||||
* Do not print offset of functions to keep title short.
|
||||
*/
|
||||
cmp = sym_strcmp(other_fn, this_fn);
|
||||
pr_err("BUG: KCSAN: data-race in %ps / %ps\n",
|
||||
cmp < 0 ? other_fn : this_fn,
|
||||
cmp < 0 ? this_fn : other_fn);
|
||||
} break;
|
||||
|
||||
case KCSAN_REPORT_RACE_UNKNOWN_ORIGIN:
|
||||
pr_err("BUG: KCSAN: data-race in %pS\n",
|
||||
(void *)stack_entries[skipnr]);
|
||||
break;
|
||||
|
||||
default:
|
||||
BUG();
|
||||
}
|
||||
|
||||
pr_err("\n");
|
||||
|
||||
/* Print information about the racing accesses. */
|
||||
switch (type) {
|
||||
case KCSAN_REPORT_RACE_SIGNAL:
|
||||
pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n",
|
||||
get_access_type(other_info.is_write), other_info.ptr,
|
||||
other_info.size, get_thread_desc(other_info.task_pid),
|
||||
other_info.cpu_id);
|
||||
|
||||
/* Print the other thread's stack trace. */
|
||||
stack_trace_print(other_info.stack_entries + other_skipnr,
|
||||
other_info.num_stack_entries - other_skipnr,
|
||||
0);
|
||||
|
||||
pr_err("\n");
|
||||
pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n",
|
||||
get_access_type(is_write), ptr, size,
|
||||
get_thread_desc(in_task() ? task_pid_nr(current) : -1),
|
||||
cpu_id);
|
||||
break;
|
||||
|
||||
case KCSAN_REPORT_RACE_UNKNOWN_ORIGIN:
|
||||
pr_err("race at unknown origin, with %s to 0x%px of %zu bytes by %s on cpu %i:\n",
|
||||
get_access_type(is_write), ptr, size,
|
||||
get_thread_desc(in_task() ? task_pid_nr(current) : -1),
|
||||
cpu_id);
|
||||
break;
|
||||
|
||||
default:
|
||||
BUG();
|
||||
}
|
||||
/* Print stack trace of this thread. */
|
||||
stack_trace_print(stack_entries + skipnr, num_stack_entries - skipnr,
|
||||
0);
|
||||
|
||||
/* Print report footer. */
|
||||
pr_err("\n");
|
||||
pr_err("Reported by Kernel Concurrency Sanitizer on:\n");
|
||||
dump_stack_print_info(KERN_DEFAULT);
|
||||
pr_err("==================================================================\n");
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
static void release_report(unsigned long *flags, enum kcsan_report_type type)
|
||||
{
|
||||
if (type == KCSAN_REPORT_RACE_SIGNAL)
|
||||
other_info.ptr = NULL; /* mark for reuse */
|
||||
|
||||
spin_unlock_irqrestore(&report_lock, *flags);
|
||||
}
|
||||
|
||||
/*
|
||||
* Depending on the report type either sets other_info and returns false, or
|
||||
* acquires the matching other_info and returns true. If other_info is not
|
||||
* required for the report type, simply acquires report_lock and returns true.
|
||||
*/
|
||||
static bool prepare_report(unsigned long *flags, const volatile void *ptr,
|
||||
size_t size, bool is_write, int cpu_id,
|
||||
enum kcsan_report_type type)
|
||||
{
|
||||
if (type != KCSAN_REPORT_CONSUMED_WATCHPOINT &&
|
||||
type != KCSAN_REPORT_RACE_SIGNAL) {
|
||||
/* other_info not required; just acquire report_lock */
|
||||
spin_lock_irqsave(&report_lock, *flags);
|
||||
return true;
|
||||
}
|
||||
|
||||
retry:
|
||||
spin_lock_irqsave(&report_lock, *flags);
|
||||
|
||||
switch (type) {
|
||||
case KCSAN_REPORT_CONSUMED_WATCHPOINT:
|
||||
if (other_info.ptr != NULL)
|
||||
break; /* still in use, retry */
|
||||
|
||||
other_info.ptr = ptr;
|
||||
other_info.size = size;
|
||||
other_info.is_write = is_write;
|
||||
other_info.task_pid = in_task() ? task_pid_nr(current) : -1;
|
||||
other_info.cpu_id = cpu_id;
|
||||
other_info.num_stack_entries = stack_trace_save(
|
||||
other_info.stack_entries, NUM_STACK_ENTRIES, 1);
|
||||
|
||||
spin_unlock_irqrestore(&report_lock, *flags);
|
||||
|
||||
/*
|
||||
* The other thread will print the summary; other_info may now
|
||||
* be consumed.
|
||||
*/
|
||||
return false;
|
||||
|
||||
case KCSAN_REPORT_RACE_SIGNAL:
|
||||
if (other_info.ptr == NULL)
|
||||
break; /* no data available yet, retry */
|
||||
|
||||
/*
|
||||
* First check if this is the other_info we are expecting, i.e.
|
||||
* matches based on how watchpoint was encoded.
|
||||
*/
|
||||
if (!matching_access((unsigned long)other_info.ptr &
|
||||
WATCHPOINT_ADDR_MASK,
|
||||
other_info.size,
|
||||
(unsigned long)ptr & WATCHPOINT_ADDR_MASK,
|
||||
size))
|
||||
break; /* mismatching watchpoint, retry */
|
||||
|
||||
if (!matching_access((unsigned long)other_info.ptr,
|
||||
other_info.size, (unsigned long)ptr,
|
||||
size)) {
|
||||
/*
|
||||
* If the actual accesses to not match, this was a false
|
||||
* positive due to watchpoint encoding.
|
||||
*/
|
||||
kcsan_counter_inc(
|
||||
KCSAN_COUNTER_ENCODING_FALSE_POSITIVES);
|
||||
|
||||
/* discard this other_info */
|
||||
release_report(flags, KCSAN_REPORT_RACE_SIGNAL);
|
||||
return false;
|
||||
}
|
||||
|
||||
/*
|
||||
* Matching & usable access in other_info: keep other_info_lock
|
||||
* locked, as this thread consumes it to print the full report;
|
||||
* unlocked in release_report.
|
||||
*/
|
||||
return true;
|
||||
|
||||
default:
|
||||
BUG();
|
||||
}
|
||||
|
||||
spin_unlock_irqrestore(&report_lock, *flags);
|
||||
goto retry;
|
||||
}
|
||||
|
||||
void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
|
||||
bool value_change, int cpu_id, enum kcsan_report_type type)
|
||||
{
|
||||
unsigned long flags = 0;
|
||||
|
||||
kcsan_disable_current();
|
||||
if (prepare_report(&flags, ptr, size, is_write, cpu_id, type)) {
|
||||
if (print_report(ptr, size, is_write, value_change, cpu_id,
|
||||
type) &&
|
||||
panic_on_warn)
|
||||
panic("panic_on_warn set ...\n");
|
||||
|
||||
release_report(&flags, type);
|
||||
}
|
||||
kcsan_enable_current();
|
||||
}
|
||||
121
kernel/kcsan/test.c
Normal file
121
kernel/kcsan/test.c
Normal file
@ -0,0 +1,121 @@
|
||||
// SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
#include <linux/init.h>
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/printk.h>
|
||||
#include <linux/random.h>
|
||||
#include <linux/types.h>
|
||||
|
||||
#include "encoding.h"
|
||||
|
||||
#define ITERS_PER_TEST 2000
|
||||
|
||||
/* Test requirements. */
|
||||
static bool test_requires(void)
|
||||
{
|
||||
/* random should be initialized for the below tests */
|
||||
return prandom_u32() + prandom_u32() != 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Test watchpoint encode and decode: check that encoding some access's info,
|
||||
* and then subsequent decode preserves the access's info.
|
||||
*/
|
||||
static bool test_encode_decode(void)
|
||||
{
|
||||
int i;
|
||||
|
||||
for (i = 0; i < ITERS_PER_TEST; ++i) {
|
||||
size_t size = prandom_u32_max(MAX_ENCODABLE_SIZE) + 1;
|
||||
bool is_write = !!prandom_u32_max(2);
|
||||
unsigned long addr;
|
||||
|
||||
prandom_bytes(&addr, sizeof(addr));
|
||||
if (WARN_ON(!check_encodable(addr, size)))
|
||||
return false;
|
||||
|
||||
/* encode and decode */
|
||||
{
|
||||
const long encoded_watchpoint =
|
||||
encode_watchpoint(addr, size, is_write);
|
||||
unsigned long verif_masked_addr;
|
||||
size_t verif_size;
|
||||
bool verif_is_write;
|
||||
|
||||
/* check special watchpoints */
|
||||
if (WARN_ON(decode_watchpoint(
|
||||
INVALID_WATCHPOINT, &verif_masked_addr,
|
||||
&verif_size, &verif_is_write)))
|
||||
return false;
|
||||
if (WARN_ON(decode_watchpoint(
|
||||
CONSUMED_WATCHPOINT, &verif_masked_addr,
|
||||
&verif_size, &verif_is_write)))
|
||||
return false;
|
||||
|
||||
/* check decoding watchpoint returns same data */
|
||||
if (WARN_ON(!decode_watchpoint(
|
||||
encoded_watchpoint, &verif_masked_addr,
|
||||
&verif_size, &verif_is_write)))
|
||||
return false;
|
||||
if (WARN_ON(verif_masked_addr !=
|
||||
(addr & WATCHPOINT_ADDR_MASK)))
|
||||
goto fail;
|
||||
if (WARN_ON(verif_size != size))
|
||||
goto fail;
|
||||
if (WARN_ON(is_write != verif_is_write))
|
||||
goto fail;
|
||||
|
||||
continue;
|
||||
fail:
|
||||
pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n",
|
||||
__func__, is_write ? "write" : "read", size,
|
||||
addr, encoded_watchpoint,
|
||||
verif_is_write ? "write" : "read", verif_size,
|
||||
verif_masked_addr);
|
||||
return false;
|
||||
}
|
||||
}
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
/* Test access matching function. */
|
||||
static bool test_matching_access(void)
|
||||
{
|
||||
if (WARN_ON(!matching_access(10, 1, 10, 1)))
|
||||
return false;
|
||||
if (WARN_ON(!matching_access(10, 2, 11, 1)))
|
||||
return false;
|
||||
if (WARN_ON(!matching_access(10, 1, 9, 2)))
|
||||
return false;
|
||||
if (WARN_ON(matching_access(10, 1, 11, 1)))
|
||||
return false;
|
||||
if (WARN_ON(matching_access(9, 1, 10, 1)))
|
||||
return false;
|
||||
return true;
|
||||
}
|
||||
|
||||
static int __init kcsan_selftest(void)
|
||||
{
|
||||
int passed = 0;
|
||||
int total = 0;
|
||||
|
||||
#define RUN_TEST(do_test) \
|
||||
do { \
|
||||
++total; \
|
||||
if (do_test()) \
|
||||
++passed; \
|
||||
else \
|
||||
pr_err("KCSAN selftest: " #do_test " failed"); \
|
||||
} while (0)
|
||||
|
||||
RUN_TEST(test_requires);
|
||||
RUN_TEST(test_encode_decode);
|
||||
RUN_TEST(test_matching_access);
|
||||
|
||||
pr_info("KCSAN selftest: %d/%d tests passed\n", passed, total);
|
||||
if (passed != total)
|
||||
panic("KCSAN selftests failed");
|
||||
return 0;
|
||||
}
|
||||
postcore_initcall(kcsan_selftest);
|
||||
@ -7,6 +7,12 @@ endif
|
||||
# that is not a function of syscall inputs. E.g. involuntary context switches.
|
||||
KCOV_INSTRUMENT := n
|
||||
|
||||
# There are numerous races here, however, most of them due to plain accesses.
|
||||
# This would make it even harder for syzbot to find reproducers, because these
|
||||
# bugs trigger without specific input. Disable by default, but should re-enable
|
||||
# eventually.
|
||||
KCSAN_SANITIZE := n
|
||||
|
||||
ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
|
||||
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
|
||||
# needed for x86 only. Why this used to be enabled for all architectures is beyond
|
||||
|
||||
@ -2086,6 +2086,8 @@ source "lib/Kconfig.kgdb"
|
||||
|
||||
source "lib/Kconfig.ubsan"
|
||||
|
||||
source "lib/Kconfig.kcsan"
|
||||
|
||||
config ARCH_HAS_DEVMEM_IS_ALLOWED
|
||||
bool
|
||||
|
||||
|
||||
118
lib/Kconfig.kcsan
Normal file
118
lib/Kconfig.kcsan
Normal file
@ -0,0 +1,118 @@
|
||||
# SPDX-License-Identifier: GPL-2.0-only
|
||||
|
||||
config HAVE_ARCH_KCSAN
|
||||
bool
|
||||
|
||||
menuconfig KCSAN
|
||||
bool "KCSAN: watchpoint-based dynamic data race detector"
|
||||
depends on HAVE_ARCH_KCSAN && !KASAN && STACKTRACE
|
||||
default n
|
||||
help
|
||||
Kernel Concurrency Sanitizer is a dynamic data race detector, which
|
||||
uses a watchpoint-based sampling approach to detect races. See
|
||||
<file:Documentation/dev-tools/kcsan.rst> for more details.
|
||||
|
||||
if KCSAN
|
||||
|
||||
config KCSAN_DEBUG
|
||||
bool "Debugging of KCSAN internals"
|
||||
default n
|
||||
|
||||
config KCSAN_SELFTEST
|
||||
bool "Perform short selftests on boot"
|
||||
default y
|
||||
help
|
||||
Run KCSAN selftests on boot. On test failure, causes kernel to panic.
|
||||
|
||||
config KCSAN_EARLY_ENABLE
|
||||
bool "Early enable during boot"
|
||||
default y
|
||||
help
|
||||
If KCSAN should be enabled globally as soon as possible. KCSAN can
|
||||
later be enabled/disabled via debugfs.
|
||||
|
||||
config KCSAN_NUM_WATCHPOINTS
|
||||
int "Number of available watchpoints"
|
||||
default 64
|
||||
help
|
||||
Total number of available watchpoints. An address range maps into a
|
||||
specific watchpoint slot as specified in kernel/kcsan/encoding.h.
|
||||
Although larger number of watchpoints may not be usable due to
|
||||
limited number of CPUs, a larger value helps to improve performance
|
||||
due to reducing cache-line contention. The chosen default is a
|
||||
conservative value; we should almost never observe "no_capacity"
|
||||
events (see /sys/kernel/debug/kcsan).
|
||||
|
||||
config KCSAN_UDELAY_TASK
|
||||
int "Delay in microseconds (for tasks)"
|
||||
default 80
|
||||
help
|
||||
For tasks, the microsecond delay after setting up a watchpoint.
|
||||
|
||||
config KCSAN_UDELAY_INTERRUPT
|
||||
int "Delay in microseconds (for interrupts)"
|
||||
default 20
|
||||
help
|
||||
For interrupts, the microsecond delay after setting up a watchpoint.
|
||||
Interrupts have tighter latency requirements, and their delay should
|
||||
be lower than for tasks.
|
||||
|
||||
config KCSAN_DELAY_RANDOMIZE
|
||||
bool "Randomize above delays"
|
||||
default y
|
||||
help
|
||||
If delays should be randomized, where the maximum is KCSAN_UDELAY_*.
|
||||
If false, the chosen delays are always KCSAN_UDELAY_* defined above.
|
||||
|
||||
config KCSAN_SKIP_WATCH
|
||||
int "Skip instructions before setting up watchpoint"
|
||||
default 4000
|
||||
help
|
||||
The number of per-CPU memory operations to skip, before another
|
||||
watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU
|
||||
memory operations are used to set up a watchpoint. A smaller value
|
||||
results in more aggressive race detection, whereas a larger value
|
||||
improves system performance at the cost of missing some races.
|
||||
|
||||
config KCSAN_SKIP_WATCH_RANDOMIZE
|
||||
bool "Randomize watchpoint instruction skip count"
|
||||
default y
|
||||
help
|
||||
If instruction skip count should be randomized, where the maximum is
|
||||
KCSAN_WATCH_SKIP. If false, the chosen value is always
|
||||
KCSAN_WATCH_SKIP.
|
||||
|
||||
# Note that, while some of the below options could be turned into boot
|
||||
# parameters, to optimize for the common use-case, we avoid this because: (a)
|
||||
# it would impact performance (and we want to avoid static branch for all
|
||||
# {READ,WRITE}_ONCE, atomic_*, bitops, etc.), and (b) complicate the design
|
||||
# without real benefit. The main purpose of the below options are for use in
|
||||
# fuzzer configs to control reported data races, and are not expected to be
|
||||
# switched frequently by a user.
|
||||
|
||||
config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
|
||||
bool "Report races of unknown origin"
|
||||
default y
|
||||
help
|
||||
If KCSAN should report races where only one access is known, and the
|
||||
conflicting access is of unknown origin. This type of race is
|
||||
reported if it was only possible to infer a race due to a data value
|
||||
change while an access is being delayed on a watchpoint.
|
||||
|
||||
config KCSAN_REPORT_VALUE_CHANGE_ONLY
|
||||
bool "Only report races where watcher observed a data value change"
|
||||
default y
|
||||
help
|
||||
If enabled and a conflicting write is observed via watchpoint, but
|
||||
the data value of the memory location was observed to remain
|
||||
unchanged, do not report the data race.
|
||||
|
||||
config KCSAN_IGNORE_ATOMICS
|
||||
bool "Do not instrument marked atomic accesses"
|
||||
default n
|
||||
help
|
||||
If enabled, never instruments marked atomic accesses. This results in
|
||||
not reporting data races where one access is atomic and the other is
|
||||
a plain access.
|
||||
|
||||
endif # KCSAN
|
||||
@ -24,6 +24,9 @@ KASAN_SANITIZE_string.o := n
|
||||
CFLAGS_string.o := $(call cc-option, -fno-stack-protector)
|
||||
endif
|
||||
|
||||
# Used by KCSAN while enabled, avoid recursion.
|
||||
KCSAN_SANITIZE_random32.o := n
|
||||
|
||||
lib-y := ctype.o string.o vsprintf.o cmdline.o \
|
||||
rbtree.o radix-tree.o timerqueue.o xarray.o \
|
||||
idr.o extable.o \
|
||||
|
||||
@ -7,6 +7,14 @@ KASAN_SANITIZE_slab_common.o := n
|
||||
KASAN_SANITIZE_slab.o := n
|
||||
KASAN_SANITIZE_slub.o := n
|
||||
|
||||
# These produce frequent data race reports: most of them are due to races on
|
||||
# the same word but accesses to different bits of that word. Re-enable KCSAN
|
||||
# for these when we have more consensus on what to do about them.
|
||||
KCSAN_SANITIZE_slab_common.o := n
|
||||
KCSAN_SANITIZE_slab.o := n
|
||||
KCSAN_SANITIZE_slub.o := n
|
||||
KCSAN_SANITIZE_page_alloc.o := n
|
||||
|
||||
# These files are disabled because they produce non-interesting and/or
|
||||
# flaky coverage that is not a function of syscall inputs. E.g. slab is out of
|
||||
# free pages, or a task is migrated between nodes.
|
||||
|
||||
6
scripts/Makefile.kcsan
Normal file
6
scripts/Makefile.kcsan
Normal file
@ -0,0 +1,6 @@
|
||||
# SPDX-License-Identifier: GPL-2.0
|
||||
ifdef CONFIG_KCSAN
|
||||
|
||||
CFLAGS_KCSAN := -fsanitize=thread
|
||||
|
||||
endif # CONFIG_KCSAN
|
||||
@ -152,6 +152,16 @@ _c_flags += $(if $(patsubst n%,, \
|
||||
$(CFLAGS_KCOV))
|
||||
endif
|
||||
|
||||
#
|
||||
# Enable KCSAN flags except some files or directories we don't want to check
|
||||
# (depends on variables KCSAN_SANITIZE_obj.o, KCSAN_SANITIZE)
|
||||
#
|
||||
ifeq ($(CONFIG_KCSAN),y)
|
||||
_c_flags += $(if $(patsubst n%,, \
|
||||
$(KCSAN_SANITIZE_$(basetarget).o)$(KCSAN_SANITIZE)y), \
|
||||
$(CFLAGS_KCSAN))
|
||||
endif
|
||||
|
||||
# $(srctree)/$(src) for including checkin headers from generated source files
|
||||
# $(objtree)/$(obj) for including generated headers from checkin source files
|
||||
ifeq ($(KBUILD_EXTMOD),)
|
||||
|
||||
@ -20,7 +20,7 @@ gen_param_check()
|
||||
# We don't write to constant parameters
|
||||
[ ${type#c} != ${type} ] && rw="read"
|
||||
|
||||
printf "\tkasan_check_${rw}(${name}, sizeof(*${name}));\n"
|
||||
printf "\t__atomic_check_${rw}(${name}, sizeof(*${name}));\n"
|
||||
}
|
||||
|
||||
#gen_param_check(arg...)
|
||||
@ -107,7 +107,7 @@ cat <<EOF
|
||||
#define ${xchg}(ptr, ...) \\
|
||||
({ \\
|
||||
typeof(ptr) __ai_ptr = (ptr); \\
|
||||
kasan_check_write(__ai_ptr, ${mult}sizeof(*__ai_ptr)); \\
|
||||
__atomic_check_write(__ai_ptr, ${mult}sizeof(*__ai_ptr)); \\
|
||||
arch_${xchg}(__ai_ptr, __VA_ARGS__); \\
|
||||
})
|
||||
EOF
|
||||
@ -148,6 +148,19 @@ cat << EOF
|
||||
|
||||
#include <linux/build_bug.h>
|
||||
#include <linux/kasan-checks.h>
|
||||
#include <linux/kcsan-checks.h>
|
||||
|
||||
static inline void __atomic_check_read(const volatile void *v, size_t size)
|
||||
{
|
||||
kasan_check_read(v, size);
|
||||
kcsan_check_atomic_read(v, size);
|
||||
}
|
||||
|
||||
static inline void __atomic_check_write(const volatile void *v, size_t size)
|
||||
{
|
||||
kasan_check_write(v, size);
|
||||
kcsan_check_atomic_write(v, size);
|
||||
}
|
||||
|
||||
EOF
|
||||
|
||||
|
||||
@ -466,6 +466,24 @@ static const char *uaccess_safe_builtin[] = {
|
||||
"__asan_report_store4_noabort",
|
||||
"__asan_report_store8_noabort",
|
||||
"__asan_report_store16_noabort",
|
||||
/* KCSAN */
|
||||
"kcsan_found_watchpoint",
|
||||
"kcsan_setup_watchpoint",
|
||||
/* KCSAN/TSAN */
|
||||
"__tsan_func_entry",
|
||||
"__tsan_func_exit",
|
||||
"__tsan_read_range",
|
||||
"__tsan_write_range",
|
||||
"__tsan_read1",
|
||||
"__tsan_read2",
|
||||
"__tsan_read4",
|
||||
"__tsan_read8",
|
||||
"__tsan_read16",
|
||||
"__tsan_write1",
|
||||
"__tsan_write2",
|
||||
"__tsan_write4",
|
||||
"__tsan_write8",
|
||||
"__tsan_write16",
|
||||
/* KCOV */
|
||||
"write_comp_data",
|
||||
"__sanitizer_cov_trace_pc",
|
||||
|
||||
Loading…
Reference in New Issue
Block a user