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kasan: move boot parameters section in documentation

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Move the "Boot parameters" section in KASAN documentation next to the
section that describes KASAN build options.

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Link: https://lkml.kernel.org/r/870628e1293b4f44edf7cbcb92374ff9eb7503d7.1652203271.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/ec9c923f35e7c5312836c4624a7f317dc1ee2c1c.1652123204.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2022-05-12 20:23:09 -07:00 committed by Andrew Morton
parent c2ec0c8f68
commit ca89f2a2e6
1 changed files with 41 additions and 41 deletions
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82
Documentation/dev-tools/kasan.rst
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@ -94,6 +94,47 @@ To include alloc and free stack traces of affected slab objects into reports,
enable ``CONFIG_STACKTRACE``. To include alloc and free stack traces of affected
physical pages, enable ``CONFIG_PAGE_OWNER`` and boot with ``page_owner=on``.
Boot parameters
~~~~~~~~~~~~~~~
KASAN is affected by the generic ``panic_on_warn`` command line parameter.
When it is enabled, KASAN panics the kernel after printing a bug report.
By default, KASAN prints a bug report only for the first invalid memory access.
With ``kasan_multi_shot``, KASAN prints a report on every invalid access. This
effectively disables ``panic_on_warn`` for KASAN reports.
Alternatively, independent of ``panic_on_warn``, the ``kasan.fault=`` boot
parameter can be used to control panic and reporting behaviour:
- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
report or also panic the kernel (default: ``report``). The panic happens even
if ``kasan_multi_shot`` is enabled.
Hardware Tag-Based KASAN mode (see the section about various modes below) is
intended for use in production as a security mitigation. Therefore, it supports
additional boot parameters that allow disabling KASAN or controlling features:
- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
- ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
is configured in synchronous, asynchronous or asymmetric mode of
execution (default: ``sync``).
Synchronous mode: a bad access is detected immediately when a tag
check fault occurs.
Asynchronous mode: a bad access detection is delayed. When a tag check
fault occurs, the information is stored in hardware (in the TFSR_EL1
register for arm64). The kernel periodically checks the hardware and
only reports tag faults during these checks.
Asymmetric mode: a bad access is detected synchronously on reads and
asynchronously on writes.
- ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc
allocations (default: ``on``).
- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
traces collection (default: ``on``).
Error reports
~~~~~~~~~~~~~
@ -208,47 +249,6 @@ traces point to places in code that interacted with the object but that are not
directly present in the bad access stack trace. Currently, this includes
call_rcu() and workqueue queuing.
Boot parameters
~~~~~~~~~~~~~~~
KASAN is affected by the generic ``panic_on_warn`` command line parameter.
When it is enabled, KASAN panics the kernel after printing a bug report.
By default, KASAN prints a bug report only for the first invalid memory access.
With ``kasan_multi_shot``, KASAN prints a report on every invalid access. This
effectively disables ``panic_on_warn`` for KASAN reports.
Alternatively, independent of ``panic_on_warn``, the ``kasan.fault=`` boot
parameter can be used to control panic and reporting behaviour:
- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN
report or also panic the kernel (default: ``report``). The panic happens even
if ``kasan_multi_shot`` is enabled.
Hardware Tag-Based KASAN mode (see the section about various modes below) is
intended for use in production as a security mitigation. Therefore, it supports
additional boot parameters that allow disabling KASAN or controlling features:
- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
- ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
is configured in synchronous, asynchronous or asymmetric mode of
execution (default: ``sync``).
Synchronous mode: a bad access is detected immediately when a tag
check fault occurs.
Asynchronous mode: a bad access detection is delayed. When a tag check
fault occurs, the information is stored in hardware (in the TFSR_EL1
register for arm64). The kernel periodically checks the hardware and
only reports tag faults during these checks.
Asymmetric mode: a bad access is detected synchronously on reads and
asynchronously on writes.
- ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc
allocations (default: ``on``).
- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
traces collection (default: ``on``).
Implementation details
----------------------