Commit Graph

309 Commits

Author SHA1 Message Date
Miguel Ojeda
df01b7cfce kbuild: rust: avoid creating temporary files
`rustc` outputs by default the temporary files (i.e. the ones saved
by `-Csave-temps`, such as `*.rcgu*` files) in the current working
directory when `-o` and `--out-dir` are not given (even if
`--emit=x=path` is given, i.e. it does not use those for temporaries).

Since out-of-tree modules are compiled from the `linux` tree,
`rustc` then tries to create them there, which may not be accessible.

Thus pass `--out-dir` explicitly, even if it is just for the temporary
files.

Similarly, do so for Rust host programs too.

Reported-by: Raphael Nestler <raphael.nestler@gmail.com>
Closes: https://github.com/Rust-for-Linux/linux/issues/1015
Reported-by: Andrea Righi <andrea.righi@canonical.com>
Tested-by: Raphael Nestler <raphael.nestler@gmail.com> # non-hostprogs
Tested-by: Andrea Righi <andrea.righi@canonical.com> # non-hostprogs
Fixes: 295d8398c6 ("kbuild: specify output names separately for each emission type from rustc")
Cc: stable@vger.kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-07-24 03:15:31 +09:00
Linus Torvalds
ad2885979e Kbuild updates for v6.5
- Remove the deprecated rule to build *.dtbo from *.dts
 
  - Refactor section mismatch detection in modpost
 
  - Fix bogus ARM section mismatch detections
 
  - Fix error of 'make gtags' with O= option
 
  - Add Clang's target triple to KBUILD_CPPFLAGS to fix a build error with
    the latest LLVM version
 
  - Rebuild the built-in initrd when KBUILD_BUILD_TIMESTAMP is changed
 
  - Ignore more compiler-generated symbols for kallsyms
 
  - Fix 'make local*config' to handle the ${CONFIG_FOO} form in Makefiles
 
  - Enable more kernel-doc warnings with W=2
 
  - Refactor <linux/export.h> by generating KSYMTAB data by modpost
 
  - Deprecate <asm/export.h> and <asm-generic/export.h>
 
  - Remove the EXPORT_DATA_SYMBOL macro
 
  - Move the check for static EXPORT_SYMBOL back to modpost, which makes
    the build faster
 
  - Re-implement CONFIG_TRIM_UNUSED_KSYMS with one-pass algorithm
 
  - Warn missing MODULE_DESCRIPTION when building modules with W=1
 
  - Make 'make clean' robust against too long argument error
 
  - Exclude more objects from GCOV to fix CFI failures with GCOV
 
  - Allow 'make modules_install' to install modules.builtin and
    modules.builtin.modinfo even when CONFIG_MODULES is disabled
 
  - Include modules.builtin and modules.builtin.modinfo in the linux-image
    Debian package even when CONFIG_MODULES is disabled
 
  - Revive "Entering directory" logging for the latest Make version
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Merge tag 'kbuild-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Remove the deprecated rule to build *.dtbo from *.dts

 - Refactor section mismatch detection in modpost

 - Fix bogus ARM section mismatch detections

 - Fix error of 'make gtags' with O= option

 - Add Clang's target triple to KBUILD_CPPFLAGS to fix a build error
   with the latest LLVM version

 - Rebuild the built-in initrd when KBUILD_BUILD_TIMESTAMP is changed

 - Ignore more compiler-generated symbols for kallsyms

 - Fix 'make local*config' to handle the ${CONFIG_FOO} form in Makefiles

 - Enable more kernel-doc warnings with W=2

 - Refactor <linux/export.h> by generating KSYMTAB data by modpost

 - Deprecate <asm/export.h> and <asm-generic/export.h>

 - Remove the EXPORT_DATA_SYMBOL macro

 - Move the check for static EXPORT_SYMBOL back to modpost, which makes
   the build faster

 - Re-implement CONFIG_TRIM_UNUSED_KSYMS with one-pass algorithm

 - Warn missing MODULE_DESCRIPTION when building modules with W=1

 - Make 'make clean' robust against too long argument error

 - Exclude more objects from GCOV to fix CFI failures with GCOV

 - Allow 'make modules_install' to install modules.builtin and
   modules.builtin.modinfo even when CONFIG_MODULES is disabled

 - Include modules.builtin and modules.builtin.modinfo in the
   linux-image Debian package even when CONFIG_MODULES is disabled

 - Revive "Entering directory" logging for the latest Make version

* tag 'kbuild-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (72 commits)
  modpost: define more R_ARM_* for old distributions
  kbuild: revive "Entering directory" for Make >= 4.4.1
  kbuild: set correct abs_srctree and abs_objtree for package builds
  scripts/mksysmap: Ignore prefixed KCFI symbols
  kbuild: deb-pkg: remove the CONFIG_MODULES check in buildeb
  kbuild: builddeb: always make modules_install, to install modules.builtin*
  modpost: continue even with unknown relocation type
  modpost: factor out Elf_Sym pointer calculation to section_rel()
  modpost: factor out inst location calculation to section_rel()
  kbuild: Disable GCOV for *.mod.o
  kbuild: Fix CFI failures with GCOV
  kbuild: make clean rule robust against too long argument error
  script: modpost: emit a warning when the description is missing
  kbuild: make modules_install copy modules.builtin(.modinfo)
  linux/export.h: rename 'sec' argument to 'license'
  modpost: show offset from symbol for section mismatch warnings
  modpost: merge two similar section mismatch warnings
  kbuild: implement CONFIG_TRIM_UNUSED_KSYMS without recursion
  modpost: use null string instead of NULL pointer for default namespace
  modpost: squash sym_update_namespace() into sym_add_exported()
  ...
2023-07-01 09:24:31 -07:00
Masahiro Yamada
5e9e95cc91 kbuild: implement CONFIG_TRIM_UNUSED_KSYMS without recursion
When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses
the directory tree to determine which EXPORT_SYMBOL to trim. If an
EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the
second traverse, where some source files are recompiled with their
EXPORT_SYMBOL() tuned into a no-op.

Linus stated negative opinions about this slowness in commits:

 - 5cf0fd591f ("Kbuild: disable TRIM_UNUSED_KSYMS option")
 - a555bdd0c5 ("Kbuild: enable TRIM_UNUSED_KSYMS again, with some guarding")

We can do this better now. The final data structures of EXPORT_SYMBOL
are generated by the modpost stage, so modpost can selectively emit
KSYMTAB entries that are really used by modules.

Commit f73edc8951 ("kbuild: unify two modpost invocations") is another
ground-work to do this in a one-pass algorithm. With the list of modules,
modpost sets sym->used if it is used by a module. modpost emits KSYMTAB
only for symbols with sym->used==true.

BTW, Nicolas explained why the trimming was implemented with recursion:

  https://lore.kernel.org/all/2o2rpn97-79nq-p7s2-nq5-8p83391473r@syhkavp.arg/

Actually, we never achieved that level of optimization where the chain
reaction of trimming comes into play because:

 - CONFIG_LTO_CLANG cannot remove any unused symbols
 - CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled only for vmlinux,
   but not modules

If deeper trimming is required, we need to revisit this, but I guess
that is unlikely to happen.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-06-22 21:21:06 +09:00
Masahiro Yamada
6d62b1c46b modpost: check static EXPORT_SYMBOL* by modpost again
Commit 31cb50b559 ("kbuild: check static EXPORT_SYMBOL* by script
instead of modpost") moved the static EXPORT_SYMBOL* check from the
mostpost to a shell script because I thought it must be checked per
compilation unit to avoid false negatives.

I came up with an idea to do this in modpost, against combined ELF
files. The relocation entries in ELF will find the correct exported
symbol even if there exist symbols with the same name in different
compilation units.

Again, the same sample code.

  Makefile:

    obj-y += foo1.o foo2.o

  foo1.c:

    #include <linux/export.h>
    static void foo(void) {}
    EXPORT_SYMBOL(foo);

  foo2.c:

    void foo(void) {}

Then, modpost can catch it correctly.

    MODPOST Module.symvers
  ERROR: modpost: vmlinux: local symbol 'foo' was exported

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2023-06-22 21:21:06 +09:00
Masahiro Yamada
ddb5cdbafa kbuild: generate KSYMTAB entries by modpost
Commit 7b4537199a ("kbuild: link symbol CRCs at final link, removing
CONFIG_MODULE_REL_CRCS") made modpost output CRCs in the same way
whether the EXPORT_SYMBOL() is placed in *.c or *.S.

For further cleanups, this commit applies a similar approach to the
entire data structure of EXPORT_SYMBOL().

The EXPORT_SYMBOL() compilation is split into two stages.

When a source file is compiled, EXPORT_SYMBOL() will be converted into
a dummy symbol in the .export_symbol section.

For example,

    EXPORT_SYMBOL(foo);
    EXPORT_SYMBOL_NS_GPL(bar, BAR_NAMESPACE);

will be encoded into the following assembly code:

    .section ".export_symbol","a"
    __export_symbol_foo:
            .asciz ""                      /* license */
            .asciz ""                      /* name space */
            .balign 8
            .quad foo                      /* symbol reference */
    .previous

    .section ".export_symbol","a"
    __export_symbol_bar:
            .asciz "GPL"                   /* license */
            .asciz "BAR_NAMESPACE"         /* name space */
            .balign 8
            .quad bar                      /* symbol reference */
    .previous

They are mere markers to tell modpost the name, license, and namespace
of the symbols. They will be dropped from the final vmlinux and modules
because the *(.export_symbol) will go into /DISCARD/ in the linker script.

Then, modpost extracts all the information about EXPORT_SYMBOL() from the
.export_symbol section, and generates the final C code:

    KSYMTAB_FUNC(foo, "", "");
    KSYMTAB_FUNC(bar, "_gpl", "BAR_NAMESPACE");

KSYMTAB_FUNC() (or KSYMTAB_DATA() if it is data) is expanded to struct
kernel_symbol that will be linked to the vmlinux or a module.

With this change, EXPORT_SYMBOL() works in the same way for *.c and *.S
files, providing the following benefits.

[1] Deprecate EXPORT_DATA_SYMBOL()

In the old days, EXPORT_SYMBOL() was only available in C files. To export
a symbol in *.S, EXPORT_SYMBOL() was placed in a separate *.c file.
arch/arm/kernel/armksyms.c is one example written in the classic manner.

Commit 22823ab419 ("EXPORT_SYMBOL() for asm") removed this limitation.
Since then, EXPORT_SYMBOL() can be placed close to the symbol definition
in *.S files. It was a nice improvement.

However, as that commit mentioned, you need to use EXPORT_DATA_SYMBOL()
for data objects on some architectures.

In the new approach, modpost checks symbol's type (STT_FUNC or not),
and outputs KSYMTAB_FUNC() or KSYMTAB_DATA() accordingly.

There are only two users of EXPORT_DATA_SYMBOL:

  EXPORT_DATA_SYMBOL_GPL(empty_zero_page)    (arch/ia64/kernel/head.S)
  EXPORT_DATA_SYMBOL(ia64_ivt)               (arch/ia64/kernel/ivt.S)

They are transformed as follows and output into .vmlinux.export.c

  KSYMTAB_DATA(empty_zero_page, "_gpl", "");
  KSYMTAB_DATA(ia64_ivt, "", "");

The other EXPORT_SYMBOL users in ia64 assembly are output as
KSYMTAB_FUNC().

EXPORT_DATA_SYMBOL() is now deprecated.

[2] merge <linux/export.h> and <asm-generic/export.h>

There are two similar header implementations:

  include/linux/export.h        for .c files
  include/asm-generic/export.h  for .S files

Ideally, the functionality should be consistent between them, but they
tend to diverge.

Commit 8651ec01da ("module: add support for symbol namespaces.") did
not support the namespace for *.S files.

This commit shifts the essential implementation part to C, which supports
EXPORT_SYMBOL_NS() for *.S files.

<asm/export.h> and <asm-generic/export.h> will remain as a wrapper of
<linux/export.h> for a while.

They will be removed after #include <asm/export.h> directives are all
replaced with #include <linux/export.h>.

[3] Implement CONFIG_TRIM_UNUSED_KSYMS in one-pass algorithm (by a later commit)

When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses
the directory tree to determine which EXPORT_SYMBOL to trim. If an
EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the
second traverse, where some source files are recompiled with their
EXPORT_SYMBOL() tuned into a no-op.

We can do this better now; modpost can selectively emit KSYMTAB entries
that are really used by modules.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2023-06-22 21:17:10 +09:00
Johannes Berg
dd203fefd9 kbuild: enable kernel-doc -Wall for W=2
For W=2, we can enable more kernel-doc warnings,
such as missing return value descriptions etc.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-06-10 16:39:27 +09:00
Johannes Berg
56b0f453db kernel-doc: don't let V=1 change outcome
The kernel-doc script currently reports a number of issues
only in "verbose" mode, but that's initialized from V=1
(via KBUILD_VERBOSE), so if you use KDOC_WERROR=1 then
adding V=1 might actually break the build. This is rather
unexpected.

Change kernel-doc to not change its behaviour wrt. errors
(or warnings) when verbose mode is enabled, but rather add
separate warning flags (and -Wall) for it. Allow enabling
those flags via environment/make variables in the kernel's
build system for easier user use, but to not have to parse
them in the script itself.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2023-06-10 16:39:02 +09:00
Miguel Ojeda
3ed03f4da0 rust: upgrade to Rust 1.68.2
This is the first upgrade to the Rust toolchain since the initial Rust
merge, from 1.62.0 to 1.68.2 (i.e. the latest).

# Context

The kernel currently supports only a single Rust version [1] (rather
than a minimum) given our usage of some "unstable" Rust features [2]
which do not promise backwards compatibility.

The goal is to reach a point where we can declare a minimum version for
the toolchain. For instance, by waiting for some of the features to be
stabilized. Therefore, the first minimum Rust version that the kernel
will support is "in the future".

# Upgrade policy

Given we will eventually need to reach that minimum version, it would be
ideal to upgrade the compiler from time to time to be as close as
possible to that goal and find any issues sooner. In the extreme, we
could upgrade as soon as a new Rust release is out. Of course, upgrading
so often is in stark contrast to what one normally would need for GCC
and LLVM, especially given the release schedule: 6 weeks for Rust vs.
half a year for LLVM and a year for GCC.

Having said that, there is no particular advantage to updating slowly
either: kernel developers in "stable" distributions are unlikely to be
able to use their distribution-provided Rust toolchain for the kernel
anyway [3]. Instead, by routinely upgrading to the latest instead,
kernel developers using Linux distributions that track the latest Rust
release may be able to use those rather than Rust-provided ones,
especially if their package manager allows to pin / hold back /
downgrade the version for some days during windows where the version may
not match. For instance, Arch, Fedora, Gentoo and openSUSE all provide
and track the latest version of Rust as they get released every 6 weeks.

Then, when the minimum version is reached, we will stop upgrading and
decide how wide the window of support will be. For instance, a year of
Rust versions. We will probably want to start small, and then widen it
over time, just like the kernel did originally for LLVM, see commit
3519c4d6e0 ("Documentation: add minimum clang/llvm version").

# Unstable features stabilized

This upgrade allows us to remove the following unstable features since
they were stabilized:

  - `feature(explicit_generic_args_with_impl_trait)` (1.63).
  - `feature(core_ffi_c)` (1.64).
  - `feature(generic_associated_types)` (1.65).
  - `feature(const_ptr_offset_from)` (1.65, *).
  - `feature(bench_black_box)` (1.66, *).
  - `feature(pin_macro)` (1.68).

The ones marked with `*` apply only to our old `rust` branch, not
mainline yet, i.e. only for code that we may potentially upstream.

With this patch applied, the only unstable feature allowed to be used
outside the `kernel` crate is `new_uninit`, though other code to be
upstreamed may increase the list.

Please see [2] for details.

# Other required changes

Since 1.63, `rustdoc` triggers the `broken_intra_doc_links` lint for
links pointing to exported (`#[macro_export]`) `macro_rules`. An issue
was opened upstream [4], but it turns out it is intended behavior. For
the moment, just add an explicit reference for each link. Later we can
revisit this if `rustdoc` removes the compatibility measure.

Nevertheless, this was helpful to discover a link that was pointing to
the wrong place unintentionally. Since that one was actually wrong, it
is fixed in a previous commit independently.

Another change was the addition of `cfg(no_rc)` and `cfg(no_sync)` in
upstream [5], thus remove our original changes for that.

Similarly, upstream now tests that it compiles successfully with
`#[cfg(not(no_global_oom_handling))]` [6], which allow us to get rid
of some changes, such as an `#[allow(dead_code)]`.

In addition, remove another `#[allow(dead_code)]` due to new uses
within the standard library.

Finally, add `try_extend_trusted` and move the code in `spec_extend.rs`
since upstream moved it for the infallible version.

# `alloc` upgrade and reviewing

There are a large amount of changes, but the vast majority of them are
due to our `alloc` fork being upgraded at once.

There are two kinds of changes to be aware of: the ones coming from
upstream, which we should follow as closely as possible, and the updates
needed in our added fallible APIs to keep them matching the newer
infallible APIs coming from upstream.

Instead of taking a look at the diff of this patch, an alternative
approach is reviewing a diff of the changes between upstream `alloc` and
the kernel's. This allows to easily inspect the kernel additions only,
especially to check if the fallible methods we already have still match
the infallible ones in the new version coming from upstream.

Another approach is reviewing the changes introduced in the additions in
the kernel fork between the two versions. This is useful to spot
potentially unintended changes to our additions.

To apply these approaches, one may follow steps similar to the following
to generate a pair of patches that show the differences between upstream
Rust and the kernel (for the subset of `alloc` we use) before and after
applying this patch:

    # Get the difference with respect to the old version.
    git -C rust checkout $(linux/scripts/min-tool-version.sh rustc)
    git -C linux ls-tree -r --name-only HEAD -- rust/alloc |
        cut -d/ -f3- |
        grep -Fv README.md |
        xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH
    git -C linux diff --patch-with-stat --summary -R > old.patch
    git -C linux restore rust/alloc

    # Apply this patch.
    git -C linux am rust-upgrade.patch

    # Get the difference with respect to the new version.
    git -C rust checkout $(linux/scripts/min-tool-version.sh rustc)
    git -C linux ls-tree -r --name-only HEAD -- rust/alloc |
        cut -d/ -f3- |
        grep -Fv README.md |
        xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH
    git -C linux diff --patch-with-stat --summary -R > new.patch
    git -C linux restore rust/alloc

Now one may check the `new.patch` to take a look at the additions (first
approach) or at the difference between those two patches (second
approach). For the latter, a side-by-side tool is recommended.

Link: https://rust-for-linux.com/rust-version-policy [1]
Link: https://github.com/Rust-for-Linux/linux/issues/2 [2]
Link: https://lore.kernel.org/rust-for-linux/CANiq72mT3bVDKdHgaea-6WiZazd8Mvurqmqegbe5JZxVyLR8Yg@mail.gmail.com/ [3]
Link: https://github.com/rust-lang/rust/issues/106142 [4]
Link: https://github.com/rust-lang/rust/pull/89891 [5]
Link: https://github.com/rust-lang/rust/pull/98652 [6]
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-By: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Tested-by: Ariel Miculas <amiculas@cisco.com>
Tested-by: David Gow <davidgow@google.com>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20230418214347.324156-4-ojeda@kernel.org
[ Removed `feature(core_ffi_c)` from `uapi` ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-05-31 17:35:03 +02:00
Benno Lossin
90e53c5e70 rust: add pin-init API core
This API is used to facilitate safe pinned initialization of structs. It
replaces cumbersome `unsafe` manual initialization with elegant safe macro
invocations.

Due to the size of this change it has been split into six commits:
1. This commit introducing the basic public interface: traits and
   functions to represent and create initializers.
2. Adds the `#[pin_data]`, `pin_init!`, `try_pin_init!`, `init!` and
   `try_init!` macros along with their internal types.
3. Adds the `InPlaceInit` trait that allows using an initializer to create
   an object inside of a `Box<T>` and other smart pointers.
4. Adds the `PinnedDrop` trait and adds macro support for it in
   the `#[pin_data]` macro.
5. Adds the `stack_pin_init!` macro allowing to pin-initialize a struct on
   the stack.
6. Adds the `Zeroable` trait and `init::zeroed` function to initialize
   types that have `0x00` in all bytes as a valid bit pattern.

--

In this section the problem that the new pin-init API solves is outlined.
This message describes the entirety of the API, not just the parts
introduced in this commit. For a more granular explanation and additional
information on pinning and this issue, view [1].

Pinning is Rust's way of enforcing the address stability of a value. When a
value gets pinned it will be impossible for safe code to move it to another
location. This is done by wrapping pointers to said object with `Pin<P>`.
This wrapper prevents safe code from creating mutable references to the
object, preventing mutable access, which is needed to move the value.
`Pin<P>` provides `unsafe` functions to circumvent this and allow
modifications regardless. It is then the programmer's responsibility to
uphold the pinning guarantee.

Many kernel data structures require a stable address, because there are
foreign pointers to them which would get invalidated by moving the
structure. Since these data structures are usually embedded in structs to
use them, this pinning property propagates to the container struct.
Resulting in most structs in both Rust and C code needing to be pinned.

So if we want to have a `mutex` field in a Rust struct, this struct also
needs to be pinned, because a `mutex` contains a `list_head`. Additionally
initializing a `list_head` requires already having the final memory
location available, because it is initialized by pointing it to itself. But
this presents another challenge in Rust: values have to be initialized at
all times. There is the `MaybeUninit<T>` wrapper type, which allows
handling uninitialized memory, but this requires using the `unsafe` raw
pointers and a casting the type to the initialized variant.

This problem gets exacerbated when considering encapsulation and the normal
safety requirements of Rust code. The fields of the Rust `Mutex<T>` should
not be accessible to normal driver code. After all if anyone can modify
the fields, there is no way to ensure the invariants of the `Mutex<T>` are
upheld. But if the fields are inaccessible, then initialization of a
`Mutex<T>` needs to be somehow achieved via a function or a macro. Because
the `Mutex<T>` must be pinned in memory, the function cannot return it by
value. It also cannot allocate a `Box` to put the `Mutex<T>` into, because
that is an unnecessary allocation and indirection which would hurt
performance.

The solution in the rust tree (e.g. this commit: [2]) that is replaced by
this API is to split this function into two parts:

1. A `new` function that returns a partially initialized `Mutex<T>`,
2. An `init` function that requires the `Mutex<T>` to be pinned and that
   fully initializes the `Mutex<T>`.

Both of these functions have to be marked `unsafe`, since a call to `new`
needs to be accompanied with a call to `init`, otherwise using the
`Mutex<T>` could result in UB. And because calling `init` twice also is not
safe. While `Mutex<T>` initialization cannot fail, other structs might
also have to allocate memory, which would result in conditional successful
initialization requiring even more manual accommodation work.

Combine this with the problem of pin-projections -- the way of accessing
fields of a pinned struct -- which also have an `unsafe` API, pinned
initialization is riddled with `unsafe` resulting in very poor ergonomics.
Not only that, but also having to call two functions possibly multiple
lines apart makes it very easy to forget it outright or during refactoring.

Here is an example of the current way of initializing a struct with two
synchronization primitives (see [3] for the full example):

    struct SharedState {
        state_changed: CondVar,
        inner: Mutex<SharedStateInner>,
    }

    impl SharedState {
        fn try_new() -> Result<Arc<Self>> {
            let mut state = Pin::from(UniqueArc::try_new(Self {
                // SAFETY: `condvar_init!` is called below.
                state_changed: unsafe { CondVar::new() },
                // SAFETY: `mutex_init!` is called below.
                inner: unsafe {
                    Mutex::new(SharedStateInner { token_count: 0 })
                },
            })?);

            // SAFETY: `state_changed` is pinned when `state` is.
            let pinned = unsafe {
                state.as_mut().map_unchecked_mut(|s| &mut s.state_changed)
            };
            kernel::condvar_init!(pinned, "SharedState::state_changed");

            // SAFETY: `inner` is pinned when `state` is.
            let pinned = unsafe {
                state.as_mut().map_unchecked_mut(|s| &mut s.inner)
            };
            kernel::mutex_init!(pinned, "SharedState::inner");

            Ok(state.into())
        }
    }

The pin-init API of this patch solves this issue by providing a
comprehensive solution comprised of macros and traits. Here is the example
from above using the pin-init API:

    #[pin_data]
    struct SharedState {
        #[pin]
        state_changed: CondVar,
        #[pin]
        inner: Mutex<SharedStateInner>,
    }

    impl SharedState {
        fn new() -> impl PinInit<Self> {
            pin_init!(Self {
                state_changed <- new_condvar!("SharedState::state_changed"),
                inner <- new_mutex!(
                    SharedStateInner { token_count: 0 },
                    "SharedState::inner",
                ),
            })
        }
    }

Notably the way the macro is used here requires no `unsafe` and thus comes
with the usual Rust promise of safe code not introducing any memory
violations. Additionally it is now up to the caller of `new()` to decide
the memory location of the `SharedState`. They can choose at the moment
`Arc<T>`, `Box<T>` or the stack.

--

The API has the following architecture:
1. Initializer traits `PinInit<T, E>` and `Init<T, E>` that act like
   closures.
2. Macros to create these initializer traits safely.
3. Functions to allow manually writing initializers.

The initializers (an `impl PinInit<T, E>`) receive a raw pointer pointing
to uninitialized memory and their job is to fully initialize a `T` at that
location. If initialization fails, they return an error (`E`) by value.

This way of initializing cannot be safely exposed to the user, since it
relies upon these properties outside of the control of the trait:
- the memory location (slot) needs to be valid memory,
- if initialization fails, the slot should not be read from,
- the value in the slot should be pinned, so it cannot move and the memory
  cannot be deallocated until the value is dropped.

This is why using an initializer is facilitated by another trait that
ensures these requirements.

These initializers can be created manually by just supplying a closure that
fulfills the same safety requirements as `PinInit<T, E>`. But this is an
`unsafe` operation. To allow safe initializer creation, the `pin_init!` is
provided along with three other variants: `try_pin_init!`, `try_init!` and
`init!`. These take a modified struct initializer as a parameter and
generate a closure that initializes the fields in sequence.
The macros take great care in upholding the safety requirements:
- A shadowed struct type is used as the return type of the closure instead
  of `()`. This is to prevent early returns, as these would prevent full
  initialization.
- To ensure every field is only initialized once, a normal struct
  initializer is placed in unreachable code. The type checker will emit
  errors if a field is missing or specified multiple times.
- When initializing a field fails, the whole initializer will fail and
  automatically drop fields that have been initialized earlier.
- Only the correct initializer type is allowed for unpinned fields. You
  cannot use a `impl PinInit<T, E>` to initialize a structurally not pinned
  field.

To ensure the last point, an additional macro `#[pin_data]` is needed. This
macro annotates the struct itself and the user specifies structurally
pinned and not pinned fields.

Because dropping a pinned struct is also not allowed to break the pinning
invariants, another macro attribute `#[pinned_drop]` is needed. This
macro is introduced in a following commit.

These two macros also have mechanisms to ensure the overall safety of the
API. Additionally, they utilize a combined proc-macro, declarative macro
design: first a proc-macro enables the outer attribute syntax `#[...]` and
does some important pre-parsing. Notably this prepares the generics such
that the declarative macro can handle them using token trees. Then the
actual parsing of the structure and the emission of code is handled by a
declarative macro.

For pin-projections the crates `pin-project` [4] and `pin-project-lite` [5]
had been considered, but were ultimately rejected:
- `pin-project` depends on `syn` [6] which is a very big dependency, around
  50k lines of code.
- `pin-project-lite` is a more reasonable 5k lines of code, but contains a
  very complex declarative macro to parse generics. On top of that it
  would require modification that would need to be maintained
  independently.

Link: https://rust-for-linux.com/the-safe-pinned-initialization-problem [1]
Link: 0a04dc4ddd [2]
Link: f509ede33f/samples/rust/rust_miscdev.rs [3]
Link: https://crates.io/crates/pin-project [4]
Link: https://crates.io/crates/pin-project-lite [5]
Link: https://crates.io/crates/syn [6]
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20230408122429.1103522-7-y86-dev@protonmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-04-12 18:41:05 +02:00
Benno Lossin
2d19d369c0 rust: enable the pin_macro feature
This feature enables the use of the `pin!` macro for the `stack_pin_init!`
macro. This feature is already stabilized in Rust version 1.68.

Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20230408122429.1103522-2-y86-dev@protonmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-04-12 18:41:04 +02:00
Asahi Lina
3c01a424a3 rust: Enable the new_uninit feature for kernel and driver crates
The unstable new_uninit feature enables various library APIs to create
uninitialized containers, such as `Box::assume_init()`. This is
necessary to build abstractions that directly initialize memory at the
target location, instead of doing copies through the stack.

Will be used by the DRM scheduler abstraction in the kernel crate, and
by field-wise initialization (e.g. using `place!()` or a future
replacement macro which may itself live in `kernel`) in driver crates.

Link: https://github.com/Rust-for-Linux/linux/issues/879
Link: https://github.com/Rust-for-Linux/linux/issues/2
Link: https://github.com/rust-lang/rust/issues/63291
Signed-off-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Link: https://lore.kernel.org/r/20230224-rust-new_uninit-v1-1-c951443d9e26@asahilina.net
[ Reworded to use `Link` tags. ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2023-04-10 05:21:15 +02:00
Masahiro Yamada
2185242fad kbuild: remove sed commands after rustc rules
rustc may put comments in dep-info, so sed is used to drop them before
passing it to fixdep.

Now that fixdep can remove comments, Makefiles do not need to run sed.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
2023-01-22 23:43:33 +09:00
Masahiro Yamada
295d8398c6 kbuild: specify output names separately for each emission type from rustc
In Kbuild, two different rules must not write to the same file, but
it happens when compiling rust source files.

For example, set CONFIG_SAMPLE_RUST_MINIMAL=m and run the following:

  $ make -j$(nproc) samples/rust/rust_minimal.o samples/rust/rust_minimal.rsi \
                    samples/rust/rust_minimal.s samples/rust/rust_minimal.ll
    [snip]
    RUSTC [M] samples/rust/rust_minimal.o
    RUSTC [M] samples/rust/rust_minimal.rsi
    RUSTC [M] samples/rust/rust_minimal.s
    RUSTC [M] samples/rust/rust_minimal.ll
  mv: cannot stat 'samples/rust/rust_minimal.d': No such file or directory
  make[3]: *** [scripts/Makefile.build:334: samples/rust/rust_minimal.ll] Error 1
  make[3]: *** Waiting for unfinished jobs....
  mv: cannot stat 'samples/rust/rust_minimal.d': No such file or directory
  make[3]: *** [scripts/Makefile.build:309: samples/rust/rust_minimal.o] Error 1
  mv: cannot stat 'samples/rust/rust_minimal.d': No such file or directory
  make[3]: *** [scripts/Makefile.build:326: samples/rust/rust_minimal.s] Error 1
  make[2]: *** [scripts/Makefile.build:504: samples/rust] Error 2
  make[1]: *** [scripts/Makefile.build:504: samples] Error 2
  make: *** [Makefile:2008: .] Error 2

The reason for the error is that 4 threads running in parallel renames
the same file, samples/rust/rust_minimal.d.

This does not happen when compiling C or assembly files because
-Wp,-MMD,$(depfile) explicitly specifies the dependency filepath.
$(depfile) is a unique path for each target.

Currently, rustc is only given --out-dir and --emit=<list-of-types>
So, all the rust build rules output the dep-info into the default
<CRATE_NAME>.d, which causes the path conflict.

Fortunately, the --emit option is able to specify the output path
individually, with the form --emit=<type>=<path>.

Add --emit=dep-info=$(depfile) to the common part. Also, remove the
redundant --out-dir because the output path is specified for each type.

The code gets much cleaner because we do not need to rename *.d files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
2023-01-22 23:43:33 +09:00
Linus Torvalds
6feb57c2fd Kbuild updates for v6.2
- Support zstd-compressed debug info
 
  - Allow W=1 builds to detect objects shared among multiple modules
 
  - Add srcrpm-pkg target to generate a source RPM package
 
  - Make the -s option detection work for future GNU Make versions
 
  - Add -Werror to KBUILD_CPPFLAGS when CONFIG_WERROR=y
 
  - Allow W=1 builds to detect -Wundef warnings in any preprocessed files
 
  - Raise the minimum supported version of binutils to 2.25
 
  - Use $(intcmp ...) to compare integers if GNU Make >= 4.4 is used
 
  - Use $(file ...) to read a file if GNU Make >= 4.2 is used
 
  - Print error if GNU Make older than 3.82 is used
 
  - Allow modpost to detect section mismatches with Clang LTO
 
  - Include vmlinuz.efi into kernel tarballs for arm64 CONFIG_EFI_ZBOOT=y
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Merge tag 'kbuild-v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Support zstd-compressed debug info

 - Allow W=1 builds to detect objects shared among multiple modules

 - Add srcrpm-pkg target to generate a source RPM package

 - Make the -s option detection work for future GNU Make versions

 - Add -Werror to KBUILD_CPPFLAGS when CONFIG_WERROR=y

 - Allow W=1 builds to detect -Wundef warnings in any preprocessed files

 - Raise the minimum supported version of binutils to 2.25

 - Use $(intcmp ...) to compare integers if GNU Make >= 4.4 is used

 - Use $(file ...) to read a file if GNU Make >= 4.2 is used

 - Print error if GNU Make older than 3.82 is used

 - Allow modpost to detect section mismatches with Clang LTO

 - Include vmlinuz.efi into kernel tarballs for arm64 CONFIG_EFI_ZBOOT=y

* tag 'kbuild-v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (29 commits)
  buildtar: fix tarballs with EFI_ZBOOT enabled
  modpost: Include '.text.*' in TEXT_SECTIONS
  padata: Mark padata_work_init() as __ref
  kbuild: ensure Make >= 3.82 is used
  kbuild: refactor the prerequisites of the modpost rule
  kbuild: change module.order to list *.o instead of *.ko
  kbuild: use .NOTINTERMEDIATE for future GNU Make versions
  kconfig: refactor Makefile to reduce process forks
  kbuild: add read-file macro
  kbuild: do not sort after reading modules.order
  kbuild: add test-{ge,gt,le,lt} macros
  Documentation: raise minimum supported version of binutils to 2.25
  kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds
  kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS
  kbuild: Port silent mode detection to future gnu make.
  init/version.c: remove #include <generated/utsrelease.h>
  firmware_loader: remove #include <generated/utsrelease.h>
  modpost: Mark uuid_le type to be suitable only for MEI
  kbuild: add ability to make source rpm buildable using koji
  kbuild: warn objects shared among multiple modules
  ...
2022-12-19 12:33:32 -06:00
Masahiro Yamada
f65a486821 kbuild: change module.order to list *.o instead of *.ko
scripts/Makefile.build replaces the suffix .o with .ko, then
scripts/Makefile.modpost calls the sed command to change .ko back
to the original .o suffix.

Instead of converting the suffixes back-and-forth, store the .o paths
in modules.order, and replace it with .ko in 'make modules_install'.

This avoids the unneeded sed command.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
2022-12-14 15:42:40 +09:00
Masahiro Yamada
598afa0504 kbuild: warn objects shared among multiple modules
If an object is shared among multiple modules, and some of them are
configured as 'm', but the others as 'y', the shared object is built
as modular, then linked to the modules and vmlinux. This is a potential
issue because the expected CFLAGS are different between modules and
builtins.

Commit 637a642f5c ("zstd: Fixing mixed module-builtin objects")
reported that this could be even more fatal in some cases such as
Clang LTO.

That commit fixed lib/zlib/zstd_{compress,decompress}, but there are
still more instances of breakage.

This commit adds a W=1 warning for shared objects, so that the kbuild
test robot, which provides build tests with W=1, will avoid a new
breakage slipping in.

Quick compile tests on v6.1-rc4 detected the following:

scripts/Makefile.build:252: ./drivers/block/rnbd/Makefile: rnbd-common.o is added to multiple modules: rnbd-client rnbd-server
scripts/Makefile.build:252: ./drivers/crypto/marvell/octeontx2/Makefile: cn10k_cpt.o is added to multiple modules: rvu_cptpf rvu_cptvf
scripts/Makefile.build:252: ./drivers/crypto/marvell/octeontx2/Makefile: otx2_cptlf.o is added to multiple modules: rvu_cptpf rvu_cptvf
scripts/Makefile.build:252: ./drivers/crypto/marvell/octeontx2/Makefile: otx2_cpt_mbox_common.o is added to multiple modules: rvu_cptpf rvu_cptvf
scripts/Makefile.build:252: ./drivers/edac/Makefile: skx_common.o is added to multiple modules: i10nm_edac skx_edac
scripts/Makefile.build:252: ./drivers/gpu/drm/bridge/imx/Makefile: imx-ldb-helper.o is added to multiple modules: imx8qm-ldb imx8qxp-ldb
scripts/Makefile.build:252: ./drivers/mfd/Makefile: rsmu_core.o is added to multiple modules: rsmu-i2c rsmu-spi
scripts/Makefile.build:252: ./drivers/mtd/tests/Makefile: mtd_test.o is added to multiple modules: mtd_nandbiterrs mtd_oobtest mtd_pagetest mtd_readtest mtd_speedtest mtd_stresstest mtd_subpagetest mtd_torturetest
scripts/Makefile.build:252: ./drivers/net/dsa/ocelot/Makefile: felix.o is added to multiple modules: mscc_felix mscc_seville
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: cn23xx_pf_device.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: cn23xx_vf_device.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: cn66xx_device.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: cn68xx_device.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: lio_core.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: lio_ethtool.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: octeon_device.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: octeon_droq.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: octeon_mailbox.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: octeon_mem_ops.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: octeon_nic.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: request_manager.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/cavium/liquidio/Makefile: response_manager.o is added to multiple modules: liquidio liquidio_vf
scripts/Makefile.build:252: ./drivers/net/ethernet/freescale/dpaa2/Makefile: dpaa2-mac.o is added to multiple modules: fsl-dpaa2-eth fsl-dpaa2-switch
scripts/Makefile.build:252: ./drivers/net/ethernet/freescale/dpaa2/Makefile: dpmac.o is added to multiple modules: fsl-dpaa2-eth fsl-dpaa2-switch
scripts/Makefile.build:252: ./drivers/net/ethernet/freescale/enetc/Makefile: enetc_cbdr.o is added to multiple modules: fsl-enetc fsl-enetc-vf
scripts/Makefile.build:252: ./drivers/net/ethernet/freescale/enetc/Makefile: enetc_ethtool.o is added to multiple modules: fsl-enetc fsl-enetc-vf
scripts/Makefile.build:252: ./drivers/net/ethernet/freescale/enetc/Makefile: enetc.o is added to multiple modules: fsl-enetc fsl-enetc-vf
scripts/Makefile.build:252: ./drivers/net/ethernet/hisilicon/hns3/Makefile: hns3_common/hclge_comm_cmd.o is added to multiple modules: hclge hclgevf
scripts/Makefile.build:252: ./drivers/net/ethernet/hisilicon/hns3/Makefile: hns3_common/hclge_comm_rss.o is added to multiple modules: hclge hclgevf
scripts/Makefile.build:252: ./drivers/net/ethernet/hisilicon/hns3/Makefile: hns3_common/hclge_comm_tqp_stats.o is added to multiple modules: hclge hclgevf
scripts/Makefile.build:252: ./drivers/net/ethernet/marvell/octeontx2/nic/Makefile: otx2_dcbnl.o is added to multiple modules: rvu_nicpf rvu_nicvf
scripts/Makefile.build:252: ./drivers/net/ethernet/marvell/octeontx2/nic/Makefile: otx2_devlink.o is added to multiple modules: rvu_nicpf rvu_nicvf
scripts/Makefile.build:252: ./drivers/net/ethernet/ti/Makefile: cpsw_ale.o is added to multiple modules: keystone_netcp keystone_netcp_ethss ti_cpsw ti_cpsw_new
scripts/Makefile.build:252: ./drivers/net/ethernet/ti/Makefile: cpsw_ethtool.o is added to multiple modules: ti_cpsw ti_cpsw_new
scripts/Makefile.build:252: ./drivers/net/ethernet/ti/Makefile: cpsw_priv.o is added to multiple modules: ti_cpsw ti_cpsw_new
scripts/Makefile.build:252: ./drivers/net/ethernet/ti/Makefile: cpsw_sl.o is added to multiple modules: ti_cpsw ti_cpsw_new
scripts/Makefile.build:252: ./drivers/net/ethernet/ti/Makefile: davinci_cpdma.o is added to multiple modules: ti_cpsw ti_cpsw_new ti_davinci_emac
scripts/Makefile.build:252: ./drivers/platform/x86/intel/int3472/Makefile: common.o is added to multiple modules: intel_skl_int3472_discrete intel_skl_int3472_tps68470
scripts/Makefile.build:252: ./sound/soc/codecs/Makefile: wcd-clsh-v2.o is added to multiple modules: snd-soc-wcd9335 snd-soc-wcd934x snd-soc-wcd938x

Once all the warnings are fixed, it can become an error without the
W= option.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Tested-by: Alexander Lobakin <alobakin@pm.me>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-11-22 23:40:05 +09:00
Masahiro Yamada
a2430b25c3 kbuild: add kbuild-file macro
While building, installing, cleaning, Kbuild visits sub-directories
and includes 'Kbuild' or 'Makefile' that exists there.

Add 'kbuild-file' macro, and reuse it from scripts/Makefie.*

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Tested-by: Alexander Lobakin <alobakin@pm.me>
2022-11-22 23:40:02 +09:00
Andrew Davis
dcad240c15 kbuild: Cleanup DT Overlay intermediate files as appropriate
%.dtbo.o and %.dtbo.S files are used to build-in DT Overlay. They should
should not be removed by Make or the kernel will be needlessly rebuilt.

These should be removed by "clean" and ignored by git like other
intermediate files.

Reported-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Andrew Davis <afd@ti.com>
Fixes: 941214a512 ("kbuild: Allow DTB overlays to built into .dtbo.S files")
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20221114205939.27994-1-afd@ti.com
Signed-off-by: Rob Herring <robh@kernel.org>
2022-11-18 14:45:30 -06:00
Nick Desaulniers
c67a85bee7 kbuild: add -fno-discard-value-names to cmd_cc_ll_c
When debugging LLVM IR, it can be handy for clang to not discard value
names used for local variables and parameters. Compare the generated IR.

-fdiscard-value-names:
  define i32 @core_sys_select(i32 %0, ptr %1, ptr %2, ptr %3, ptr %4) {
    %6 = alloca i64
    %7 = alloca %struct.poll_wqueues
    %8 = alloca [64 x i32]

-fno-discard-value-names:
  define i32 @core_sys_select(i32 %n, ptr %inp, ptr %outp, ptr %exp,
                              ptr %end_time) {
    %expire.i = alloca i64
    %table.i = alloca %struct.poll_wqueues
    %stack_fds = alloca [64 x i32]

The rule for generating human readable LLVM IR (.ll) is only useful as a
debugging feature:

$ make LLVM=1 fs/select.ll

As Fangrui notes:
  A LLVM_ENABLE_ASSERTIONS=off build of Clang defaults to
  -fdiscard-value-names.

  A LLVM_ENABLE_ASSERTIONS=on build of Clang defaults to
  -fno-discard-value-names.

Explicitly enable -fno-discard-value-names so that the IR always contains
value names regardless of whether assertions were enabled or not.
Assertions generally are not enabled in releases of clang packaged by
distributions.

Link: https://github.com/ClangBuiltLinux/linux/issues/1467
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-10-15 05:22:29 +09:00
Linus Torvalds
8afc66e8d4 Kbuild updates for v6.1
- Remove potentially incomplete targets when Kbuid is interrupted by
    SIGINT etc. in case GNU Make may miss to do that when stderr is piped
    to another program.
 
  - Rewrite the single target build so it works more correctly.
 
  - Fix rpm-pkg builds with V=1.
 
  - List top-level subdirectories in ./Kbuild.
 
  - Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in kallsyms.
 
  - Avoid two different modules in lib/zstd/ having shared code, which
    potentially causes building the common code as build-in and modular
    back-and-forth.
 
  - Unify two modpost invocations to optimize the build process.
 
  - Remove head-y syntax in favor of linker scripts for placing particular
    sections in the head of vmlinux.
 
  - Bump the minimal GNU Make version to 3.82.
 
  - Clean up misc Makefiles and scripts.
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Merge tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Remove potentially incomplete targets when Kbuid is interrupted by
   SIGINT etc in case GNU Make may miss to do that when stderr is piped
   to another program.

 - Rewrite the single target build so it works more correctly.

 - Fix rpm-pkg builds with V=1.

 - List top-level subdirectories in ./Kbuild.

 - Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in
   kallsyms.

 - Avoid two different modules in lib/zstd/ having shared code, which
   potentially causes building the common code as build-in and modular
   back-and-forth.

 - Unify two modpost invocations to optimize the build process.

 - Remove head-y syntax in favor of linker scripts for placing
   particular sections in the head of vmlinux.

 - Bump the minimal GNU Make version to 3.82.

 - Clean up misc Makefiles and scripts.

* tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits)
  docs: bump minimal GNU Make version to 3.82
  ia64: simplify esi object addition in Makefile
  Revert "kbuild: Check if linker supports the -X option"
  kbuild: rebuild .vmlinux.export.o when its prerequisite is updated
  kbuild: move modules.builtin(.modinfo) rules to Makefile.vmlinux_o
  zstd: Fixing mixed module-builtin objects
  kallsyms: ignore __kstrtab_* and __kstrtabns_* symbols
  kallsyms: take the input file instead of reading stdin
  kallsyms: drop duplicated ignore patterns from kallsyms.c
  kbuild: reuse mksysmap output for kallsyms
  mksysmap: update comment about __crc_*
  kbuild: remove head-y syntax
  kbuild: use obj-y instead extra-y for objects placed at the head
  kbuild: hide error checker logs for V=1 builds
  kbuild: re-run modpost when it is updated
  kbuild: unify two modpost invocations
  kbuild: move vmlinux.o rule to the top Makefile
  kbuild: move .vmlinux.objs rule to Makefile.modpost
  kbuild: list sub-directories in ./Kbuild
  Makefile.compiler: replace cc-ifversion with compiler-specific macros
  ...
2022-10-10 12:00:45 -07:00
Masahiro Yamada
cc306abd19 kbuild: fix and refactor single target build
The single target build has a subtle bug for the combination for
an individual file and a subdirectory.

[1] 'make kernel/fork.i' builds only kernel/fork.i

  $ make kernel/fork.i
    CALL    scripts/checksyscalls.sh
    DESCEND objtool
    CPP     kernel/fork.i

[2] 'make kernel/' builds only under the kernel/ directory.

  $ make kernel/
    CALL    scripts/checksyscalls.sh
    DESCEND objtool
    CC      kernel/fork.o
    CC      kernel/exec_domain.o
       [snip]
    CC      kernel/rseq.o
    AR      kernel/built-in.a

But, if you try to do [1] and [2] in a single command, you will get
only [1] with a weird log:

  $ make kernel/fork.i kernel/
    CALL    scripts/checksyscalls.sh
    DESCEND objtool
    CPP     kernel/fork.i
  make[2]: Nothing to be done for 'kernel/'.

With 'make kernel/fork.i kernel/', you should get both [1] and [2].

Rewrite the single target build.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-09-29 04:40:15 +09:00
Masahiro Yamada
d724b578a1 kbuild: do not deduplicate modules.order
The AWK code was added to deduplicate modules.order in case $(obj-m)
contains the same module multiple times, but it is actually unneeded
since commit b2c8855491 ("kbuild: update modules.order only when
contained modules are updated").

The list is already deduplicated before being processed by AWK because
$^ is the deduplicated list of prerequisites.
(Please note the real-prereqs macro uses $^)

Yet, modules.order will contain duplication if two different Makefiles
build the same module:

  foo/Makefile:

      obj-m += bar/baz.o

  foo/bar/Makefile:

      obj-m += baz.o

However, the parallel builds cannot properly handle this case in the
first place. So, it is better to let it fail (as already done by
scripts/modules-check.sh).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-09-29 04:40:14 +09:00
Miguel Ojeda
2f7ab1267d Kbuild: add Rust support
Having most of the new files in place, we now enable Rust support
in the build system, including `Kconfig` entries related to Rust,
the Rust configuration printer and a few other bits.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Finn Behrens <me@kloenk.de>
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Co-developed-by: Sven Van Asbroeck <thesven73@gmail.com>
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Signed-off-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Co-developed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Co-developed-by: Douglas Su <d0u9.su@outlook.com>
Signed-off-by: Douglas Su <d0u9.su@outlook.com>
Co-developed-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Signed-off-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Co-developed-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Signed-off-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Co-developed-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Co-developed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Co-developed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2022-09-28 09:02:20 +02:00
Masahiro Yamada
5439d4d4dc kbuild: remove sed command from cmd_ar_builtin
Replace a pipeline of echo and sed with printf to decrease process forks.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2022-07-27 21:17:59 +09:00
Kevin Locke
7bf179de5b kbuild: avoid regex RS for POSIX awk
In 22f26f2177 awk was added to deduplicate *.mod files.  The awk
invocation passes -v RS='( |\n)' to match a space or newline character
as the record separator.  Unfortunately, POSIX states[1]

> If RS contains more than one character, the results are unspecified.

Some implementations (such as the One True Awk[2] used by the BSDs) do
not treat RS as a regular expression.  When awk does not support regex
RS, build failures such as the following are produced (first error using
allmodconfig):

      CC [M]  arch/x86/events/intel/uncore.o
      CC [M]  arch/x86/events/intel/uncore_nhmex.o
      CC [M]  arch/x86/events/intel/uncore_snb.o
      CC [M]  arch/x86/events/intel/uncore_snbep.o
      CC [M]  arch/x86/events/intel/uncore_discovery.o
      LD [M]  arch/x86/events/intel/intel-uncore.o
    ld: cannot find uncore_nhmex.o: No such file or directory
    ld: cannot find uncore_snb.o: No such file or directory
    ld: cannot find uncore_snbep.o: No such file or directory
    ld: cannot find uncore_discovery.o: No such file or directory
    make[3]: *** [scripts/Makefile.build:422: arch/x86/events/intel/intel-uncore.o] Error 1
    make[2]: *** [scripts/Makefile.build:487: arch/x86/events/intel] Error 2
    make[1]: *** [scripts/Makefile.build:487: arch/x86/events] Error 2
    make: *** [Makefile:1839: arch/x86] Error 2

To avoid this, use printf(1) to produce a newline between each object
path, instead of the space produced by echo(1), so that the default RS
can be used by awk.

[1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html
[2]: https://github.com/onetrueawk/awk

Fixes: 22f26f2177 ("kbuild: get rid of duplication in *.mod files")
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-06-08 01:27:26 +09:00
Masahiro Yamada
b42d230650 kbuild: factor out the common objtool arguments
scripts/Makefile.build and scripts/link-vmlinux.sh have similar setups
for the objtool arguments.

It was difficult to factor out them because all the vmlinux build rules
were written in a shell script. It is somewhat tedious to touch the two
files every time a new objtool option is supported.

To reduce the code duplication, move the objtool for vmlinux.o into
scripts/Makefile.vmlinux_o. Then, move the common macros to Makefile.lib
so they are shared between Makefile.build and Makefile.vmlinux_o.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-06-05 06:20:57 +09:00
Masahiro Yamada
f6b66ca4f3 kbuild: rebuild multi-object modules when objtool is updated
When CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT is enabled, objtool for
multi-object modules is postponed until the objects are linked together.

Make sure to re-run objtool and re-link multi-object modules when
objtool is updated.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-06-01 23:07:29 +09:00
Masahiro Yamada
c6031b1dbb kbuild: make *.mod rule robust against too long argument error
Like built-in.a, the command length of the *.mod rule scales with
the depth of the directory times the number of objects in the Makefile.

Add $(obj)/ by the shell command (awk) instead of by Make's builtin
function.

In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.

For example, you can build i915 as a module (CONFIG_DRM_I915=m) and
compare drivers/gpu/drm/i915/.i915.mod.cmd with/without this commit.

The issue is more critical for external modules because the M= path
can be very long as Jeff Johnson reported before [1].

[1] https://lore.kernel.org/linux-kbuild/4c02050c4e95e4cb8cc04282695f8404@codeaurora.org/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-06-01 23:07:29 +09:00
Masahiro Yamada
cd968b97c4 kbuild: make built-in.a rule robust against too long argument error
Kbuild runs at the top of objtree instead of changing the working
directory to subdirectories. I think this design is nice overall but
some commands have a scalability issue.

The build command of built-in.a is one of them whose length scales with:

    O(D * N)

Here, D is the length of the directory path (i.e. $(obj)/ prefix),
N is the number of objects in the Makefile, O() is the big O notation.

The deeper directory the Makefile directory is located, the more easily
it will hit the too long argument error.

We can make it better. Trim the $(obj)/ by Make's builtin function, and
restore it by a shell command (sed).

With this, the command length scales with:

    O(D + N)

In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.

For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and
compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-06-01 23:07:29 +09:00
Masahiro Yamada
31cb50b559 kbuild: check static EXPORT_SYMBOL* by script instead of modpost
The 'static' specifier and EXPORT_SYMBOL() are an odd combination.

Commit 15bfc2348d ("modpost: check for static EXPORT_SYMBOL*
functions") tried to detect it, but this check has false negatives.

Here is the sample code.

  Makefile:

    obj-y += foo1.o foo2.o

  foo1.c:

    #include <linux/export.h>
    static void foo(void) {}
    EXPORT_SYMBOL(foo);

  foo2.c:

    void foo(void) {}

foo1.c exports the static symbol 'foo', but modpost cannot catch it
because it is fooled by foo2.c, which has a global symbol with the
same name.

s->is_static is cleared if a global symbol with the same name is found
somewhere, but EXPORT_SYMBOL() and the global symbol do not necessarily
belong to the same compilation unit.

This check should be done per compilation unit, but I do not know how
to do it in modpost. modpost runs against vmlinux.o or modules, which
merges multiple objects, then forgets their origin.

modpost cannot parse individual objects because they may not be ELF but
LLVM IR when CONFIG_LTO_CLANG=y.

Add a simple bash script to parse the output from ${NM}. This works for
CONFIG_LTO_CLANG=y because llvm-nm can dump symbols of LLVM IR files.

Revert 15bfc2348d.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-06-01 23:07:02 +09:00
Masahiro Yamada
c25e1c5582 kbuild: do not create *.prelink.o for Clang LTO or IBT
When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted
to ELF.

CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until
objects are merged together.

This commit stops generating *.prelink.o, so the build flow will look
similar with/without LTO.

The following figures show how the LTO build currently works, and
how this commit is changing it.

Current build flow
==================

 [1] single-object module

                                      $(LD)
           $(CC)                     +objtool              $(LD)
    foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko
                              (LLVM IR)          (ELF)       |    (ELF)
                                                             |
                                                 foo.mod.o --/
                                                 (LLVM IR)

 [2] multi-object module
                                      $(LD)
           $(CC)         $(AR)       +objtool               $(LD)
    foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko
                           |  (archive)          (ELF)       |    (ELF)
    foo2.c -----> foo2.o --/                                 |
                 (LLVM IR)                       foo.mod.o --/
                                                 (LLVM IR)

  One confusion is that foo.o in multi-object module is an archive
  despite of its suffix.

New build flow
==============

 [1] single-object module

  Since there is only one object, there is no need to keep the LLVM IR.
  Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO
  is disabled, $(LD) is unneeded because $(CC) produces an ELF object.

               $(CC)+$(LD)+objtool              $(LD)
    foo.c ----------------------------> foo.o ---------> foo.ko
                                        (ELF)     |      (ELF)
                                                  |
                                      foo.mod.o --/
                                      (LLVM IR)

 [2] multi-object module

  Previously, $(AR) was used to combine LLVM IR files into an archive,
  but there was no technical reason to do so. Use $(LD) to merge them
  into a single ELF object.

                               $(LD)
             $(CC)            +objtool          $(LD)
    foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko
                                 |      (ELF)     |      (ELF)
    foo2.c ---------> foo2.o ----/                |
                     (LLVM IR)        foo.mod.o --/
                                      (LLVM IR)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
2022-05-29 18:39:35 +09:00
Masahiro Yamada
0cfd90060d kbuild: replace $(linked-object) with CONFIG options
*.prelink.o is created when CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT
is enabled.

Replace $(linked-object) with $(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT)
so you will get a quick idea of when the --link option is passed.

No functional change is intended.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14
2022-05-29 18:39:35 +09:00
Linus Torvalds
df202b452f Kbuild updates for v5.19
- Add HOSTPKG_CONFIG env variable to allow users to override pkg-config
 
  - Support W=e as a shorthand for KCFLAGS=-Werror
 
  - Fix CONFIG_IKHEADERS build to support toybox cpio
 
  - Add scripts/dummy-tools/pahole to ease distro packagers' life
 
  - Suppress false-positive warnings from checksyscalls.sh for W=2 build
 
  - Factor out the common code of arch/*/boot/install.sh into
    scripts/install.sh
 
  - Support 'kernel-install' tool in scripts/prune-kernel
 
  - Refactor module-versioning to link the symbol versions at the final
    link of vmlinux and modules
 
  - Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in
    an arch-agnostic way
 
  - Refactor modpost, Makefiles
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Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Add HOSTPKG_CONFIG env variable to allow users to override pkg-config

 - Support W=e as a shorthand for KCFLAGS=-Werror

 - Fix CONFIG_IKHEADERS build to support toybox cpio

 - Add scripts/dummy-tools/pahole to ease distro packagers' life

 - Suppress false-positive warnings from checksyscalls.sh for W=2 build

 - Factor out the common code of arch/*/boot/install.sh into
   scripts/install.sh

 - Support 'kernel-install' tool in scripts/prune-kernel

 - Refactor module-versioning to link the symbol versions at the final
   link of vmlinux and modules

 - Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in
   an arch-agnostic way

 - Refactor modpost, Makefiles

* tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (56 commits)
  genksyms: adjust the output format to modpost
  kbuild: stop merging *.symversions
  kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS
  modpost: extract symbol versions from *.cmd files
  modpost: add sym_find_with_module() helper
  modpost: change the license of EXPORT_SYMBOL to bool type
  modpost: remove left-over cross_compile declaration
  kbuild: record symbol versions in *.cmd files
  kbuild: generate a list of objects in vmlinux
  modpost: move *.mod.c generation to write_mod_c_files()
  modpost: merge add_{intree_flag,retpoline,staging_flag} to add_header
  scripts/prune-kernel: Use kernel-install if available
  kbuild: factor out the common installation code into scripts/install.sh
  modpost: split new_symbol() to symbol allocation and hash table addition
  modpost: make sym_add_exported() always allocate a new symbol
  modpost: make multiple export error
  modpost: dump Module.symvers in the same order of modules.order
  modpost: traverse the namespace_list in order
  modpost: use doubly linked list for dump_lists
  modpost: traverse unresolved symbols in order
  ...
2022-05-26 12:09:50 -07:00
Linus Torvalds
22922deae1 Objtool changes for this cycle were:
- Comprehensive interface overhaul:
    =================================
 
    Objtool's interface has some issues:
 
      - Several features are done unconditionally, without any way to turn
        them off.  Some of them might be surprising.  This makes objtool
        tricky to use, and prevents porting individual features to other
        arches.
 
      - The config dependencies are too coarse-grained.  Objtool enablement is
        tied to CONFIG_STACK_VALIDATION, but it has several other features
        independent of that.
 
      - The objtool subcmds ("check" and "orc") are clumsy: "check" is really
        a subset of "orc", so it has all the same options.  The subcmd model
        has never really worked for objtool, as it only has a single purpose:
        "do some combination of things on an object file".
 
      - The '--lto' and '--vmlinux' options are nonsensical and have
        surprising behavior.
 
    Overhaul the interface:
 
       - get rid of subcmds
 
       - make all features individually selectable
 
       - remove and/or clarify confusing/obsolete options
 
       - update the documentation
 
       - fix some bugs found along the way
 
  - Fix x32 regression
 
  - Fix Kbuild cleanup bugs
 
  - Add scripts/objdump-func helper script to disassemble a single function from an object file.
 
  - Rewrite scripts/faddr2line to be section-aware, by basing it on 'readelf',
    moving it away from 'nm', which doesn't handle multiple sections well,
    which can result in decoding failure.
 
  - Rewrite & fix symbol handling - which had a number of bugs wrt. object files
    that don't have global symbols - which is rare but possible. Also fix a
    bunch of symbol handling bugs found along the way.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'objtool-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool updates from Ingo Molnar:

 - Comprehensive interface overhaul:
   =================================

   Objtool's interface has some issues:

     - Several features are done unconditionally, without any way to
       turn them off. Some of them might be surprising. This makes
       objtool tricky to use, and prevents porting individual features
       to other arches.

     - The config dependencies are too coarse-grained. Objtool
       enablement is tied to CONFIG_STACK_VALIDATION, but it has several
       other features independent of that.

     - The objtool subcmds ("check" and "orc") are clumsy: "check" is
       really a subset of "orc", so it has all the same options.

       The subcmd model has never really worked for objtool, as it only
       has a single purpose: "do some combination of things on an object
       file".

     - The '--lto' and '--vmlinux' options are nonsensical and have
       surprising behavior.

   Overhaul the interface:

      - get rid of subcmds

      - make all features individually selectable

      - remove and/or clarify confusing/obsolete options

      - update the documentation

      - fix some bugs found along the way

 - Fix x32 regression

 - Fix Kbuild cleanup bugs

 - Add scripts/objdump-func helper script to disassemble a single
   function from an object file.

 - Rewrite scripts/faddr2line to be section-aware, by basing it on
   'readelf', moving it away from 'nm', which doesn't handle multiple
   sections well, which can result in decoding failure.

 - Rewrite & fix symbol handling - which had a number of bugs wrt.
   object files that don't have global symbols - which is rare but
   possible. Also fix a bunch of symbol handling bugs found along the
   way.

* tag 'objtool-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
  objtool: Fix objtool regression on x32 systems
  objtool: Fix symbol creation
  scripts/faddr2line: Fix overlapping text section failures
  scripts: Create objdump-func helper script
  objtool: Remove libsubcmd.a when make clean
  objtool: Remove inat-tables.c when make clean
  objtool: Update documentation
  objtool: Remove --lto and --vmlinux in favor of --link
  objtool: Add HAVE_NOINSTR_VALIDATION
  objtool: Rename "VMLINUX_VALIDATION" -> "NOINSTR_VALIDATION"
  objtool: Make noinstr hacks optional
  objtool: Make jump label hack optional
  objtool: Make static call annotation optional
  objtool: Make stack validation frame-pointer-specific
  objtool: Add CONFIG_OBJTOOL
  objtool: Extricate sls from stack validation
  objtool: Rework ibt and extricate from stack validation
  objtool: Make stack validation optional
  objtool: Add option to print section addresses
  objtool: Don't print parentheses in function addresses
  ...
2022-05-24 10:36:38 -07:00
Masahiro Yamada
5ce2176b81 genksyms: adjust the output format to modpost
Make genksyms output symbol versions in the format modpost expects,
so the 'sed' is unneeded.

This commit makes *.symversions completely unneeded.

I will keep *.symversions in .gitignore and 'make clean' for a while.
Otherwise, 'git status' might be surprising.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-05-24 16:33:20 +09:00
Masahiro Yamada
7375cbcf23 kbuild: stop merging *.symversions
Now modpost reads symbol versions from .*.cmd files.

The merged *.symversions are no longer needed.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-05-24 16:33:20 +09:00
Masahiro Yamada
7b4537199a kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS
include/{linux,asm-generic}/export.h defines a weak symbol, __crc_*
as a placeholder.

Genksyms writes the version CRCs into the linker script, which will be
used for filling the __crc_* symbols. The linker script format depends
on CONFIG_MODULE_REL_CRCS. If it is enabled, __crc_* holds the offset
to the reference of CRC.

It is time to get rid of this complexity.

Now that modpost parses text files (.*.cmd) to collect all the CRCs,
it can generate C code that will be linked to the vmlinux or modules.

Generate a new C file, .vmlinux.export.c, which contains the CRCs of
symbols exported by vmlinux. It is compiled and linked to vmlinux in
scripts/link-vmlinux.sh.

Put the CRCs of symbols exported by modules into the existing *.mod.c
files. No additional build step is needed for modules. As before,
*.mod.c are compiled and linked to *.ko in scripts/Makefile.modfinal.

No linker magic is used here. The new C implementation works in the
same way, whether CONFIG_RELOCATABLE is enabled or not.
CONFIG_MODULE_REL_CRCS is no longer needed.

Previously, Kbuild invoked additional $(LD) to update the CRCs in
objects, but this step is unneeded too.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-05-24 16:33:20 +09:00
Linus Torvalds
c5a3d3c01e - Remove a bunch of chicken bit options to turn off CPU features which
are not really needed anymore
 
 - Misc fixes and cleanups
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Merge tag 'x86_cpu_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 CPU feature updates from Borislav Petkov:

 - Remove a bunch of chicken bit options to turn off CPU features which
   are not really needed anymore

 - Misc fixes and cleanups

* tag 'x86_cpu_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/speculation: Add missing prototype for unpriv_ebpf_notify()
  x86/pm: Fix false positive kmemleak report in msr_build_context()
  x86/speculation/srbds: Do not try to turn mitigation off when not supported
  x86/cpu: Remove "noclflush"
  x86/cpu: Remove "noexec"
  x86/cpu: Remove "nosmep"
  x86/cpu: Remove CONFIG_X86_SMAP and "nosmap"
  x86/cpu: Remove "nosep"
  x86/cpu: Allow feature bit names from /proc/cpuinfo in clearcpuid=
2022-05-23 18:01:31 -07:00
Masahiro Yamada
78e9e56af3 kbuild: record symbol versions in *.cmd files
When CONFIG_MODVERSIONS=y, the output from genksyms is saved in
separate *.symversions files, and will be used much later when
CONFIG_LTO_CLANG=y because it is impossible to update LLVM bit code
here.

This approach is not robust because:

 - *.symversions may or may not exist. If *.symversions does not
   exist, we never know if it is missing for legitimate reason
   (i.e. no EXPORT_SYMBOL) or something bad has happened (for
   example, the user accidentally deleted it). Once it occurs,
   it is not self-healing because *.symversions is generated
   as a side effect.

 - stale (i.e. invalid) *.symversions might be picked up if an
   object is generated in a non-ordinary way, and corresponding
   *.symversions (, which was generated by old builds) just happen
   to exist.

A more robust approach is to save symbol versions in *.cmd files
because:

 - *.cmd always exists (if the object is generated by if_changed
   rule or friends). Even if the user accidentally deletes it,
   it will be regenerated in the next build.

 - *.cmd is always re-generated when the object is updated. This
   avoid stale version information being picked up.

I will remove *.symversions later.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
2022-05-11 21:46:39 +09:00
Masahiro Yamada
feb7d79fea kbuild: read *.mod to get objects passed to $(LD) or $(AR)
ld and ar support @file, which command-line options are read from.

Now that *.mod lists the member objects in the correct order, without
duplication, it is ready to be passed to ld and ar.

By using the @file syntax, people will not be worried about the pitfall
described in the NOTE.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2022-05-08 03:16:59 +09:00
Masahiro Yamada
fc93a4cdce kbuild: make *.mod not depend on *.o
The dependency

    $(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o

... exists because *.mod files previously contained undefined symbols,
which are computed from *.o files when CONFIG_TRIM_UNUSED_KSYMS=y.

Now that the undefined symbols are put into separate *.usyms files,
there is no reason to make *.mod depend on *.o files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-05-08 03:16:59 +09:00
Masahiro Yamada
22f26f2177 kbuild: get rid of duplication in *.mod files
It is allowed to add the same objects multiple times to obj-y / obj-m:

  obj-y += foo.o foo.o foo.o
  obj-m += bar.o bar.o bar.o

It is also allowed to add the same objects multiple times to a composite
module:

  obj-m += foo.o
  foo-y := foo1.o foo2.o foo2.o foo1.o

This flexibility is useful because the same object might be selected by
different CONFIG options, like this:

  obj-m               += foo.o
  foo-y               := foo1.o
  foo-$(CONFIG_FOO_X) += foo2.o
  foo-$(CONFIG_FOO_Y) += foo2.o

The duplicated objects are omitted at link time. It works naturally in
Makefiles because GNU Make removes duplication in $^ without changing
the order.

It is working well, almost...

A small flaw I notice is, *.mod contains duplication in such a case.

This is probably not a big deal. As far as I know, the only small
problem is scripts/mod/sumversion.c parses the same file multiple
times.

I am fixing this because I plan to reuse *.mod for other purposes,
where the duplication can be problematic.

The code change is quite simple. We already use awk to drop duplicated
lines in modules.order (see cmd_modules_order in the same file).
I copied the code, but changed RS to use spaces as record separators.

I also changed the file format to list one object per line.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-05-08 03:16:59 +09:00
Masahiro Yamada
9413e76405 kbuild: split the second line of *.mod into *.usyms
The *.mod files have two lines; the first line lists the member objects
of the module, and the second line, if CONFIG_TRIM_UNUSED_KSYMS=y, lists
the undefined symbols.

Currently, we generate *.mod after constructing composite modules,
otherwise, we cannot compute the second line. No prerequisite is
required to print the first line.

They are orthogonal. Splitting them into separate commands will ease
further cleanups.

This commit splits the list of undefined symbols out to *.usyms files.

Previously, the list of undefined symbols ended up with a very long
line, but now it has one symbol per line.

Use sed like we did before commit 7d32358be8 ("kbuild: avoid split
lines in .mod files").

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-05-08 03:16:59 +09:00
Masahiro Yamada
b3591e0619 kbuild: reuse real-search to simplify cmd_mod
The first command in cmd_mod is similar to the real-search macro.
Reuse it.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2022-05-08 03:16:59 +09:00
Masahiro Yamada
7cfa2fcbac kbuild: refactor cmd_modversions_S
Split the code into two macros, cmd_gen_symversions_S for running
genksyms, and cmd_modversions for running $(LD) to update the object
with CRCs.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2022-05-08 03:16:58 +09:00
Masahiro Yamada
8017ce5064 kbuild: refactor cmd_modversions_c
cmd_modversions_c implements two parts; run genksyms to calculate CRCs
of exported symbols, run $(LD) to update the object with the CRCs. The
latter is not executed for CONFIG_LTO_CLANG=y since the object is not
ELF but LLVM bit code at this point.

The first part can be unified because we can always use $(NM) instead
of "$(OBJDUMP) -h" to dump the symbols.

Split the code into the two macros, cmd_gen_symversions_c and
cmd_modversions.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2022-05-08 03:16:58 +09:00
Josh Poimboeuf
753da4179d objtool: Remove --lto and --vmlinux in favor of --link
The '--lto' option is a confusing way of telling objtool to do stack
validation despite it being a linked object.  It's no longer needed now
that an explicit '--stackval' option exists.  The '--vmlinux' option is
also redundant.

Remove both options in favor of a straightforward '--link' option which
identifies a linked object.

Also, implicitly set '--link' with a warning if the user forgets to do
so and we can tell that it's a linked object.  This makes it easier for
manual vmlinux runs.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/dcd3ceffd15a54822c6183e5766d21ad06082b45.1650300597.git.jpoimboe@redhat.com
2022-04-22 12:32:05 +02:00
Josh Poimboeuf
22102f4559 objtool: Make noinstr hacks optional
Objtool has some hacks in place to workaround toolchain limitations
which otherwise would break no-instrumentation rules.  Make the hacks
explicit (and optional for other arches) by turning it into a cmdline
option and kernel config option.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/b326eeb9c33231b9dfbb925f194ed7ee40edcd7c.1650300597.git.jpoimboe@redhat.com
2022-04-22 12:32:04 +02:00
Josh Poimboeuf
4ab7674f59 objtool: Make jump label hack optional
Objtool secretly does a jump label hack to overcome the limitations of
the toolchain.  Make the hack explicit (and optional for other arches)
by turning it into a cmdline option and kernel config option.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/3bdcbfdd27ecb01ddec13c04bdf756a583b13d24.1650300597.git.jpoimboe@redhat.com
2022-04-22 12:32:04 +02:00
Josh Poimboeuf
26e176896a objtool: Make static call annotation optional
As part of making objtool more modular, put the existing static call
code behind a new '--static-call' option.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/d59ac57ef3d6d8380cdce20322314c9e2e556750.1650300597.git.jpoimboe@redhat.com
2022-04-22 12:32:03 +02:00