locking: Introduce __cleanup() based infrastructure

Use __attribute__((__cleanup__(func))) to build:

- simple auto-release pointers using __free()

- 'classes' with constructor and destructor sem

locking: Introduce __cleanup() based infrastructure

Use __attribute__((__cleanup__(func))) to build:

- simple auto-release pointers using __free()

- 'classes' with constructor and destructor semantics for
scope-based resource management.

- lock guards based on the above classes.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org

show more ...

kmsan: introduce __no_sanitize_memory and __no_kmsan_checks

__no_sanitize_memory is a function attribute that instructs KMSAN to skip
a function during instrumentation. This is needed to e.g. impl

kmsan: introduce __no_sanitize_memory and __no_kmsan_checks

__no_sanitize_memory is a function attribute that instructs KMSAN to skip
a function during instrumentation. This is needed to e.g. implement the
noinstr functions.

__no_kmsan_checks is a function attribute that makes KMSAN ignore the
uninitialized values coming from the function's inputs, and initialize the
function's outputs.

Functions marked with this attribute can't be inlined into functions not
marked with it, and vice versa. This behavior is overridden by
__always_inline.

__SANITIZE_MEMORY__ is a macro that's defined iff the file is instrumented
with KMSAN. This is not the same as CONFIG_KMSAN, which is defined for
every file.

Link: https://lkml.kernel.org/r/20220915150417.722975-8-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

show more ...

cfi: Switch to -fsanitize=kcfi

Switch from Clang's original forward-edge control-flow integrity
implementation to -fsanitize=kcfi, which is better suited for the
kernel, as it doesn't require LTO, d

cfi: Switch to -fsanitize=kcfi

Switch from Clang's original forward-edge control-flow integrity
implementation to -fsanitize=kcfi, which is better suited for the
kernel, as it doesn't require LTO, doesn't use a jump table that
requires altering function references, and won't break cross-module
function address equality.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220908215504.3686827-6-samitolvanen@google.com

show more ...

cfi: Use __builtin_function_start

Clang 14 added support for the __builtin_function_start function,
which allows us to implement the function_nocfi macro without
architecture-specific inline assembl

cfi: Use __builtin_function_start

Clang 14 added support for the __builtin_function_start function,
which allows us to implement the function_nocfi macro without
architecture-specific inline assembly and in a way that also works
with static initializers.

Change CONFIG_CFI_CLANG to depend on Clang >= 14, define
function_nocfi using __builtin_function_start, and remove the arm64
inline assembly implementation.

Link: https://github.com/llvm/llvm-project/commit/ec2e26eaf63558934f5b73a6e530edc453cf9508
Link: https://github.com/ClangBuiltLinux/linux/issues/1353
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will@kernel.org> # arm64
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220405221618.633743-1-samitolvanen@google.com

show more ...

compiler_types.h: Add unified __diag_ignore_all for GCC/LLVM

Add a __diag_ignore_all macro, to ignore warnings for both GCC and LLVM,
without having to specify the compiler type and version. By defa

compiler_types.h: Add unified __diag_ignore_all for GCC/LLVM

Add a __diag_ignore_all macro, to ignore warnings for both GCC and LLVM,
without having to specify the compiler type and version. By default, GCC
8 and clang 11 are used. This will be used by bpf subsystem to ignore
-Wmissing-prototypes warning for functions that are meant to be global
functions so that they are in vmlinux BTF, but don't have a prototype.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220304224645.3677453-7-memxor@gmail.com

show more ...

compiler-clang.h: Add __diag infrastructure for clang

Add __diag macros similar to those in compiler-gcc.h, so that warnings
that need to be adjusted for specific cases but not globally can be
ignor

compiler-clang.h: Add __diag infrastructure for clang

Add __diag macros similar to those in compiler-gcc.h, so that warnings
that need to be adjusted for specific cases but not globally can be
ignored when building with clang.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220304224645.3677453-6-memxor@gmail.com

[ Kartikeya: wrote commit message ]

show more ...

compiler.h: drop fallback overflow checkers

Once upgrading the minimum supported version of GCC to 5.1, we can drop
the fallback code for !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW.

This is effectively

compiler.h: drop fallback overflow checkers

Once upgrading the minimum supported version of GCC to 5.1, we can drop
the fallback code for !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW.

This is effectively a revert of commit f0907827a8a9 ("compiler.h: enable
builtin overflow checkers and add fallback code")

Link: https://github.com/ClangBuiltLinux/linux/issues/1438#issuecomment-916745801
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

kcov: add __no_sanitize_coverage to fix noinstr for all architectures

Until now no compiler supported an attribute to disable coverage
instrumentation as used by KCOV.

To work around this limitatio

kcov: add __no_sanitize_coverage to fix noinstr for all architectures

Until now no compiler supported an attribute to disable coverage
instrumentation as used by KCOV.

To work around this limitation on x86, noinstr functions have their
coverage instrumentation turned into nops by objtool. However, this
solution doesn't scale automatically to other architectures, such as
arm64, which are migrating to use the generic entry code.

Clang [1] and GCC [2] have added support for the attribute recently.
[1] https://github.com/llvm/llvm-project/commit/280333021e9550d80f5c1152a34e33e81df1e178
[2] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=cec4d4a6782c9bd8d071839c50a239c49caca689
The changes will appear in Clang 13 and GCC 12.

Add __no_sanitize_coverage for both compilers, and add it to noinstr.

Note: In the Clang case, __has_feature(coverage_sanitizer) is only true if
the feature is enabled, and therefore we do not require an additional
defined(CONFIG_KCOV) (like in the GCC case where __has_attribute(..) is
always true) to avoid adding redundant attributes to functions if KCOV is
off. That being said, compilers that support the attribute will not
generate errors/warnings if the attribute is redundantly used; however,
where possible let's avoid it as it reduces preprocessed code size and
associated compile-time overheads.

[elver@google.com: Implement __has_feature(coverage_sanitizer) in Clang]
Link: https://lkml.kernel.org/r/20210527162655.3246381-1-elver@google.com
[elver@google.com: add comment explaining __has_feature() in Clang]
Link: https://lkml.kernel.org/r/20210527194448.3470080-1-elver@google.com

Link: https://lkml.kernel.org/r/20210525175819.699786-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

cfi: add __cficanonical

With CONFIG_CFI_CLANG, the compiler replaces a function address taken
in C code with the address of a local jump table entry, which passes
runtime indirect call checks. Howev

cfi: add __cficanonical

With CONFIG_CFI_CLANG, the compiler replaces a function address taken
in C code with the address of a local jump table entry, which passes
runtime indirect call checks. However, the compiler won't replace
addresses taken in assembly code, which will result in a CFI failure
if we later jump to such an address in instrumented C code. The code
generated for the non-canonical jump table looks this:

<noncanonical.cfi_jt>: /* In C, &noncanonical points here */
jmp noncanonical
...
<noncanonical>: /* function body */
...

This change adds the __cficanonical attribute, which tells the
compiler to use a canonical jump table for the function instead. This
means the compiler will rename the actual function to <function>.cfi
and points the original symbol to the jump table entry instead:

<canonical>: /* jump table entry */
jmp canonical.cfi
...
<canonical.cfi>: /* function body */
...

As a result, the address taken in assembly, or other non-instrumented
code always points to the jump table and therefore, can be used for
indirect calls in instrumented code without tripping CFI checks.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> # pci.h
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-3-samitolvanen@google.com

show more ...

add support for Clang CFI

This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect fu

add support for Clang CFI

This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect function call to ensure
the target is a valid function with the correct static type. This
restricts possible call targets and makes it more difficult for
an attacker to exploit bugs that allow the modification of stored
function pointers. For more details, see:

https://clang.llvm.org/docs/ControlFlowIntegrity.html

Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain
visibility to possible call targets. Kernel modules are supported
with Clang’s cross-DSO CFI mode, which allows checking between
independently compiled components.

With CFI enabled, the compiler injects a __cfi_check() function into
the kernel and each module for validating local call targets. For
cross-module calls that cannot be validated locally, the compiler
calls the global __cfi_slowpath_diag() function, which determines
the target module and calls the correct __cfi_check() function. This
patch includes a slowpath implementation that uses __module_address()
to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a
shadow map that speeds up module look-ups by ~3x.

Clang implements indirect call checking using jump tables and
offers two methods of generating them. With canonical jump tables,
the compiler renames each address-taken function to <function>.cfi
and points the original symbol to a jump table entry, which passes
__cfi_check() validation. This isn’t compatible with stand-alone
assembly code, which the compiler doesn’t instrument, and would
result in indirect calls to assembly code to fail. Therefore, we
default to using non-canonical jump tables instead, where the compiler
generates a local jump table entry <function>.cfi_jt for each
address-taken function, and replaces all references to the function
with the address of the jump table entry.

Note that because non-canonical jump table addresses are local
to each component, they break cross-module function address
equality. Specifically, the address of a global function will be
different in each module, as it's replaced with the address of a local
jump table entry. If this address is passed to a different module,
it won’t match the address of the same function taken there. This
may break code that relies on comparing addresses passed from other
components.

CFI checking can be disabled in a function with the __nocfi attribute.
Additionally, CFI can be disabled for an entire compilation unit by
filtering out CC_FLAGS_CFI.

By default, CFI failures result in a kernel panic to stop a potential
exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the
kernel prints out a rate-limited warning instead, and allows execution
to continue. This option is helpful for locating type mismatches, but
should only be enabled during development.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com

show more ...

linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*

Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
definitions of the three HAVE_BUILTIN_BSWAP macros, which requires fallin

linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*

Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
definitions of the three HAVE_BUILTIN_BSWAP macros, which requires falling
back to the open-coded version and hoping that the compiler detects it.

Since all versions of clang support the __builtin_bswap interfaces, add
back the flags and have the headers pick these up automatically.

This results in a 4% improvement of compilation speed for arm defconfig.

Note: it might also be worth revisiting which architectures set
CONFIG_ARCH_USE_BUILTIN_BSWAP for one compiler or the other, today this is
set on six architectures (arm32, csky, mips, powerpc, s390, x86), while
another ten architectures define custom helpers (alpha, arc, ia64, m68k,
mips, nios2, parisc, sh, sparc, xtensa), and the rest (arm64, h8300,
hexagon, microblaze, nds32, openrisc, riscv) just get the unoptimized
version and rely on the compiler to detect it.

A long time ago, the compiler builtins were architecture specific, but
nowadays, all compilers that are able to build the kernel have correct
implementations of them, though some may not be as optimized as the inline
asm versions.

The patch that dropped the optimization landed in v4.19, so as discussed
it would be fairly safe to backport this revert to stable kernels to the
4.19/5.4/5.10 stable kernels, but there is a remaining risk for
regressions, and it has no known side-effects besides compile speed.

Link: https://lkml.kernel.org/r/20210226161151.2629097-1-arnd@kernel.org
Link: https://lore.kernel.org/lkml/20210225164513.3667778-1-arnd@kernel.org/
Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Guo Ren <guoren@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

kbuild: check the minimum compiler version in Kconfig

Paul Gortmaker reported a regression in the GCC version check. [1]
If you use GCC 4.8, the build breaks before showing the error message
"error

kbuild: check the minimum compiler version in Kconfig

Paul Gortmaker reported a regression in the GCC version check. [1]
If you use GCC 4.8, the build breaks before showing the error message
"error Sorry, your version of GCC is too old - please use 4.9 or newer."

I do not want to apply his fix-up since it implies we would not be able
to remove any cc-option test. Anyway, I admit checking the GCC version
in <linux/compiler-gcc.h> is too late.

Almost at the same time, Linus also suggested to move the compiler
version error to Kconfig time. [2]

I unified the two similar scripts, gcc-version.sh and clang-version.sh
into cc-version.sh. The old scripts invoked the compiler multiple times
(3 times for gcc-version.sh, 4 times for clang-version.sh). I refactored
the code so the new one invokes the compiler just once, and also tried
my best to use shell-builtin commands where possible.

The new script runs faster.

$ time ./scripts/clang-version.sh clang
120000

real 0m0.029s
user 0m0.012s
sys 0m0.021s

$ time ./scripts/cc-version.sh clang
Clang 120000

real 0m0.009s
user 0m0.006s
sys 0m0.004s

cc-version.sh also shows an error message if the compiler is too old:

$ make defconfig CC=clang-9
*** Default configuration is based on 'x86_64_defconfig'
***
*** Compiler is too old.
*** Your Clang version: 9.0.1
*** Minimum Clang version: 10.0.1
***
scripts/Kconfig.include:46: Sorry, this compiler is not supported.
make[1]: *** [scripts/kconfig/Makefile:81: defconfig] Error 1
make: *** [Makefile:602: defconfig] Error 2

The new script takes care of ICC because we have <linux/compiler-intel.h>
although I am not sure if building the kernel with ICC is well-supported.

[1]: https://lore.kernel.org/r/20210110190807.134996-1-paul.gortmaker@windriver.com
[2]: https://lore.kernel.org/r/CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com

Fixes: 87de84c9140e ("kbuild: remove cc-option test of -Werror=date-time")
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

show more ...

kcov: add __no_sanitize_coverage to fix noinstr for all architectures

[ Upstream commit 540540d06e9d9b3769b46d88def90f7e7c002322 ]

Until now no compiler supported an attribute to disable coverage
i

kcov: add __no_sanitize_coverage to fix noinstr for all architectures

[ Upstream commit 540540d06e9d9b3769b46d88def90f7e7c002322 ]

Until now no compiler supported an attribute to disable coverage
instrumentation as used by KCOV.

To work around this limitation on x86, noinstr functions have their
coverage instrumentation turned into nops by objtool. However, this
solution doesn't scale automatically to other architectures, such as
arm64, which are migrating to use the generic entry code.

Clang [1] and GCC [2] have added support for the attribute recently.
[1] https://github.com/llvm/llvm-project/commit/280333021e9550d80f5c1152a34e33e81df1e178
[2] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=cec4d4a6782c9bd8d071839c50a239c49caca689
The changes will appear in Clang 13 and GCC 12.

Add __no_sanitize_coverage for both compilers, and add it to noinstr.

Note: In the Clang case, __has_feature(coverage_sanitizer) is only true if
the feature is enabled, and therefore we do not require an additional
defined(CONFIG_KCOV) (like in the GCC case where __has_attribute(..) is
always true) to avoid adding redundant attributes to functions if KCOV is
off. That being said, compilers that support the attribute will not
generate errors/warnings if the attribute is redundantly used; however,
where possible let's avoid it as it reduces preprocessed code size and
associated compile-time overheads.

[elver@google.com: Implement __has_feature(coverage_sanitizer) in Clang]
Link: https://lkml.kernel.org/r/20210527162655.3246381-1-elver@google.com
[elver@google.com: add comment explaining __has_feature() in Clang]
Link: https://lkml.kernel.org/r/20210527194448.3470080-1-elver@google.com

Link: https://lkml.kernel.org/r/20210525175819.699786-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*

commit 97e4910232fa1f81e806aa60c25a0450276d99a2 upstream.

Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
definitions of

linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*

commit 97e4910232fa1f81e806aa60c25a0450276d99a2 upstream.

Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
definitions of the three HAVE_BUILTIN_BSWAP macros, which requires falling
back to the open-coded version and hoping that the compiler detects it.

Since all versions of clang support the __builtin_bswap interfaces, add
back the flags and have the headers pick these up automatically.

This results in a 4% improvement of compilation speed for arm defconfig.

Note: it might also be worth revisiting which architectures set
CONFIG_ARCH_USE_BUILTIN_BSWAP for one compiler or the other, today this is
set on six architectures (arm32, csky, mips, powerpc, s390, x86), while
another ten architectures define custom helpers (alpha, arc, ia64, m68k,
mips, nios2, parisc, sh, sparc, xtensa), and the rest (arm64, h8300,
hexagon, microblaze, nds32, openrisc, riscv) just get the unoptimized
version and rely on the compiler to detect it.

A long time ago, the compiler builtins were architecture specific, but
nowadays, all compilers that are able to build the kernel have correct
implementations of them, though some may not be as optimized as the inline
asm versions.

The patch that dropped the optimization landed in v4.19, so as discussed
it would be fairly safe to backport this revert to stable kernels to the
4.19/5.4/5.10 stable kernels, but there is a remaining risk for
regressions, and it has no known side-effects besides compile speed.

Link: https://lkml.kernel.org/r/20210226161151.2629097-1-arnd@kernel.org
Link: https://lore.kernel.org/lkml/20210225164513.3667778-1-arnd@kernel.org/
Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Guo Ren <guoren@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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compiler-clang: remove version check for BPF Tracing

bpftrace parses the kernel headers and uses Clang under the hood.

Remove the version check when __BPF_TRACING__ is defined (as bpftrace
does) so

compiler-clang: remove version check for BPF Tracing

bpftrace parses the kernel headers and uses Clang under the hood.

Remove the version check when __BPF_TRACING__ is defined (as bpftrace
does) so that this tool can continue to parse kernel headers, even with
older clang sources.

Fixes: commit 1f7a44f63e6c ("compiler-clang: add build check for clang 10.0.1")
Reported-by: Chen Yu <yu.chen.surf@gmail.com>
Reported-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lkml.kernel.org/r/20201104191052.390657-1-ndesaulniers@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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compiler.h: fix barrier_data() on clang

Commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") neglected to copy barrier_data() from
compiler-gcc.h into compiler-cla

compiler.h: fix barrier_data() on clang

Commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") neglected to copy barrier_data() from
compiler-gcc.h into compiler-clang.h.

The definition in compiler-gcc.h was really to work around clang's more
aggressive optimization, so this broke barrier_data() on clang, and
consequently memzero_explicit() as well.

For example, this results in at least the memzero_explicit() call in
lib/crypto/sha256.c:sha256_transform() being optimized away by clang.

Fix this by moving the definition of barrier_data() into compiler.h.

Also move the gcc/clang definition of barrier() into compiler.h,
__memory_barrier() is icc-specific (and barrier() is already defined
using it in compiler-intel.h) and doesn't belong in compiler.h.

[rdunlap@infradead.org: fix ALPHA builds when SMP is not enabled]

Link: https://lkml.kernel.org/r/20201101231835.4589-1-rdunlap@infradead.org
Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201014212631.207844-1-nivedita@alum.mit.edu
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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compiler-clang: add build check for clang 10.0.1

Patch series "set clang minimum version to 10.0.1", v3.

Adds a compile time #error to compiler-clang.h setting the effective
minimum supported versi

compiler-clang: add build check for clang 10.0.1

Patch series "set clang minimum version to 10.0.1", v3.

Adds a compile time #error to compiler-clang.h setting the effective
minimum supported version to clang 10.0.1. A separate patch has already
been picked up into the Documentation/ tree also confirming the version.

Next are a series of reverts. One for 32b arm is a partial revert.

Then Marco suggested fixes to KASAN docs.

Finally, improve the warning for GCC too as per Kees.

This patch (of 7):

During Plumbers 2020, we voted to just support the latest release of Clang
for now. Add a compile time check for this.

We plan to remove workarounds for older versions now, which will break in
subtle and not so subtle ways.

Suggested-by: Sedat Dilek <sedat.dilek@gmail.com>
Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Acked-by: Marco Elver <elver@google.com>
Acked-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20200902225911.209899-1-ndesaulniers@google.com
Link: https://lkml.kernel.org/r/20200902225911.209899-2-ndesaulniers@google.com
Link: https://github.com/ClangBuiltLinux/linux/issues/9
Link: https://github.com/ClangBuiltLinux/linux/issues/941
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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include/linux/compiler-clang.h: drop duplicated word in a comment

Drop the doubled word "the" in a comment.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@li

include/linux/compiler-clang.h: drop duplicated word in a comment

Drop the doubled word "the" in a comment.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Link: http://lkml.kernel.org/r/6a18c301-3505-742f-4dd7-0f38d0e537b9@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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compiler: Remove uninitialized_var() macro

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused vari

compiler: Remove uninitialized_var() macro

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

As recommended[2] by[3] Linus[4], remove the macro. With the recent
change to disable -Wmaybe-uninitialized in v5.7 in commit 78a5255ffb6a
("Stop the ad-hoc games with -Wno-maybe-initialized"), this is likely
the best time to make this treewide change.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Bart van Assche <bvanassche@acm.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

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compiler_types.h: Add __no_sanitize_{address,undefined} to noinstr

Adds the portable definitions for __no_sanitize_address, and
__no_sanitize_undefined, and subsequently changes noinstr to use the
a

compiler_types.h: Add __no_sanitize_{address,undefined} to noinstr

Adds the portable definitions for __no_sanitize_address, and
__no_sanitize_undefined, and subsequently changes noinstr to use the
attributes to disable instrumentation via KASAN or UBSAN.

Reported-by: syzbot+dc1fa714cb070b184db5@syzkaller.appspotmail.com
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://lore.kernel.org/lkml/000000000000d2474c05a6c938fe@google.com/

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scs: Add support for Clang's Shadow Call Stack (SCS)

This change adds generic support for Clang's Shadow Call Stack,
which uses a shadow stack to protect return addresses from being
overwritten by a

scs: Add support for Clang's Shadow Call Stack (SCS)

This change adds generic support for Clang's Shadow Call Stack,
which uses a shadow stack to protect return addresses from being
overwritten by an attacker. Details are available here:

https://clang.llvm.org/docs/ShadowCallStack.html

Note that security guarantees in the kernel differ from the ones
documented for user space. The kernel must store addresses of
shadow stacks in memory, which means an attacker capable reading
and writing arbitrary memory may be able to locate them and hijack
control flow by modifying the stacks.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
[will: Numerous cosmetic changes]
Signed-off-by: Will Deacon <will@kernel.org>

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kcsan: Improve various small stylistic details

Tidy up a few bits:

- Fix typos and grammar, improve wording.

- Remove spurious newlines that are col80 warning artifacts where the
resulting

kcsan: Improve various small stylistic details

Tidy up a few bits:

- Fix typos and grammar, improve wording.

- Remove spurious newlines that are col80 warning artifacts where the
resulting line-break is worse than the disease it's curing.

- Use core kernel coding style to improve readability and reduce
spurious code pattern variations.

- Use better vertical alignment for structure definitions and initialization
sequences.

- Misc other small details.

No change in functionality intended.

Cc: linux-kernel@vger.kernel.org
Cc: Marco Elver <elver@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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kcsan: Add Kernel Concurrency Sanitizer infrastructure

Kernel Concurrency Sanitizer (KCSAN) is a dynamic data-race detector for
kernel space. KCSAN is a sampling watchpoint-based data-race detector.

kcsan: Add Kernel Concurrency Sanitizer infrastructure

Kernel Concurrency Sanitizer (KCSAN) is a dynamic data-race detector for
kernel space. KCSAN is a sampling watchpoint-based data-race detector.
See the included Documentation/dev-tools/kcsan.rst for more details.

This patch adds basic infrastructure, but does not yet enable KCSAN for
any architecture.

Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR

Since commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") clang no longer reuses the OPTIMIZER_HIDE_VAR macro
fr

include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR

Since commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") clang no longer reuses the OPTIMIZER_HIDE_VAR macro
from compiler-gcc - instead it gets the version in
include/linux/compiler.h. Unfortunately that version doesn't actually
prevent compiler from optimizing out the variable.

Fix up by moving the macro out from compiler-gcc.h to compiler.h.
Compilers without incline asm support will keep working
since it's protected by an ifdef.

Also fix up comments to match reality since we are no longer overriding
any macros.

Build-tested with gcc and clang.

Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

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kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one

kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
that exists now);
2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.

The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
another hardware tag-based KASAN mode, that will rely on hardware memory
tagging support in arm64.

With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
instrument kernel files with -fsantize=kernel-hwaddress (except the ones
for which KASAN_SANITIZE := n is set).

Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.

This commit also adds empty placeholder (for now) implementation of
tag-based KASAN specific hooks inserted by the compiler and adjusts
common hooks implementation.

While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option
is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will
enable once all the infrastracture code has been added.

Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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