linux.git/scripts/Makefile.kasan, branch v6.12.80

kasan: fix GCC mem-intrinsic prefix with sw tags

2025-09-09T16:58:16+00:00

commit 51337a9a3a404fde0f5337662ffc7699793dfeb5 upstream.

GCC doesn't support "hwasan-kernel-mem-intrinsic-prefix", only
"asan-kernel-mem-intrinsic-prefix"[0], while LLVM supports both.  This is
already taken into account when checking
"CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX", but not in the KASAN Makefile
adding those parameters when "CONFIG_KASAN_SW_TAGS" is enabled.

Replace the version check with "CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX",
which already validates that mem-intrinsic prefix parameter can be used,
and choose the correct name depending on compiler.

GCC 13 and above trigger "CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX" which
prevents `mem{cpy,move,set}()` being redefined in "mm/kasan/shadow.c"
since commit 36be5cba99f6 ("kasan: treat meminstrinsic as builtins in
uninstrumented files"), as we expect the compiler to prefix those calls
with `__(hw)asan_` instead.  But as the option passed to GCC has been
incorrect, the compiler has not been emitting those prefixes, effectively
never calling the instrumented versions of `mem{cpy,move,set}()` with
"CONFIG_KASAN_SW_TAGS" enabled.

If "CONFIG_FORTIFY_SOURCES" is enabled, this issue would be mitigated as
it redefines `mem{cpy,move,set}()` and properly aliases the
`__underlying_mem*()` that will be called to the instrumented versions.

Link: https://lkml.kernel.org/r/20250821120735.156244-1-ada.coupriediaz@arm.com
Link: https://gcc.gnu.org/onlinedocs/gcc-13.4.0/gcc/Optimize-Options.html [0]
Signed-off-by: Ada Couprie Diaz 
Fixes: 36be5cba99f6 ("kasan: treat meminstrinsic as builtins in uninstrumented files")
Reviewed-by: Yeoreum Yun 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Andrey Ryabinin 
Cc: Dmitriy Vyukov 
Cc: Marco Elver 
Cc: Marc Rutland 
Cc: Michael Ellerman 
Cc: Nathan Chancellor 
Cc: Vincenzo Frascino 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

kbuild: rust: Enable KASAN support

2024-09-16T16:04:37+00:00

Rust supports KASAN via LLVM, but prior to this patch, the flags aren't
set properly.

Suggested-by: Miguel Ojeda 
Signed-off-by: Matthew Maurer 
Reviewed-by: Andrey Konovalov 
Link: https://lore.kernel.org/r/20240820194910.187826-4-mmaurer@google.com
[ Applied "SW_TAGS KASAN" nit. - Miguel ]
Signed-off-by: Miguel Ojeda

kasan: simplify and clarify Makefile

2024-09-16T16:04:32+00:00

When KASAN support was being added to the Linux kernel, GCC did not yet
support all of the KASAN-related compiler options. Thus, the KASAN
Makefile had to probe the compiler for supported options.

Nowadays, the Linux kernel GCC version requirement is 5.1+, and thus we
don't need the probing of the -fasan-shadow-offset parameter: it exists in
all 5.1+ GCCs.

Simplify the KASAN Makefile to drop CFLAGS_KASAN_MINIMAL.

Also add a few more comments and unify the indentation.

Signed-off-by: Andrey Konovalov 
Acked-by: Marco Elver 
Link: https://lore.kernel.org/r/20240814161052.10374-1-andrey.konovalov@linux.dev
Signed-off-by: Miguel Ojeda

kasan: remove hwasan-kernel-mem-intrinsic-prefix=1 for clang-14

2023-04-18T23:29:43+00:00

Some unknown -mllvm options (i.e.  those starting with the letter "h")
don't cause an error to be returned by clang, so the cc-option helper adds
the unknown hwasan-kernel-mem-intrinsic-prefix=1 flag to CFLAGS with
compilers that are new enough for hwasan but too old for this option.

This causes a rather unreadable build failure:

fixdep: error opening file: scripts/mod/.empty.o.d: No such file or directory
make[4]: *** [/home/arnd/arm-soc/scripts/Makefile.build:252: scripts/mod/empty.o] Error 2
fixdep: error opening file: scripts/mod/.devicetable-offsets.s.d: No such file or directory
make[4]: *** [/home/arnd/arm-soc/scripts/Makefile.build:114: scripts/mod/devicetable-offsets.s] Error 2

Add a version check to only allow this option with clang-15, gcc-13
or later versions.

Link: https://lkml.kernel.org/r/20230418122350.1646391-1-arnd@kernel.org
Fixes: 51287dcb00cc ("kasan: emit different calls for instrumentable memintrinsics")
Link: https://lore.kernel.org/all/CANpmjNMwYosrvqh4ogDO8rgn+SeDHM2b-shD21wTypm_6MMe=g@mail.gmail.com/
Signed-off-by: Arnd Bergmann 
Reviewed-by: Marco Elver 
Reviewed-by: Nathan Chancellor 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Andrey Ryabinin 
Cc: Dmitry Vyukov 
Cc: Masahiro Yamada 
Cc: Michael Ellerman 
Cc: Nick Desaulniers 
Cc: Nicolas Schier 
Cc: Peter Zijlstra 
Cc: Tom Rix 
Cc: Vincenzo Frascino 
Signed-off-by: Andrew Morton

kasan: treat meminstrinsic as builtins in uninstrumented files

2023-03-03T05:54:22+00:00

Where the compiler instruments meminstrinsics by generating calls to
__asan/__hwasan_ prefixed functions, let the compiler consider
memintrinsics as builtin again.

To do so, never override memset/memmove/memcpy if the compiler does the
correct instrumentation - even on !GENERIC_ENTRY architectures.

[elver@google.com: powerpc: don't rename memintrinsics if compiler adds prefixes]
  Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/ [1]
  Link: https://lkml.kernel.org/r/20230227094726.3833247-1-elver@google.com
Link: https://lkml.kernel.org/r/20230224085942.1791837-2-elver@google.com
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver 
Reviewed-by: Andrey Konovalov 
Tested-by: Linux Kernel Functional Testing 
Tested-by: Naresh Kamboju 
Acked-by: Michael Ellerman  (powerpc)
Cc: Alexander Potapenko 
Cc: Andrey Ryabinin 
Cc: Borislav Petkov (AMD) 
Cc: Dave Hansen 
Cc: Dmitry Vyukov 
Cc: Ingo Molnar 
Cc: Jakub Jelinek 
Cc: Kees Cook 
Cc: Nathan Chancellor 
Cc: Nick Desaulniers 
Cc: Nicolas Schier 
Cc: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Cc: Vincenzo Frascino 
Signed-off-by: Andrew Morton

kasan: emit different calls for instrumentable memintrinsics

2023-03-03T05:54:22+00:00

Clang 15 provides an option to prefix memcpy/memset/memmove calls with
__asan_/__hwasan_ in instrumented functions:
https://reviews.llvm.org/D122724

GCC will add support in future:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777

Use it to regain KASAN instrumentation of memcpy/memset/memmove on
architectures that require noinstr to be really free from instrumented
mem*() functions (all GENERIC_ENTRY architectures).

Link: https://lkml.kernel.org/r/20230224085942.1791837-1-elver@google.com
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver 
Acked-by: Peter Zijlstra (Intel) 
Reviewed-by: Andrey Konovalov 
Tested-by: Linux Kernel Functional Testing 
Tested-by: Naresh Kamboju 
Cc: Alexander Potapenko 
Cc: Andrey Ryabinin 
Cc: Borislav Petkov (AMD) 
Cc: Dave Hansen 
Cc: Dmitry Vyukov 
Cc: Ingo Molnar 
Cc: Jakub Jelinek 
Cc: kasan-dev@googlegroups.com
Cc: Kees Cook 
Cc: Linux Kernel Functional Testing 
Cc: Nathan Chancellor  # build only
Cc: Nick Desaulniers 
Cc: Nicolas Schier 
Cc: Thomas Gleixner 
Cc: Vincenzo Frascino 
Signed-off-by: Andrew Morton

kasan: always respect CONFIG_KASAN_STACK

2021-09-24T23:13:35+00:00

Currently, the asan-stack parameter is only passed along if
CFLAGS_KASAN_SHADOW is not empty, which requires KASAN_SHADOW_OFFSET to
be defined in Kconfig so that the value can be checked.  In RISC-V's
case, KASAN_SHADOW_OFFSET is not defined in Kconfig, which means that
asan-stack does not get disabled with clang even when CONFIG_KASAN_STACK
is disabled, resulting in large stack warnings with allmodconfig:

  drivers/video/fbdev/omap2/omapfb/displays/panel-lgphilips-lb035q02.c:117:12: error: stack frame size (14400) exceeds limit (2048) in function 'lb035q02_connect' [-Werror,-Wframe-larger-than]
  static int lb035q02_connect(struct omap_dss_device *dssdev)
             ^
  1 error generated.

Ensure that the value of CONFIG_KASAN_STACK is always passed along to
the compiler so that these warnings do not happen when
CONFIG_KASAN_STACK is disabled.

Link: https://github.com/ClangBuiltLinux/linux/issues/1453
References: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 and earlier")
Link: https://lkml.kernel.org/r/20210922205525.570068-1-nathan@kernel.org
Signed-off-by: Nathan Chancellor 
Reviewed-by: Marco Elver 
Cc: Andrey Ryabinin 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Dmitry Vyukov 
Cc: Nick Desaulniers 
Cc: Arnd Bergmann 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kasan: arm64: support specialized outlined tag mismatch checks

2021-05-26T22:31:26+00:00

By using outlined checks we can achieve a significant code size
improvement by moving the tag-based ASAN checks into separate
functions. Unlike the existing CONFIG_KASAN_OUTLINE mode these
functions have a custom calling convention that preserves most
registers and is specialized to the register containing the address
and the type of access, and as a result we can eliminate the code
size and performance overhead of a standard calling convention such
as AAPCS for these functions.

This change depends on a separate series of changes to Clang [1] to
support outlined checks in the kernel, although the change works fine
without them (we just don't get outlined checks). This is because the
flag -mllvm -hwasan-inline-all-checks=0 has no effect until the Clang
changes land. The flag was introduced in the Clang 9.0 timeframe as
part of the support for outlined checks in userspace and because our
minimum Clang version is 10.0 we can pass it unconditionally.

Outlined checks require a new runtime function with a custom calling
convention. Add this function to arch/arm64/lib.

I measured the code size of defconfig + tag-based KASAN, as well
as boot time (i.e. time to init launch) on a DragonBoard 845c with
an Android arm64 GKI kernel. The results are below:

                               code size    boot time
CONFIG_KASAN_INLINE=y before    92824064      6.18s
CONFIG_KASAN_INLINE=y after     38822400      6.65s
CONFIG_KASAN_OUTLINE=y          39215616     11.48s

We can see straight away that specialized outlined checks beat the
existing CONFIG_KASAN_OUTLINE=y on both code size and boot time
for tag-based ASAN.

As for the comparison between CONFIG_KASAN_INLINE=y before and after
we saw similar performance numbers in userspace [2] and decided
that since the performance overhead is minimal compared to the
overhead of tag-based ASAN itself as well as compared to the code
size improvements we would just replace the inlined checks with the
specialized outlined checks without the option to select between them,
and that is what I have implemented in this patch.

Signed-off-by: Peter Collingbourne 
Acked-by: Andrey Konovalov 
Reviewed-by: Mark Rutland 
Tested-by: Mark Rutland 
Link: https://linux-review.googlesource.com/id/I1a30036c70ab3c3ee78d75ed9b87ef7cdc3fdb76
Link: [1] https://reviews.llvm.org/D90426
Link: [2] https://reviews.llvm.org/D56954
Link: https://lore.kernel.org/r/20210526174927.2477847-3-pcc@google.com
Signed-off-by: Will Deacon

kasan: remove redundant config option

2021-04-16T23:10:36+00:00

CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
instrumentation, but we should only need one config, so that we remove
CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable.  see [1].

When enable KASAN stack instrumentation, then for gcc we could do no
prompt and default value y, and for clang prompt and default value n.

This patch fixes the following compilation warning:

  include/linux/kasan.h:333:30: warning: 'CONFIG_KASAN_STACK' is not defined, evaluates to 0 [-Wundef]

[akpm@linux-foundation.org: fix merge snafu]

Link: https://bugzilla.kernel.org/show_bug.cgi?id=210221 [1]
Link: https://lkml.kernel.org/r/20210226012531.29231-1-walter-zh.wu@mediatek.com
Fixes: d9b571c885a8 ("kasan: fix KASAN_STACK dependency for HW_TAGS")
Signed-off-by: Walter Wu 
Suggested-by: Dmitry Vyukov 
Reviewed-by: Nathan Chancellor 
Acked-by: Arnd Bergmann 
Reviewed-by: Andrey Konovalov 
Cc: Andrey Ryabinin 
Cc: Dmitry Vyukov 
Cc: Alexander Potapenko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kasan: fix hwasan build for gcc

2021-04-16T23:10:36+00:00

gcc-11 adds support for -fsanitize=kernel-hwaddress, so it becomes
possible to enable CONFIG_KASAN_SW_TAGS.

Unfortunately this fails to build at the moment, because the
corresponding command line arguments use llvm specific syntax.

Change it to use the cc-param macro instead, which works on both clang
and gcc.

[elver@google.com: fixup for "kasan: fix hwasan build for gcc"]
  Link: https://lkml.kernel.org/r/YHQZVfVVLE/LDK2v@elver.google.com

Link: https://lkml.kernel.org/r/20210323124112.1229772-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann 
Signed-off-by: Marco Elver 
Reviewed-by: Marco Elver 
Acked-by: Andrey Konovalov 
Cc: Masahiro Yamada 
Cc: Michal Marek 
Cc: Andrey Ryabinin 
Cc: Nathan Chancellor 
Cc: Nick Desaulniers 
Cc: Alexander Potapenko 
Cc: Dmitry Vyukov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds