diff options
| author | Nathan Chancellor <nathan@kernel.org> | 2021-07-12 14:46:37 -0700 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-07-13 16:31:31 +0100 |
| commit | 8cdd23c23c3d481a43b4aa03dcb5738812831115 (patch) | |
| tree | 42880cdc96c3cca8f652b6e76bcba4cefd390f6c /arch | |
| parent | c1132702c71f4b95db9435bac5fdc912881563e0 (diff) | |
arm64: Restrict ARM64_BTI_KERNEL to clang 12.0.0 and newer
Commit 97fed779f2a6 ("arm64: bti: Provide Kconfig for kernel mode BTI")
disabled CONFIG_ARM64_BTI_KERNEL when CONFIG_GCOV_KERNEL was enabled and
compiling with clang because of warnings that were seen with
allmodconfig because LLVM was not emitting PAC/BTI instructions for
compiler generated functions:
| warning: some functions compiled with BTI and some compiled without BTI
| warning: not setting BTI in feature flags
This dependency was fine for avoiding the warnings with allmodconfig
until commit 51c2ee6d121c ("Kconfig: Introduce ARCH_WANTS_NO_INSTR and
CC_HAS_NO_PROFILE_FN_ATTR"), which prevents CONFIG_GCOV_KERNEL from
being enabled with clang 12.0.0 or older because those versions do not
support the no_profile_instrument_function attribute.
As a result, CONFIG_ARM64_BTI_KERNEL gets enabled with allmodconfig and
there are more warnings like the ones above due to CONFIG_KASAN, which
suffers from the same problem as CONFIG_GCOV_KERNEL. This was most
likely not noticed at the time because allmodconfig +
CONFIG_GCOV_KERNEL=n was not tested. defconfig + CONFIG_KASAN=y is
enough to reproduce the same warnings as above.
The root cause of the warnings was resolved in LLVM during the 12.0.0
release so rather than play whack-a-mole with the dependencies, just
update CONFIG_ARM64_BTI_KERNEL to require clang 12.0.0, which will have
all of the issues ironed out.
Link: https://github.com/ClangBuiltLinux/linux/issues/1428
Link: https://github.com/ClangBuiltLinux/continuous-integration2/runs/3010034706?check_suite_focus=true
Link: https://github.com/ClangBuiltLinux/continuous-integration2/runs/3010035725?check_suite_focus=true
Link: https://github.com/llvm/llvm-project/commit/a88c722e687e6780dcd6a58718350dc76fcc4cc9
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20210712214636.3134425-1-nathan@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/Kconfig | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index e07e7de9ac49..b5b13a932561 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1605,7 +1605,8 @@ config ARM64_BTI_KERNEL depends on CC_HAS_BRANCH_PROT_PAC_RET_BTI # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94697 depends on !CC_IS_GCC || GCC_VERSION >= 100100 - depends on !(CC_IS_CLANG && GCOV_KERNEL) + # https://github.com/llvm/llvm-project/commit/a88c722e687e6780dcd6a58718350dc76fcc4cc9 + depends on !CC_IS_CLANG || CLANG_VERSION >= 120000 depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_REGS) help Build the kernel with Branch Target Identification annotations |