lkml.org 
[lkml]   [2022]   [Sep]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.10 034/141] arm64: Restrict ARM64_BTI_KERNEL to clang 12.0.0 and newer
    Date
    From: Nathan Chancellor <nathan@kernel.org>

    [ Upstream commit 8cdd23c23c3d481a43b4aa03dcb5738812831115 ]

    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>
    Stable-dep-of: c0a454b9044f ("arm64/bti: Disable in kernel BTI when cross section thunks are broken")
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm64/Kconfig | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
    index 1116a8d092c0..662311a513f0 100644
    --- a/arch/arm64/Kconfig
    +++ b/arch/arm64/Kconfig
    @@ -1654,7 +1654,8 @@ 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
    --
    2.35.1


    \
     
     \ /
      Last update: 2022-09-26 12:56    [W:3.843 / U:0.040 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site