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    Subject[PATCH 5.17 182/343] x86/Kconfig: Do not allow CONFIG_X86_X32_ABI=y with llvm-objcopy
    Date
    From: Nathan Chancellor <nathan@kernel.org>

    [ Upstream commit aaeed6ecc1253ce1463fa1aca0b70a4ccbc9fa75 ]

    There are two outstanding issues with CONFIG_X86_X32_ABI and
    llvm-objcopy, with similar root causes:

    1. llvm-objcopy does not properly convert .note.gnu.property when going
    from x86_64 to x86_x32, resulting in a corrupted section when
    linking:

    https://github.com/ClangBuiltLinux/linux/issues/1141

    2. llvm-objcopy produces corrupted compressed debug sections when going
    from x86_64 to x86_x32, also resulting in an error when linking:

    https://github.com/ClangBuiltLinux/linux/issues/514

    After commit 41c5ef31ad71 ("x86/ibt: Base IBT bits"), the
    .note.gnu.property section is always generated when
    CONFIG_X86_KERNEL_IBT is enabled, which causes the first issue to become
    visible with an allmodconfig build:

    ld.lld: error: arch/x86/entry/vdso/vclock_gettime-x32.o:(.note.gnu.property+0x1c): program property is too short

    To avoid this error, do not allow CONFIG_X86_X32_ABI to be selected when
    using llvm-objcopy. If the two issues ever get fixed in llvm-objcopy,
    this can be turned into a feature check.

    Signed-off-by: Nathan Chancellor <nathan@kernel.org>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lore.kernel.org/r/20220314194842.3452-3-nathan@kernel.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/Kconfig | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index 9f5bd41bf660..d0ecc4005df3 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -2837,6 +2837,11 @@ config IA32_AOUT
    config X86_X32
    bool "x32 ABI for 64-bit mode"
    depends on X86_64
    + # llvm-objcopy does not convert x86_64 .note.gnu.property or
    + # compressed debug sections to x86_x32 properly:
    + # https://github.com/ClangBuiltLinux/linux/issues/514
    + # https://github.com/ClangBuiltLinux/linux/issues/1141
    + depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm)
    help
    Include code to run binaries for the x32 native 32-bit ABI
    for 64-bit processors. An x32 process gets access to the
    --
    2.35.1


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