Messages in this thread | | | Date | Fri, 30 Jul 2021 15:59:36 -0700 | From | Fangrui Song <> | Subject | Re: [PATCH] vmlinux.lds.h: Handle clang's module.{c,d}tor sections |
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On 2021-07-30, Nick Desaulniers wrote: >On Fri, Jul 30, 2021 at 3:38 PM Nathan Chancellor <nathan@kernel.org> wrote: >> >> A recent change in LLVM causes module_{c,d}tor sections to appear when >> CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings >> because these are not handled anywhere: >> >> ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor' >> ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor' >> ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor' > >^ .text.tsan.*
I was wondering why the orphan section warning only arose recently. Now I see: the function asan.module_ctor has the SHF_GNU_RETAIN flag, so it is in a separate section even with -fno-function-sections (default).
It seems that with -ffunction-sections the issue should have been caught much earlier.
>> >> Place them in the TEXT_TEXT section so that these technologies continue >> to work with the newer compiler versions. All of the KASAN and KCSAN >> KUnit tests continue to pass after this change. >> >> Cc: stable@vger.kernel.org >> Link: https://github.com/ClangBuiltLinux/linux/issues/1432 >> Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865 >> Signed-off-by: Nathan Chancellor <nathan@kernel.org> >> --- >> include/asm-generic/vmlinux.lds.h | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h >> index 17325416e2de..3b79b1e76556 100644 >> --- a/include/asm-generic/vmlinux.lds.h >> +++ b/include/asm-generic/vmlinux.lds.h >> @@ -586,6 +586,7 @@ >> NOINSTR_TEXT \ >> *(.text..refcount) \ >> *(.ref.text) \ >> + *(.text.asan .text.asan.*) \ > >Will this match .text.tsan.module_ctor?
asan.module_ctor is the only function AddressSanitizer synthesizes in the instrumented translation unit. There is no function called "asan".
(Even if a function "asan" exists due to -ffunction-sections -funique-section-names, TEXT_MAIN will match .text.asan, so the .text.asan pattern will match nothing.)
>Do we want to add these conditionally on >CONFIG_KASAN_GENERIC/CONFIG_KCSAN like we do for SANITIZER_DISCARDS? > >> TEXT_CFI_JT \ >> MEM_KEEP(init.text*) \ >> MEM_KEEP(exit.text*) \ >> >> base-commit: 4669e13cd67f8532be12815ed3d37e775a9bdc16 >> -- > > >-- >Thanks, >~Nick Desaulniers
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