Messages in this thread | | | Subject | Re: [PATCH] vmlinux.lds.h: Handle clang's module.{c,d}tor sections | From | Nathan Chancellor <> | Date | Fri, 30 Jul 2021 17:32:33 -0700 |
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On 7/30/2021 3:59 PM, Fangrui Song wrote: > 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).
Thanks for the explanation, I will add this to the commit message.
> 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?
No, I forgot to test CONFIG_KCSAN with this version, rather than the prior one I had on GitHub so I will send v2 shortly.
> 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.)
Sounds good, I will update it to remove the .text.asan and replace it with .text.tsan.*
>> Do we want to add these conditionally on >> CONFIG_KASAN_GENERIC/CONFIG_KCSAN like we do for SANITIZER_DISCARDS?
I do not think there is a point in doing so but I can if others feel strongly.
Thank you both for the comments for the comments!
Cheers, Nathan
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