linux-kernel - Re: [PATCH] vmlinux.lds.h: Handle clang's module.{c,d}tor sections

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Date:   Fri, 30 Jul 2021 15:42:08 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        Fangrui Song <maskray@...gle.com>,
        Marco Elver <elver@...gle.com>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        clang-built-linux@...glegroups.com, stable@...r.kernel.org
Subject: Re: [PATCH] vmlinux.lds.h: Handle clang's module.{c,d}tor sections

On Fri, Jul 30, 2021 at 3:38 PM Nathan Chancellor <nathan@...nel.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.*

>
> 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@...r.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@...nel.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?

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