linux-kernel - Re: [PATCH 2/8] init.h: Disable sanitizer coverage for __init and _

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Message-ID: <CANpmjNPcYPvnQzMT3p+Vc2=EiEbR1WnykUEjuYc0bH2HOFi6HQ@mail.gmail.com>
Date: Thu, 8 May 2025 14:22:47 +0200
From: Marco Elver <elver@...gle.com>
To: Kees Cook <kees@...nel.org>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Alexander Potapenko <glider@...gle.com>, Aleksandr Nogikh <nogikh@...gle.com>
Cc: Arnd Bergmann <arnd@...db.de>, Andrey Konovalov <andreyknvl@...il.com>, 
	Andrey Ryabinin <ryabinin.a.a@...il.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Hou Wenlong <houwenlong.hwl@...group.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Masahiro Yamada <masahiroy@...nel.org>, 
	"Peter Zijlstra (Intel)" <peterz@...radead.org>, Luis Chamberlain <mcgrof@...nel.org>, 
	Sami Tolvanen <samitolvanen@...gle.com>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	kasan-dev@...glegroups.com, "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
	Christoph Hellwig <hch@....de>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, linux-riscv@...ts.infradead.org, 
	linux-s390@...r.kernel.org, linux-efi@...r.kernel.org, 
	linux-hardening@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-security-module@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	sparclinux@...r.kernel.org, llvm@...ts.linux.dev, 
	syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH 2/8] init.h: Disable sanitizer coverage for __init and __head

+Cc KCOV maintainers

On Wed, 7 May 2025 at 20:16, Kees Cook <kees@...nel.org> wrote:
>
> While __noinstr already contained __no_sanitize_coverage, it needs to
> be added to __init and __head section markings to support the Clang
> implementation of CONFIG_STACKLEAK. This is to make sure the stack depth
> tracking callback is not executed in unsupported contexts.
>
> The other sanitizer coverage options (trace-pc and trace-cmp) aren't
> needed in __head nor __init either ("We are interested in code coverage
> as a function of a syscall inputs"[1]), so this appears safe to disable
> for them as well.

@ Dmitry, Aleksandr - Will this produce some unwanted side-effects for
syzbot? I also think it's safe, but just double checking.

> Link: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/kcov.c?h=v6.14#n179 [1]
> Signed-off-by: Kees Cook <kees@...nel.org>

Acked-by: Marco Elver <elver@...gle.com>

> ---
> Cc: Marco Elver <elver@...gle.com>
> Cc: Andrey Konovalov <andreyknvl@...il.com>
> Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: <x86@...nel.org>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Hou Wenlong <houwenlong.hwl@...group.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Masahiro Yamada <masahiroy@...nel.org>
> Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
> Cc: Luis Chamberlain <mcgrof@...nel.org>
> Cc: Sami Tolvanen <samitolvanen@...gle.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: <kasan-dev@...glegroups.com>
> ---
>  arch/x86/include/asm/init.h | 2 +-
>  include/linux/init.h        | 4 +++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
> index 8b1b1abcef15..6bfdaeddbae8 100644
> --- a/arch/x86/include/asm/init.h
> +++ b/arch/x86/include/asm/init.h
> @@ -5,7 +5,7 @@
>  #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000
>  #define __head __section(".head.text") __no_sanitize_undefined __no_stack_protector
>  #else
> -#define __head __section(".head.text") __no_sanitize_undefined
> +#define __head __section(".head.text") __no_sanitize_undefined __no_sanitize_coverage
>  #endif
>
>  struct x86_mapping_info {
> diff --git a/include/linux/init.h b/include/linux/init.h
> index ee1309473bc6..c65a050d52a7 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -49,7 +49,9 @@
>
>  /* These are for everybody (although not all archs will actually
>     discard it in modules) */
> -#define __init         __section(".init.text") __cold  __latent_entropy __noinitretpoline
> +#define __init         __section(".init.text") __cold __latent_entropy \
> +                                               __noinitretpoline       \
> +                                               __no_sanitize_coverage
>  #define __initdata     __section(".init.data")
>  #define __initconst    __section(".init.rodata")
>  #define __exitdata     __section(".exit.data")
> --
> 2.34.1
>