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

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Message-Id: <20250507181615.1947159-2-kees@kernel.org>
Date: Wed,  7 May 2025 11:16:08 -0700
From: Kees Cook <kees@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Kees Cook <kees@...nel.org>,
	Marco Elver <elver@...gle.com>,
	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>,
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Subject: [PATCH 2/8] init.h: Disable sanitizer coverage for __init and __head

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.

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>
---
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