linux-kernel - [PATCH v2 12/14] kstack_erase: Support Clang stack depth tracking

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Message-Id: <20250523043935.2009972-12-kees@kernel.org>
Date: Thu, 22 May 2025 21:39:22 -0700
From: Kees Cook <kees@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Kees Cook <kees@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Marco Elver <elver@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-kbuild@...r.kernel.org,
	kasan-dev@...glegroups.com,
	linux-hardening@...r.kernel.org,
	Christoph Hellwig <hch@....de>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	linux-kernel@...r.kernel.org,
	x86@...nel.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-security-module@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	sparclinux@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH v2 12/14] kstack_erase: Support Clang stack depth tracking

Wire up CONFIG_KSTACK_ERASE to Clang 21's new stack depth tracking
callback[1] option.

Link: https://clang.llvm.org/docs/SanitizerCoverage.html#tracing-stack-depth [1]
Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Masahiro Yamada <masahiroy@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nicolas Schier <nicolas.schier@...ux.dev>
Cc: Marco Elver <elver@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: <linux-kbuild@...r.kernel.org>
Cc: <kasan-dev@...glegroups.com>
Cc: <linux-hardening@...r.kernel.org>
---
 security/Kconfig.hardening    | 5 ++++-
 scripts/Makefile.kstack_erase | 6 ++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index f7aa2024ab25..b9a5bc3430aa 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -82,10 +82,13 @@ choice
 
 endchoice
 
+config CC_HAS_SANCOV_STACK_DEPTH_CALLBACK
+	def_bool $(cc-option,-fsanitize-coverage-stack-depth-callback-min=1)
+
 config KSTACK_ERASE
 	bool "Poison kernel stack before returning from syscalls"
 	depends on HAVE_ARCH_KSTACK_ERASE
-	depends on GCC_PLUGINS
+	depends on GCC_PLUGINS || CC_HAS_SANCOV_STACK_DEPTH_CALLBACK
 	help
 	  This option makes the kernel erase the kernel stack before
 	  returning from system calls. This has the effect of leaving
diff --git a/scripts/Makefile.kstack_erase b/scripts/Makefile.kstack_erase
index 5223d3a35817..c7bc2379e113 100644
--- a/scripts/Makefile.kstack_erase
+++ b/scripts/Makefile.kstack_erase
@@ -8,6 +8,12 @@ kstack-erase-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) += -fplugin-arg-stack
 DISABLE_KSTACK_ERASE := -fplugin-arg-stackleak_plugin-disable
 endif
 
+ifdef CONFIG_CC_IS_CLANG
+kstack-erase-cflags-y += -fsanitize-coverage=stack-depth
+kstack-erase-cflags-y += -fsanitize-coverage-stack-depth-callback-min=$(CONFIG_KSTACK_ERASE_TRACK_MIN_SIZE)
+DISABLE_KSTACK_ERASE  := -fno-sanitize-coverage=stack-depth
+endif
+
 KSTACK_ERASE_CFLAGS   := $(kstack-erase-cflags-y)
 
 export STACKLEAK_CFLAGS DISABLE_KSTACK_ERASE
-- 
2.34.1