[PATCH 6/8] stackleak: Support Clang stack depth tracking

[Kees Cook]

Wire up CONFIG_STACKLEAK 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 at kernel.org>
---
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Masahiro Yamada <masahiroy at kernel.org>
Cc: Nathan Chancellor <nathan at kernel.org>
Cc: Nicolas Schier <nicolas.schier at linux.dev>
Cc: Marco Elver <elver at google.com>
Cc: Andrey Konovalov <andreyknvl at gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a at gmail.com>
Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: "Gustavo A. R. Silva" <gustavoars at kernel.org>
Cc: <linux-kbuild at vger.kernel.org>
Cc: <kasan-dev at googlegroups.com>
Cc: <linux-hardening at vger.kernel.org>
---
 security/Kconfig.hardening | 5 ++++-
 scripts/Makefile.stackleak | 6 ++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 2be6aed71c92..94aa8612c4e4 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -158,10 +158,13 @@ config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 	  initialized. Since not all existing initializers are detected
 	  by the plugin, this can produce false positive warnings.
 
+config CC_HAS_SANCOV_STACK_DEPTH_CALLBACK
+	def_bool $(cc-option,-fsanitize-coverage-stack-depth-callback-min=1)
+
 config STACKLEAK
 	bool "Poison kernel stack before returning from syscalls"
 	depends on HAVE_ARCH_STACKLEAK
-	depends on GCC_PLUGINS
+	depends on GCC_PLUGINS || CC_HAS_SANCOV_STACK_DEPTH_CALLBACK
 	help
 	  This option makes the kernel erase the kernel stack before
 	  returning from system calls. This has the effect of leaving
diff --git a/scripts/Makefile.stackleak b/scripts/Makefile.stackleak
index 1db0835b29d4..639cc32bcd1d 100644
--- a/scripts/Makefile.stackleak
+++ b/scripts/Makefile.stackleak
@@ -8,6 +8,12 @@ stackleak-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) += -fplugin-arg-stacklea
 DISABLE_STACKLEAK  := -fplugin-arg-stackleak_plugin-disable
 endif
 
+ifdef CONFIG_CC_IS_CLANG
+stackleak-cflags-y += -fsanitize-coverage=stack-depth
+stackleak-cflags-y += -fsanitize-coverage-stack-depth-callback-min=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE)
+DISABLE_STACKLEAK  := -fno-sanitize-coverage=stack-depth
+endif
+
 STACKLEAK_CFLAGS   := $(stackleak-cflags-y)
 
 export STACKLEAK_CFLAGS DISABLE_STACKLEAK
-- 
2.34.1