Commit 6676fd3c authored Jul 26, 2025 by Kees Cook

kstack_erase: Add -mgeneral-regs-only to silence Clang warnings

Once CONFIG_KSTACK_ERASE is enabled with Clang on i386, the build warns:

kernel/kstack_erase.c:168:2: warning: function with attribute 'no_caller_saved_registers' should only call a function with attribute 'no_caller_saved_registers' or be compiled with '-mgeneral-regs-only' [-Wexcessive-regsave]

Add -mgeneral-regs-only for the kstack_erase handler, to make Clang feel
better (it is effectively a no-op flag for the kernel). No binary
changes encountered.

Build & boot tested with Clang 21 on x86_64, and i386.
Build tested with GCC 14.2.0 on x86_64, i386, arm64, and arm.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/all/20250726004313.GA3650901@ax162

Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <kees@kernel.org>

parent 381a38ea

kernel/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -140,6 +140,7 @@ obj-$(CONFIG_RESOURCE_KUNIT_TEST) += resource_kunit.o
		obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o

		CFLAGS_kstack_erase.o += $(DISABLE_KSTACK_ERASE)
		CFLAGS_kstack_erase.o += $(call cc-option,-mgeneral-regs-only)
		obj-$(CONFIG_KSTACK_ERASE) += kstack_erase.o
		KASAN_SANITIZE_kstack_erase.o := n
		KCSAN_SANITIZE_kstack_erase.o := n