* [PATCH] kstack_erase: Add -mgeneral-regs-only to silence Clang warnings
@ 2025-07-26 21:26 Kees Cook
2025-07-27 15:51 ` Nathan Chancellor
0 siblings, 1 reply; 2+ messages in thread
From: Kees Cook @ 2025-07-26 21:26 UTC (permalink / raw)
To: Nathan Chancellor
Cc: Kees Cook, Nick Desaulniers, Bill Wendling, Justin Stitt,
Ingo Molnar, Andrew Morton, Mike Rapoport (Microsoft),
Pratyush Yadav, Jonathan Cameron, Coiby Xu, Josh Poimboeuf,
Alexander Graf, linux-kernel, llvm, linux-hardening
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
Signed-off-by: Kees Cook <kees@kernel.org>
---
kernel/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/Makefile b/kernel/Makefile
index e4f01f1d4d0c..0ee9afd8b7cf 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -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
--
2.34.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] kstack_erase: Add -mgeneral-regs-only to silence Clang warnings
2025-07-26 21:26 [PATCH] kstack_erase: Add -mgeneral-regs-only to silence Clang warnings Kees Cook
@ 2025-07-27 15:51 ` Nathan Chancellor
0 siblings, 0 replies; 2+ messages in thread
From: Nathan Chancellor @ 2025-07-27 15:51 UTC (permalink / raw)
To: Kees Cook
Cc: Nick Desaulniers, Bill Wendling, Justin Stitt, Ingo Molnar,
Andrew Morton, Mike Rapoport (Microsoft), Pratyush Yadav,
Jonathan Cameron, Coiby Xu, Josh Poimboeuf, Alexander Graf,
linux-kernel, llvm, linux-hardening
On Sat, Jul 26, 2025 at 02:26:19PM -0700, Kees Cook wrote:
> 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
> Signed-off-by: Kees Cook <kees@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
> ---
> kernel/Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/Makefile b/kernel/Makefile
> index e4f01f1d4d0c..0ee9afd8b7cf 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -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
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2025-07-27 15:51 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-07-26 21:26 [PATCH] kstack_erase: Add -mgeneral-regs-only to silence Clang warnings Kees Cook
2025-07-27 15:51 ` Nathan Chancellor
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).