On Thu, 23 Sep 2021 07:59:46 PDT (-0700), nathan@xxxxxxxxxx wrote:
On Thu, Sep 23, 2021 at 12:07:17PM +0200, Marco Elver wrote:
On Wed, 22 Sept 2021 at 22:55, Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
> Currently, the asan-stack parameter is only passed along if
> CFLAGS_KASAN_SHADOW is not empty, which requires KASAN_SHADOW_OFFSET to
> be defined in Kconfig so that the value can be checked. In RISC-V's
> case, KASAN_SHADOW_OFFSET is not defined in Kconfig, which means that
> asan-stack does not get disabled with clang even when CONFIG_KASAN_STACK
> is disabled, resulting in large stack warnings with allmodconfig:
>
> drivers/video/fbdev/omap2/omapfb/displays/panel-lgphilips-lb035q02.c:117:12:
> error: stack frame size (14400) exceeds limit (2048) in function
> 'lb035q02_connect' [-Werror,-Wframe-larger-than]
> static int lb035q02_connect(struct omap_dss_device *dssdev)
> ^
> 1 error generated.
>
> Ensure that the value of CONFIG_KASAN_STACK is always passed along to
> the compiler so that these warnings do not happen when
> CONFIG_KASAN_STACK is disabled.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1453
> References: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 and earlier")
> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Thanks!
[ Which tree are you planning to take it through? ]
Gah, I was intending for it to go through -mm, then I cc'd neither
Andrew nor linux-mm... :/ Andrew, do you want me to resend or can you
grab it from LKML?
Acked-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
(assuming you still want it through somewhere else)
Note, arch/riscv/include/asm/kasan.h mentions KASAN_SHADOW_OFFSET in
comment (copied from arm64). Did RISC-V just forget to copy over the
Kconfig option?
I do see it defined in that file as well but you are right that they did
not copy the Kconfig logic, even though it was present in the tree when
RISC-V KASAN was implemented. Perhaps they should so that they get
access to the other flags in the "else" branch?
Ya, looks like we just screwed this up. I'm seeing some warnings like
cc1: warning: ‘-fsanitize=kernel-address’ with stack protection is not supported without ‘-fasan-shadow-offset=’ for this target
which is how I ended up here, I'm assuming that's what you're talking
about here? LMK if you were planning on sending along a fix or if you
want me to go figure it out.
> ---
> scripts/Makefile.kasan | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 801c415bac59..b9e94c5e7097 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -33,10 +33,11 @@ else
> CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
> $(call cc-param,asan-globals=1) \
> $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> - $(call cc-param,asan-stack=$(stack_enable)) \
> $(call cc-param,asan-instrument-allocas=1)
> endif
>
> +CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
> +
> endif # CONFIG_KASAN_GENERIC
>
> ifdef CONFIG_KASAN_SW_TAGS
>
> base-commit: 4057525736b159bd456732d11270af2cc49ec21f
> --
> 2.33.0.514.g99c99ed825
>
>
