On Wed, Jul 30, 2025 at 01:00:39AM +0200, Marco Elver wrote: > On Wed, 30 Jul 2025 at 00:43, Kees Cook <[email protected]> wrote: > > > > In order to support Clang's stack depth tracking (for Linux's kstack_erase > > feature), the coverage sanitizer needed to be disabled for __init (and > > __head) section code. Doing this universally (i.e. for GCC too), created > > a number of unexpected problems, ranging from changes to inlining logic > > to failures to DCE code on earlier GCC versions. > > > > Since this change is only needed for Clang, specialize it so that GCC > > doesn't see the change as it isn't needed there (the GCC implementation > > of kstack_erase uses a GCC plugin that removes stack depth tracking > > instrumentation from __init sections during a late pass in the IR). > > > > Successful build and boot tested with GCC 12 and Clang 22. > > > > Fixes: 381a38ea53d2 ("init.h: Disable sanitizer coverage for __init and > > __head") > > Reported-by: kernel test robot <[email protected]> > > Closes: > > https://lore.kernel.org/oe-kbuild-all/[email protected]/ > > Reported-by: [email protected] > > Closes: > > https://lore.kernel.org/all/[email protected]/ > > Signed-off-by: Kees Cook <[email protected]> > > --- > > Cc: Linus Torvalds <[email protected]> > > Cc: Thomas Gleixner <[email protected]> > > Cc: Ingo Molnar <[email protected]> > > Cc: Borislav Petkov <[email protected]> > > Cc: Dave Hansen <[email protected]> > > Cc: <[email protected]> > > Cc: "H. Peter Anvin" <[email protected]> > > Cc: Ard Biesheuvel <[email protected]> > > Cc: Marco Elver <[email protected]> > > Cc: Hou Wenlong <[email protected]> > > Cc: Kirill A. Shutemov <[email protected]> > > Cc: Miguel Ojeda <[email protected]> > > Cc: Nathan Chancellor <[email protected]> > > Cc: Przemek Kitszel <[email protected]> > > Cc: Andrew Morton <[email protected]> > > Cc: Masahiro Yamada <[email protected]> > > Cc: Peter Zijlstra <[email protected]> > > Cc: Wei Yang <[email protected]> > > Cc: Sami Tolvanen <[email protected]> > > Cc: Arnd Bergmann <[email protected]> > > Cc: Christophe Leroy <[email protected]> > > --- > > arch/x86/include/asm/init.h | 2 +- > > include/linux/compiler_types.h | 7 +++++++ > > include/linux/init.h | 2 +- > > 3 files changed, 9 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h > > index 6bfdaeddbae8..5a68e9db6518 100644 > > --- a/arch/x86/include/asm/init.h > > +++ b/arch/x86/include/asm/init.h > > @@ -5,7 +5,7 @@ > > #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000 > > #define __head __section(".head.text") __no_sanitize_undefined > > __no_stack_protector > > #else > > -#define __head __section(".head.text") __no_sanitize_undefined > > __no_sanitize_coverage > > +#define __head __section(".head.text") __no_sanitize_undefined > > __no_kstack_erase > > #endif > > > > struct x86_mapping_info { > > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > > index 2b77d12e07b2..89e2c01fc8b1 100644 > > --- a/include/linux/compiler_types.h > > +++ b/include/linux/compiler_types.h > > @@ -378,6 +378,13 @@ struct ftrace_likely_data { > > # define __signed_wrap > > #endif > > > > +/* GCC does not like splitting sanitizer coverage across section inlines */ > > +#ifdef CC_IS_CLANG > > +#define __no_kstack_erase __no_sanitize_coverage > > +#else > > +#define __no_kstack_erase > > +#endif > > I think this belongs into compiler-clang.h, we've typically refrained > from ifdef CC_IS_CLANG/GCC in the generic headers. > See __nocfi for an example, where compiler_types.h provides a default > empty definition, and compiler-clang.h provides a non-empty > definition.
Oh, good point. I will rearrange this to use the #ifndef style handling! -- Kees Cook
