From: Marco Elver <elver@xxxxxxxxxx> Subject: x86: use static_cpu_has in uaccess region to avoid instrumentation This patch is a pre-requisite for enabling KASAN bitops instrumentation; using static_cpu_has instead of boot_cpu_has avoids instrumentation of test_bit inside the uaccess region. With instrumentation, the KASAN check would otherwise be flagged by objtool. For consistency, kernel/signal.c was changed to mirror this change, however, is never instrumented with KASAN (currently unsupported under x86 32bit). Link: http://lkml.kernel.org/r/20190613125950.197667-3-elver@xxxxxxxxxx Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Suggested-by: H. Peter Anvin <hpa@xxxxxxxxx> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/ia32/ia32_signal.c | 2 +- arch/x86/kernel/signal.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) --- a/arch/x86/ia32/ia32_signal.c~x86-use-static_cpu_has-in-uaccess-region-to-avoid-instrumentation +++ a/arch/x86/ia32/ia32_signal.c @@ -358,7 +358,7 @@ int ia32_setup_rt_frame(int sig, struct put_user_ex(ptr_to_compat(&frame->uc), &frame->puc); /* Create the ucontext. */ - if (boot_cpu_has(X86_FEATURE_XSAVE)) + if (static_cpu_has(X86_FEATURE_XSAVE)) put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags); else put_user_ex(0, &frame->uc.uc_flags); --- a/arch/x86/kernel/signal.c~x86-use-static_cpu_has-in-uaccess-region-to-avoid-instrumentation +++ a/arch/x86/kernel/signal.c @@ -391,7 +391,7 @@ static int __setup_rt_frame(int sig, str put_user_ex(&frame->uc, &frame->puc); /* Create the ucontext. */ - if (boot_cpu_has(X86_FEATURE_XSAVE)) + if (static_cpu_has(X86_FEATURE_XSAVE)) put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags); else put_user_ex(0, &frame->uc.uc_flags); _
