LGTM On Mon, Nov 24, 2014 at 9:02 PM, Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> wrote: > Reading irq_stack_union.gs_base after load_segment creates troubles for kasan. > Compiler inserts __asan_load in between load_segment and wrmsrl. If kernel > built with stackprotector this will result in boot failure because __asan_load > has stackprotector. > > To avoid this irq_stack_union.gs_base stored to temporary variable before > load_segment, so __asan_load will be called before load_segment(). > > There are two alternative ways to fix this: > a) Add __attribute__((no_sanitize_address)) to load_percpu_segment(), > which tells compiler to not instrument this function. However this > will result in build failure with CONFIG_KASAN=y and CONFIG_OPTIMIZE_INLINING=y. > > b) Add -fno-stack-protector for mm/kasan/kasan.c > > Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> > --- > arch/x86/kernel/cpu/common.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 8779d63..97f56f6 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -389,8 +389,10 @@ void load_percpu_segment(int cpu) > #ifdef CONFIG_X86_32 > loadsegment(fs, __KERNEL_PERCPU); > #else > + void *gs_base = per_cpu(irq_stack_union.gs_base, cpu); > + > loadsegment(gs, 0); > - wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu)); > + wrmsrl(MSR_GS_BASE, (unsigned long)gs_base); > #endif > load_stack_canary_segment(); > } > -- > 2.1.3 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>