lkml.org 
[lkml]   [2014]   [Nov]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v7 02/12] x86_64: load_percpu_segment: read irq_stack_union.gs_base before load_segment
LGTM

On Mon, Nov 24, 2014 at 9:02 PM, Andrey Ryabinin <a.ryabinin@samsung.com> 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@samsung.com>
> ---
> 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
>


\
 
 \ /
  Last update: 2014-11-25 14:21    [W:0.320 / U:28.188 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site