lkml.org 
[lkml]   [2014]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v6 02/11] x86_64: load_percpu_segment: read irq_stack_union.gs_base before load_segment
    Date
    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 4b4f78c..ee5c286 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: 2014-11-05 16:01    [W:2.435 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site