lkml.org 
[lkml]   [2008]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: v2.6.27-rc7: x86: #GP on panic?
    On Thu, Sep 25, 2008 at 10:53 AM, H. Peter Anvin <hpa@zytor.com> wrote:
    > Ingo Molnar wrote:
    >>
    >> * Vegard Nossum <vegard.nossum@gmail.com> wrote:
    >>
    >>> Hi,
    >>>
    >>> With 2.6.27-rc7 on qemu-x86_64, it seems that panic will trigger a
    >>> General Protection Fault. I haven't seen it before.
    >>
    >>> [ 4.523641] Code: eb fd 55 48 89 e5 53 51 83 3d 25 e8 78 00 00 75
    >>> 1a 31 d2 31 f6 48 c7 c7 e1 9c 01 81 e8 f7 a4 03 00 9c 5b fa e8 94 09
    >>> 00 00 53 9d <5a> 5b c9 c3 55 31 c0 48 89 e5 89 04 25 b0 c0 5f ff 65 83
    >>> 04 25
    >>
    >> hm, 0x5a is a simple pop %rdx. A #GP there means the stack segment is
    >> bust?
    >>
    >
    > No, that would be #SS (and segments don't really exist in 64-bit mode
    > anyway.) In 32-bit mode it could mean a code segment overrun.
    >
    > *However*...
    >
    > [ 4.523477] general protection fault: fff2 [1] SMP
    >
    > There is an error code attached to the #GP, which is supposed to mean that
    > somehow a segment selector was involved. This doesn't look like a very valid
    > segment selector at all.
    >
    >> hm:
    >>
    >>> ffffffff8101a6b9 <disable_local_APIC>
    >>> ffffffff81019d25: 53 push %rbx
    >>> ffffffff81019d26: 9d popfq
    >>> ffffffff81019d27: 5a pop %rdx
    >>
    >> so it's preceded by a popfq and on the next instruction we #GP.
    >>
    >> but the stack and flags state looks good:
    >>
    >> [ 4.523641] RSP: 0018:ffff880007867d70 EFLAGS: 00000286
    >>
    >
    > My guess is that the popfq enables interrupts, and we try to take an
    > interrupt through an IDT entry which isn't set up correctly.

    I'm sorry for the false alarm. I discovered that it did not happen on
    a clean kernel. My kernel was using this patch.

    diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
    index a11f5d4..abf5bc8 100644
    --- a/arch/x86/kernel/cpu/common_64.c
    +++ b/arch/x86/kernel/cpu/common_64.c
    @@ -261,6 +261,8 @@ void __init early_cpu_init(void)
    cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
    early_cpu_support_print();
    early_identify_cpu(&boot_cpu_data);
    +
    + setup_clear_cpu_cap(X86_FEATURE_PSE);
    }

    /* Do some early cpuid on the boot CPU to get some parameter that are
    :-(


    Vegard

    --
    "The animistic metaphor of the bug that maliciously sneaked in while
    the programmer was not looking is intellectually dishonest as it
    disguises that the error is the programmer's own creation."
    -- E. W. Dijkstra, EWD1036


    \
     
     \ /
      Last update: 2008-09-25 16:09    [W:0.023 / U:0.412 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site