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Re: [Xen-devel] Hunting down an oops in Xen 3.1.0's 2.6.18 kernel

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Hunting down an oops in Xen 3.1.0's 2.6.18 kernel
From: "Michael Marineau" <mike@xxxxxxxxxxxx>
Date: Mon, 17 Sep 2007 16:56:21 -0700
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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On 9/15/07, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:
> On 14/9/07 23:51, "Michael Marineau" <mike@xxxxxxxxxxxx> wrote:
> > I have been unable to reproduce this with 3.0.4's 2.6.16 kernel but
> > 2.6.18 will oops on both 3.0.4 and 3.1.0. Also, x86_64 appears to be
> > ok.
> >
> > I'm guessing this issue is the same as the oops reported here:
> > http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=975
> >
> > Below is an example of the oops on my 2.6.18 pae kernel with a couple
> > extra debuging lines added:
> Looks like xen_l1_entry_update() is passed a virtual address which has no
> corresponding machine address. So the pte page or its mapping is corrupted
> somehow. deadbeef in the register dumps is also not a good sign. I'll have a
> go at repro'ing.
>  -- Keir

As for the deadbeef, I'm kind of doubt it is important. Those values
show up after the hypercall to xen. Using the attached patch which
checks for the bogus value prior to the call I get the following oops:

virtptr: f57b40c0 machineptr: 7fffffff0c0
------------[ cut here ]------------
kernel BUG at arch/i386/mm/hypervisor.c:64!
invalid opcode: 0000 [#1]
Modules linked in:
CPU:    0
EIP:    0061:[<c0117893>]    Not tainted VLI
EFLAGS: 00010286   (2.6.18-xen-r5-try2 #10)
EIP is at xen_l1_entry_update+0xd7/0x100
eax: 0000002d   ebx: 00000000   ecx: 00000000   edx: 00000001
esi: fffff0c0   edi: 000007ff   ebp: ed45cd10   esp: ed45ccd8
ds: 007b   es: 007b   ss: 0069
Process bash (pid: 5044, ti=ed45c000 task=ec835a70 task.ti=ed45c000)
Stack: c037b964 f57b40c0 fffff0c0 000007ff 00000000 00000000 f57b40c0 fffff0c0
       000007ff 00000000 00000000 00000000 00000000 00000000 ed45cd84 c01586b7
       35371025 00000000 ecd95ec0 ecd95f08 c04bce70 00000000 00000004 00000000
Call Trace:
 [<c01586b7>] zap_pte_range+0x265/0x658
 [<c0158c16>] unmap_page_range+0x16c/0x2b4
 [<c0158e2c>] unmap_vmas+0xce/0x1cb
 [<c015f0b8>] exit_mmap+0x7d/0xf4
 [<c011e0f3>] mmput+0x36/0x8c
 [<c01782d3>] exec_mmap+0x156/0x229
 [<c0178a78>] flush_old_exec+0x59/0x25a
 [<c0198a18>] load_elf_binary+0x33c/0xc52
 [<c0178f2a>] search_binary_handler+0x89/0x23c
 [<c017922f>] do_execve+0x152/0x1be
 [<c010391c>] sys_execve+0x32/0x84
 [<c0104dfb>] syscall_call+0x7/0xb
 [<b7efd899>] 0xb7efd899
Code: b4 97 fe ff 85 c0 78 42 83 c4 2c 5b 5e 5f 5d c3 8b 45 e0 89 74
24 08 89 7c 24 0
EIP: [<c0117893>] xen_l1_entry_update+0xd7/0x100 SS:ESP 0069:ed45ccd8

Michael Marineau
Oregon State University

Attachment: bogus-ptr-check.patch
Description: Binary data

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