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Date: Fri, 23 Mar 2007 09:23:04 +0100
From: Michal Piotrowski <michal.k.k.piotrowski@...il.com>
To: vgoyal@...ibm.com
CC: Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.21-rc4-rt0-kdump
Vivek Goyal napisał(a):
> On Thu, Mar 22, 2007 at 02:27:25PM +0100, Michal Piotrowski wrote:
>> Michal Piotrowski napisał(a):
>>> On 22/03/07, Ingo Molnar <mingo@...e.hu> wrote:
>>>> * Michal Piotrowski <michal.k.k.piotrowski@...il.com> wrote:
>>>>
>>>>> Hi Ingo,
>>>>> 2.6.21-rc4-rt0
>>>>> BUG: at kernel/fork.c:1033 copy_process()
>>>> thanks Michal - this is a real bug that affects upstream too. Find the
>>>> fix below - i've test-booted it and it fixes the warning.
>>> Problem is fixed, thanks.
>> BTW. It seems that nobody uses -rt as a crash dump kernel ;)
>>
>> BUG: unable to handle kernel paging request at virtual address f7ebf8c4
>> printing eip:
>> c1610192
>> *pde = 00000000
>> stopped custom tracer.
>> Oops: 0000 [#1]
>> PREEMPT
>> Modules linked in:
>> CPU: 0
>> EIP: 0060:[<c1610192>] Not tainted VLI
>> EFLAGS: 00010206 (2.6.21-rc4-rt0-kdump #3)
>> EIP is at copy_oldmem_page+0x4a/0xd0
>> eax: 000008c4 ebx: f7ebf000 ecx: 00000100 edx: 00000246
>> esi: f7ebf8c4 edi: c4c520fc ebp: c4d54e30 esp: c4d54e18
>> ds: 007b es: 007b fs: 00d8 gs: 0000 ss: 0068 preempt:00000001
>> Process swapper (pid: 1, ti=c4d54000 task=c4d52c20 task.ti=c4d54000)
>> Stack: c17ab7e0 c183f982 c1969658 00000400 00000400 00037ebf c4d54e5c c16af187
>> 00037ebf c4c520fc 00000400 000008c4 00000000 00000000 c4c696e0 00000400
>> c4c520fc c4d54f94 c19a9cfd c4c520fc 00000400 c4d54f78 00000000 c1840996
>> Call Trace:
>> [<c16af187>] read_from_oldmem+0x73/0x98
>> [<c19a9cfd>] vmcore_init+0x26c/0xab7
>> [<c199979b>] init+0xaa/0x287
>> [<c16044eb>] kernel_thread_helper+0x7/0x10
>> =======================
>>
>> l *copy_oldmem_page+0x4a/0xd0
>> 0xc1610148 is in copy_oldmem_page (arch/i386/kernel/crash_dump.c:35).
>> 30 * copying the data to a pre-allocated kernel page and then copying to user
>> 31 * space in non-atomic context.
>> 32 */
>> 33 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
>> 34 size_t csize, unsigned long offset, int userbuf)
>> 35 {
>> 36 void *vaddr;
>> 37
>> 38 if (!csize)
>> 39 return 0;
>>
>
> Can you please paste the disassembly of copy_oldmem_page() on your system.
disassemble *copy_oldmem_page
Dump of assembler code for function copy_oldmem_page:
0xc1610148 <copy_oldmem_page+0>: push %ebp
0xc1610149 <copy_oldmem_page+1>: mov %esp,%ebp
0xc161014b <copy_oldmem_page+3>: push %edi
0xc161014c <copy_oldmem_page+4>: push %esi
0xc161014d <copy_oldmem_page+5>: push %ebx
0xc161014e <copy_oldmem_page+6>: sub $0xc,%esp
0xc1610151 <copy_oldmem_page+9>: call 0xc160f5c4 <mcount>
0xc1610156 <copy_oldmem_page+14>: mov 0x8(%ebp),%ebx
0xc1610159 <copy_oldmem_page+17>: xor %edx,%edx
0xc161015b <copy_oldmem_page+19>: cmpl $0x0,0x10(%ebp)
0xc161015f <copy_oldmem_page+23>: je 0xc161020d <copy_oldmem_page+197>
0xc1610165 <copy_oldmem_page+29>: call 0xc1661258 <pagefault_disable>
0xc161016a <copy_oldmem_page+34>: shl $0x5,%ebx
0xc161016d <copy_oldmem_page+37>: add 0xc1d68e60,%ebx
0xc1610173 <copy_oldmem_page+43>: mov %ebx,(%esp)
0xc1610176 <copy_oldmem_page+46>: call 0xc1613577 <kmap>
0xc161017b <copy_oldmem_page+51>: mov %eax,%ebx
0xc161017d <copy_oldmem_page+53>: cmpl $0x0,0x18(%ebp)
0xc1610181 <copy_oldmem_page+57>: jne 0xc16101ad <copy_oldmem_page+101>
0xc1610183 <copy_oldmem_page+59>: mov 0x10(%ebp),%ecx
0xc1610186 <copy_oldmem_page+62>: shr $0x2,%ecx
0xc1610189 <copy_oldmem_page+65>: mov 0x14(%ebp),%eax
0xc161018c <copy_oldmem_page+68>: lea (%ebx,%eax,1),%esi
0xc161018f <copy_oldmem_page+71>: mov 0xc(%ebp),%edi
0xc1610192 <copy_oldmem_page+74>: rep movsl %ds:(%esi),%es:(%edi)
0xc1610194 <copy_oldmem_page+76>: mov 0x10(%ebp),%ecx
0xc1610197 <copy_oldmem_page+79>: and $0x3,%ecx
0xc161019a <copy_oldmem_page+82>: je 0xc161019e <copy_oldmem_page+86>
0xc161019c <copy_oldmem_page+84>: rep movsb %ds:(%esi),%es:(%edi)
0xc161019e <copy_oldmem_page+86>: call 0xc166126e <pagefault_enable>
0xc16101a3 <copy_oldmem_page+91>: mov %ebx,(%esp)
0xc16101a6 <copy_oldmem_page+94>: call 0xc1613533 <kunmap_virt>
0xc16101ab <copy_oldmem_page+99>: jmp 0xc161020a <copy_oldmem_page+194>
0xc16101ad <copy_oldmem_page+101>: mov 0xc19d4004,%edi
0xc16101b3 <copy_oldmem_page+107>: test %edi,%edi
0xc16101b5 <copy_oldmem_page+109>: jne 0xc16101ca <copy_oldmem_page+130>
0xc16101b7 <copy_oldmem_page+111>: movl $0xc18bbc93,(%esp)
0xc16101be <copy_oldmem_page+118>: call 0xc1619671 <printk>
0xc16101c3 <copy_oldmem_page+123>: mov $0xfffffff2,%edx
0xc16101c8 <copy_oldmem_page+128>: jmp 0xc161020d <copy_oldmem_page+197>
0xc16101ca <copy_oldmem_page+130>: mov $0x400,%ecx
0xc16101cf <copy_oldmem_page+135>: mov %eax,%esi
0xc16101d1 <copy_oldmem_page+137>: rep movsl %ds:(%esi),%es:(%edi)
0xc16101d3 <copy_oldmem_page+139>: call 0xc166126e <pagefault_enable>
0xc16101d8 <copy_oldmem_page+144>: mov %ebx,(%esp)
0xc16101db <copy_oldmem_page+147>: call 0xc1613533 <kunmap_virt>
0xc16101e0 <copy_oldmem_page+152>: mov 0x10(%ebp),%eax
0xc16101e3 <copy_oldmem_page+155>: mov %eax,0x8(%esp)
0xc16101e7 <copy_oldmem_page+159>: mov 0xc19d4004,%eax
0xc16101ec <copy_oldmem_page+164>: add %eax,0x14(%ebp)
0xc16101ef <copy_oldmem_page+167>: mov 0x14(%ebp),%eax
0xc16101f2 <copy_oldmem_page+170>: mov %eax,0x4(%esp)
0xc16101f6 <copy_oldmem_page+174>: mov 0xc(%ebp),%eax
0xc16101f9 <copy_oldmem_page+177>: mov %eax,(%esp)
0xc16101fc <copy_oldmem_page+180>: call 0xc1700e98 <copy_to_user>
0xc1610201 <copy_oldmem_page+185>: mov $0xfffffff2,%edx
0xc1610206 <copy_oldmem_page+190>: test %eax,%eax
0xc1610208 <copy_oldmem_page+192>: jne 0xc161020d <copy_oldmem_page+197>
0xc161020a <copy_oldmem_page+194>: mov 0x10(%ebp),%edx
0xc161020d <copy_oldmem_page+197>: mov %edx,%eax
0xc161020f <copy_oldmem_page+199>: add $0xc,%esp
0xc1610212 <copy_oldmem_page+202>: pop %ebx
0xc1610213 <copy_oldmem_page+203>: pop %esi
0xc1610214 <copy_oldmem_page+204>: pop %edi
0xc1610215 <copy_oldmem_page+205>: pop %ebp
0xc1610216 <copy_oldmem_page+206>: ret
End of assembler dump.
> Not sure from where this faulting address 0xf7ebf8c4 is coming. We are still
> in vmcore_init(), so we should be copying the data to kernel buffers only.
> This looks like a valid kernel address.
>
> Can you also put some printk() here to find out from where 0xf7ebf8c4 has
> come? It does not look like a fixed kernel virutual address returned by
> kmap_atomic_pfn(). Then is it passed by kernel as a parameter to
> copy_oldmem_page()?
>
> Thanks
> Vivek
>
Regards,
Michal
--
Michal K. K. Piotrowski
LTG - Linux Testers Group (PL)
(http://www.stardust.webpages.pl/ltg/)
LTG - Linux Testers Group (EN)
(http://www.stardust.webpages.pl/linux_testers_group_en/)
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