Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Hi,
>>>
>>> any thoughts on this BUG? Happens with ipipe-2.0-07 on 2.6.24.7,
>>> obviously during module loading.
>>>
>>> kernel BUG at arch/x86/mm/fault_64.c:258!
>>> invalid opcode: 0000 [1] SMP
>>> CPU 3
>>> Modules linked in: ide_core ide_disk scsi_mod sd_mod serverworks libata
>>> sata_svw scsi_transport_sas mptbase mptscsih mptsas sg fan edd
>>> pata_serverworks jbd mbcache ext3 usbcore hwmon i2c_core k8temp
>>> pci_hotplug i2c_piix4 shpchp ehci_hcd ohci_hcd rtc_lib rtc_core rtc_cmos
>>> tg3
>>> Pid: 1683, comm: modprobe Not tainted 2.6.24.7-xeno #1
>>> RIP: 0010:[<ffffffff80224e8c>] [<ffffffff80224e8c>]
>>> vmalloc_sync_one+0x6f/0x197
>>> RSP: 0018:ffff81023b0c1c98 EFLAGS: 00010287
>>> RAX: 00003ffffffff000 RBX: ffff81023feeea88 RCX: ffff810000000000
>>> RDX: ffff81023c423000 RSI: 000000023c423000 RDI: ffff81023b1e7c20
>>> RBP: ffff81023b0c1cc8 R08: ffffffff80201c20 R09: 0000000000000800
>>> R10: ffffffff8099a380 R11: 0000000000000002 R12: 0000000000000c20
>>> R13: ffffc20001888000 R14: ffffc20001888000 R15: 0000000000000000
>>> FS: 00002ac2367716d0(0000) GS:ffff81023c31d5c0(0000)
>>> knlGS:0000000000000000
>>> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>>> CR2: 00002ac236442000 CR3: 000000023b139000 CR4: 00000000000006e0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>>> Process modprobe (pid: 1683, threadinfo ffff81023b0c0000, task
>>> ffff81023c3ba7f0)
>>> Stack: ffffc2000188bfff ffff81023feeea88 0000000000000c20
>>> ffffc20001888000
>>> ffffc2000188c000 0000000000000000 ffff81023b0c1d08 ffffffff802252ac
>>> ffffc2000188c000 0000000000000000 ffffc2000188c000 ffff81013a1cf468
>>> Call Trace:
>>> [<ffffffff802252ac>] __ipipe_pin_range_globally+0x9a/0xe4
>>> [<ffffffff802dac08>] map_vm_area+0x29f/0x2b0
>>> [<ffffffff802db28b>] __vmalloc_area_node+0x173/0x199
>>> [<ffffffff802db30e>] __vmalloc_node+0x5d/0x6a
>>> [<ffffffff802db34d>] __vmalloc+0x11/0x13
>>> [<ffffffff802db40a>] vmalloc+0x1d/0x1f
>>> [<ffffffff8025c73b>] sys_init_module+0x71/0x18ba
>>> [<ffffffff8022453c>] mcount+0x4c/0x72
>>> [<ffffffff8022453c>] mcount+0x4c/0x72
>>> [<ffffffff80223f54>] __ipipe_syscall_root+0xc/0x197
>>> [<ffffffff8047fb11>] __ipipe_syscall_root_thunk+0x35/0x6a
>>> [<ffffffff8020c172>] system_call+0x92/0x97
>>>
>>>
>>> Code: 0f 0b eb fe 49 8b 00 4c 89 f2 49 bf 00 f0 ff ff ff 3f 00 00
>>> RIP [<ffffffff80224e8c>] vmalloc_sync_one+0x6f/0x197
>>> RSP <ffff81023b0c1c98>
>>>
>>>
>>> The relevant code in fault_64.c:
>>>
>>> static int vmalloc_sync_one(pgd_t *pgd, unsigned long address)
>>> {
>>> pgd_t *pgd_ref;
>>> pud_t *pud, *pud_ref;
>>> pmd_t *pmd, *pmd_ref;
>>> pte_t *pte, *pte_ref;
>>>
>>> /* Copy kernel mappings over when needed. This can also
>>> happen within a race in page table update. In the later
>>> case just flush. */
>>>
>>> pgd_ref = pgd_offset_k(address);
>>> if (pgd_none(*pgd_ref))
>>> return -1;
>>> if (pgd_none(*pgd))
>>> set_pgd(pgd, *pgd_ref);
>>> else
>>> BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
>>>
>>> This one triggers.
>> I think there is something missing in the I-pipe patch: when a vmalloc
>> occurs we update all page directories, but when a vfree occurs, we do
>> nothing. Is there any chance that the bug you observed is in fact a
>> vmalloc which reuses an address which has been vfreed recently ?
>
> Maybe. This happens during boot-up, probably while issuing modprobes in
> a row where you also tend to release some temporary memory again. That
> said, I cannot provide a precise test case. And according to the
> reporter, this only happens fairly sporadically.
Ok. Maybe printing pgd_page_vaddr(*pgd) and pgd_page_vaddr(*pgd_ref)
would help ?
--
Gilles.
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