[Qemu-devel] Re: kqemu causing kernel oops on startup

[walt <w41ter@gmail.com>]

walt wrote:
> I'm following qemu.svn and linus.git on two different machines, and
> only one machine has this problem when I start qemu:
>
> QEMU Accelerator Module version 1.4.0, Copyright (c) 2005-2008 Fabrice
> Bellard
> KQEMU installed, max_locked_mem=452780kB.
> QEMU Accelerator Module version 1.4.0, Copyright (c) 2005-2008 Fabrice
> Bellard
> KQEMU installed, max_locked_mem=452780kB.
> BUG: unable to handle kernel NULL pointer dereference at 00000001
> IP: [<f8adfd64>] memcpy+0x24/0x40 [kqemu]
> *pde = 00000000
> Oops: 0002 [#1] PREEMPT
> last sysfs file:
> /sys/devices/pci0000:00/0000:00:11.1/ide0/0.0/block/hda/hda2/stat
> Modules linked in: kqemu snd_pcm_oss snd_mixer_oss snd_seq_oss
> snd_seq_midi_event snd_seq usb_storage snd_via82xx snd_ac97_codec
> ac97_bus snd_pcm snd_timer snd_page_alloc snd_mpu401_uart snd_rawmidi
> snd_seq_device uhci_hcd ehci_hcd via_rhine snd i2c_viapro mii via_agp
> agpgart bitrev crc32 usbcore i2c_core parport_pc parport [last unloaded:
> kqemu]
>
> Pid: 15409, comm: qemu Not tainted (2.6.29-rc2 #16) VT8367-8235
> EIP: 0060:[<f8adfd64>] EFLAGS: 00210246 CPU: 0
> EIP is at memcpy+0x24/0x40 [kqemu]
> EAX: 0000002f EBX: f7318424 ECX: f7318424 EDX: 00000000
> ESI: 00000001 EDI: 00000000 EBP: efbcb1a0 ESP: f4f31e70
> DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
> Process qemu (pid: 15409, ti=f4f30000 task=f7bb0720 task.ti=f4f30000)
> Stack:
> f7318420 efbcb1a0 f8adf0c3 00000001 f7318424 f7318424 c032a840 0000003c
> c022a6d8 d3950ca0 00000000 f78ac4a0 00000000 d3950ca0 c0157e4c efbcb1a0
> 0000003c efbcb1a0 d3950ca0 00000000 c0157d04 c0154354 f780cd20 dc61ca94
> Call Trace:
> [<f8adf0c3>] kqemu_open+0x41/0x53 [kqemu]
> [<c022a6d8>] misc_open+0x145/0x1c9
> [<c0157e4c>] chrdev_open+0x148/0x160
> [<c0157d04>] chrdev_open+0x0/0x160
> [<c0154354>] __dentry_open+0x125/0x218
> [<c0155047>] nameidata_to_filp+0x28/0x3b
> [<c015e58c>] do_filp_open+0x367/0x656
> [<c0147c53>] handle_mm_fault+0x1f0/0x49e
> [<c016539d>] alloc_fd+0x52/0xcc
> [<c015415c>] do_sys_open+0x42/0xb6
> [<c0154214>] sys_open+0x1e/0x23
> [<c0102af1>] sysenter_do_call+0x12/0x25
> Code: 01 d0 c3 8d 74 26 00 56 53 8b 4c 24 14 8b 74 24 0c 8b 5c 24 10 85
> c9 74 1a 31 d2 8d b6 00 00 00 00 8d bf 00 00 00 00 0f b6 04 1a <88> 04
> 32 42 39 ca 75 f4 5b 89 f0 5e c3 eb 0d 90 90 90 90 90 90
> EIP: [<f8adfd64>] memcpy+0x24/0x40 [kqemu] SS:ESP 0068:f4f31e70
> ---[ end trace ad5fcfebf4164d66 ]---

For the benefit of future googlers, this oops was caused by using
gcc-4.1.* to compile kqemu.  I have another machine with gcc-4.3.x
and that works okay.  Evidently gcc-4.1.* fell through the cracks.