[Xen-devel] Module Error

Hi.

Im writing a kernel module to extract some information from kernel,
the module is working really fine in an AMD (AMD Athlon(tm) 64 X2 Dual
Core Processor 3800+), but, when trying to run the module in a i7
(Intel(R) Core(TM) i7 CPU 930 @ 2.80GHz) Im facing some strange errors
(see below). The kernel versions are just the same on both machines
(2.6.34.10-0.2-xen #1 SMP x86_64 x86_64 x86_64 GNU/Linux). The
difference are the amount of memory AND processor vendor. I noted that
the line of code that hangs my machine is this one:

if(end->host==NULL) {

The end->host points to an Inode type (end is an address_space type).
If I remove this line, the module works (but, obviously, do not return
what I want). I tried the same code in a kernel without xen
(2.6.34.10-0.2-desktop #1 SMP x86_64 x86_64 x86_64 GNU/Linux) and
worked fine, so I suppose that this error is due to something in Xen
running in a intel processor (I tried the module in an intel quad, and
got the same error). Follow some outputs:

The error stack:
Oct 28 23:40:35 goku kernel: [ 4472.129718] BUG: unable to handle
kernel paging request at 000003d600000004
Oct 28 23:40:35 goku kernel: [ 4472.129933] IP: [<ffffffffa08d118c>]
get_files+0x6c/0x220 [pagecache]
Oct 28 23:40:35 goku kernel: [ 4472.130098] PGD 0
Oct 28 23:40:35 goku kernel: [ 4472.130250] Oops: 0000 [#4] SMP
Oct 28 23:40:35 goku kernel: [ 4472.130452] last sysfs file:
/sys/devices/system/cpu/cpu7/online
Oct 28 23:40:35 goku kernel: [ 4472.130562] CPU 0
Oct 28 23:40:35 goku kernel: [ 4472.130615] Modules linked in:
pagecache ocfs2_dlmfs ocfs2_stack_o2cb ocfs2_dlm ocfs2_nodemanager
ocfs2_stackglue configfs drbd crc32c libcrc32c bridge stp llc nfsd
lockd nfs_acl snd_pcm_oss auth_rpcgss snd_mixer_oss usbbk gntdev netbk
blkbk blkback_pagemap blktap domctl xenbus_be snd_seq evtchn
snd_seq_device sunrpc exportfs edd fuse loop snd_hda_codec_realtek
firewire_ohci snd_hda_intel firewire_core snd_hda_codec crc_itu_t
snd_hwdep snd_pcm snd_timer ohci1394 iTCO_wdt snd soundcore sr_mod
xhci_hcd ieee1394 i2c_i801 iTCO_vendor_support pcspkr snd_page_alloc
sg r8169 wmi serio_raw ext4 jbd2 crc16 linear uhci_hcd sd_mod nouveau
ehci_hcd ttm drm_kms_helper usbcore drm agpgart i2c_algo_bit i2c_core
button dm_snapshot dm_mod xenblk cdrom xennet fan processor ata_piix
ahci pata_jmicron ata_generic libata scsi_mod thermal thermal_sys
hwmon
Oct 28 23:40:35 goku kernel: [ 4472.132037]
Oct 28 23:40:35 goku kernel: [ 4472.132037] Pid: 4641, comm: cat
Tainted: G      D    2.6.34.10-0.2-xen #1 X58A-UD3R/X58A-UD3R
Oct 28 23:40:35 goku kernel: [ 4472.132037] RIP:
e030:[<ffffffffa08d118c>]  [<ffffffffa08d118c>] get_files+0x6c/0x220
[pagecache]
Oct 28 23:40:35 goku kernel: [ 4472.132037] RSP: e02b:ffff8801ded93c88
 EFLAGS: 00010246
Oct 28 23:40:35 goku kernel: [ 4472.132037] RAX: 8000000004000400 RBX:
ffff8801e8ea5bd0 RCX: 0000000000000001
Oct 28 23:40:35 goku kernel: [ 4472.132037] RDX: ffff8801efc8c7e8 RSI:
ffffffffa08d15c0 RDI: ffff8801e8ea4c28
Oct 28 23:40:35 goku kernel: [ 4472.132037] RBP: 0000000000000001 R08:
ffff8801eed81e00 R09: 0000000000000000
Oct 28 23:40:35 goku kernel: [ 4472.132037] R10: ffff8801e8ea5c00 R11:
0000000000000000 R12: 00000000001e6000
Oct 28 23:40:35 goku kernel: [ 4472.132037] R13: 0000000006a50000 R14:
ffff8801e8ea5b88 R15: 000003d600000004
Oct 28 23:40:35 goku kernel: [ 4472.132037] FS:
00007fcb81c3b700(0000) GS:ffff88000200b000(0000)
knlGS:0000000000000000
Oct 28 23:40:35 goku kernel: [ 4472.132037] CS:  e033 DS: 0000 ES:
0000 CR0: 0000000080050033
Oct 28 23:40:35 goku kernel: [ 4472.132037] CR2: 000003d600000004 CR3:
00000001edecf000 CR4: 0000000000002660
Oct 28 23:40:35 goku kernel: [ 4472.132037] DR0: 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000
Oct 28 23:40:35 goku kernel: [ 4472.132037] DR3: 0000000000000000 DR6:
00000000ffff0ff0 DR7: 0000000000000400
Oct 28 23:40:35 goku kernel: [ 4472.132037] Process cat (pid: 4641,
threadinfo ffff8801ded92000, task ffff8801eedfa780)
Oct 28 23:40:35 goku kernel: [ 4472.132037] Stack:
Oct 28 23:40:35 goku kernel: [ 4472.132037]  0000000101baa5b4
0000000200000002 0000000000000000 ffff8801f16ffae8
Oct 28 23:40:35 goku kernel: [ 4472.132037] <0> 0000000000000000
ffff8801ee7c6500 ffff8801efd32bc0 ffff8801e45de2d0
Oct 28 23:40:35 goku kernel: [ 4472.132037] <0> ffff8801ee7c6500
ffff8801f05d80f8 ffffffff801314f0 ffffffffa08d1349
Oct 28 23:40:35 goku kernel: [ 4472.132037] Call Trace:
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffffa08d1349>]
cache_open+0x9/0x20 [pagecache]
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffff8016c529>]
proc_reg_open+0xb9/0x240
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffff8011060b>]
__dentry_open+0xeb/0x340
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffff801206a8>]
finish_open+0xe8/0x1c0
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffff80120f40>]
do_filp_open+0x1a0/0x630
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffff8011214a>]
do_sys_open+0x6a/0x140
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<ffffffff80007438>]
system_call_fastpath+0x16/0x1b
Oct 28 23:40:35 goku kernel: [ 4472.132037]  [<00007fcb817a7130>] 0x7fcb817a7130
Oct 28 23:40:35 goku kernel: [ 4472.132037] Code: 03 05 69 9d f9 df 4c
8b 78 18 4d 85 ff 0f 84 9c 00 00 00 41 f6 c7 01 0f 85 92 00 00 00 48
8b 00 a9 00 00 02 00 0f 85 84 00 00 00 <49> 8b 1f 48 85 db 0f 84 78 00
00 00 48 83 7b 40 00 74 71 4c 8b
Oct 28 23:40:35 goku kernel: [ 4472.132037] RIP  [<ffffffffa08d118c>]
get_files+0x6c/0x220 [pagecache]
Oct 28 23:40:35 goku kernel: [ 4472.132037]  RSP <ffff8801ded93c88>
Oct 28 23:40:35 goku kernel: [ 4472.132037] CR2: 000003d600000004
Oct 28 23:40:35 goku kernel: [ 4472.143966] ---[ end trace a998217447e12d1d ]---

Peace of code (simplified):
int init_module () {

        unsigned long pfn;
        struct inode *ino;
        unsigned char * c;
        struct address_space *end;
        struct dentry *dentry;
        int fl;

        struct filepage * temp;
        struct filepage *pos;

        for (pfn = 0; pfn < num_physpages; pfn++) {
                struct page *page;
                if (!pfn_valid(pfn))
                        continue;
                page = pfn_to_page(pfn);
                                if((page->mapping!=NULL) && (!PageAnon(page)) 
&& (!PageSwapCache(page))) {
                                                end = page->mapping;
                                                if(end->host==NULL) {  <- 
without this line, no hangs, but the
module returns wrong data to me...
                                                        printk(KERN_INFO 
"Cool... found an valid inode \n");
                                                }
                                }                               
                                        
        }
return 0;
}

Thanks in advance.

Att.
Artur Baruchi

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[Xen-devel] Module Error
