[PATCH] Fix DEBUG_PAGEALLOC on 603/e300
Xianghua Xiao
xiaoxianghua at gmail.com
Tue May 4 00:19:53 EST 2010
On Sun, May 2, 2010 at 5:27 AM, Maindoor <sanjeevfiles at yahoo.com> wrote:
> Any updates on this ? I need something similar.
>
> Thanks,
> Maindoor.
>
> --- On *Thu, 4/29/10, Benjamin Herrenschmidt <benh at kernel.crashing.org>*wrote:
>
>
> From: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Subject: Re: [PATCH] Fix DEBUG_PAGEALLOC on 603/e300
> To: "Xianghua Xiao" <xiaoxianghua at gmail.com>
> Cc: "linuxppc-dev" <linuxppc-dev at lists.ozlabs.org>
> Date: Thursday, April 29, 2010, 3:59 AM
>
> On Wed, 2010-04-28 at 14:15 -0500, Xianghua Xiao wrote:
> > This change works me on a 834x(e300) platform, tested with lmbench and
> > a production-ready application with 2.6.33.3.
>
> But have you tested that DEBUG_PAGEALLOC actually works ? :-)
>
> A way to do that is to
>
> - get_free_pages a page
> - read from it
> - free it
> - write to it
>
> It should oops on the write, and I suspect that without my patch it
> doesn't.
>
> Cheers,
> Ben.
>
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev at lists.ozlabs.org<http://mc/compose?to=Linuxppc-dev@lists.ozlabs.org>
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
>
> Ok here is the test result I did this morning, in short with/without Ben's
patch it will oops if you write to a freed page.
1. With DEBUG_PAGEALLOC on, after applied Ben's patch and wrote to a freed
page, it will oops:
--------------------------------------
Read from allocated page
Write to freed page
Unable to handle kernel paging request for data at address 0xce33c000
Faulting instruction address: 0xd004d07c
Oops: Kernel access of bad area, sig: 11 [#1]
PREEMPT DEBUG_PAGEALLOC 834x SYS
Modules linked in: e300page(+)
NIP: d004d07c LR: d004d074 CTR: 00000001
REGS: cf231e30 TRAP: 0300 Not tainted (2.6.33.3-rt17)
MSR: 00009032 <EE,ME,IR,DR> CR: 24000422 XER: 20000000
DAR: ce33c000, DSISR: 22000000
TASK = ce312e10[1395] 'insmod' THREAD: cf230000
GPR00: 00000061 cf231ee0 ce312e10 0000001a 00003b0d ffffffff c047c4d6
00004000
GPR08: c047c8c4 ce33c000 00003fff ce312e10 24000422 100bbc1c 0fffd000
ffffffff
GPR16: 00000001 00000000 007fff00 00000000 00000000 0fffa1a0 00000000
100b90a0
GPR24: 4800e4ac bfd2ff80 c043d388 00000000 d004d000 c0480000 cf230000
d0050000
NIP [d004d07c] e300page_init+0x7c/0xb8 [e300page]
LR [d004d074] e300page_init+0x74/0xb8 [e300page]
Call Trace:
[cf231ee0] [d004d074] e300page_init+0x74/0xb8 [e300page] (unreliable)
[cf231ef0] [c00038b4] do_one_initcall+0x54/0x210
[cf231f20] [c0058ba4] sys_init_module+0x120/0x240
[cf231f40] [c0012afc] ret_from_syscall+0x0/0x38
--- Exception: c01 at 0xfe5baa0
LR = 0x10027de0
Instruction dump:
4e800020 3c60d005 3863a094 48000031 807fa214 38800000 48000045 3c60d005
3863a0b4 48000019 813fa214 38000061 <98090000> 4bffffb8 00000000 3d60c035
---[ end trace 4b412bd05f6f6d8d ]---
# rmmod e300page
rmmod: e300page: Device or resource busy
2. Without Ben's patch, there is also oops observed:
# insmod ./e300page.ko
Oops: Kernel access of bad area, sig: 11 [#1]
PREEMPT DEBUG_PAGEALLOC 834x SYS
Modules linked in: e300page(+)
NIP: d004d07c LR: d004d074 CTR: 00000001
REGS: ce30be30 TRAP: 0300 Not tainted (2.6.33.3-rt17)
MSR: 00009032 <EE,ME,IR,DR> CR: 22000422 XER: 20000000
DAR: ce172000, DSISR: 22000000
TASK = ce306120[1392] 'insmod' THREAD: ce30a000
GPR00: 00000061 ce30bee0 ce306120 0000001a 00003b0d ffffffff c047c4d6
00004000
GPR08: c047c8c4 ce172000 00003fff ce306120 22000422 100bbc1c 0fffd000
ffffffff
GPR16: 00000001 00000000 007fff00 00000000 00000000 0fffa1a0 00000000
100b90a0
GPR24: 4800e4ac bf876f10 c043d388 00000000 d004d000 c0480000 ce30a000
d0050000
NIP [d004d07c] e300page_init+0x7c/0xb8 [e300page]
LR [d004d074] e300page_init+0x74/0xb8 [e300page]
Call Trace:
[ce30bee0] [d004d074] e300page_init+0x74/0xb8 [e300page] (unreliable)
[ce30bef0] [c00038b4] do_one_initcall+0x54/0x210
[ce30bf20] [c0058bb0] sys_init_module+0x120/0x240
[ce30bf40] [c0012afc] ret_from_syscall+0x0/0x38
--- Exception: c01 at 0xfe5baa0
LR = 0x10027de0
Instruction dump:
4e800020 3c60d005 3863a094 48000031 807fa214 38800000 48000045 3c60d005
3863a0b4 48000019 813fa214 38000061 <98090000> 4bffffb8 00000000 3d60c035
---[ end trace a05c5135ddb62734 ]---
Segmentation fault
Checking dmesg(where you can see the printk msg from the module):
Read from allocated page
Write to freed page
Unable to handle kernel paging request for data at address 0xce172000
Faulting instruction address: 0xd004d07c
Oops: Kernel access of bad area, sig: 11 [#1]
PREEMPT DEBUG_PAGEALLOC 834x SYS
Modules linked in: e300page(+)
NIP: d004d07c LR: d004d074 CTR: 00000001
REGS: ce30be30 TRAP: 0300 Not tainted (2.6.33.3-rt17)
MSR: 00009032 <EE,ME,IR,DR> CR: 22000422 XER: 20000000
DAR: ce172000, DSISR: 22000000
TASK = ce306120[1392] 'insmod' THREAD: ce30a000
GPR00: 00000061 ce30bee0 ce306120 0000001a 00003b0d ffffffff c047c4d6
00004000
GPR08: c047c8c4 ce172000 00003fff ce306120 22000422 100bbc1c 0fffd000
ffffffff
GPR16: 00000001 00000000 007fff00 00000000 00000000 0fffa1a0 00000000
100b90a0
GPR24: 4800e4ac bf876f10 c043d388 00000000 d004d000 c0480000 ce30a000
d0050000
NIP [d004d07c] e300page_init+0x7c/0xb8 [e300page]
LR [d004d074] e300page_init+0x74/0xb8 [e300page]
Call Trace:
[ce30bee0] [d004d074] e300page_init+0x74/0xb8 [e300page] (unreliable)
[ce30bef0] [c00038b4] do_one_initcall+0x54/0x210
[ce30bf20] [c0058bb0] sys_init_module+0x120/0x240
[ce30bf40] [c0012afc] ret_from_syscall+0x0/0x38
--- Exception: c01 at 0xfe5baa0
LR = 0x10027de0
Instruction dump:
4e800020 3c60d005 3863a094 48000031 807fa214 38800000 48000045 3c60d005
3863a0b4 48000019 813fa214 38000061 <98090000> 4bffffb8 00000000 3d60c035
---[ end trace a05c5135ddb62734 ]---
# lsmod
Module Size Used by Tainted: G
e300page 1549 1
# rmmod e300page
rmmod: e300page: Device or resource busy
Module source is below:
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
static int __init e300page_init (void)
{
static char *kpage;
char ch;
if (!(kpage = (char *)__get_free_pages (GFP_KERNEL, 0))) {
printk (KERN_ERR " __get_free_pages failed\n");
return 0;
}
printk(KERN_INFO "Read from allocated page\n");
ch = kpage[0];
free_pages ((unsigned long)kpage, 0);
printk(KERN_INFO "Write to freed page\n");
kpage[0]='a';
return 0;
}
static void __exit e300page_exit (void)
{
printk (KERN_INFO "e300page exiting\n");
}
module_init (e300page_init);
module_exit (e300page_exit);
MODULE_AUTHOR ("Xianghua Xiao");
MODULE_DESCRIPTION ("Test PageAlloc on e300");
MODULE_LICENSE ("GPL v2");
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ozlabs.org/pipermail/linuxppc-dev/attachments/20100503/9599b5f6/attachment-0001.htm>
More information about the Linuxppc-dev
mailing list