On Sun, May 2, 2010 at 5:27 AM, Maindoor <sanjeevfi...@yahoo.com> wrote:
> Any updates on this ? I need something similar. > > Thanks, > Maindoor. > > --- On *Thu, 4/29/10, Benjamin Herrenschmidt <b...@kernel.crashing.org>*wrote: > > > From: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Subject: Re: [PATCH] Fix DEBUG_PAGEALLOC on 603/e300 > To: "Xianghua Xiao" <xiaoxiang...@gmail.com> > Cc: "linuxppc-dev" <linuxppc-dev@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@lists.ozlabs.org<http://mc/compose?to=linuxppc-...@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");
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