On Tue, 2016-02-16 at 14:57 +0100, Petr Mladek wrote: > > Some dugging has shown an Oops in the fucntion int_to_scsilun() > called from ibmvscsi_queuecommand(). So, I rebooted and > did the following test: > > $> echo ibmvscsi_queuecommand >/sys/kernel/debug/tracing/set_ftrace_filter > $> echo function > /sys/kernel/debug/tracing/current_tracer > $> echo 1 > /sys/kernel/debug/tracing/tracing_on > $> cat /sys/kernel/debug/tracing/trace > # tracer: function > # > # entries-in-buffer/entries-written: 7/7 #P:4 > # > # _-----=> irqs-off > # / _----=> need-resched > # | / _---=> hardirq/softirq > # || / _--=> preempt-depth > # ||| / delay > # TASK-PID CPU# |||| TIMESTAMP FUNCTION > # | | | |||| | | > bash-3488 [000] .... 100.278622: ibmvscsi_queuecommand <-scsi_dispatch_cmd > kworker/1:2-223 [001] .... 101.048569: ibmvscsi_queuecommand <-scsi_dispatch_cmd > kworker/1:2-223 [001] .... 103.048575: ibmvscsi_queuecommand <-scsi_dispatch_cmd > jbd2/sda3-8-1021 [003] .... 104.008645: ibmvscsi_queuecommand <-scsi_dispatch_cmd > jbd2/sda3-8-1021 [003] .... 104.008883: ibmvscsi_queuecommand <-scsi_dispatch_cmd > <idle>-0 [000] ..s. 104.017672: ibmvscsi_queuecommand <-scsi_dispatch_cmd > <idle>-0 [003] ..s. 104.017771: ibmvscsi_queuecommand <-scsi_dispatch_cmd > > It means that ibmvscsi_queuecommand can be traced. Then I did > > c79:/sys/kernel/debug/tracing # echo int_to_scsilun >set_ftrace_filter > > BANG! > > Unable to handle kernel paging request for data at address 0xd00000000108b148 > Faulting instruction address: 0xd000000000bde35c > Oops: Kernel access of bad area, sig: 11 [#1] > SMP NR_CPUS=2048 NUMA pSeries > Modules linked in: af_packet(E) dm_mod(E) e1000(E) rtc_generic(E) ext4(E) crc16(E) mbcache(E) jbd2(E) sr_mod(E) cdrom(E) sd_mod(E) ibmvscsi(E) scsi_transport_srp(E) sg(E) scsi_mod(E) autofs4(E) > CPU: 1 PID: 223 Comm: kworker/1:2 Tainted: G E 4.5.0-rc2-11-default+ #90 > Workqueue: events_freezable_power_ disk_events_workfn > task: c0000000f7d99aa0 ti: c0000000f7cb8000 task.ti: c0000000f7cb8000 > NIP: d000000000bde35c LR: d000000000bcffec CTR: d000000000bcffe0 > REGS: c0000000f7cbb3b0 TRAP: 0300 Tainted: G E (4.5.0-rc2-11-default+) > MSR: 8000000100009033 <SF,EE,ME,IR,DR,RI,LE,TM[E]> CR: 24c82220 XER: 00000000 > CFAR: d000000000bdd144 DAR: d00000000108b148 DSISR: 40000000 SOFTE: 0 > GPR00: d0000000010a21cc c0000000f7cbb630 d0000000010aeda0 0000000000008200 > GPR04: c0000000fa0b33fc 000000000000014a c0000000fa0b3408 0000000000000010 > GPR08: 0000000000000008 c00000000370a4e0 0000000000000000 d00000000108b128 > GPR12: d000000000bcffe0 c000000007e80300 c0000000000d8b18 c0000000fe04ba80 > GPR16: 0000000000000000 c0000000f7b6f208 0000000000000000 0000000000010000 > GPR20: c0000000f7b6f144 c0000000f7b6f140 d000000000bcbcf0 0000000000000000 > GPR24: 0000000000000200 0000000000000000 0000000000000001 c0000000f7b6f810 > GPR28: c0000000f7b6f000 c0000000f7b6f000 c0000000fa0b33a0 c0000000fe837e00 > NIP [d000000000bde35c] scsi_inq_str+0x21b0/0x41ac [scsi_mod] > LR [d000000000bcffec] int_to_scsilun+0xc/0x60 [scsi_mod] > Call Trace: > [c0000000f7cbb630] [d0000000010a21cc] ibmvscsi_queuecommand+0x10c/0x4e0 [ibmvscsi] (unreliable) > [c0000000f7cbb6e0] [d000000000bcbea8] scsi_dispatch_cmd+0xe8/0x2c0 [scsi_mod] > [c0000000f7cbb760] [d000000000bceb0c] scsi_request_fn+0x50c/0x8b0 [scsi_mod] > [c0000000f7cbb850] [c000000000407280] __blk_run_queue+0x60/0x90 > [c0000000f7cbb880] [c000000000413640] blk_execute_rq_nowait+0x100/0x1a0 > [c0000000f7cbb8d0] [c000000000413768] blk_execute_rq+0x88/0x170 > [c0000000f7cbb9b0] [d000000000bca048] scsi_execute+0x108/0x1d0 [scsi_mod] > [c0000000f7cbba20] [d000000000bca2e8] scsi_execute_req_flags+0xc8/0x150 [scsi_mod] > [c0000000f7cbbae0] [d0000000012209e4] sr_check_events+0xb4/0x340 [sr_mod] > [c0000000f7cbbb90] [d0000000011c00b4] cdrom_check_events+0x44/0x80 [cdrom] > [c0000000f7cbbbc0] [d000000001220fa4] sr_block_check_events+0x44/0x60 [sr_mod] > [c0000000f7cbbbe0] [c0000000004222f8] disk_check_events+0x78/0x1b0 > [c0000000f7cbbc50] [c0000000000d0610] process_one_work+0x1a0/0x480 > [c0000000f7cbbce0] [c0000000000d0998] worker_thread+0xa8/0x5c0 > [c0000000f7cbbd80] [c0000000000d8c24] kthread+0x114/0x140 > [c0000000f7cbbe30] [c000000000009538] ret_from_kernel_thread+0x5c/0xa4 > Instruction dump: > 396bc360 f8410018 e98b0020 7d8903a6 4e800420 00000000 00000000 0044fb30 > c0000000 3d62fffe 396bc388 60000000 <e98b0020> 7d8903a6 4e800420 00000000 > ---[ end trace 3b830c669dd7adb5 ]--- > > > Note that ibmvscsi_queuecommand() handle TOC and int_to_scsilun() > does not handle TOC > > $> objdump -hdr drivers/scsi/ibmvscsi/ibmvscsi.ko > 00000000000020c0 <ibmvscsi_queuecommand>: > 20c0: 00 00 4c 3c addis r2,r12,0 > 20c0: R_PPC64_REL16_HA .TOC. > 20c4: 00 00 42 38 addi r2,r2,0 > 20c4: R_PPC64_REL16_LO .TOC.+0x4 > 20c8: a6 02 08 7c mflr r0 > 20cc: 10 00 01 f8 std r0,16(r1) > 20d0: 01 00 00 48 bl 20d0 <ibmvscsi_queuecommand+0x10> > 20d0: R_PPC64_REL24 _mcount > 20d4: a6 02 08 7c mflr r0 > > > $> objdump -hdr drivers/scsi/scsi_mod.ko > [...] > 000000000000ffe0 <int_to_scsilun>: > ffe0: a6 02 08 7c mflr r0 > ffe4: 10 00 01 f8 std r0,16(r1) > ffe8: 01 00 00 48 bl ffe8 <int_to_scsilun+0x8> > ffe8: R_PPC64_REL24 _mcount > ffec: a6 02 08 7c mflr r0 > fff0: 10 00 01 f8 std r0,16(r1) > fff4: e1 ff 21 f8 stdu r1,-32(r1) > > > I am able to trace int_to_scsilun() if I add a global call > into this fucntion. > > I could trace any function when everything is built into the kernel. > > > I am not sure where the problem is but even normal tracing does not > work with this patchset and when -pg -mprofile-kernel is used. When you call into ibmvscsi_queuecommand() it sets up r2 to hold the TOC for ibmvscsi.ko. It then calls int_to_scsilun(). int_to_scsilun() does no TOC setup, and tries to call _mcount. It can't call _mcount() directly (because int_to_scsilun() is in a module), it has to go via a stub. That stub uses r2 to find the location of itself, but it only works if r2 holds the TOC for scsi_mod.ko. In this case r2 still contains ibmvscsi.ko's TOC. So when the stub calculates the address of itself it gets the wrong value, and then when it does a load using that address it either faults (as in your case), or you get some bogus value and jump into a random piece of code. cheers -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
