linux-kernel - Re: [PATCH v8 8/8] livepatch: Detect offset for the ftrace location during build

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Message-ID: <56CD53E7.3010108@gmail.com>
Date:	Wed, 24 Feb 2016 17:55:35 +1100
From:	Balbir Singh <bsingharora@...il.com>
To:	Torsten Duwe <duwe@....de>, Michael Ellerman <mpe@...erman.id.au>
Cc:	Petr Mladek <pmladek@...e.com>, Jessica Yu <jeyu@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	live-patching@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v8 8/8] livepatch: Detect offset for the ftrace location
 during build

<snip>

We need to remove the SQUASH_TOC_SAVE_INSNS bits as well, now that the ppc64_profile_stub_insns does not save r2
> Looks like we are getting closer to the final solution Thanks, Balbir 

With the SQUASH_TOC_SAVE_INSNS removed, ftrace function seems to work, but function_graph is broken. I've not yet debugged this.

[   77.182430] b'Oops: Kernel access of bad area, sig: 11 [#1]'
[   77.182464] b'SMP NR_CPUS=32 NUMA pSeries'
[   77.182513] b'Modules linked in: sr_mod cdrom virtio_blk virtio_net ibmvscsi scsi_transport_srp scsi_mod virtio_pci virtio_ring virtio'
[   77.182661] b'CPU: 1 PID: 2287 Comm: sshd Not tainted 4.5.0-rc4-00007-g1968536-dirty #143'
[   77.182709] b'task: c000000037b6bc00 ti: c00000003e8c4000 task.ti: c00000003e8c4000'
[   77.182757] b'NIP: c000000000194ebc LR: c000000000049d4c CTR: d0000000004f1434'
[   77.182804] b'REGS: c00000003e8c72a0 TRAP: 0300   Not tainted  (4.5.0-rc4-00007-g1968536-dirty)'
[   77.182858] b'MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 28282828  XER: 20000000'
[   77.183008] b'CFAR: c00000000017f400 DAR: d000000000653c70 DSISR: 40000000 SOFTE: 1 '
[   77.183008] b'GPR00: c000000000009f3c c00000003e8c7520 d0000000004fde40 c00000000077da34 '
[   77.183008] b'GPR04: d0000000004f1430 c00000003e008100 c00000003719e520 c00000003719e008 '
[   77.183008] b'GPR08: c00000000113ea50 d00000000064de40 d0000000004f57b8 c000000000009d1c '
[   77.183008] b'GPR12: c00000000077da34 c00000000fff8400 00000000000005a8 0000000040000000 '
[   77.183008] b'GPR16: 0000000022000000 00000000000346db c00000003e8c7720 c00000000113fbe0 '
[   77.183008] b'GPR20: 0000000000000000 c00000000113fbd0 c000000037a9dc00 0000000000000000 '
[   77.183008] b'GPR24: 0000000000000000 c00000000113fbe0 c000000037077000 c000000037077090 '
[   77.183008] b'GPR28: c0000000379982d8 d0000000004f1430 c00000000077da34 c000000037077068 '
[   77.183788] b'NIP [c000000000194ebc] ftrace_graph_is_dead+0xc/0x20'
[   77.183850] b'LR [c000000000049d4c] prepare_ftrace_return+0x2c/0x110'
---Type <return> to continue, or q <return> to quit---
[   77.183890] b'Call Trace:'
[   77.183911] b'[c00000003e8c7520] [c000000037a9dc00] 0xc000000037a9dc00 (unreliable)'
[   77.183987] b'[c00000003e8c7570] [c000000000009f3c] ftrace_graph_caller+0x34/0x74'
[   77.184080] b'[c00000003e8c75e0] [c00000000077da34] dev_hard_start_xmit+0x374/0x4e0'
[   77.184139] b'[c00000003e8c76c0] [c000000000009f7c] return_to_handler+0x0/0x58 (bad_page_fault+0x130/0x150)'
[   77.184210] b'[c00000003e8c7760] [c000000000009f7c] return_to_handler+0x0/0x58 (handle_page_fault+0x2c/0x30)'
[   77.184281] b'[c00000003e8c7800] [c000000000009f7c] return_to_handler+0x0/0x58 (sch_direct_xmit+0xe0/0x2d0)'
[   77.184369] b'[c00000003e8c7860] [c000000000009f7c] return_to_handler+0x0/0x58 (__dev_queue_xmit+0x2d4/0x6a0)'
[   77.184473] b'[c00000003e8c78f0] [c000000000009f7c] return_to_handler+0x0/0x58 (return_to_handler+0x0/0x58)'
[   77.184544] b'[c00000003e8c7930] [c000000000009f7c] return_to_handler+0x0/0x58 (ip_finish_output2+0x348/0x420)'
[   77.184614] b'[c00000003e8c79a0] [c000000000009f7c] return_to_handler+0x0/0x58 (return_to_handler+0x0/0x58)'
[   77.184684] b'[c00000003e8c7a70] [c000000000009f7c] return_to_handler+0x0/0x58 (ip_output+0xd0/0x160)'
[   77.184754] b'[c00000003e8c7ae0] [c000000000009f7c] return_to_handler+0x0/0x58 (ip_local_out+0x6c/0x90)'
[   77.184823] b'[c00000003e8c7b30] [c000000000009f7c] return_to_handler+0x0/0x58 (return_to_handler+0x0/0x58)'
[   77.184893] b'[c00000003e8c7c00] [c000000000009f7c] return_to_handler+0x0/0x58 (tcp_transmit_skb+0x980/0xa50)'
[   77.184969] b'[c00000003e8c7c40] [c000000000009f7c] return_to_handler+0x0/0x58 (tcp_write_xmit+0xd9c/0x1120)'
[   77.185039] b'[c00000003e8c7c60] [c000000000009f7c] return_to_handler+0x0/0x58 (__tcp_push_pending_frames+0x50/0x130)'
[   77.185117] b'[c00000003e8c7d00] [c000000000009f7c] return_to_handler+0x0/0x58 (tcp_push+0x194/0x1e0)'
[   77.185192] b'[c00000003e8c7d90] [c000000000009f7c] return_to_handler+0x0/0x58 (tcp_sendmsg+0xa54/0xce0)'
[   77.185262] b'[c00000003e8c7de0] [c000000000009f7c] return_to_handler+0x0/0x58 (inet_sendmsg+0xd8/0x100)'
[   77.185342] b'[c00000003e8c7e30] [c000000000009f7c] return_to_handler+0x0/0x58 (sock_sendmsg+0x38/0x60)'
[   77.185416] b'Instruction dump:'
[   77.185469] b'60000000 4bfe3b89 60000000 e8610020 38210030 e8010010 7c0803a6 4bffff40 '
[   77.185566] b'60420000 3c4c00fa 3842e750 3d220015 <88695e30> 4e800020 60000000 60000000 '
[   77.185668] b'---[ end trace 78e882547ec0a563 ]---'
[   79.191159] b'Kernel panic - not syncing: Fatal exception in interrupt'

Warm Regards,
Balbir Singh.