[RFC v2 0/4] arm64: ftrace: fix incorrect output from stack tracer
From: AKASHI Takahiro
Date: Tue Aug 04 2015 - 03:44:47 EST
See the following threads [1],[2] for the background.
With this patch series, I'm trying to fix several problems I noticed
with stack tracer on arm64. But it is rather experimental, and there still
remained are several issues.
Patch #1 modifies ftrace framework so that we can provide arm64-specific
stack tracer later.
(Well, I know there is some room for further refactoring, but this is
just a prototype code.)
Patch #2 implements this arch_check_stack() using unwind_stackframe() to
traverse stack frames and identify a stack index for each traced function.
Patch #3 addresses an issue that stack tracer doesn't work well in
conjuction with function graph tracer.
Patch #4 addresses an issue that unwind_stackframe() misses a function
that is the one when an exception happens by setting up a stack frame
for exception handler.
See below for the result with those patches.
Issues include:
a) Size of gic_handle_irq() is 48 (#13), but should be 64.
b) We cannot identify a location of function which is being returned
and hooked temporarily by return_to_handler() (#18)
c) A meaningless entry (#62) as well as a bogus size for the first
function, el0_svc (#61)
d) Size doesn't contain a function's "dynamically allocated local
variables," if any, but instead is sumed up in child's size.
(See details in [3].)
I'm afraid that we cannot fix issue b) unless we can do *atomically*
push/pop a return adress in current->ret_stack[], increment/decrement
current->curr_ret_stack and restore lr register.
We will be able to fix issue d) once we know all the locations in
the list, including b).
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/354126.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/355920.html
[3] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/358034.html
=== stack tracer with function graph tracer
# cat /sys/kernel/debug/tracing/stack_max_size /sys/kernel/debug/tracing/stack_t
race
5376
Depth Size Location (63 entries)
----- ---- --------
0) 5376 64 notifier_call_chain+0x2c/0x94
1) 5312 48 raw_notifier_call_chain+0x34/0x44
2) 5264 64 timekeeping_update+0xe4/0x150
3) 5200 128 update_wall_time+0x400/0x6e4
4) 5072 80 tick_do_update_jiffies64+0xd8/0x154
5) 4992 32 tick_sched_do_timer+0x50/0x60
6) 4960 48 tick_sched_timer+0x34/0x90
7) 4912 112 __hrtimer_run_queues+0xbc/0x278
8) 4800 112 hrtimer_interrupt+0xa0/0x214
9) 4688 32 arch_timer_handler_phys+0x38/0x48
10) 4656 64 handle_percpu_devid_irq+0x84/0x188
11) 4592 32 generic_handle_irq+0x38/0x54
12) 4560 64 __handle_domain_irq+0x68/0xbc
13) 4496 48 gic_handle_irq+0x38/0x88
14) 4448 288 el1_irq+0x68/0xdc
15) 4160 64 sched_clock+0x38/0x88
16) 4096 32 trace_clock_local+0x1c/0x54
17) 4064 96 ftrace_return_to_handler+0x64/0x120
18) 3968 80 (null)
19) 3888 96 xprt_complete_rqst+0xfc/0x1b0
20) 3792 48 xs_udp_data_ready+0x168/0x170
21) 3744 48 sock_queue_rcv_skb+0x1fc/0x270
22) 3696 48 __udp_queue_rcv_skb+0x58/0x19c
23) 3648 96 udp_queue_rcv_skb+0x258/0x3e4
24) 3552 32 __udp4_lib_rcv+0x424/0x684
25) 3520 48 udp_rcv+0x2c/0x3c
26) 3472 64 ip_local_deliver+0xa4/0x224
27) 3408 128 ip_rcv+0x360/0x580
28) 3280 32 __netif_receive_skb_core+0x4d0/0x80c
29) 3248 80 __netif_receive_skb+0x24/0x84
30) 3168 160 process_backlog+0x9c/0x15c
31) 3008 128 net_rx_action+0x1ec/0x32c
32) 2880 32 __do_softirq+0x10c/0x2e8
33) 2848 32 do_softirq+0x60/0x68
34) 2816 96 __local_bh_enable_ip+0xb0/0xd4
35) 2720 64 ip_finish_output2+0x1b8/0x4b8
36) 2656 64 ip_finish_output+0x124/0x1cc
37) 2592 32 ip_output+0xf0/0x120
38) 2560 48 ip_local_out_sk+0x40/0x50
39) 2512 80 ip_send_skb+0x24/0xbc
40) 2432 272 udp_send_skb+0xfc/0x2f4
41) 2160 48 udp_sendmsg+0x2a8/0x7a0
42) 2112 32 inet_sendmsg+0xa0/0xd0
43) 2080 64 sock_sendmsg+0x30/0x78
44) 2016 176 kernel_sendmsg+0x48/0x58
45) 1840 112 xs_send_kvec+0xdc/0xec
46) 1728 64 xs_sendpages+0x88/0x254
47) 1664 64 xs_udp_send_request+0x4c/0xf0
48) 1600 48 xprt_transmit+0x54/0x264
49) 1552 112 call_transmit+0x168/0x200
50) 1440 48 __rpc_execute+0x68/0x37c
51) 1392 32 rpc_execute+0x6c/0xec
52) 1360 112 rpc_run_task+0x90/0xb4
53) 1248 80 rpc_call_sync+0x60/0xdc
54) 1168 48 nfs_proc_getattr+0x54/0x64
55) 1120 96 __nfs_revalidate_inode+0xd0/0x25c
56) 1024 80 nfs_lookup_revalidate+0x468/0x4a0
57) 944 192 lookup_dcache+0x74/0xc8
58) 752 272 path_openat+0x3f4/0xe8c
59) 480 112 do_filp_open+0x70/0xec
60) 368 64 SyS_openat+0x38/0x48
61) 304 -7600 el0_svc_naked+0x20/0x28
62) 7904 7904 0x471e04
AKASHI Takahiro (4):
ftrace: allow arch-specific check_stack()
arm64: ftrace: add arch-specific stack tracer
arm64: ftrace: fix a stack trace result under function graph tracer
arm64: ftrace: add a stack frame for exception handler
arch/arm64/include/asm/ftrace.h | 2 +
arch/arm64/kernel/entry.S | 4 ++
arch/arm64/kernel/ftrace.c | 37 +++++++++++++++
arch/arm64/kernel/stacktrace.c | 97 ++++++++++++++++++++++++++++++++++++++-
include/linux/stacktrace.h | 4 ++
kernel/trace/trace_stack.c | 88 ++++++++++++++++++++---------------
6 files changed, 194 insertions(+), 38 deletions(-)
--
1.7.9.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/