There's a problem with relying on backtrace data from 'perf trace' the
way the trace+probe_libc_inet_pton does. This test inserts uprobe within
ping binary and checks that it gets its sample using 'perf trace'.
It also checks it gets proper backtrace from sample and that's where the
issue is.
The 'perf trace' does not sort events (by definition) so it can happen
that it processes the event sample before the ping binary memory map
event. This can (very rarely) happen as proved by this events dump
output (from custom added debug output):
...
7680/7680: [0x7f4e29718000(0x204000) @ 0 fd:00 33611321 4230892504]: r-xp /usr/lib64/libdl-2.17.so
7680/7680: [0x7f4e29502000(0x216000) @ 0 fd:00 33617257 2606846872]: r-xp /usr/lib64/libz.so.1.2.7
(IP, 0x2): 7680/7680: 0x7f4e29c2ed60 period: 1 addr: 0
7680/7680: [0x564842ef0000(0x233000) @ 0 fd:00 83 1989280200]: r-xp /usr/bin/ping
7680/7680: [0x7f4e2aca2000(0x224000) @ 0 fd:00 33611308 1219144940]: r-xp /usr/lib64/ld-2.17.so
...
In this case 'perf trace' fails to resolve the last callchain IP (within
the ping binary) because it does not know about the ping binary memory
map yet and the test fails like this:
PING ::1(::1) 56 data bytes
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.037 ms
--- ::1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.037/0.037/0.037/0.000 ms
0.000 probe_libc:inet_pton:(7f4e29c2ed60))
__GI___inet_pton (/usr/lib64/libc-2.17.so)
getaddrinfo (/usr/lib64/libc-2.17.so)
[0] ([unknown])
FAIL: expected backtrace entry 8 ".*\(.*/bin/ping.*\)$" got "[0] ([unknown])"
Switching the test to use 'perf record' and 'perf script' instead of
'perf trace'.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180301165215.6780-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
a18ee796f8