Messages in this thread | | | Date | Tue, 2 Aug 2016 16:51:02 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | perf test BPF failing on f24: fix |
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Hi Wang,
Something changed and a function used in a perf test for BPF is not anymore appearing on vmlinux, albeit still available on /proc/kallsyms:
# readelf -wi /lib/modules/4.7.0+/build/vmlinux | grep -w sys_epoll_wait #
But:
[root@jouet ~]# grep -i sys_epoll_wait /proc/kallsyms ffffffffbd295b50 T SyS_epoll_wait ffffffffbd295b50 T sys_epoll_wait [root@jouet ~]#
I noticed that it is some sort of aliasing so I checked the other variant:
[root@jouet ~]# readelf -wi /lib/modules/4.7.0+/build/vmlinux | grep -w SyS_epoll_wait <2bc9b85> DW_AT_name : (indirect string, offset: 0xe7524): SyS_epoll_wait [root@jouet ~]#
Trying to use perf probe also produces the same resuls I notice when running the perf test that is failing:
[root@jouet ~]# perf probe sys_epoll_wait Failed to find debug information for address ffffffffbd295b50 Probe point 'sys_epoll_wait' not found. Error: Failed to add events. [root@jouet ~]# perf probe SyS_epoll_wait Added new events: probe:SyS_epoll_wait (on SyS_epoll_wait) probe:SyS_epoll_wait_1 (on SyS_epoll_wait) probe:SyS_epoll_wait_2 (on SyS_epoll_wait)
You can now use it in all perf tools, such as:
perf record -e probe:SyS_epoll_wait_2 -aR sleep 1
[root@jouet ~]#
So I am changing the BPF perf test to use the CamelCase notation alias:
Failing (with sys_epoll_wait):
[root@jouet ~]# perf test BPF 37: Test BPF filter : 37.1: Test basic BPF filtering : FAILED! 37.2: Test BPF prologue generation : Skip 37.3: Test BPF relocation checker : Skip [root@jouet ~]#
Changing to (SyS_epoll_wait):
[root@jouet ~]# perf test BPF 37: Test BPF filter : 37.1: Test basic BPF filtering : Ok 37.2: Test BPF prologue generation : Ok 37.3: Test BPF relocation checker : Ok [root@jouet ~]#
I'm adding a fix that just makes it use SyS_epoll_wait.
- Arnaldo
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