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
