When buildiing kernel with GCC10 [2] in Debian on an Arm64 machine, it was
found the new "inter-procedural optimization improvements" [1] makes symbol
name 'finish_task_switch' changed to 'finish_task_switch.isra.0'.

Details:
The results, when built with gcc 9.3:
nm ../linux.buildout/kernel/sched/core.o | grep finish_task_switch
0000000000001288 t finish_task_switch

However, when built with gcc 10.2:
nm ../linux.buildout/kernel/sched/core.o | grep finish_task_switch
00000000000012d0 t finish_task_switch.isra.0

The same symbols (with xxx.isra.0 or without, respectively of course) also
appear in final file 'System.map' and in '/proc/kallsyms' when booting. This
negatively impact the tracing tools commonly used in kernel debugging, such
as bcc tools offcputime and runqlat. They hardcode 'finish_task_switch'
(without the .isra.0 suffix) into their scripts.

This patch fix the issue by changing the hardcoded 'finish_task_switch' string
to a python regular expression pattern who can match both the traditional form
'finish_task_switch' and the new gcc10 form 'finish_task_switch.isra.0'
(with single digit at the end). attach_kprobe()'s input parameter 'event_re'
is used for this type of pattern matching.

[1] https://gcc.gnu.org/gcc-10/changes.html


[2] ARCH=arm64 make Image

Signed-off-by: Guodong Xu <guodong.xu@linaro.org>