Re: [PATCH 1/3] perf probe: Set retprobe flag when probe in address-based alternative mode

Arnaldo Carvalho de Melo
2015-04-13T14:42:50Z

Em Mon, Apr 13, 2015 at 11:39:03AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Apr 13, 2015 at 07:41:28PM +0800, He Kuang escreveu:
> > Perf probe misses to set retprobe flag back when falling back to
> > address-based alternative mode.

> Humm, noticed one other problem, but not with your patch, about this message:

> "Could not open debuginfo. Try to use symbols."

> That is really not clear, specially that "try to use symbols" :-)

> [root@ssdandy ~]# ls -la /root/.debug/.build-id/dd/32e51921ede0fd46f034091b7f6a0f2e01ebda
> lrwxrwxrwx. 1 root root 86 Apr 10 18:02 /root/.debug/.build-id/dd/32e51921ede0fd46f034091b7f6a0f2e01ebda -> ../../home/acme/git/build/v4.0.0-rc6+/vmlinux/dd32e51921ede0fd46f034091b7f6a0f2e01ebda
> [root@ssdandy ~]# ls -la /root/.debug/.build-id/dd/../../home/acme/git/build/v4.0.0-rc6+/vmlinux/dd32e51921ede0fd46f034091b7f6a0f2e01ebda
> -rwxr-xr-x. 1 root root 22698661 Apr 10 18:02 /root/.debug/.build-id/dd/../../home/acme/git/build/v4.0.0-rc6+/vmlinux/dd32e51921ede0fd46f034091b7f6a0f2e01ebda
> [root@ssdandy ~]# ls -la /root/.debug/.build-id/dd/../../home/acme/git/build/v4.0.0-rc6+/vmlinux/dd32e51921ede0fd46f034091b7f6a0f2e01ebda

> I.e. it managed to read the debuginfo, its just that it has no symbols in it :-)

> Anyway, digression ended.

Interesting is that when testing your next patch I see:

[root@ssdandy linux]# perf probe -s ./kernel_src/ --add='fs/super.c;s->s_count=1;'
The /root/.debug/.build-id/dd/32e51921ede0fd46f034091b7f6a0f2e01ebda file has no debug information.
Rebuild with CONFIG_DEBUG_INFO=y, or install an appropriate debuginfo package.
Error: Failed to add events.
[root@ssdandy linux]#

Much, much clear message about that debuginfo file :-)

But then, to test your [2/3] patch I'll have to figure out how to setup the
environment so that I can match your results, shouldn't be hard, but would
save reviewing time if you stated it in the commit log message.

- Arnaldo