Re: [PATCH] perf probe: Adjust dso->long_name for offline module

[Wangnan (F)]

On 2015/11/26 3:35, Arnaldo Carvalho de Melo wrote:
> Em Wed, Nov 25, 2015 at 11:30:59AM +0000, Wang Nan escreveu:
> > If libelf unable to open debuginfo for an offline module but the ko has
> > symtab, something unexpected may happen.
> >
> >   # rm -rf ~/.debug/
> >   # mv /usr/lib64/elfutils/libebl_x86_64.so{,.bak}
> >   # ./perf probe -m /home/wangnan/kmodule/mymodule.ko my_func
> >   [mymodule] with build id 326ab42550ef3d24944f53c817533728367effeb not found, continuing without symbols
> >   Failed to find symbol my_func in /home/wangnan/kmodule/mymodule.ko
> Understood, since we are giving the path to that module, we can, if its
> build-id matches the one for the online module, use it, is that the
> case, i.e. do we check, int his scenario, that the build-id matches?

Please see my test result in v2 patch [1]. In symsrc__init() build-id
would be checked.

[1] 
http://lkml.kernel.org/r/1448507949-187812-1-git-send-email-wangnan0@xxxxxxxxxx

 # ./perf probe -m ./mymodule.ko my_func
 Added new event:
   probe:my_func        (on my_func in /home/wangnan/kmodule/mymodule.ko)

 You can now use it in all perf tools, such as:

 	perf record -e probe:my_func -aR sleep 1

 # ./perf probe -d '*'
 Removed event: probe:my_func
 # mv ./mymodule.{ko,.bak}
 # mv ./moduleb.ko mymodule.ko
 # ./perf probe -m ./mymodule.ko my_func
 /home/wangnan/kmodule/mymodule.ko with build id 326ab42550ef3d24944f53c817533728367effeb not found, continuing without symbols
 Failed to find symbol my_func in /home/wangnan/kmodule/mymodule.ko
   Error: Failed to add events.

 # ./perf probe -v -m ./mymodule.ko my_func
 probe-definition(0): my_func
 symbol:my_funcfile:(null)  line:0 offset:0 return:0 lazy:(null)
 0 arguments
 Could not open debuginfo. Try to use symbols.
 symsrc__init: build id mismatch for /home/wangnan/kmodule/mymodule.ko.
 /home/wangnan/kmodule/mymodule.ko with build id 326ab42550ef3d24944f53c817533728367effeb not found, continuing without symbols
 Failed to find symbol my_func in /home/wangnan/kmodule/mymodule.ko
   Error: Failed to add events. Reason: No such file or directory (Code: -2)



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