linux-kernel - Re: [PATCH 1/2] tools lib traceevent: Export dynamic symbols used by traceevent plugins

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Date:	Tue, 12 May 2015 14:42:10 +0800
From:	He Kuang <hekuang@...wei.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	<jolsa@...nel.org>, <a.p.zijlstra@...llo.nl>, <acme@...nel.org>,
	<mingo@...hat.com>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>,
	Mathias Krause <minipli@...glemail.com>
Subject: Re: [PATCH 1/2] tools lib traceevent: Export dynamic symbols used by
 traceevent plugins

Hi, jirka

On 2015/5/11 22:33, Jiri Olsa wrote:
> On Mon, May 11, 2015 at 09:35:26AM +0000, He Kuang wrote:
>> Traceevent plugins need dynamic symbols exported from libtraceevent.a,
>> otherwise a dlopen error will occur during plugins loading.
>>
>> This patch uses dynamic-list-file to export dynamic symbols which will
>> be used in plugins to perf executable.
>>
>> The problem is covered up if feature-libpython is enabled, because
>> PYTHON_EMBED_LDOPTS contains '-Xlinker --export-dynamic' which adds all
>> symbols to the dynamic symbol table. So we should reproduce the problem
>> by setting NO_LIBPYTHON=1.
> there's was another patch taking the shortcut:
>    http://marc.info/?l=linux-kernel&m=142885447432384&w=2
>
> it seems it's not merged yet, but I like this one better
>
> SNIP
>
>
>> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
>> index 03409cc..19c61e0 100644
>> --- a/tools/perf/Makefile.perf
>> +++ b/tools/perf/Makefile.perf
>> @@ -172,6 +172,7 @@ endif
>>   
>>   LIBTRACEEVENT = $(TE_PATH)libtraceevent.a
>>   export LIBTRACEEVENT
>> +LIBTRACEEVENT_DYNAMIC_LIST = $(TE_PATH)libtraceevent-dynamic-list
>>   
>>   LIBAPI = $(LIB_PATH)libapi.a
>>   export LIBAPI
>> @@ -278,8 +279,9 @@ build := -f $(srctree)/tools/build/Makefile.build dir=. obj
>>   $(PERF_IN): $(OUTPUT)PERF-VERSION-FILE $(OUTPUT)common-cmds.h FORCE
>>   	$(Q)$(MAKE) $(build)=perf
>>   
>> -$(OUTPUT)perf: $(PERFLIBS) $(PERF_IN)
>> -	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(PERF_IN) $(LIBS) -o $@
>> +LD_LIBTRACEEVENT_FLAGS += -Xlinker --dynamic-list=$(LIBTRACEEVENT_DYNAMIC_LIST)
>> +$(OUTPUT)perf: $(PERFLIBS) $(PERF_IN) $(LIBTRACEEVENT_DYNAMIC_LIST)
>> +	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(LD_LIBTRACEEVENT_FLAGS) $(PERF_IN) $(LIBS) -o $@
>>   
>>   $(GTK_IN): FORCE
>>   	$(Q)$(MAKE) $(build)=gtk
>> @@ -375,6 +377,9 @@ LIBTRACEEVENT_FLAGS += plugin_dir=$(plugindir_SQ)
>>   $(LIBTRACEEVENT): FORCE
>>   	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent.a plugins
>>   
>> +$(LIBTRACEEVENT_DYNAMIC_LIST): $(LIBTRACEEVENT)
>> +	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent-dynamic-list
> hum, do we need extra target in Makefile.perf, it could be rebuilt any time
> 'plugins:' target in lib/tracevent/Makefile is called
>
> jirka

Yes, the dynamic-list-file should be rebuilt when plugins
changed, and not depends on $(LIBTRACEEVENT).

I sent a new version, please review that patch.

   $ touch ../lib/traceevent/plugin_function.c
   $ make
   CC       plugin_function.o
   LD       plugin_function-in.o
   LINK     plugin_function.so
   GEN      libtraceevent-dynamic-list
   LINK     perf

Thanks.


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