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SubjectRe: [PATCH 1/2] tools lib traceevent: Export dynamic symbols used by traceevent plugins
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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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