On Mon, 3 Apr 2017 11:46:58 -0300 Arnaldo Carvalho de Melo <a...@kernel.org> wrote:
> > > But apart from those problems, I think that one should be able to ask > > > for a versioned symbol, to probe just apps using that specific version, > > > I agree, but wasn't trying to tackle that at the moment. I can look into > > it, though. > > > > for instance, we should consider the whole name as two functions, which > > > in fact, they are, no? > > > I'm not sure I understand what you mean here. Do you mean we should set a > > probe at every version of a given symbol name? For example, if there are > > symbols: > > a@@V2 > > a@V1.1 > > a@V1 > > > ...for a request to set a probe at "a", we'd actually set a probe at all 3? > > I think that we should just probe the default for that symbol and have a > way to probe all of them, perhaps using the wildcard, i.e.: > > [root@jouet linux]# nm /lib64/libpthread-2.24.so | grep ' > pthread_cond_timedwait' > 000000000000dd90 T pthread_cond_timedwait@GLIBC_2.2.5 > 000000000000d6e0 T pthread_cond_timedwait@@GLIBC_2.3.2 > [root@jouet linux]# > > # perf probe -x /lib64/libpthread-2.24.so pthread_cond_timedwait > > should be equivalent to: > > # perf probe -x /lib64/libpthread-2.24.so > pthread_cond_timedwait@@GLIBC_2.3.2 > > Which matches how these versioned symbols are resolved by the linker, > no? > > I.e. when 'pthread_cond_timedwait' is specified and the symbol table > lookup fails, I think we should re-lookup for > 'pthread_cond_timedwait@@*', i.e. we should have a > symbol__find_default_by_name(), which will take the > "pthread_cond_timedwait" and use a symbol comparison using > strncmp(strlen(key)), matching, should then look at right after the > common part looking for the double @@. Hm, this 'fallback'process sounds good idea to me. BTW, how would we support other SYMBOL@VERSION, since we already use '@' for specifying source code? One possible way is to support it directly in perf-probe. If it failed to find probe point from dwarf, try to find from symbol map by using '@VERSION' suffix. Thank you, -- Masami Hiramatsu <mhira...@kernel.org>
