Em Tue, Apr 04, 2017 at 11:18:02PM +0900, Masami Hiramatsu escreveu: > On Mon, 3 Apr 2017 11:46:58 -0300 > Arnaldo Carvalho de Melo <[email protected]> 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 > > > [email protected] > > > 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.
This is just trying to keep the semantics used by the original user of this syntax, i.e. the linker. > 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. Right, we would be overloading that @ symbol, since version numbers usually are very different of file source names :-) - Arnaldo
