Messages in this thread | | | Date | Tue, 28 Nov 2017 11:50:30 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: Question to perf annotate handling mov ...(%rip) instructions |
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Em Tue, Nov 28, 2017 at 11:42:16AM +0100, Thomas-Mich Richter escreveu: > I am confused by perf annotate internals. > > Perf annotate examines a perf.data file and shows disassembler output. > However the output differs depending on the output option specified:
Well, we started with the --stdio code, and then, for the TUI, went on improving to be able to navigate, etc.
The --stdio code was then left for us to compare outputs and see if some regression was being added.
I think that the right thing is to have the --stdio use what is in --tui, modulo the interactive bits.
The --tui has knobs to disable its beautifications, see H in the tui annotation browser to see the toggle hotkeys.
> ‑‑stdio: Output to stdout, also selected implicitly when output piped to another > process or redirected to a file. The function call sequence is > > symbol__tty_annotate() –> symbol__annotate_printf() –> disasm_line__print(). > > This output style does not annotate the branch instructions nor does it use special > printing functions in the util/annotate.c, for example mov__scnprintf(). > > ‑‑tui: Default. there are annotations to augment branches, jumps, fct returns > with arrows for interactive usage. The function call stack starts with > symbol__tui_annotate(). > There is also special treatment for the Intel mov instructions of the form:
The cases where intel has special treatment are bugs, should be moved to arch specific callbacks.
> 00000000000060b0 <_init@@Base>: > .... > 60b4: 48 8b 05 35 cd 22 00 mov 0x22cd35(%rip),%rax # 232df0 <__gmon_start__> > > Commit 6de783b6f50f7f1db18a3fda0aa34b2e84b5771d ("perf annotate: Resolve symbols > using objdump comment") added this support. > > Special code for Intel platform handles the mov at address 60b4: > This is dynamic linkage against the PLT. Function mov__parse() is always called > to parse the objdump comment following the '#' character. > However the function mov__scnprintf() to replace the text '0x22cd35(%rip)' by the > target function name __gmon_start__ is only called in tui mode and not in stdio mode. > > Now to the confusion: > Function mov__parse() calls comment__symbol() which contains: > > static int comment__symbol(char *raw, char *comment, u64 *addrp, char **namep) > { > char *endptr, *name, *t; > > if (strstr(raw, "(%rip)") == NULL) > return 0; > > This is architecture specific and does not work for non-Intel platforms. > > I would like to fix perf annotate for s390x and above move instruction on s390x > is > > 655a: c0 10 00 01 9c eb larl %r1,39f30 <__gmon_start__> > > There is a need to handle PLT resolution in an architecture independent way. > > Ideas and suggestions?
Some historical background there, busy now, but you seem to be on the right track and IIRC you already sent a patch for this, right? I'll try to look at it.
Jiri may as well, since he worked a lot recently in this codebase, to refactor it some more to make it useful for annotating python code, perl next, other scripted languages should follow too.
- Arnaldo
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