Question to perf annotate handling mov ...(%rip) instructions

[Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>]

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:

‑‑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:

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?

-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
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