From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: perf trace report with time consumed
Date: Fri, 1 Apr 2016 10:01:40 -0300
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To: Milian Wolff <milian.wolff@kdab.com>
Cc: Jiri Olsa <jolsa@kernel.org>, perf group <linux-perf-users@vger.kernel.org>

Em Fri, Apr 01, 2016 at 12:34:44AM +0200, Milian Wolff escreveu:
> Nice, so the frame point unwinding seems to work already. But I'm a user-space 
> person and none of my tools have that. So let's try dwarf:

> ~~~~~~~~~~~~~~~~~
> perf trace -e nanosleep --call-graph dwarf path/to/ex_sleep
> perf: Segmentation fault
> Obtained 10 stack frames.
> perf(sighandler_dump_stack+0x4f) [0x5637fdcfc85f]
> /usr/lib/libc.so.6(+0x3332f) [0x7fe888b2132f]
> /usr/lib/libc.so.6(__vsnprintf_chk+0x6b) [0x7fe888be38db]
> perf(+0xb3f93) [0x5637fdc56f93]
> perf(+0xb8fec) [0x5637fdc5bfec]
> perf(cmd_trace+0x1c14) [0x5637fdc5e5c4]
> perf(+0xe6bae) [0x5637fdc89bae]
> perf(main+0x6e3) [0x5637fdc23a83]
> /usr/lib/libc.so.6(__libc_start_main+0xef) [0x7fe888b0e70f]
> perf(_start+0x28) [0x5637fdc23bc8]
> Segmentation fault (core dumped)
> ~~~~~~~~~~~~~~~~~
 
> Ouch :( Valgrind gives me:
 
> ~~~~~~~~~~~~~~~~~
> ==8053== Syscall param msync(start) points to uninitialised byte(s)
> ==8053==    at 0x528A700: __msync_nocancel (in /usr/lib/libpthread-2.23.so)
> ==8053==    by 0x4E396D6: validate_mem (Ginit.c:137)
> ==8053==    by 0x4E396D6: access_mem (Ginit.c:171)
> ==8053==    by 0x4E3F79D: dwarf_get (libunwind_i.h:168)
> ==8053==    by 0x4E3F79D: apply_reg_state (Gparser.c:819)
> ==8053==    by 0x4E3EE72: _ULx86_64_dwarf_find_save_locs (Gparser.c:907)
> ==8053==    by 0x4E4126A: _ULx86_64_dwarf_step (Gstep.c:34)
> ==8053==    by 0x4E3A873: _ULx86_64_step (Gstep.c:71)
> ==8053==    by 0x4E3B9CF: trace_init_addr (Gtrace.c:248)
> ==8053==    by 0x4E3B9CF: trace_lookup (Gtrace.c:330)
> ==8053==    by 0x4E3B9CF: _ULx86_64_tdep_trace (Gtrace.c:447)
> ==8053==    by 0x4E38C8F: backtrace (backtrace.c:69)
> ==8053==    by 0x26185F: dump_stack (util.c:338)
> ==8053==    by 0x26185F: sighandler_dump_stack (util.c:356)
> ==8053==    by 0x69B232F: ??? (in /usr/lib/libc-2.23.so)
> ==8053==    by 0x6A748DA: __vsnprintf_chk (in /usr/lib/libc-2.23.so)
> ==8053==    by 0x1BBF93: vsnprintf (stdio2.h:77)
> ==8053==    by 0x1BBF93: scnprintf (kernel.h:91)
> ==8053==  Address 0xffeffa000 is on thread 1's stack
> ==8053==  in frame #7, created by backtrace (backtrace.c:59)
> ~~~~~~~~~~~~~~~~
 
> Any idea what I'm missing in the setup routine? It works fine for `perf trace 
> record --call-graph dwarf`.

Jiri?

I have to investigate this, I cooked up a patch almost the same as
yours, only using the top callchain OPT_ stuff because it also sets
those symbol_conf globals, but ended up having trouble with libunwind
:-\

BTW: Those callchain related globals have to go, finally, because I want
to be able to enable callchain collection/reporting per event, i.e.
output that shows callchains for some 'perf probe' events while not for
all syscalls except for futex(), etc.

- Arnaldo