Messages in this thread | | | Date | Fri, 16 Jun 2017 08:14:56 +0200 | From | Jan Kratochvil <> | Subject | Re: perf report: fix off-by-one for non-activation frames |
| |
On Mon, 15 May 2017 17:04:44 +0200, Milian Wolff wrote:
commit 1982ad48fc82c284a5cc55697a012d3357e84d01 Author: Milian Wolff <milian.wolff@kdab.com> Date: Wed May 24 15:21:25 2017 +0900
> --- a/tools/perf/util/unwind-libdw.c > +++ b/tools/perf/util/unwind-libdw.c > @@ -168,12 +168,16 @@ frame_callback(Dwfl_Frame *state, void *arg) ... > + if (!isactivation) > + --pc; > +
FYI I find it as a regression a bit:
perf-4.11.4-200.fc25.x86_64 30c563 gdb_main (/usr/libexec/gdb) fae48 main (/usr/libexec/gdb) 0x000055555564ee43 <+51>: callq 0x55555585f340 <gdb_main(captured_main_args*)> 0x000055555564ee48 <+56>: mov 0x18(%rsp),%rcx
perf-4.12.0-0.rc5.git0.1.fc27.x86_64 39e32e gdb_main (/usr/libexec/gdb) 10b6fa main (/usr/libexec/gdb) 0x000055555565f6f6 <+54>: callq 0x5555558f17a0 <gdb_main(captured_main_args*)> 0x000055555565f6fb <+59>: mov 0x18(%rsp),%rcx
In backtraces it is correct to show the source line of the calling line - as perf does now after your fix - but one still should report PC address of the start of the next instruction. At least this is what debuggers are used to do:
#9 gdb_main (args=0x7fffffffe2e0) at ../../gdb/main.c:1257 #10 0x000055555565f6fb in main (argc=<optimized out>, argv=<optimized out>) at ../../gdb/gdb.c:40 0x000055555565f6f6 <+54>: callq 0x5555558f17a0 <gdb_main(captured_main_args*)> => 0x000055555565f6fb <+59>: mov 0x18(%rsp),%rcx Line 40 of "../../gdb/gdb.c" starts at address 0x55555565f6f6 <main(int, char**)+54> and ends at 0x55555565f6fb <main(int, char**)+59>. Line 41 of "../../gdb/gdb.c" starts at address 0x55555565f6fb <main(int, char**)+59> and ends at 0x55555565f715.
You see "gdb.c:40" and 0x000055555565f6fb in the backtrace despite 0x55555565f6fb is already line 41.
This is also why elfutils reports separately PC and 'isactivation' flag. Instead of just reporting decreased PC.
Jan
| |