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author | 2019-01-09 11:18:33 +0200 | |
---|---|---|
committer | 2019-02-06 10:00:40 -0300 | |
commit | f08046cb3082b313e7b08dc35838cf8bd902c36b (patch) | |
tree | 01ab2af620c66c6f595e14b235299679cabf24e0 /tools/perf/util/thread-stack.c | |
parent | perf thread-stack: Tidy thread_stack__no_call_return() by adding more local v... (diff) | |
download | linux-f08046cb3082b313e7b08dc35838cf8bd902c36b.tar.gz linux-f08046cb3082b313e7b08dc35838cf8bd902c36b.tar.bz2 linux-f08046cb3082b313e7b08dc35838cf8bd902c36b.zip |
perf thread-stack: Represent jmps to the start of a different symbol
The compiler might optimize a call/ret combination by making it a jmp.
However the thread-stack does not presently cater for that, so that such
control flow is not visible in the call graph. Make it visible by
recording on the stack a branch to the start of a different symbol.
Note, that means when a ret pops the stack, all jmps must be popped off
first.
Example:
$ cat jmp-to-fn.c
__attribute__((noinline)) int bar(void)
{
return -1;
}
__attribute__((noinline)) int foo(void)
{
return bar() + 1;
}
int main()
{
return foo();
}
$ gcc -ggdb3 -Wall -Wextra -O2 -o jmp-to-fn jmp-to-fn.c
$ objdump -d jmp-to-fn
<SNIP>
0000000000001040 <main>:
1040: 31 c0 xor %eax,%eax
1042: e9 09 01 00 00 jmpq 1150 <foo>
<SNIP>
0000000000001140 <bar>:
1140: b8 ff ff ff ff mov $0xffffffff,%eax
1145: c3 retq
<SNIP>
0000000000001150 <foo>:
1150: 31 c0 xor %eax,%eax
1152: e8 e9 ff ff ff callq 1140 <bar>
1157: 83 c0 01 add $0x1,%eax
115a: c3 retq
<SNIP>
$ perf record -o jmp-to-fn.perf.data -e intel_pt/cyc/u ./jmp-to-fn
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0,017 MB jmp-to-fn.perf.data ]
$ perf script -i jmp-to-fn.perf.data --itrace=be -s ~/libexec/perf-core/scripts/python/export-to-sqlite.py jmp-to-fn.db branches calls
2019-01-08 13:24:58.783069 Creating database...
2019-01-08 13:24:58.794650 Writing records...
2019-01-08 13:24:59.008050 Adding indexes
2019-01-08 13:24:59.015802 Done
$ ~/libexec/perf-core/scripts/python/exported-sql-viewer.py jmp-to-fn.db
Before:
main
-> bar
After:
main
-> foo
-> bar
Committer testing:
Install the python2-pyside package, then select these menu options
on the GUI:
"Reports"
"Context sensitive callgraphs"
Then go on expanding the symbols, to get, full picture when doing this
on a fedora:29 with gcc version 8.2.1 20181215 (Red Hat 8.2.1-6) (GCC):
jmp-to-fn
PID:TID
_start (ld-2.28.so)
__libc_start_main
main
foo
bar
To verify that indeed, this fixes the problem.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20190109091835.5570-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/thread-stack.c')
-rw-r--r-- | tools/perf/util/thread-stack.c | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c index 7f8eff018c16..f52c0f90915d 100644 --- a/tools/perf/util/thread-stack.c +++ b/tools/perf/util/thread-stack.c @@ -38,6 +38,7 @@ * @cp: call path * @no_call: a 'call' was not seen * @trace_end: a 'call' but trace ended + * @non_call: a branch but not a 'call' to the start of a different symbol */ struct thread_stack_entry { u64 ret_addr; @@ -47,6 +48,7 @@ struct thread_stack_entry { struct call_path *cp; bool no_call; bool trace_end; + bool non_call; }; /** @@ -268,6 +270,8 @@ static int thread_stack__call_return(struct thread *thread, cr.flags |= CALL_RETURN_NO_CALL; if (no_return) cr.flags |= CALL_RETURN_NO_RETURN; + if (tse->non_call) + cr.flags |= CALL_RETURN_NON_CALL; return crp->process(&cr, crp->data); } @@ -510,6 +514,7 @@ static int thread_stack__push_cp(struct thread_stack *ts, u64 ret_addr, tse->cp = cp; tse->no_call = no_call; tse->trace_end = trace_end; + tse->non_call = false; return 0; } @@ -531,14 +536,16 @@ static int thread_stack__pop_cp(struct thread *thread, struct thread_stack *ts, timestamp, ref, false); } - if (ts->stack[ts->cnt - 1].ret_addr == ret_addr) { + if (ts->stack[ts->cnt - 1].ret_addr == ret_addr && + !ts->stack[ts->cnt - 1].non_call) { return thread_stack__call_return(thread, ts, --ts->cnt, timestamp, ref, false); } else { size_t i = ts->cnt - 1; while (i--) { - if (ts->stack[i].ret_addr != ret_addr) + if (ts->stack[i].ret_addr != ret_addr || + ts->stack[i].non_call) continue; i += 1; while (ts->cnt > i) { @@ -757,6 +764,25 @@ int thread_stack__process(struct thread *thread, struct comm *comm, err = thread_stack__trace_begin(thread, ts, sample->time, ref); } else if (sample->flags & PERF_IP_FLAG_TRACE_END) { err = thread_stack__trace_end(ts, sample, ref); + } else if (sample->flags & PERF_IP_FLAG_BRANCH && + from_al->sym != to_al->sym && to_al->sym && + to_al->addr == to_al->sym->start) { + struct call_path_root *cpr = ts->crp->cpr; + struct call_path *cp; + + /* + * The compiler might optimize a call/ret combination by making + * it a jmp. Make that visible by recording on the stack a + * branch to the start of a different symbol. Note, that means + * when a ret pops the stack, all jmps must be popped off first. + */ + cp = call_path__findnew(cpr, ts->stack[ts->cnt - 1].cp, + to_al->sym, sample->addr, + ts->kernel_start); + err = thread_stack__push_cp(ts, 0, sample->time, ref, cp, false, + false); + if (!err) + ts->stack[ts->cnt - 1].non_call = true; } return err; |