From f08046cb3082b313e7b08dc35838cf8bd902c36b Mon Sep 17 00:00:00 2001
From: Adrian Hunter <adrian.hunter@intel.com>
Date: Wed, 9 Jan 2019 11:18:33 +0200
Subject: 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>
---
tools/perf/scripts/python/export-to-sqlite.py | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'tools/perf/scripts/python/export-to-sqlite.py')
diff --git a/tools/perf/scripts/python/export-to-sqlite.py b/tools/perf/scripts/python/export-to-sqlite.py
index 245caf2643ed..ed237f2ed03f 100644
--- a/tools/perf/scripts/python/export-to-sqlite.py
+++ b/tools/perf/scripts/python/export-to-sqlite.py
@@ -320,7 +320,7 @@ if perf_db_export_calls:
'branch_count,'
'call_id,'
'return_id,'
- 'CASE WHEN flags=1 THEN \'no call\' WHEN flags=2 THEN \'no return\' WHEN flags=3 THEN \'no call/return\' ELSE \'\' END AS flags,'
+ 'CASE WHEN flags=0 THEN \'\' WHEN flags=1 THEN \'no call\' WHEN flags=2 THEN \'no return\' WHEN flags=3 THEN \'no call/return\' WHEN flags=6 THEN \'jump\' ELSE flags END AS flags,'
'parent_call_path_id'
' FROM calls INNER JOIN call_paths ON call_paths.id = call_path_id')
--
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