[PATCH 5.10 084/103] perf annotate: Fix jump parsing for C++ code.

From: Greg Kroah-Hartman
Date: Wed Sep 01 2021 - 08:44:42 EST

From: Martin Liška <mliska@xxxxxxx>

commit 1f0e6edcd968ff19211245f7da6039e983aa51e5 upstream.

Considering the following testcase:

int
foo(int a, int b)
{
for (unsigned i = 0; i < 1000000000; i++)
a += b;
return a;
}

int main()
{
foo (3, 4);
return 0;
}

'perf annotate' displays:

86.52 │40055e: → ja 40056c <foo(int, int)+0x26>
13.37 │400560: mov -0x18(%rbp),%eax
│400563: add %eax,-0x14(%rbp)
│400566: addl $0x1,-0x4(%rbp)
0.11 │40056a: → jmp 400557 <foo(int, int)+0x11>
│40056c: mov -0x14(%rbp),%eax
│40056f: pop %rbp

and the 'ja 40056c' does not link to the location in the function. It's
caused by fact that comma is wrongly parsed, it's part of function
signature.

With my patch I see:

86.52 │ ┌──ja 26
13.37 │ │ mov -0x18(%rbp),%eax
│ │ add %eax,-0x14(%rbp)
│ │ addl $0x1,-0x4(%rbp)
0.11 │ │↑ jmp 11
│26:└─→mov -0x14(%rbp),%eax

and 'o' output prints:

86.52 │4005┌── ↓ ja 40056c <foo(int, int)+0x26>
13.37 │4005│0: mov -0x18(%rbp),%eax
│4005│3: add %eax,-0x14(%rbp)
│4005│6: addl $0x1,-0x4(%rbp)
0.11 │4005│a: ↑ jmp 400557 <foo(int, int)+0x11>
│4005└─→ mov -0x14(%rbp),%eax

On the contrary, compiling the very same file with gcc -x c, the parsing
is fine because function arguments are not displayed:

jmp 400543 <foo+0x1d>

Committer testing:

Before:

$ cat cpp_args_annotate.c
int
foo(int a, int b)
{
for (unsigned i = 0; i < 1000000000; i++)
a += b;
return a;
}

int main()
{
foo (3, 4);
return 0;
}
$ gcc --version |& head -1
gcc (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)
$ gcc -g cpp_args_annotate.c -o cpp_args_annotate
$ perf record ./cpp_args_annotate
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.275 MB perf.data (7188 samples) ]
$ perf annotate --stdio2 foo
Samples: 7K of event 'cycles:u', 4000 Hz, Event count (approx.): 7468429289, [percent: local period]
foo() /home/acme/c/cpp_args_annotate
Percent
0000000000401106 <foo>:
foo():
int
foo(int a, int b)
{
push %rbp
mov %rsp,%rbp
mov %edi,-0x14(%rbp)
mov %esi,-0x18(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
movl $0x0,-0x4(%rbp)
↓ jmp 1d
a += b;
13.45 13: mov -0x18(%rbp),%eax
add %eax,-0x14(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
addl $0x1,-0x4(%rbp)
0.09 1d: cmpl $0x3b9ac9ff,-0x4(%rbp)
86.46 ↑ jbe 13
return a;
mov -0x14(%rbp),%eax
}
pop %rbp
← retq
$

I.e. works for C, now lets switch to C++:

$ g++ -g cpp_args_annotate.c -o cpp_args_annotate
$ perf record ./cpp_args_annotate
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.268 MB perf.data (6976 samples) ]
$ perf annotate --stdio2 foo
Samples: 6K of event 'cycles:u', 4000 Hz, Event count (approx.): 7380681761, [percent: local period]
foo() /home/acme/c/cpp_args_annotate
Percent
0000000000401106 <foo(int, int)>:
foo(int, int):
int
foo(int a, int b)
{
push %rbp
mov %rsp,%rbp
mov %edi,-0x14(%rbp)
mov %esi,-0x18(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
movl $0x0,-0x4(%rbp)
cmpl $0x3b9ac9ff,-0x4(%rbp)
86.53 → ja 40112c <foo(int, int)+0x26>
a += b;
13.32 mov -0x18(%rbp),%eax
0.00 add %eax,-0x14(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
addl $0x1,-0x4(%rbp)
0.15 → jmp 401117 <foo(int, int)+0x11>
return a;
mov -0x14(%rbp),%eax
}
pop %rbp
← retq
$

Reproduced.

Now with this patch:

Reusing the C++ built binary, as we can see here:

$ readelf -wi cpp_args_annotate | grep producer
<c> DW_AT_producer : (indirect string, offset: 0x2e): GNU C++14 10.2.1 20201125 (Red Hat 10.2.1-9) -mtune=generic -march=x86-64 -g
$

And furthermore:

$ file cpp_args_annotate
cpp_args_annotate: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=4fe3cab260204765605ec630d0dc7a7e93c361a9, for GNU/Linux 3.2.0, with debug_info, not stripped
$ perf buildid-list -i cpp_args_annotate
4fe3cab260204765605ec630d0dc7a7e93c361a9
$ perf buildid-list | grep cpp_args_annotate
4fe3cab260204765605ec630d0dc7a7e93c361a9 /home/acme/c/cpp_args_annotate
$

It now works:

$ perf annotate --stdio2 foo
Samples: 6K of event 'cycles:u', 4000 Hz, Event count (approx.): 7380681761, [percent: local period]
foo() /home/acme/c/cpp_args_annotate
Percent
0000000000401106 <foo(int, int)>:
foo(int, int):
int
foo(int a, int b)
{
push %rbp
mov %rsp,%rbp
mov %edi,-0x14(%rbp)
mov %esi,-0x18(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
movl $0x0,-0x4(%rbp)
11: cmpl $0x3b9ac9ff,-0x4(%rbp)
86.53 ↓ ja 26
a += b;
13.32 mov -0x18(%rbp),%eax
0.00 add %eax,-0x14(%rbp)
for (unsigned i = 0; i < 1000000000; i++)
addl $0x1,-0x4(%rbp)
0.15 ↑ jmp 11
return a;
26: mov -0x14(%rbp),%eax
}
pop %rbp
← retq
$

Signed-off-by: Martin Liška <mliska@xxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Link: http://lore.kernel.org/lkml/13e1a405-edf9-e4c2-4327-a9b454353730@xxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Hanjun Guo <guohanjun@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/perf/util/annotate.c | 8 ++++++++
tools/perf/util/annotate.h | 1 +
2 files changed, 9 insertions(+)

--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -317,12 +317,18 @@ bool ins__is_call(const struct ins *ins)
/*
* Prevents from matching commas in the comment section, e.g.:
* ffff200008446e70: b.cs ffff2000084470f4 <generic_exec_single+0x314> // b.hs, b.nlast
+ *
+ * and skip comma as part of function arguments, e.g.:
+ * 1d8b4ac <linemap_lookup(line_maps const*, unsigned int)+0xcc>
*/
static inline const char *validate_comma(const char *c, struct ins_operands *ops)
{
if (ops->raw_comment && c > ops->raw_comment)
return NULL;

+ if (ops->raw_func_start && c > ops->raw_func_start)
+ return NULL;
+
return c;
}

@@ -337,6 +343,8 @@ static int jump__parse(struct arch *arch
u64 start, end;

ops->raw_comment = strchr(ops->raw, arch->objdump.comment_char);
+ ops->raw_func_start = strchr(ops->raw, '<');
+
c = validate_comma(c, ops);

/*
--- a/tools/perf/util/annotate.h
+++ b/tools/perf/util/annotate.h
@@ -32,6 +32,7 @@ struct ins {
struct ins_operands {
char *raw;
char *raw_comment;
+ char *raw_func_start;
struct {
char *raw;
char *name;