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Subject[PATCH 1/2] perf script: Show virtual addresses instead of offsets
Date
When perf data is recorded with the call-graph option enabled,
the callchain shown by perf script shows the binary offsets of
the symbols as the ip. This is incorrect for kernel symbols as
the ip values are always off by a fixed offset depending on the
architecture. If the offsets from the start of the symbols are
printed, they are also incorrect for both kernel and userspace
symbols.

Without the call-graph option, the callchain shows the virtual
addresses of the symbols rather than their binary offsets. The
offsets printed in this case are also correct.

This fixes the inconsistency in perf script's output.

This can be verified on a powerpc64le system running Fedora 27
as follows:

# cat /proc/kallsyms | grep sys_write
...
c0000000004025a0 T sys_write
c0000000004025a0 T __se_sys_write
...

# perf probe -a sys_write

Before applying this patch:

# perf record -e probe:sys_write -g ~/test
# perf script -F ip,sym,symoff

4125b0 sys_write+0x8000000000008010
1b9e0 system_call+0x8000000000008058
118234 __GI___libc_write+0xffff0000f52c0024
92c74 _IO_file_write@@GLIBC_2.17+0xffff0000f52c0044
5afbfd8a [unknown]
91a60 new_do_write+0xffff0000f52c0090
94638 _IO_do_write@@GLIBC_2.17+0xffff0000f52c0038
94bbc _IO_file_overflow@@GLIBC_2.17+0xffff0000f52c014c
95a24 __overflow+0xffff0000f52c0064
84548 _IO_puts+0xffff0000f52c0218
440 main+0xffffffffe0000020
236a0 generic_start_main.isra.0+0xffff0000f52c0140
23898 __libc_start_main+0xffff0000f52c00b8
0 [unknown]
...

# perf record -e probe:sys_write ~/test
# perf script -F ip,sym,symoff

c0000000004025b0 sys_write+0x10
...

After applying this patch:

# perf record -e probe:sys_write -g ~/test
# perf script -F ip,sym,symoff

c0000000004025b0 sys_write+0x10
c00000000000b9e0 system_call+0x58
7fffb70d8234 __GI___libc_write+0x24
7fffb7052c74 _IO_file_write@@GLIBC_2.17+0x44
5afc1818 [unknown]
7fffb7051a60 new_do_write+0x90
7fffb7054638 _IO_do_write@@GLIBC_2.17+0x38
7fffb7054bbc _IO_file_overflow@@GLIBC_2.17+0x14c
7fffb7055a24 __overflow+0x64
7fffb7044548 _IO_puts+0x218
10000440 main+0x20
7fffb6fe36a0 generic_start_main.isra.0+0x140
7fffb6fe3898 __libc_start_main+0xb8
0 [unknown]
...

# perf record -e probe:sys_write ~/test
# perf script -F ip,sym,symoff

c0000000004025b0 sys_write+0x10
...

Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
---
tools/perf/util/machine.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 72a351613d85..7c777cb32806 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1764,7 +1764,7 @@ static int add_callchain_ip(struct thread *thread,
}

srcline = callchain_srcline(al.map, al.sym, al.addr);
- return callchain_cursor_append(cursor, al.addr, al.map, al.sym,
+ return callchain_cursor_append(cursor, ip, al.map, al.sym,
branch, flags, nr_loop_iter,
iter_cycles, branch_from, srcline);
}
--
2.14.3
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