linux-kernel - [RESEND PATCH 1/2] perf tools: Record text offset in dso to calculate objdump address

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Message-ID: <1460024671-64774-2-git-send-email-wangnan0@huawei.com>
Date:	Thu, 7 Apr 2016 10:24:30 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...hat.com>
CC:	<lizefan@...wei.com>, <pi3orama@....com>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Cody P Schafer <dev@...yps.com>,
	He Kuang <hekuang@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
	Kirill Smelkov <kirr@...edi.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: [RESEND PATCH 1/2] perf tools: Record text offset in dso to calculate objdump address

In this patch, the offset of '.text' section is stored into dso
and used here to re-calculate address to objdump.

In most of the cases, executable code is in '.text' section, so the
adjustment made to a symbol in dso__load_sym (using
sym.st_value -= shdr.sh_addr - shdr.sh_offset) should equal to
'sym.st_value -= dso->text_offset'. Therefore, adding text_offset back
get objdump address from symbol address (rip). However, it is not true
for kernel and kernel module since there could be multiple executable
sections with different offset. Exclude kernel for this reason.

After this patch, even dso->adjust_symbols is set to true for shared
objects, map__rip_2objdump() and map__objdump_2mem() would return
correct result, so perf behavior of annotate won't be changed.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Cody P Schafer <dev@...yps.com>
Cc: He Kuang <hekuang@...wei.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Kirill Smelkov <kirr@...edi.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Li Zefan <lizefan@...wei.com>
Cc: pi3orama@....com
---
 tools/perf/util/map.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 171b6d1..02c3186 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -431,6 +431,13 @@ u64 map__rip_2objdump(struct map *map, u64 rip)
 	if (map->dso->rel)
 		return rip - map->pgoff;
 
+	/*
+	 * kernel modules also have DSO_TYPE_USER in dso->kernel,
+	 * but all kernel modules are ET_REL, so won't get here.
+	 */
+	if (map->dso->kernel == DSO_TYPE_USER)
+		return rip + map->dso->text_offset;
+
 	return map->unmap_ip(map, rip) - map->reloc;
 }
 
@@ -454,6 +461,13 @@ u64 map__objdump_2mem(struct map *map, u64 ip)
 	if (map->dso->rel)
 		return map->unmap_ip(map, ip + map->pgoff);
 
+	/*
+	 * kernel modules also have DSO_TYPE_USER in dso->kernel,
+	 * but all kernel modules are ET_REL, so won't get here.
+	 */
+	if (map->dso->kernel == DSO_TYPE_USER)
+		return map->unmap_ip(map, ip - map->dso->text_offset);
+
 	return ip + map->reloc;
 }
 
-- 
1.8.3.4