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Message-ID: <1450793243-191120-1-git-send-email-wangnan0@huawei.com>
Date: Tue, 22 Dec 2015 14:07:23 +0000
From: Wang Nan <wangnan0@...wei.com>
To: <acme@...nel.org>, <masami.hiramatsu.pt@...achi.com>,
<namhyung@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <pi3orama@....com>,
Wang Nan <wangnan0@...wei.com>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Li Zefan <lizefan@...wei.com>
Subject: [PATCH] perf tools: Fix symbols searching for offline module in buildid-cache
Before this patch, if a sample is triggered inside an offline module
(module not in /lib/modules/`uname -r`/), even if the module is in
buildid-cache, 'perf report' is still unable to get correct symbol.
For example:
# rm -rf ~/.debug/
# perf buildid-cache -a ./mymodule.ko
# perf probe -m ./mymodule.ko -a get_mymodule_val
Added new event:
probe:get_mymodule_val (on get_mymodule_val in mymodule)
You can now use it in all perf tools, such as:
perf record -e probe:get_mymodule_val -aR sleep 1
# perf record -e probe:get_mymodule_val cat /proc/mymodule
mymodule:3
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.011 MB perf.data (1 samples) ]
# perf report --stdio
[SNIP]
#
# Overhead Command Shared Object Symbol
# ........ ....... ................ ......................
#
100.00% cat [mymodule] [k] 0x0000000000000001
# perf report -vvvv --stdio
dso__load_sym: adjusting symbol: st_value: 0 sh_addr: 0 sh_offset: 0x70
symbol__new: get_mymodule_val 0x70-0x8a
[SNIP]
This is caused by dso__load() -> dso__load_sym(). In dso__load(), kmod
is true only when dso is regular kernel module. All files loaded from
buildid-cache is treated as user programs. Following dso__load_sym()
set map->pgoff incorrectly.
This patch gives kernel modules in buildid-cache a chance to adjust
value of kmod. After dso__load() get the type of symbols, if it is
buildid, check the last 3 chars of original filename against '.ko',
and adjust the value of kmod if the file is a kernel module.
Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Li Zefan <lizefan@...wei.com>
---
tools/perf/util/build-id.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/build-id.h | 1 +
tools/perf/util/symbol.c | 4 ++++
3 files changed, 49 insertions(+)
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 6a7e273..6b18082 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -166,6 +166,50 @@ char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size)
return build_id__filename(build_id_hex, bf, size);
}
+bool dso__build_id_is_kmod(const struct dso *dso, char *bf, size_t size)
+{
+ char *id_name, *ch;
+ struct stat sb;
+
+ id_name = dso__build_id_filename(dso, bf, size);
+ if (!id_name)
+ goto err;
+ if (access(id_name, F_OK))
+ goto err;
+ if (lstat(id_name, &sb) == -1)
+ goto err;
+ if ((size_t)sb.st_size > size - 1)
+ goto err;
+ if (readlink(id_name, bf, size - 1) < 0)
+ goto err;
+
+ bf[sb.st_size] = '\0';
+
+ /*
+ * link should be:
+ * ../../lib/modules/4.4.0-rc4/kernel/net/ipv4/netfilter/nf_nat_ipv4.ko/a09fe3eb3147dafa4e3b31dbd6257e4d696bdc92
+ */
+ ch = strrchr(bf, '/');
+ if (!ch)
+ goto err;
+ if (ch - 3 < bf)
+ goto err;
+
+ return strncmp(".ko", ch - 3, 3) == 0;
+err:
+ /*
+ * If dso__build_id_filename work, get id_name again,
+ * because id_name points to bf and is broken.
+ */
+ if (id_name)
+ id_name = dso__build_id_filename(dso, bf, size);
+ pr_err("Invalid build id: %s\n", id_name ? :
+ dso->long_name ? :
+ dso->short_name ? :
+ "[unknown]");
+ return false;
+}
+
#define dsos__for_each_with_build_id(pos, head) \
list_for_each_entry(pos, head, node) \
if (!pos->has_build_id) \
diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index 27a14a8..64af3e2 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -16,6 +16,7 @@ int sysfs__sprintf_build_id(const char *root_dir, char *sbuild_id);
int filename__sprintf_build_id(const char *pathname, char *sbuild_id);
char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size);
+bool dso__build_id_is_kmod(const struct dso *dso, char *bf, size_t size);
int build_id__mark_dso_hit(struct perf_tool *tool, union perf_event *event,
struct perf_sample *sample, struct perf_evsel *evsel,
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index d51abd2..ec0f042 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1524,6 +1524,10 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
if (!runtime_ss && syms_ss)
runtime_ss = syms_ss;
+ if (syms_ss && syms_ss->type == DSO_BINARY_TYPE__BUILD_ID_CACHE)
+ if (dso__build_id_is_kmod(dso, name, PATH_MAX))
+ kmod = true;
+
if (syms_ss)
ret = dso__load_sym(dso, map, syms_ss, runtime_ss, filter, kmod);
else
--
1.8.3.4
--
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