perf symbols: Fix symbols searching for module in buildid-cache
Before this patch, if a sample is triggered inside a module not in
/lib/modules/`uname -r`/, even if the module is in buildid-cache, 'perf
report' will still be unable to find the 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 its file is found in some well know directories. All
files loaded from buildid-cache are 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@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Cody P Schafer <dev@codyps.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jeremie Galarneau <jeremie.galarneau@efficios.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kirill Smelkov <kirr@nexedi.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1454680939-24963-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index b28100e..f1479ee 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -166,6 +166,50 @@
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) \
