summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorNamhyung Kim <namhyung@kernel.org>2014-11-04 10:14:33 +0900
committerArnaldo Carvalho de Melo <acme@redhat.com>2014-11-05 10:14:08 -0300
commitb837a8bdc48925e6512412973b845c53cbe2b412 (patch)
tree4500fe49d11b079e963cd63d5fe8617fa4c88761
parent00dc865798a31d3d5300dd5d70166a4a85f76a20 (diff)
perf tools: Fix build-id matching on vmlinux
There's a problem on finding correct kernel symbols when perf report runs on a different kernel. Although a part of the problem was solved by the prior commit 0a7e6d1b6844 ("perf tools: Check recorded kernel version when finding vmlinux"), there's a remaining problem still. When perf records samples, it synthesizes the kernel map using machine__mmap_name() and ref_reloc_sym like "[kernel.kallsyms]_text". You can easily see it using 'perf report -D' command. After finishing record, it goes through the recorded events to find maps/dsos actually used. And then record build-id info of them. During this process, it needs to load symbols in a dso and it'd call dso__load_vmlinux_path() since the default value of the symbol_conf. try_vmlinux_path is true. However it changes dso->long_name to a real path of the vmlinux file (e.g. /lib/modules/3.16.4/build/vmlinux) if one is running on a custom kernel. It resulted in that perf report reads the build-id of the vmlinux, but cannot use it since it only knows about the [kernel.kallsyms] map. It then falls back to possible vmlinux paths by using the recorded kernel version (in case of a recent version) or a running kernel silently. Even with the recent tools, this still has a possibility of breaking the result. As the build directory is a symbolic link, if one built a new kernel in the same directory with different source/config, the old link to vmlinux will point the new file. So it's absolutely needed to use build-id when finding a kernel image. In this patch, it's now changed to try to search a kernel dso in the existing dso list which was constructed during build-id table parsing so it'll always have a build-id. If not found, search "[kernel.kallsyms]". Before: $ perf report # Children Self Command Shared Object Symbol # ........ ........ ....... ................. ............................... # 72.15% 0.00% swapper [kernel.kallsyms] [k] set_curr_task_rt 72.15% 0.00% swapper [kernel.kallsyms] [k] native_calibrate_tsc 72.15% 0.00% swapper [kernel.kallsyms] [k] tsc_refine_calibration_work 71.87% 71.87% swapper [kernel.kallsyms] [k] module_finalize ... After (for the same perf.data): 72.15% 0.00% swapper vmlinux [k] cpu_startup_entry 72.15% 0.00% swapper vmlinux [k] arch_cpu_idle 72.15% 0.00% swapper vmlinux [k] default_idle 71.87% 71.87% swapper vmlinux [k] native_safe_halt ... Signed-off-by: Namhyung Kim <namhyung@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org> Link: http://lkml.kernel.org/r/20140924073356.GB1962@gmail.com Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/r/1415063674-17206-8-git-send-email-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-rw-r--r--tools/perf/util/header.c2
-rw-r--r--tools/perf/util/machine.c16
2 files changed, 15 insertions, 3 deletions
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 3e2c156d9c64..76442caca37e 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1269,7 +1269,7 @@ static int __event_process_build_id(struct build_id_event *bev,
dso__set_build_id(dso, &bev->build_id);
- if (filename[0] == '[')
+ if (!is_kernel_module(filename, NULL))
dso->kernel = dso_type;
build_id__sprintf(dso->build_id, sizeof(dso->build_id),
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 946c7d62cb6e..53f90e9c65fe 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1085,8 +1085,20 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
* Should be there already, from the build-id table in
* the header.
*/
- struct dso *kernel = __dsos__findnew(&machine->kernel_dsos,
- kmmap_prefix);
+ struct dso *kernel = NULL;
+ struct dso *dso;
+
+ list_for_each_entry(dso, &machine->kernel_dsos.head, node) {
+ if (is_kernel_module(dso->long_name, NULL))
+ continue;
+
+ kernel = dso;
+ break;
+ }
+
+ if (kernel == NULL)
+ kernel = __dsos__findnew(&machine->kernel_dsos,
+ kmmap_prefix);
if (kernel == NULL)
goto out_problem;