Messages in this thread Patch in this message | | | From | Wang Nan <> | Subject | [PATCH] perf probe: Fix module probing with shortname | Date | Tue, 22 Sep 2015 03:34:32 +0000 |
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After commit 3d39ac538629e4f00a6e1c38d46346f1b8e69505 ("perf machine: No need to have two DSOs lists"), perf probe with module short name doesn't work again. For example:
# lsmod | grep e1000e e1000e 233472 0
# cat /proc/modules | grep e1000e e1000e 233472 0 - Live 0xffffffffa0073000
# cat /proc/kallsyms | grep '\<e1000e_up\>' ffffffffa0093860 t e1000e_up[e1000e]
# perf probe -v -m e1000e --add e1000e_up probe-definition(0): e1000e_up symbol:e1000e_up file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Failed to find module e1000e. Could not open debuginfo. Try to use symbols. Looking at the vmlinux_path (7 entries long) Using /lib/modules/4.2.0-rc7+/build/vmlinux for symbols e1000e_up is out of .text, skip it. Error: Failed to add events. Reason: No such file or directory (Code: -2)
This is caused by a misunderstood of dso->kernel in kernel_get_module_dso() that, for kernel module, dso->kernel is DSO_TYPE_USER. dso->kernel is DSO_TYPE_KERNEL iff dso is vmlinux.
This patch fix 'perf probe -m' with an ad-hoc way.
After this patch:
# perf probe -v -m e1000e --add e1000e_up probe-definition(0): e1000e_up symbol:e1000e_up file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Open Debuginfo file: /lib/modules/4.2.0-rc7+/kernel/drivers/net/ethernet/intel/e1000e/e1000e.ko Try to find probe point from debuginfo. Matched function: e1000e_up Probe point found: e1000e_up+0 Found 1 probe_trace_events. Opening /sys/kernel/debug/tracing//kprobe_events write=1 Writing event: p:probe/e1000e_up e1000e:e1000e_up+0 Added new event: probe:e1000e_up (on e1000e_up in e1000e)
You can now use it in all perf tools, such as:
perf record -e probe:e1000e_up -aR sleep 1
# perf probe -l Failed to find debug information for address ffffffffa0093860 probe:e1000e_up (on e1000e_up in e1000e)
Signed-off-by: Wang Nan <wangnan0@huawei.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> ---
I think there may be other places where dso->kernel is misused. machine__process_kernel_mmap_event() may be one of them. If I understand correctly, 'dso->kernel && is_kernel_module(dso->long_name)' should always false theoretically. However, I don't have enough time to check whether that code really cause problem.
--- tools/perf/util/probe-event.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 2b78e8f..c7d6d3d 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -270,7 +270,7 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso) if (module) { list_for_each_entry(dso, &host_machine->dsos.head, node) { - if (!dso->kernel) + if (dso->kernel) continue; if (strncmp(dso->short_name + 1, module, dso->short_name_len - 2) == 0) -- 1.8.3.4
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