[PATCH 08/10] perf probe: Allow probing on kmodules without dwarf

From: Arnaldo Carvalho de Melo
Date: Fri Oct 02 2015 - 16:28:48 EST


From: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>

Allow probing on kernel modules when 'perf' is built without debuginfo
support.

Currently perf-probe --module requires linking with libdw, but this
doesn't make sense.

E.g.
----
# make NO_DWARF=1
# ./perf probe -m pcspkr pcspkr_event%return
Error: unknown switch `m'
----

With this patch
----
# ./perf probe -m pcspkr pcspkr_event%return
Added new event:
probe:pcspkr_event (on pcspkr_event%return in pcspkr)

You can now use it in all perf tools, such as:

perf record -e probe:pcspkr_event -aR sleep 1
----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20151002125832.18617.78721.stgit@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/builtin-probe.c | 8 +++-----
tools/perf/util/probe-event.c | 8 +++++---
2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index f7882ae9ebc6..530c3a28a58c 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -182,10 +182,8 @@ static int opt_set_target(const struct option *opt, const char *str,
if (str) {
if (!strcmp(opt->long_name, "exec"))
params.uprobes = true;
-#ifdef HAVE_DWARF_SUPPORT
else if (!strcmp(opt->long_name, "module"))
params.uprobes = false;
-#endif
else
return ret;

@@ -490,9 +488,6 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
"file", "vmlinux pathname"),
OPT_STRING('s', "source", &symbol_conf.source_prefix,
"directory", "path to kernel source"),
- OPT_CALLBACK('m', "module", NULL, "modname|path",
- "target module name (for online) or path (for offline)",
- opt_set_target),
OPT_BOOLEAN('\0', "no-inlines", &probe_conf.no_inlines,
"Don't search inlined functions"),
#endif
@@ -509,6 +504,9 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
opt_set_filter),
OPT_CALLBACK('x', "exec", NULL, "executable|path",
"target executable name or path", opt_set_target),
+ OPT_CALLBACK('m', "module", NULL, "modname|path",
+ "target module name (for online) or path (for offline)",
+ opt_set_target),
OPT_BOOLEAN(0, "demangle", &symbol_conf.demangle,
"Enable symbol demangling"),
OPT_BOOLEAN(0, "demangle-kernel", &symbol_conf.demangle_kernel,
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 3010abc071ff..b51a8bfb40f9 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2543,7 +2543,8 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
goto out;
}

- if (!pev->uprobes && !pp->retprobe) {
+ /* Note that the symbols in the kmodule are not relocated */
+ if (!pev->uprobes && !pp->retprobe && !pev->target) {
reloc_sym = kernel_get_ref_reloc_sym();
if (!reloc_sym) {
pr_warning("Relocated base symbol is not found!\n");
@@ -2580,8 +2581,9 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
}
/* Add one probe point */
tp->address = map->unmap_ip(map, sym->start) + pp->offset;
- /* If we found a wrong one, mark it by NULL symbol */
- if (!pev->uprobes &&
+
+ /* Check the kprobe (not in module) is within .text */
+ if (!pev->uprobes && !pev->target &&
kprobe_warn_out_range(sym->name, tp->address)) {
tp->symbol = NULL; /* Skip it */
skipped++;
--
2.1.0

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