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Subject[PATCH 20/20] perf probe: Support adding probes on offline kernel modules
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Support adding probes on offline kernel modules. This enables
perf-probe to trace kernel-module init functions via perf-probe.
If user gives the path of module with -m option, perf-probe
expects the module is offline.
This feature works with --add, --funcs, and --vars.

E.g)
# perf probe -m /lib/modules/`uname -r`/kernel/fs/btrfs/btrfs.ko \
-a "extent_io_init:5 extent_state_cache"
Add new events:
probe:extent_io_init (on extent_io_init:5 with extent_state_cache)
probe:extent_io_init_1 (on extent_io_init:5 with extent_state_cache)

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

perf record -e probe:extent_io_init_1 -aR sleep 1

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Link: http://lkml.kernel.org/r/20110627072751.6528.10230.stgit@fedora15
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
tools/perf/Documentation/perf-probe.txt | 6 ++-
tools/perf/builtin-probe.c | 3 +-
tools/perf/util/probe-event.c | 52 +++++++++++++++++++++++++-----
3 files changed, 49 insertions(+), 12 deletions(-)
diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 02bafce..2780d9c 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -34,9 +34,11 @@ OPTIONS
Specify vmlinux path which has debuginfo (Dwarf binary).

-m::
---module=MODNAME::
+--module=MODNAME|PATH::
Specify module name in which perf-probe searches probe points
- or lines.
+ or lines. If a path of module file is passed, perf-probe
+ treat it as an offline module (this means you can add a probe on
+ a module which has not been loaded yet).

-s::
--source=PATH::
diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 2c0e64d..5f2a5c7 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -242,7 +242,8 @@ static const struct option options[] = {
OPT_STRING('s', "source", &symbol_conf.source_prefix,
"directory", "path to kernel source"),
OPT_STRING('m', "module", &params.target_module,
- "modname", "target module name"),
+ "modname|path",
+ "target module name (for online) or path (for offline)"),
#endif
OPT__DRY_RUN(&probe_event_dry_run),
OPT_INTEGER('\0', "max-probes", &params.max_probe_points,
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index ee3f41e..b82d54f 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -117,6 +117,10 @@ static struct map *kernel_get_module_map(const char *module)
struct rb_node *nd;
struct map_groups *grp = &machine.kmaps;

+ /* A file path -- this is an offline module */
+ if (module && strchr(module, '/'))
+ return machine__new_module(&machine, 0, module);
+
if (!module)
module = "kernel";

@@ -173,12 +177,19 @@ const char *kernel_get_module_path(const char *module)
/* Open new debuginfo of given module */
static struct debuginfo *open_debuginfo(const char *module)
{
- const char *path = kernel_get_module_path(module);
+ const char *path;

- if (!path) {
- pr_err("Failed to find path of %s module.\n",
- module ?: "kernel");
- return NULL;
+ /* A file path -- this is an offline module */
+ if (module && strchr(module, '/'))
+ path = module;
+ else {
+ path = kernel_get_module_path(module);
+
+ if (!path) {
+ pr_err("Failed to find path of %s module.\n",
+ module ?: "kernel");
+ return NULL;
+ }
}
return debuginfo__new(path);
}
@@ -229,13 +240,36 @@ static int kprobe_convert_to_perf_probe(struct probe_trace_point *tp,
static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
int ntevs, const char *module)
{
- int i;
+ int i, ret = 0;
+ char *tmp;
+
+ if (!module)
+ return 0;
+
+ tmp = strrchr(module, '/');
+ if (tmp) {
+ /* This is a module path -- get the module name */
+ module = strdup(tmp + 1);
+ if (!module)
+ return -ENOMEM;
+ tmp = strchr(module, '.');
+ if (tmp)
+ *tmp = '\0';
+ tmp = (char *)module; /* For free() */
+ }
+
for (i = 0; i < ntevs; i++) {
tevs[i].point.module = strdup(module);
- if (!tevs[i].point.module)
- return -ENOMEM;
+ if (!tevs[i].point.module) {
+ ret = -ENOMEM;
+ break;
+ }
}
- return 0;
+
+ if (tmp)
+ free(tmp);
+
+ return ret;
}

/* Try to find perf_probe_event with debuginfo */
--
1.7.5.4



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