perf probe: Support adding probes on offline kernel modules

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>

3 files changed, 49 insertions, 12 deletions

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 02bafce4b341..2780d9ce48bf 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 2c0e64d0b4aa..5f2a5c7046df 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 ee3f41eec5c1..b82d54fa2c56 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 */