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tracing/kprobes: Support module init function probing
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To support probing module init functions, kprobe-tracer allows
user to define a probe on non-existed function when it is given
with a module name. This also enables user to set a probe on
a function on a specific module, even if a same name (but different)
function is locally defined in another module.

The module name must be in the front of function name and separated
by a ':'. e.g. btrfs:btrfs_init_sysfs

Signed-off-by: Masami Hiramatsu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Link: http://lkml.kernel.org/r/20110627072656.6528.89970.stgit@fedora15
Signed-off-by: Steven Rostedt <[email protected]>
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@mhiramathitachi @rostedt
mhiramathitachi authored and rostedt committed Jul 15, 2011
1 parent bc81d48 commit 6142431
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Showing 2 changed files with 143 additions and 30 deletions.
9 changes: 5 additions & 4 deletions Documentation/trace/kprobetrace.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,14 +22,15 @@ current_tracer. Instead of that, add probe points via

Synopsis of kprobe_events
-------------------------
p[:[GRP/]EVENT] SYMBOL[+offs]|MEMADDR [FETCHARGS] : Set a probe
r[:[GRP/]EVENT] SYMBOL[+0] [FETCHARGS] : Set a return probe
p[:[GRP/]EVENT] [MOD:]SYM[+offs]|MEMADDR [FETCHARGS] : Set a probe
r[:[GRP/]EVENT] [MOD:]SYM[+0] [FETCHARGS] : Set a return probe
-:[GRP/]EVENT : Clear a probe

GRP : Group name. If omitted, use "kprobes" for it.
EVENT : Event name. If omitted, the event name is generated
based on SYMBOL+offs or MEMADDR.
SYMBOL[+offs] : Symbol+offset where the probe is inserted.
based on SYM+offs or MEMADDR.
MOD : Module name which has given SYM.
SYM[+offs] : Symbol+offset where the probe is inserted.
MEMADDR : Address where the probe is inserted.

FETCHARGS : Arguments. Each probe can have up to 128 args.
Expand Down
164 changes: 138 additions & 26 deletions kernel/trace/trace_kprobe.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -536,6 +536,7 @@ struct probe_arg {
/* Flags for trace_probe */
#define TP_FLAG_TRACE 1
#define TP_FLAG_PROFILE 2
#define TP_FLAG_REGISTERED 4

struct trace_probe {
struct list_head list;
Expand Down Expand Up @@ -565,6 +566,39 @@ static __kprobes const char *trace_probe_symbol(struct trace_probe *tp)
return tp->symbol ? tp->symbol : "unknown";
}

static __kprobes unsigned long trace_probe_offset(struct trace_probe *tp)
{
return tp->rp.kp.offset;
}

static __kprobes bool trace_probe_is_enabled(struct trace_probe *tp)
{
return !!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE));
}

static __kprobes bool trace_probe_is_registered(struct trace_probe *tp)
{
return !!(tp->flags & TP_FLAG_REGISTERED);
}

static __kprobes bool trace_probe_has_gone(struct trace_probe *tp)
{
return !!(kprobe_gone(&tp->rp.kp));
}

static __kprobes bool trace_probe_within_module(struct trace_probe *tp,
struct module *mod)
{
int len = strlen(mod->name);
const char *name = trace_probe_symbol(tp);
return strncmp(mod->name, name, len) == 0 && name[len] == ':';
}

static __kprobes bool trace_probe_is_on_module(struct trace_probe *tp)
{
return !!strchr(trace_probe_symbol(tp), ':');
}

static int register_probe_event(struct trace_probe *tp);
static void unregister_probe_event(struct trace_probe *tp);

Expand Down Expand Up @@ -689,7 +723,8 @@ static int enable_trace_probe(struct trace_probe *tp, int flag)
int ret = 0;

tp->flags |= flag;
if (tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) {
if (trace_probe_is_enabled(tp) && trace_probe_is_registered(tp) &&
!trace_probe_has_gone(tp)) {
if (trace_probe_is_return(tp))
ret = enable_kretprobe(&tp->rp);
else
Expand All @@ -703,21 +738,72 @@ static int enable_trace_probe(struct trace_probe *tp, int flag)
static void disable_trace_probe(struct trace_probe *tp, int flag)
{
tp->flags &= ~flag;
if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
if (!trace_probe_is_enabled(tp) && trace_probe_is_registered(tp)) {
if (trace_probe_is_return(tp))
disable_kretprobe(&tp->rp);
else
disable_kprobe(&tp->rp.kp);
}
}

/* Unregister a trace_probe and probe_event: call with locking probe_lock */
static void unregister_trace_probe(struct trace_probe *tp)
/* Internal register function - just handle k*probes and flags */
static int __register_trace_probe(struct trace_probe *tp)
{
int ret;

if (trace_probe_is_registered(tp))
return -EINVAL;

/* Set/clear disabled flag according to tp->flag */
if (trace_probe_is_enabled(tp))
tp->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
else
tp->rp.kp.flags |= KPROBE_FLAG_DISABLED;

if (trace_probe_is_return(tp))
unregister_kretprobe(&tp->rp);
ret = register_kretprobe(&tp->rp);
else
unregister_kprobe(&tp->rp.kp);
ret = register_kprobe(&tp->rp.kp);

if (ret == 0)
tp->flags |= TP_FLAG_REGISTERED;
else {
pr_warning("Could not insert probe at %s+%lu: %d\n",
trace_probe_symbol(tp), trace_probe_offset(tp), ret);
if (ret == -ENOENT && trace_probe_is_on_module(tp)) {
pr_warning("This probe might be able to register after"
"target module is loaded. Continue.\n");
ret = 0;
} else if (ret == -EILSEQ) {
pr_warning("Probing address(0x%p) is not an "
"instruction boundary.\n",
tp->rp.kp.addr);
ret = -EINVAL;
}
}

return ret;
}

/* Internal unregister function - just handle k*probes and flags */
static void __unregister_trace_probe(struct trace_probe *tp)
{
if (trace_probe_is_registered(tp)) {
if (trace_probe_is_return(tp))
unregister_kretprobe(&tp->rp);
else
unregister_kprobe(&tp->rp.kp);
tp->flags &= ~TP_FLAG_REGISTERED;
/* Cleanup kprobe for reuse */
if (tp->rp.kp.symbol_name)
tp->rp.kp.addr = NULL;
}
}

/* Unregister a trace_probe and probe_event: call with locking probe_lock */
static void unregister_trace_probe(struct trace_probe *tp)
{
__unregister_trace_probe(tp);
list_del(&tp->list);
unregister_probe_event(tp);
}
Expand All @@ -730,41 +816,65 @@ static int register_trace_probe(struct trace_probe *tp)

mutex_lock(&probe_lock);

/* register as an event */
/* Delete old (same name) event if exist */
old_tp = find_trace_probe(tp->call.name, tp->call.class->system);
if (old_tp) {
/* delete old event */
unregister_trace_probe(old_tp);
free_trace_probe(old_tp);
}

/* Register new event */
ret = register_probe_event(tp);
if (ret) {
pr_warning("Failed to register probe event(%d)\n", ret);
goto end;
}

tp->rp.kp.flags |= KPROBE_FLAG_DISABLED;
if (trace_probe_is_return(tp))
ret = register_kretprobe(&tp->rp);
else
ret = register_kprobe(&tp->rp.kp);

if (ret) {
pr_warning("Could not insert probe(%d)\n", ret);
if (ret == -EILSEQ) {
pr_warning("Probing address(0x%p) is not an "
"instruction boundary.\n",
tp->rp.kp.addr);
ret = -EINVAL;
}
/* Register k*probe */
ret = __register_trace_probe(tp);
if (ret < 0)
unregister_probe_event(tp);
} else
else
list_add_tail(&tp->list, &probe_list);

end:
mutex_unlock(&probe_lock);
return ret;
}

/* Module notifier call back, checking event on the module */
static int trace_probe_module_callback(struct notifier_block *nb,
unsigned long val, void *data)
{
struct module *mod = data;
struct trace_probe *tp;
int ret;

if (val != MODULE_STATE_COMING)
return NOTIFY_DONE;

/* Update probes on coming module */
mutex_lock(&probe_lock);
list_for_each_entry(tp, &probe_list, list) {
if (trace_probe_within_module(tp, mod)) {
__unregister_trace_probe(tp);
ret = __register_trace_probe(tp);
if (ret)
pr_warning("Failed to re-register probe %s on"
"%s: %d\n",
tp->call.name, mod->name, ret);
}
}
mutex_unlock(&probe_lock);

return NOTIFY_DONE;
}

static struct notifier_block trace_probe_module_nb = {
.notifier_call = trace_probe_module_callback,
.priority = 1 /* Invoked after kprobe module callback */
};

/* Split symbol and offset. */
static int split_symbol_offset(char *symbol, unsigned long *offset)
{
Expand Down Expand Up @@ -990,8 +1100,8 @@ static int create_trace_probe(int argc, char **argv)
{
/*
* Argument syntax:
* - Add kprobe: p[:[GRP/]EVENT] KSYM[+OFFS]|KADDR [FETCHARGS]
* - Add kretprobe: r[:[GRP/]EVENT] KSYM[+0] [FETCHARGS]
* - Add kprobe: p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS]
* - Add kretprobe: r[:[GRP/]EVENT] [MOD:]KSYM[+0] [FETCHARGS]
* Fetch args:
* $retval : fetch return value
* $stack : fetch stack address
Expand Down Expand Up @@ -1186,7 +1296,6 @@ static void release_all_trace_probes(void)
mutex_unlock(&probe_lock);
}


/* Probes listing interfaces */
static void *probes_seq_start(struct seq_file *m, loff_t *pos)
{
Expand Down Expand Up @@ -1827,6 +1936,9 @@ static __init int init_kprobe_trace(void)
struct dentry *d_tracer;
struct dentry *entry;

if (register_module_notifier(&trace_probe_module_nb))
return -EINVAL;

d_tracer = tracing_init_dentry();
if (!d_tracer)
return 0;
Expand Down

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