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Date: Fri, 31 May 2024 18:48:06 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: don <zds100@...il.com>,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org,
mhiramat@...nel.org
Subject: [PATCH] tracing/fprobe: Support raw tracepoint events on modules
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Support raw tracepoint event on module by fprobe events.
Since it only uses for_each_kernel_tracepoint() to find a tracepoint,
the tracepoints on modules are not handled. Thus if user specified a
tracepoint on a module, it shows an error.
This adds new for_each_module_tracepoint() API to tracepoint subsystem,
and uses it to find tracepoints on modules.
Reported-by: don <zds100@...il.com>
Closes: https://lore.kernel.org/all/20240530215718.aeec973a1d0bf058d39cb1e3@kernel.org/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
include/linux/tracepoint.h | 7 +++++++
kernel/trace/trace_fprobe.c | 46 ++++++++++++++++++++++++++++++++++++-------
kernel/tracepoint.c | 19 ++++++++++++++++++
3 files changed, 64 insertions(+), 8 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 689b6d71590e..46e6a5e759fd 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -65,6 +65,8 @@ struct tp_module {
bool trace_module_has_bad_taint(struct module *mod);
extern int register_tracepoint_module_notifier(struct notifier_block *nb);
extern int unregister_tracepoint_module_notifier(struct notifier_block *nb);
+void for_each_module_tracepoint(void (*fct)(struct tracepoint *, void *),
+ void *priv);
#else
static inline bool trace_module_has_bad_taint(struct module *mod)
{
@@ -80,6 +82,11 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb)
{
return 0;
}
+static inline
+void for_each_module_tracepoint(void (*fct)(struct tracepoint *, void *),
+ void *priv)
+{
+}
#endif /* CONFIG_MODULES */
/*
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 62e6a8f4aae9..1d8a983e1edc 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -385,6 +385,7 @@ static struct trace_fprobe *alloc_trace_fprobe(const char *group,
const char *event,
const char *symbol,
struct tracepoint *tpoint,
+ struct module *mod,
int maxactive,
int nargs, bool is_return)
{
@@ -405,6 +406,7 @@ static struct trace_fprobe *alloc_trace_fprobe(const char *group,
tf->fp.entry_handler = fentry_dispatcher;
tf->tpoint = tpoint;
+ tf->mod = mod;
tf->fp.nr_maxactive = maxactive;
ret = trace_probe_init(&tf->tp, event, group, false, nargs);
@@ -895,8 +897,23 @@ static struct notifier_block tracepoint_module_nb = {
struct __find_tracepoint_cb_data {
const char *tp_name;
struct tracepoint *tpoint;
+ struct module *mod;
};
+static void __find_tracepoint_module_cb(struct tracepoint *tp, void *priv)
+{
+ struct __find_tracepoint_cb_data *data = priv;
+
+ if (!data->tpoint && !strcmp(data->tp_name, tp->name)) {
+ data->tpoint = tp;
+ data->mod = __module_text_address((unsigned long)tp->probestub);
+ if (!try_module_get(data->mod)) {
+ data->tpoint = NULL;
+ data->mod = NULL;
+ }
+ }
+}
+
static void __find_tracepoint_cb(struct tracepoint *tp, void *priv)
{
struct __find_tracepoint_cb_data *data = priv;
@@ -905,14 +922,28 @@ static void __find_tracepoint_cb(struct tracepoint *tp, void *priv)
data->tpoint = tp;
}
-static struct tracepoint *find_tracepoint(const char *tp_name)
+/*
+ * Find a tracepoint from kernel and module. If the tracepoint is in a module,
+ * this increments the module refcount to prevent unloading until the
+ * trace_fprobe is registered to the list. After registering the trace_fprobe
+ * on the trace_fprobe list, the module refcount is decremented because
+ * tracepoint_probe_module_cb will handle it.
+ */
+static struct tracepoint *find_tracepoint(const char *tp_name,
+ struct module **tp_mod)
{
struct __find_tracepoint_cb_data data = {
.tp_name = tp_name,
+ .mod = NULL,
};
for_each_kernel_tracepoint(__find_tracepoint_cb, &data);
+ if (!data.tpoint && IS_ENABLED(CONFIG_MODULES)) {
+ for_each_module_tracepoint(__find_tracepoint_module_cb, &data);
+ *tp_mod = data.mod;
+ }
+
return data.tpoint;
}
@@ -996,6 +1027,7 @@ static int __trace_fprobe_create(int argc, const char *argv[])
char abuf[MAX_BTF_ARGS_LEN];
char *dbuf = NULL;
bool is_tracepoint = false;
+ struct module *tp_mod = NULL;
struct tracepoint *tpoint = NULL;
struct traceprobe_parse_context ctx = {
.flags = TPARG_FL_KERNEL | TPARG_FL_FPROBE,
@@ -1080,7 +1112,7 @@ static int __trace_fprobe_create(int argc, const char *argv[])
if (is_tracepoint) {
ctx.flags |= TPARG_FL_TPOINT;
- tpoint = find_tracepoint(symbol);
+ tpoint = find_tracepoint(symbol, &tp_mod);
if (!tpoint) {
trace_probe_log_set_index(1);
trace_probe_log_err(0, NO_TRACEPOINT);
@@ -1110,8 +1142,8 @@ static int __trace_fprobe_create(int argc, const char *argv[])
goto out;
/* setup a probe */
- tf = alloc_trace_fprobe(group, event, symbol, tpoint, maxactive,
- argc, is_return);
+ tf = alloc_trace_fprobe(group, event, symbol, tpoint, tp_mod,
+ maxactive, argc, is_return);
if (IS_ERR(tf)) {
ret = PTR_ERR(tf);
/* This must return -ENOMEM, else there is a bug */
@@ -1119,10 +1151,6 @@ static int __trace_fprobe_create(int argc, const char *argv[])
goto out; /* We know tf is not allocated */
}
- if (is_tracepoint)
- tf->mod = __module_text_address(
- (unsigned long)tf->tpoint->probestub);
-
/* parse arguments */
for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
trace_probe_log_set_index(i + 2);
@@ -1155,6 +1183,8 @@ static int __trace_fprobe_create(int argc, const char *argv[])
}
out:
+ if (tp_mod)
+ module_put(tp_mod);
traceprobe_finish_parse(&ctx);
trace_probe_log_clear();
kfree(new_argv);
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 8d1507dd0724..981b60199413 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -735,6 +735,25 @@ static __init int init_tracepoints(void)
return ret;
}
__initcall(init_tracepoints);
+
+void for_each_module_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
+ void *priv)
+{
+ struct tp_module *tp_mod;
+ struct module *mod;
+
+ if (!mod->num_tracepoints)
+ return;
+
+ mutex_lock(&tracepoint_module_list_mutex);
+ list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
+ mod = tp_mod->mod;
+ for_each_tracepoint_range(mod->__start___tracepoints_ptrs,
+ mod->tracepoints_ptrs + mod->num_tracepoints,
+ fct, priv);
+ }
+ mutex_unlock(&tracepoint_module_list_mutex);
+}
#endif /* CONFIG_MODULES */
/**
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