mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

tracing: Have dynamic events have a ref counter 

As dynamic events are not created by modules, if something is attached to
one, calling "try_module_get()" on its "mod" field, is not going to keep
the dynamic event from going away.

Since dynamic events do not need the "mod" pointer of the event structure,
make a union out of it in order to save memory (there's one structure for
each of the thousand+ events in the kernel), and have any event with the
DYNAMIC flag set to use a ref counter instead.

Link: https://lore.kernel.org/linux-trace-devel/20210813004448.51c7de69ce432d338f4d226b@kernel.org/
Link: https://lkml.kernel.org/r/20210817035027.174869074@goodmis.org

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2021-08-16 23:42:57 -04:00
parent 8b0e6c744f
commit 1d18538e6a
9 changed files with 124 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
include/linux/trace_events.h
View File

@ -350,7 +350,14 @@ struct trace_event_call {
struct trace_event event;
char *print_fmt;
struct event_filter *filter;
void *mod;
/*
* Static events can disappear with modules,
* where as dynamic ones need their own ref count.
*/
union {
void *module;
atomic_t refcnt;
};
void *data;
/* See the TRACE_EVENT_FL_* flags above */
@ -366,6 +373,42 @@ struct trace_event_call {
#endif
};
#ifdef CONFIG_DYNAMIC_EVENTS
bool trace_event_dyn_try_get_ref(struct trace_event_call *call);
void trace_event_dyn_put_ref(struct trace_event_call *call);
bool trace_event_dyn_busy(struct trace_event_call *call);
#else
static inline bool trace_event_dyn_try_get_ref(struct trace_event_call *call)
{
/* Without DYNAMIC_EVENTS configured, nothing should be calling this */
return false;
}
static inline void trace_event_dyn_put_ref(struct trace_event_call *call)
{
}
static inline bool trace_event_dyn_busy(struct trace_event_call *call)
{
/* Nothing should call this without DYNAIMIC_EVENTS configured. */
return true;
}
#endif
static inline bool trace_event_try_get_ref(struct trace_event_call *call)
{
if (call->flags & TRACE_EVENT_FL_DYNAMIC)
return trace_event_dyn_try_get_ref(call);
else
return try_module_get(call->module);
}
static inline void trace_event_put_ref(struct trace_event_call *call)
{
if (call->flags & TRACE_EVENT_FL_DYNAMIC)
trace_event_dyn_put_ref(call);
else
module_put(call->module);
}
#ifdef CONFIG_PERF_EVENTS
static inline bool bpf_prog_array_valid(struct trace_event_call *call)
{

4
kernel/trace/trace.c
View File

@ -3697,11 +3697,11 @@ static bool trace_safe_str(struct trace_iterator *iter, const char *str)
return false;
event = container_of(trace_event, struct trace_event_call, event);
if (!event->mod)
if ((event->flags & TRACE_EVENT_FL_DYNAMIC) || !event->module)
return false;
/* Would rather have rodata, but this will suffice */
if (within_module_core(addr, event->mod))
if (within_module_core(addr, event->module))
return true;
return false;

38
kernel/trace/trace_dynevent.c
View File

@ -13,11 +13,49 @@
#include <linux/tracefs.h>
#include "trace.h"
#include "trace_output.h" /* for trace_event_sem */
#include "trace_dynevent.h"
static DEFINE_MUTEX(dyn_event_ops_mutex);
static LIST_HEAD(dyn_event_ops_list);
bool trace_event_dyn_try_get_ref(struct trace_event_call *dyn_call)
{
struct trace_event_call *call;
bool ret = false;
if (WARN_ON_ONCE(!(dyn_call->flags & TRACE_EVENT_FL_DYNAMIC)))
return false;
down_read(&trace_event_sem);
list_for_each_entry(call, &ftrace_events, list) {
if (call == dyn_call) {
atomic_inc(&dyn_call->refcnt);
ret = true;
}
}
up_read(&trace_event_sem);
return ret;
}
void trace_event_dyn_put_ref(struct trace_event_call *call)
{
if (WARN_ON_ONCE(!(call->flags & TRACE_EVENT_FL_DYNAMIC)))
return;
if (WARN_ON_ONCE(atomic_read(&call->refcnt) <= 0)) {
atomic_set(&call->refcnt, 0);
return;
}
atomic_dec(&call->refcnt);
}
bool trace_event_dyn_busy(struct trace_event_call *call)
{
return atomic_read(&call->refcnt) != 0;
}
int dyn_event_register(struct dyn_event_operations *ops)
{
if (!ops || !ops->create || !ops->show || !ops->is_busy ||

6
kernel/trace/trace_event_perf.c
View File

@ -177,7 +177,7 @@ static void perf_trace_event_unreg(struct perf_event *p_event)
}
}
out:
module_put(tp_event->mod);
trace_event_put_ref(tp_event);
}
static int perf_trace_event_open(struct perf_event *p_event)
@ -224,10 +224,10 @@ int perf_trace_init(struct perf_event *p_event)
list_for_each_entry(tp_event, &ftrace_events, list) {
if (tp_event->event.type == event_id &&
tp_event->class && tp_event->class->reg &&
try_module_get(tp_event->mod)) {
trace_event_try_get_ref(tp_event)) {
ret = perf_trace_event_init(tp_event, p_event);
if (ret)
module_put(tp_event->mod);
trace_event_put_ref(tp_event);
break;
}
}

22
kernel/trace/trace_events.c
View File

@ -2525,7 +2525,10 @@ __register_event(struct trace_event_call *call, struct module *mod)
return ret;
list_add(&call->list, &ftrace_events);
call->mod = mod;
if (call->flags & TRACE_EVENT_FL_DYNAMIC)
atomic_set(&call->refcnt, 0);
else
call->module = mod;
return 0;
}
@ -2839,7 +2842,9 @@ static void trace_module_remove_events(struct module *mod)
down_write(&trace_event_sem);
list_for_each_entry_safe(call, p, &ftrace_events, list) {
if (call->mod == mod)
if ((call->flags & TRACE_EVENT_FL_DYNAMIC) || !call->module)
continue;
if (call->module == mod)
__trace_remove_event_call(call);
}
up_write(&trace_event_sem);
@ -2982,7 +2987,7 @@ struct trace_event_file *trace_get_event_file(const char *instance,
}
/* Don't let event modules unload while in use */
ret = try_module_get(file->event_call->mod);
ret = trace_event_try_get_ref(file->event_call);
if (!ret) {
trace_array_put(tr);
ret = -EBUSY;
@ -3012,7 +3017,7 @@ EXPORT_SYMBOL_GPL(trace_get_event_file);
void trace_put_event_file(struct trace_event_file *file)
{
mutex_lock(&event_mutex);
module_put(file->event_call->mod);
trace_event_put_ref(file->event_call);
mutex_unlock(&event_mutex);
trace_array_put(file->tr);
@ -3147,7 +3152,7 @@ static int free_probe_data(void *data)
if (!edata->ref) {
/* Remove the SOFT_MODE flag */
__ftrace_event_enable_disable(edata->file, 0, 1);
module_put(edata->file->event_call->mod);
trace_event_put_ref(edata->file->event_call);
kfree(edata);
}
return 0;
@ -3280,7 +3285,7 @@ event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
out_reg:
/* Don't let event modules unload while probe registered */
ret = try_module_get(file->event_call->mod);
ret = trace_event_try_get_ref(file->event_call);
if (!ret) {
ret = -EBUSY;
goto out_free;
@ -3310,7 +3315,7 @@ event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
out_disable:
__ftrace_event_enable_disable(file, 0, 1);
out_put:
module_put(file->event_call->mod);
trace_event_put_ref(file->event_call);
out_free:
kfree(data);
goto out;
@ -3376,7 +3381,8 @@ void __trace_early_add_events(struct trace_array *tr)
list_for_each_entry(call, &ftrace_events, list) {
/* Early boot up should not have any modules loaded */
if (WARN_ON_ONCE(call->mod))
if (!(call->flags & TRACE_EVENT_FL_DYNAMIC) &&
WARN_ON_ONCE(call->module))
continue;
ret = __trace_early_add_new_event(call, tr);

19
kernel/trace/trace_events_synth.c
View File

@ -1369,13 +1369,15 @@ static int destroy_synth_event(struct synth_event *se)
int ret;
if (se->ref)
ret = -EBUSY;
else {
ret = unregister_synth_event(se);
if (!ret) {
dyn_event_remove(&se->devent);
free_synth_event(se);
}
return -EBUSY;
if (trace_event_dyn_busy(&se->call))
return -EBUSY;
ret = unregister_synth_event(se);
if (!ret) {
dyn_event_remove(&se->devent);
free_synth_event(se);
}
return ret;
@ -2102,6 +2104,9 @@ static int synth_event_release(struct dyn_event *ev)
if (event->ref)
return -EBUSY;
if (trace_event_dyn_busy(&event->call))
return -EBUSY;
ret = unregister_synth_event(event);
if (ret)
return ret;

6
kernel/trace/trace_events_trigger.c
View File

@ -1334,7 +1334,7 @@ void event_enable_trigger_free(struct event_trigger_ops *ops,
if (!data->ref) {
/* Remove the SOFT_MODE flag */
trace_event_enable_disable(enable_data->file, 0, 1);
module_put(enable_data->file->event_call->mod);
trace_event_put_ref(enable_data->file->event_call);
trigger_data_free(data);
kfree(enable_data);
}
@ -1481,7 +1481,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
out_reg:
/* Don't let event modules unload while probe registered */
ret = try_module_get(event_enable_file->event_call->mod);
ret = trace_event_try_get_ref(event_enable_file->event_call);
if (!ret) {
ret = -EBUSY;
goto out_free;
@ -1510,7 +1510,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops,
out_disable:
trace_event_enable_disable(event_enable_file, 0, 1);
out_put:
module_put(event_enable_file->event_call->mod);
trace_event_put_ref(event_enable_file->event_call);
out_free:
if (cmd_ops->set_filter)
cmd_ops->set_filter(NULL, trigger_data, NULL);

4
kernel/trace/trace_kprobe.c
View File

@ -543,6 +543,10 @@ static int unregister_trace_kprobe(struct trace_kprobe *tk)
if (trace_probe_is_enabled(&tk->tp))
return -EBUSY;
/* If there's a reference to the dynamic event */
if (trace_event_dyn_busy(trace_probe_event_call(&tk->tp)))
return -EBUSY;
/* Will fail if probe is being used by ftrace or perf */
if (unregister_kprobe_event(tk))
return -EBUSY;

4
kernel/trace/trace_uprobe.c
View File

@ -393,6 +393,10 @@ static int unregister_trace_uprobe(struct trace_uprobe *tu)
if (trace_probe_has_sibling(&tu->tp))
goto unreg;
/* If there's a reference to the dynamic event */
if (trace_event_dyn_busy(trace_probe_event_call(&tu->tp)))
return -EBUSY;
ret = unregister_uprobe_event(tu);
if (ret)
return ret;