On Wed, 05 Feb 2025 17:50:39 -0500
Steven Rostedt <rost...@goodmis.org> wrote:
> From: Steven Rostedt <rost...@goodmis.org>
>
> When a module is loaded and a persistent buffer is actively tracing, add
> it to the list of modules in the persistent memory.
>
> Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
> ---
> kernel/trace/trace.c | 25 +++++++++++++++++++++++
> kernel/trace/trace.h | 2 ++
> kernel/trace/trace_events.c | 40 ++++++++++++++++++++++++++-----------
> 3 files changed, 55 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 7b4027804cd4..443f2bc5b856 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -10088,6 +10088,30 @@ static void trace_module_remove_evals(struct module
> *mod)
> static inline void trace_module_remove_evals(struct module *mod) { }
> #endif /* CONFIG_TRACE_EVAL_MAP_FILE */
>
> +static bool trace_array_active(struct trace_array *tr)
> +{
> + if (tr->current_trace != &nop_trace)
> + return true;
> +
> + /* 0 is no events, 1 is all disabled */
> + return trace_events_enabled(tr, NULL) > 1;
> +}
> +
> +static void trace_module_record(struct module *mod)
> +{
> + struct trace_array *tr;
> +
> + list_for_each_entry(tr, &ftrace_trace_arrays, list) {
> + /* Update any persistent trace array that has already been
> started */
> + if ((tr->flags & (TRACE_ARRAY_FL_BOOT |
> TRACE_ARRAY_FL_LAST_BOOT)) ==
> + TRACE_ARRAY_FL_BOOT) {
> + /* Only update if the trace array is active */
> + if (trace_array_active(tr))
Do we really need this check? It seems that we can just save_mod() if the
above condition is true.
> + save_mod(mod, tr);
> + }
> + }
> +}
> +
> static int trace_module_notify(struct notifier_block *self,
> unsigned long val, void *data)
> {
> @@ -10096,6 +10120,7 @@ static int trace_module_notify(struct notifier_block
> *self,
> switch (val) {
> case MODULE_STATE_COMING:
> trace_module_add_evals(mod);
> + trace_module_record(mod);
> break;
> case MODULE_STATE_GOING:
> trace_module_remove_evals(mod);
Don't we need to remove the module entry when a module is removed?
(everytime we remove a module, trace data is cleared?)
Thank you,
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 3a020fb82a34..90493220c362 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -786,6 +786,8 @@ extern void trace_find_cmdline(int pid, char comm[]);
> extern int trace_find_tgid(int pid);
> extern void trace_event_follow_fork(struct trace_array *tr, bool enable);
>
> +extern int trace_events_enabled(struct trace_array *tr, const char *system);
> +
> #ifdef CONFIG_DYNAMIC_FTRACE
> extern unsigned long ftrace_update_tot_cnt;
> extern unsigned long ftrace_number_of_pages;
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 4cb275316e51..107767afe0ab 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1811,28 +1811,28 @@ event_enable_write(struct file *filp, const char
> __user *ubuf, size_t cnt,
> return cnt;
> }
>
> -static ssize_t
> -system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
> - loff_t *ppos)
> +/*
> + * Returns:
> + * 0 : no events exist?
> + * 1 : all events are disabled
> + * 2 : all events are enabled
> + * 3 : some events are enabled and some are enabled
> + */
> +int trace_events_enabled(struct trace_array *tr, const char *system)
> {
> - const char set_to_char[4] = { '?', '0', '1', 'X' };
> - struct trace_subsystem_dir *dir = filp->private_data;
> - struct event_subsystem *system = dir->subsystem;
> struct trace_event_call *call;
> struct trace_event_file *file;
> - struct trace_array *tr = dir->tr;
> - char buf[2];
> int set = 0;
> - int ret;
>
> - mutex_lock(&event_mutex);
> + guard(mutex)(&event_mutex);
> +
> list_for_each_entry(file, &tr->events, list) {
> call = file->event_call;
> if ((call->flags & TRACE_EVENT_FL_IGNORE_ENABLE) ||
> !trace_event_name(call) || !call->class ||
> !call->class->reg)
> continue;
>
> - if (system && strcmp(call->class->system, system->name) != 0)
> + if (system && strcmp(call->class->system, system) != 0)
> continue;
>
> /*
> @@ -1848,7 +1848,23 @@ system_enable_read(struct file *filp, char __user
> *ubuf, size_t cnt,
> if (set == 3)
> break;
> }
> - mutex_unlock(&event_mutex);
> +
> + return set;
> +}
> +
> +static ssize_t
> +system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
> + loff_t *ppos)
> +{
> + const char set_to_char[4] = { '?', '0', '1', 'X' };
> + struct trace_subsystem_dir *dir = filp->private_data;
> + struct event_subsystem *system = dir->subsystem;
> + struct trace_array *tr = dir->tr;
> + char buf[2];
> + int set;
> + int ret;
> +
> + set = trace_events_enabled(tr, system ? system->name : NULL);
>
> buf[0] = set_to_char[set];
> buf[1] = '\n';
> --
> 2.45.2
>
>
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
