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Date: Mon, 30 Mar 2015 11:41:00 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [RFC][PATCH 02/10] tracing: Allow for modules to export their
trace enums as well
On Fri, Mar 27, 2015 at 05:37:06PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
>
> Update the infrastructure such that modules that declare TRACE_DEFINE_ENUM()
> will have those enums shown in the enum_map files in the tracing directory.
>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
> include/linux/module.h | 2 +
> kernel/module.c | 3 +
> kernel/trace/trace.c | 184 ++++++++++++++++++++++++++++++++++++++++++++-----
> 3 files changed, 173 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 42999fe2dbd0..53dc41dd5c62 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -338,6 +338,8 @@ struct module {
> #ifdef CONFIG_EVENT_TRACING
> struct ftrace_event_call **trace_events;
> unsigned int num_trace_events;
> + struct trace_enum_map **trace_enums;
> + unsigned int num_trace_enums;
> #endif
> #ifdef CONFIG_FTRACE_MCOUNT_RECORD
> unsigned int num_ftrace_callsites;
> diff --git a/kernel/module.c b/kernel/module.c
> index b3d634ed06c9..d8f8ab271c2b 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2753,6 +2753,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
> mod->trace_events = section_objs(info, "_ftrace_events",
> sizeof(*mod->trace_events),
> &mod->num_trace_events);
> + mod->trace_enums = section_objs(info, "_ftrace_enum_map",
> + sizeof(*mod->trace_enums),
> + &mod->num_trace_enums);
> #endif
> #ifdef CONFIG_TRACING
> mod->trace_bprintk_fmt_start = section_objs(info, "__trace_printk_fmt",
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 53b449c522a7..97031878eb3d 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -124,7 +124,38 @@ enum ftrace_dump_mode ftrace_dump_on_oops;
> int __disable_trace_on_warning;
>
> /* Map of enums to their values, for "enum_map" file */
> -static struct trace_enum_map *trace_enum_maps;
> +struct trace_enum_map_head {
> + struct module *mod;
> + unsigned long length;
> +};
> +
> +union trace_enum_map_item;
> +
> +struct trace_enum_map_tail {
> + /*
> + * "end" is first and points to NULL as it must be different
> + * than "mod" or "enum_string"
> + */
> + const char *end; /* points to NULL */
> + union trace_enum_map_item *next;
> +};
> +
> +static DEFINE_MUTEX(trace_enum_mutex);
> +
> +/*
> + * The trace_enum_maps are saved in an array whith two extra elements,
s/whith/with/
> + * one at the beginning, and one at the end. The beginning item contains
> + * the count of the saved maps (head.length), and the module they
> + * belong to if not built in (head.mod). The ending item contains a
> + * pointer to the next array of saved enum_map items.
> + */
> +union trace_enum_map_item {
> + struct trace_enum_map map;
> + struct trace_enum_map_head head;
> + struct trace_enum_map_tail tail;
> +};
> +
> +static union trace_enum_map_item *trace_enum_maps;
>
> static int tracing_set_tracer(struct trace_array *tr, const char *buf);
>
> @@ -3911,29 +3942,47 @@ static const struct file_operations tracing_saved_cmdlines_size_fops = {
> .write = tracing_saved_cmdlines_size_write,
> };
>
> +static union trace_enum_map_item *
> +update_enum_map(union trace_enum_map_item *ptr)
> +{
> + if (!ptr->map.enum_string) {
> + if (ptr->tail.next) {
> + ptr = ptr->tail.next;
> + ptr++;
I guess this additional increment is to skip head item. Maybe it
deserves a comment. :)
> + } else
> + return NULL;
> + }
> + return ptr;
> +}
> +
> static void *enum_map_next(struct seq_file *m, void *v, loff_t *pos)
> {
> - struct trace_enum_map *ptr = v;
> + union trace_enum_map_item *ptr = v;
>
> - if (!ptr->enum_string)
> + ptr = update_enum_map(ptr);
Again, is this necessary?
> + if (!ptr)
> return NULL;
>
> ptr++;
>
> (*pos)++;
>
> - if (!ptr->enum_string)
> - return NULL;
> + ptr = update_enum_map(ptr);
>
> return ptr;
> }
>
> static void *enum_map_start(struct seq_file *m, loff_t *pos)
> {
> - struct trace_enum_map *v;
> + union trace_enum_map_item *v;
> loff_t l = 0;
>
> + mutex_lock(&trace_enum_mutex);
> +
> v = trace_enum_maps;
> + if (v)
> + v++;
> +
> while (v && l < *pos) {
> v = enum_map_next(m, v, &l);
> }
> @@ -3943,13 +3992,15 @@ static void *enum_map_start(struct seq_file *m, loff_t *pos)
>
> static void enum_map_stop(struct seq_file *m, void *v)
> {
> + mutex_unlock(&trace_enum_mutex);
> }
>
> static int enum_map_show(struct seq_file *m, void *v)
> {
> - struct trace_enum_map *ptr = v;
> + union trace_enum_map_item *ptr = v;
> +
> + seq_printf(m, "%s %ld\n", ptr->map.enum_string, ptr->map.enum_value);
>
> - seq_printf(m, "%s %ld\n", ptr->enum_string, ptr->enum_value);
> return 0;
> }
>
> @@ -3975,29 +4026,56 @@ static const struct file_operations tracing_enum_map_fops = {
> .release = seq_release,
> };
>
> -static void
> -trace_insert_enum_map(struct trace_enum_map **start, struct trace_enum_map **stop)
> +static void trace_insert_enum_map(struct module *mod,
> + struct trace_enum_map **start, int len)
> {
> + struct trace_enum_map **stop;
> struct trace_enum_map **map;
> - struct trace_enum_map *map_array;
> - int len = stop - start;
> + union trace_enum_map_item *map_array;
> + union trace_enum_map_item *ptr;
>
> if (len <= 0)
> return;
>
> - map_array = kmalloc(sizeof(*map_array) * (len + 1), GFP_KERNEL);
> + stop = start + len;
> +
> + /*
> + * The trace_enum_maps contains the map plus a head and tail item,
> + * where the head holds the module and length of array, and the
> + * tail holds a pointer to the next list.
> + */
> + map_array = kmalloc(sizeof(*map_array) * (len + 2), GFP_KERNEL);
> if (!map_array) {
> pr_warning("Unable to allocate trace enum mapping\n");
> return;
> }
>
> - trace_enum_maps = map_array;
> + mutex_lock(&trace_enum_mutex);
> +
> + if (!trace_enum_maps)
> + trace_enum_maps = map_array;
> + else {
> + ptr = trace_enum_maps;
> + for (;;) {
> + ptr = ptr + ptr->head.length + 1;
Looks like access to tail item is used frequently. How about adding a
helper function like enum_maps_tail_item()?
Thanks,
Namhyung
> + if (!ptr->tail.next)
> + break;
> + ptr = ptr->tail.next;
> +
> + }
> + ptr->tail.next = map_array;
> + }
> + map_array->head.mod = mod;
> + map_array->head.length = len;
> + map_array++;
>
> for (map = start; (unsigned long)map < (unsigned long)stop; map++) {
> - *map_array = **map;
> + map_array->map = **map;
> map_array++;
> }
> memset(map_array, 0, sizeof(*map_array));
> +
> + mutex_unlock(&trace_enum_mutex);
> }
>
>
> @@ -6640,9 +6718,79 @@ extern struct trace_enum_map *__stop_ftrace_enum_maps[];
>
> static void __init trace_enum_init(void)
> {
> - trace_insert_enum_map(__start_ftrace_enum_maps, __stop_ftrace_enum_maps);
> + int len;
> +
> + len = __stop_ftrace_enum_maps - __start_ftrace_enum_maps;
> + trace_insert_enum_map(NULL, __start_ftrace_enum_maps, len);
> }
>
> +#ifdef CONFIG_MODULES
> +static void trace_module_add_enums(struct module *mod)
> +{
> + if (!mod->num_trace_enums)
> + return;
> +
> + /*
> + * Modules with bad taint do not have events created, do
> + * not bother with enums either.
> + */
> + if (trace_module_has_bad_taint(mod))
> + return;
> +
> + trace_insert_enum_map(mod, mod->trace_enums, mod->num_trace_enums);
> +}
> +
> +static void trace_module_remove_enums(struct module *mod)
> +{
> + union trace_enum_map_item *map;
> + union trace_enum_map_item **last = &trace_enum_maps;
> +
> + if (!mod->num_trace_enums)
> + return;
> +
> + mutex_lock(&trace_enum_mutex);
> +
> + map = trace_enum_maps;
> +
> + while (map) {
> + if (map->head.mod == mod)
> + break;
> + map += map->head.length + 1;
> + last = &map->tail.next;
> + map = map->tail.next;
> + }
> + if (!map)
> + goto out;
> +
> + *last = map[map->head.length + 1].tail.next;
> + kfree(map);
> + out:
> + mutex_unlock(&trace_enum_mutex);
> +}
> +
> +static int trace_module_notify(struct notifier_block *self,
> + unsigned long val, void *data)
> +{
> + struct module *mod = data;
> +
> + switch (val) {
> + case MODULE_STATE_COMING:
> + trace_module_add_enums(mod);
> + break;
> + case MODULE_STATE_GOING:
> + trace_module_remove_enums(mod);
> + break;
> + }
> +
> + return 0;
> +}
> +
> +static struct notifier_block trace_module_nb = {
> + .notifier_call = trace_module_notify,
> + .priority = 0,
> +};
> +#endif
> +
> static __init int tracer_init_debugfs(void)
> {
> struct dentry *d_tracer;
> @@ -6672,6 +6820,10 @@ static __init int tracer_init_debugfs(void)
> trace_create_file("enum_map", 0444, d_tracer,
> NULL, &tracing_enum_map_fops);
>
> +#ifdef CONFIG_MODULES
> + register_module_notifier(&trace_module_nb);
> +#endif
> +
> #ifdef CONFIG_DYNAMIC_FTRACE
> trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
> &ftrace_update_tot_cnt, &tracing_dyn_info_fops);
> --
> 2.1.4
>
>
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