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Subject[RFC][PATCH 07/17 v2] tracing: Allow for modules to export their trace enums as well
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.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.

Link: http://lkml.kernel.org/r/87vbhjp74q.fsf@rustcorp.com.au

Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/module.h | 2 +
kernel/module.c | 3 +
kernel/trace/trace.c | 149 +++++++++++++++++++++++++++++++++++++++++---
kernel/trace/trace_events.c | 2 +-
4 files changed, 145 insertions(+), 11 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 c64f8d848aa1..c9a714a42b7b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -124,7 +124,36 @@ enum ftrace_dump_mode ftrace_dump_on_oops;
int __disable_trace_on_warning;

/* Map of enums to their values */
-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;
+};
+
+/*
+ * The trace_enum_maps are saved in an array with two extra elements,
+ * 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);

@@ -3911,32 +3940,62 @@ static const struct file_operations tracing_saved_cmdlines_size_fops = {
.write = tracing_saved_cmdlines_size_write,
};

-static void
-trace_insert_enum_map(struct trace_enum_map **start, struct trace_enum_map **stop)
+static inline union trace_enum_map_item *
+trace_enum_jmp_to_tail(union trace_enum_map_item *ptr)
+{
+ /* Return tail of array given the head */
+ return ptr + ptr->head.length + 1;
+}
+
+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;
+ if (!trace_enum_maps)
+ trace_enum_maps = map_array;
+ else {
+ ptr = trace_enum_maps;
+ for (;;) {
+ ptr = trace_enum_jmp_to_tail(ptr);
+ 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));

/* Pass in the start of the array (-len) */
- trace_event_enum_update(&map_array[-len], len);
+ trace_event_enum_update(&map_array[-len].map, len);
}

static ssize_t
@@ -6578,9 +6637,75 @@ 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;
+
+ map = trace_enum_maps;
+
+ while (map) {
+ if (map->head.mod == mod)
+ break;
+ map = trace_enum_jmp_to_tail(map);
+ last = &map->tail.next;
+ map = map->tail.next;
+ }
+ if (!map)
+ return;
+
+ *last = trace_enum_jmp_to_tail(map)->tail.next;
+ kfree(map);
+}
+
+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;
@@ -6607,6 +6732,10 @@ static __init int tracer_init_debugfs(void)

trace_enum_init();

+#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);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 6b7fd0bf5d28..d5571d88d48d 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2011,7 +2011,7 @@ static int trace_module_notify(struct notifier_block *self,

static struct notifier_block trace_module_nb = {
.notifier_call = trace_module_notify,
- .priority = 0,
+ .priority = 1, /* higher than trace.c module notify */
};
#endif /* CONFIG_MODULES */

--
2.1.4



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