2 files changed, 269 insertions, 4 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a5da09c899dd..fedbdd7d5d1e 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -599,6 +599,34 @@ config RING_BUFFER_STARTUP_TEST
 
          If unsure, say N
 
+config TRACE_ENUM_MAP_FILE
+       bool "Show enum mappings for trace events"
+       depends on TRACING
+       help
+        The "print fmt" of the trace events will show the enum names instead
+        of their values. This can cause problems for user space tools that
+        use this string to parse the raw data as user space does not know
+        how to convert the string to its value.
+
+        To fix this, there's a special macro in the kernel that can be used
+        to convert the enum into its value. If this macro is used, then the
+        print fmt strings will have the enums converted to their values.
+
+        If something does not get converted properly, this option can be
+        used to show what enums the kernel tried to convert.
+
+        This option is for debugging the enum conversions. A file is created
+        in the tracing directory called "enum_map" that will show the enum
+        names matched with their values and what trace event system they
+        belong too.
+
+        Normally, the mapping of the strings to values will be freed after
+        boot up or module load. With this option, they will not be freed, as
+        they are needed for the "enum_map" file. Enabling this option will
+        increase the memory footprint of the running kernel.
+
+        If unsure, say N
+
 endif # FTRACE
 
 endif # TRACING_SUPPORT
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 28e6654e640d..39e69568302e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -123,6 +123,42 @@ enum ftrace_dump_mode ftrace_dump_on_oops;
 /* When set, tracing will stop when a WARN*() is hit */
 int __disable_trace_on_warning;
 
+#ifdef CONFIG_TRACE_ENUM_MAP_FILE
+/* Map of enums to their values, for "enum_map" file */
+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"
+         */
+        union trace_enum_map_item       *next;
+        const char                      *end;   /* points to NULL */
+};
+
+static DEFINE_MUTEX(trace_enum_mutex);
+
+/*
+ * 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;
+#endif /* CONFIG_TRACE_ENUM_MAP_FILE */
+
 static int tracing_set_tracer(struct trace_array *tr, const char *buf);
 
 #define MAX_TRACER_SIZE         100
@@ -3908,7 +3944,169 @@ 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, int len)
+#ifdef CONFIG_TRACE_ENUM_MAP_FILE
+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;
+                        /* Set ptr to the next real item (skip head) */
+                        ptr++;
+                } else
+                        return NULL;
+        }
+        return ptr;
+}
+
+static void *enum_map_next(struct seq_file *m, void *v, loff_t *pos)
+{
+        union trace_enum_map_item *ptr = v;
+
+        /*
+         * Paranoid! If ptr points to end, we don't want to increment past it.
+         * This really should never happen.
+         */
+        ptr = update_enum_map(ptr);
+        if (WARN_ON_ONCE(!ptr))
+                return NULL;
+
+        ptr++;
+
+        (*pos)++;
+
+        ptr = update_enum_map(ptr);
+
+        return ptr;
+}
+
+static void *enum_map_start(struct seq_file *m, loff_t *pos)
+{
+        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);
+        }
+
+        return v;
+}
+
+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)
+{
+        union trace_enum_map_item *ptr = v;
+
+        seq_printf(m, "%s %ld (%s)\n",
+                   ptr->map.enum_string, ptr->map.enum_value,
+                   ptr->map.system);
+
+        return 0;
+}
+
+static const struct seq_operations tracing_enum_map_seq_ops = {
+        .start          = enum_map_start,
+        .next           = enum_map_next,
+        .stop           = enum_map_stop,
+        .show           = enum_map_show,
+};
+
+static int tracing_enum_map_open(struct inode *inode, struct file *filp)
+{
+        if (tracing_disabled)
+                return -ENODEV;
+
+        return seq_open(filp, &tracing_enum_map_seq_ops);
+}
+
+static const struct file_operations tracing_enum_map_fops = {
+        .open           = tracing_enum_map_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
+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_file(struct module *mod, struct trace_enum_map **start,
+                           int len)
+{
+        struct trace_enum_map **stop;
+        struct trace_enum_map **map;
+        union trace_enum_map_item *map_array;
+        union trace_enum_map_item *ptr;
+
+        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;
+        }
+
+        mutex_lock(&trace_enum_mutex);
+
+        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;
+                map_array++;
+        }
+        memset(map_array, 0, sizeof(*map_array));
+
+        mutex_unlock(&trace_enum_mutex);
+}
+
+static void trace_create_enum_file(struct dentry *d_tracer)
+{
+        trace_create_file("enum_map", 0444, d_tracer,
+                          NULL, &tracing_enum_map_fops);
+}
+
+#else /* CONFIG_TRACE_ENUM_MAP_FILE */
+static inline void trace_create_enum_file(struct dentry *d_tracer) { }
+static inline void trace_insert_enum_map_file(struct module *mod,
+                              struct trace_enum_map **start, int len) { }
+#endif /* !CONFIG_TRACE_ENUM_MAP_FILE */
+
+static void trace_insert_enum_map(struct module *mod,
+                                  struct trace_enum_map **start, int len)
 {
         struct trace_enum_map **map;
 
@@ -3918,6 +4116,8 @@ static void trace_insert_enum_map(struct trace_enum_map **start, int len)
         map = start;
 
         trace_event_enum_update(map, len);
+
+        trace_insert_enum_map_file(mod, start, len);
 }
 
 static ssize_t
@@ -6562,7 +6762,7 @@ static void __init trace_enum_init(void)
         int len;
 
         len = __stop_ftrace_enum_maps - __start_ftrace_enum_maps;
-        trace_insert_enum_map(__start_ftrace_enum_maps, len);
+        trace_insert_enum_map(NULL, __start_ftrace_enum_maps, len);
 }
 
 #ifdef CONFIG_MODULES
@@ -6578,9 +6778,41 @@ static void trace_module_add_enums(struct module *mod)
         if (trace_module_has_bad_taint(mod))
                 return;
 
-        trace_insert_enum_map(mod->trace_enums, mod->num_trace_enums);
+        trace_insert_enum_map(mod, mod->trace_enums, mod->num_trace_enums);
 }
 
+#ifdef CONFIG_TRACE_ENUM_MAP_FILE
+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 = trace_enum_jmp_to_tail(map);
+                last = &map->tail.next;
+                map = map->tail.next;
+        }
+        if (!map)
+                goto out;
+
+        *last = trace_enum_jmp_to_tail(map)->tail.next;
+        kfree(map);
+ out:
+        mutex_unlock(&trace_enum_mutex);
+}
+#else
+static inline void trace_module_remove_enums(struct module *mod) { }
+#endif /* CONFIG_TRACE_ENUM_MAP_FILE */
+
 static int trace_module_notify(struct notifier_block *self,
                                unsigned long val, void *data)
 {
@@ -6590,6 +6822,9 @@ static int trace_module_notify(struct notifier_block *self,
         case MODULE_STATE_COMING:
                 trace_module_add_enums(mod);
                 break;
+        case MODULE_STATE_GOING:
+                trace_module_remove_enums(mod);
+                break;
         }
 
         return 0;
@@ -6599,7 +6834,7 @@ static struct notifier_block trace_module_nb = {
         .notifier_call = trace_module_notify,
         .priority = 0,
 };
-#endif
+#endif /* CONFIG_MODULES */
 
 static __init int tracer_init_debugfs(void)
 {
@@ -6627,6 +6862,8 @@ static __init int tracer_init_debugfs(void)
 
         trace_enum_init();
 
+        trace_create_enum_file(d_tracer);
+
 #ifdef CONFIG_MODULES
         register_module_notifier(&trace_module_nb);
 #endif