tracing: add __print_flags for events
Developers have been asking for the ability in the ftrace event tracer
to display names of bits in a flags variable.
Instead of printing out c2, it would be easier to read FOO|BAR|GOO,
assuming that FOO is bit 1, BAR is bit 6 and GOO is bit 7.
Some examples where this would be useful are the state flags in a context
switch, kmalloc flags, and even permision flags in accessing files.
[
v2 changes include:
Frederic Weisbecker's idea of using a mask instead of bits,
thus we can output GFP_KERNEL instead of GPF_WAIT|GFP_IO|GFP_FS.
Li Zefan's idea of allowing the caller of __print_flags to add their
own delimiter (or no delimiter) where we can get for file permissions
rwx instead of r|w|x.
]
[
v3 changes:
Christoph Hellwig's idea of using an array instead of va_args.
]
[ Impact: better displaying of flags in trace output ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 7136420..a4840c2 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -15,6 +15,9 @@
#define EVENT_HASHSIZE 128
static DECLARE_RWSEM(trace_event_mutex);
+
+DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
+
static struct hlist_head event_hash[EVENT_HASHSIZE] __read_mostly;
static int next_event_type = __TRACE_LAST_TYPE + 1;
@@ -212,6 +215,42 @@
return 0;
}
+const char *
+ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
+ unsigned long flags,
+ const struct trace_print_flags *flag_array)
+{
+ unsigned long mask;
+ const char *str;
+ int i;
+
+ trace_seq_init(p);
+
+ for (i = 0; flag_array[i].name && flags; i++) {
+
+ mask = flag_array[i].mask;
+ if ((flags & mask) != mask)
+ continue;
+
+ str = flag_array[i].name;
+ flags &= ~mask;
+ if (p->len && delim)
+ trace_seq_puts(p, delim);
+ trace_seq_puts(p, str);
+ }
+
+ /* check for left over flags */
+ if (flags) {
+ if (p->len && delim)
+ trace_seq_puts(p, delim);
+ trace_seq_printf(p, "0x%lx", flags);
+ }
+
+ trace_seq_putc(p, 0);
+
+ return p->buffer;
+}
+
#ifdef CONFIG_KRETPROBES
static inline const char *kretprobed(const char *name)
{