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Commit be74b73a authored by Steven Rostedt's avatar Steven Rostedt Committed by Frederic Weisbecker
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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: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 0e907c99

include/linux/ftrace_event.h

+12 −1
Original line number Diff line number Diff line
@@ -3,12 +3,23 @@ 


#include <linux/trace_seq.h>

#include <linux/ring_buffer.h>



#include <linux/percpu.h>



struct trace_array;

struct tracer;

struct dentry;



DECLARE_PER_CPU(struct trace_seq, ftrace_event_seq);



struct trace_print_flags {

	unsigned long		mask;

	const char		*name;

};



const char *ftrace_print_flags_seq(struct trace_seq *p, const char *delim,

				   unsigned long flags,

				   const struct trace_print_flags *flag_array);



/*

 * The trace entry - the most basic unit of tracing. This is what

 * is printed in the end as a single line in the trace output, such as:

include/trace/ftrace.h

+14 −0
Original line number Diff line number Diff line
@@ -87,6 +87,7 @@ 
 *	struct trace_seq *s = &iter->seq;

 *	struct ftrace_raw_<call> *field; <-- defined in stage 1

 *	struct trace_entry *entry;

 *	struct trace_seq *p;

 *	int ret;

 *

 *	entry = iter->ent;
@@ -98,7 +99,9 @@ 
 *

 *	field = (typeof(field))entry;

 *

 *	p = get_cpu_var(ftrace_event_seq);

 *	ret = trace_seq_printf(s, <TP_printk> "\n");

 *	put_cpu();

 *	if (!ret)

 *		return TRACE_TYPE_PARTIAL_LINE;

 *
@@ -119,6 +122,14 @@ 
#undef __get_str

#define __get_str(field)	((char *)__entry + __entry->__str_loc_##field)



#undef __print_flags

#define __print_flags(flag, delim, flag_array...)			\

	({								\

		static const struct trace_print_flags flags[] =		\

			{ flag_array, { -1, NULL }};			\

		ftrace_print_flags_seq(p, delim, flag, flags);		\

	})



#undef TRACE_EVENT

#define TRACE_EVENT(call, proto, args, tstruct, assign, print)		\

enum print_line_t							\
@@ -127,6 +138,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ 
	struct trace_seq *s = &iter->seq;				\

	struct ftrace_raw_##call *field;				\

	struct trace_entry *entry;					\

	struct trace_seq *p;						\

	int ret;							\

									\

	entry = iter->ent;						\
@@ -138,7 +150,9 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ 
									\

	field = (typeof(field))entry;					\

									\

	p = &get_cpu_var(ftrace_event_seq);				\

	ret = trace_seq_printf(s, #call ": " print);			\

	put_cpu();							\

	if (!ret)							\

		return TRACE_TYPE_PARTIAL_LINE;				\

									\

kernel/trace/trace_output.c

+39 −0
Original line number Diff line number Diff line
@@ -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 @@ int trace_seq_path(struct trace_seq *s, struct path *path) 
	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)

{