Commit be74b73a authored by Steven Rostedt's avatar Steven Rostedt Committed by Frederic Weisbecker
Browse files

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
......@@ -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:
......
......@@ -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; \
\
......
......@@ -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)
{
......
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