From 981d081ec8b958b7d962ee40d433581a55d40fc5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 2 Mar 2009 13:53:59 -0500 Subject: [PATCH] tracing: add format file to describe event struct fields This patch adds the "format" file to the trace point event directory. This is based off of work by Tom Zanussi, in which a file is exported to be tread from user land such that a user space app may read the binary record stored in the ring buffer. # cat /debug/tracing/events/sched/sched_switch/format field:pid_t prev_pid; offset:12; size:4; field:int prev_prio; offset:16; size:4; field special:char next_comm[TASK_COMM_LEN]; offset:20; size:16; field:pid_t next_pid; offset:36; size:4; field:int next_prio; offset:40; size:4; Idea-from: Tom Zanussi Signed-off-by: Steven Rostedt --- kernel/trace/trace.h | 1 + kernel/trace/trace_events.c | 56 ++++++++++++++++++++++++++++++++++++- kernel/trace/trace_events_stage_2.h | 52 ++++++++++++++++++++++++++++++++++ kernel/trace/trace_events_stage_3.h | 2 ++ 4 files changed, 110 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index cf6ba41..e606633 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -754,6 +754,7 @@ struct ftrace_event_call { int (*raw_init)(void); int (*raw_reg)(void); void (*raw_unreg)(void); + int (*show_format)(struct trace_seq *s); }; void event_trace_printk(unsigned long ip, const char *fmt, ...); diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 26069fa..d57a772 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -3,6 +3,9 @@ * * Copyright (C) 2008 Red Hat Inc, Steven Rostedt * + * - Added format output of fields of the trace point. + * This was based off of work by Tom Zanussi . + * */ #include @@ -444,6 +447,42 @@ event_available_types_read(struct file *filp, char __user *ubuf, size_t cnt, return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); } +static ssize_t +event_format_read(struct file *filp, char __user *ubuf, size_t cnt, + loff_t *ppos) +{ + struct ftrace_event_call *call = filp->private_data; + struct trace_seq *s; + char *buf; + int r; + + s = kmalloc(sizeof(*s), GFP_KERNEL); + if (!s) + return -ENOMEM; + + trace_seq_init(s); + + if (*ppos) + return 0; + + r = call->show_format(s); + if (!r) { + /* + * ug! The format output is bigger than a PAGE!! + */ + buf = "FORMAT TOO BIG\n"; + r = simple_read_from_buffer(ubuf, cnt, ppos, + buf, strlen(buf)); + goto out; + } + + r = simple_read_from_buffer(ubuf, cnt, ppos, + s->buffer, s->len); + out: + kfree(s); + return r; +} + static const struct seq_operations show_event_seq_ops = { .start = t_start, .next = t_next, @@ -490,6 +529,11 @@ static const struct file_operations ftrace_available_types_fops = { .read = event_available_types_read, }; +static const struct file_operations ftrace_event_format_fops = { + .open = tracing_open_generic, + .read = event_format_read, +}; + static struct dentry *event_trace_events_dir(void) { static struct dentry *d_tracer; @@ -602,7 +646,17 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events) &ftrace_available_types_fops); if (!entry) pr_warning("Could not create debugfs " - "'%s/type' available_types\n", call->name); + "'%s/available_types' entry\n", call->name); + + /* A trace may not want to export its format */ + if (!call->show_format) + return 0; + + entry = debugfs_create_file("format", 0444, call->dir, call, + &ftrace_event_format_fops); + if (!entry) + pr_warning("Could not create debugfs " + "'%s/format' entry\n", call->name); return 0; } diff --git a/kernel/trace/trace_events_stage_2.h b/kernel/trace/trace_events_stage_2.h index dc79fe3..3a80ea4 100644 --- a/kernel/trace/trace_events_stage_2.h +++ b/kernel/trace/trace_events_stage_2.h @@ -74,3 +74,55 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags) \ } #include + +/* + * Setup the showing format of trace point. + * + * int + * ftrace_format_##call(struct trace_seq *s) + * { + * struct ftrace_raw_##call field; + * int ret; + * + * ret = trace_seq_printf(s, #type " " #item ";" + * " size:%d; offset:%d;\n", + * sizeof(field.type), + * offsetof(struct ftrace_raw_##call, + * item)); + * + * } + */ + +#undef TRACE_FIELD +#define TRACE_FIELD(type, item, assign) \ + ret = trace_seq_printf(s, "\tfield:" #type " " #item ";\t" \ + "offset:%lu;\tsize:%lu;\n", \ + offsetof(typeof(field), item), \ + sizeof(field.item)); \ + if (!ret) \ + return 0; + + +#undef TRACE_FIELD_SPECIAL +#define TRACE_FIELD_SPECIAL(type_item, item, cmd) \ + ret = trace_seq_printf(s, "\tfield special:" #type_item ";\t" \ + "offset:%lu;\tsize:%lu;\n", \ + offsetof(typeof(field), item), \ + sizeof(field.item)); \ + if (!ret) \ + return 0; + +#undef TRACE_EVENT_FORMAT +#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \ +int \ +ftrace_format_##call(struct trace_seq *s) \ +{ \ + struct ftrace_raw_##call field; \ + int ret; \ + \ + tstruct; \ + \ + return ret; \ +} + +#include diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h index 2ab65e9..c62a4d2 100644 --- a/kernel/trace/trace_events_stage_3.h +++ b/kernel/trace/trace_events_stage_3.h @@ -101,6 +101,7 @@ * .raw_init = ftrace_raw_init_event_, * .raw_reg = ftrace_raw_reg_event_, * .raw_unreg = ftrace_raw_unreg_event_, + * .show_format = ftrace_format_, * } * */ @@ -230,4 +231,5 @@ __attribute__((section("_ftrace_events"))) event_##call = { \ .raw_init = ftrace_raw_init_event_##call, \ .raw_reg = ftrace_raw_reg_event_##call, \ .raw_unreg = ftrace_raw_unreg_event_##call, \ + .show_format = ftrace_format_##call, \ } -- 2.7.4