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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/**
2 * @file event_buffer.c
3 *
4 * @remark Copyright 2002 OProfile authors
5 * @remark Read the file COPYING
6 *
7 * @author John Levon <levon@movementarian.org>
8 *
9 * This is the global event buffer that the user-space
10 * daemon reads from. The event buffer is an untyped array
11 * of unsigned longs. Entries are prefixed by the
12 * escape value ESCAPE_CODE followed by an identifying code.
13 */
14
15#include <linux/vmalloc.h>
16#include <linux/oprofile.h>
17#include <linux/sched.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080018#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070019#include <linux/dcookies.h>
20#include <linux/fs.h>
21#include <asm/uaccess.h>
Robert Richter6a180372008-10-16 15:01:40 +020022
Linus Torvalds1da177e2005-04-16 15:20:36 -070023#include "oprof.h"
24#include "event_buffer.h"
25#include "oprofile_stats.h"
26
Markus Armbruster59cc1852006-06-25 05:47:33 -070027DEFINE_MUTEX(buffer_mutex);
Robert Richter6a180372008-10-16 15:01:40 +020028
Linus Torvalds1da177e2005-04-16 15:20:36 -070029static unsigned long buffer_opened;
30static DECLARE_WAIT_QUEUE_HEAD(buffer_wait);
Robert Richter25ad2912008-09-05 17:12:36 +020031static unsigned long *event_buffer;
Linus Torvalds1da177e2005-04-16 15:20:36 -070032static unsigned long buffer_size;
33static unsigned long buffer_watershed;
34static size_t buffer_pos;
Markus Armbruster59cc1852006-06-25 05:47:33 -070035/* atomic_t because wait_event checks it outside of buffer_mutex */
Linus Torvalds1da177e2005-04-16 15:20:36 -070036static atomic_t buffer_ready = ATOMIC_INIT(0);
37
Robert Richterc0868932009-10-09 03:17:44 +020038/*
39 * Add an entry to the event buffer. When we get near to the end we
40 * wake up the process sleeping on the read() of the file. To protect
41 * the event_buffer this function may only be called when buffer_mutex
42 * is set.
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 */
44void add_event_entry(unsigned long value)
45{
David Rientjes066b3aa2009-09-09 15:02:33 +020046 /*
Robert Richterc0868932009-10-09 03:17:44 +020047 * This shouldn't happen since all workqueues or handlers are
48 * canceled or flushed before the event buffer is freed.
David Rientjes066b3aa2009-09-09 15:02:33 +020049 */
Robert Richterc0868932009-10-09 03:17:44 +020050 if (!event_buffer) {
51 WARN_ON_ONCE(1);
David Rientjes066b3aa2009-09-09 15:02:33 +020052 return;
Robert Richterc0868932009-10-09 03:17:44 +020053 }
David Rientjes066b3aa2009-09-09 15:02:33 +020054
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 if (buffer_pos == buffer_size) {
56 atomic_inc(&oprofile_stats.event_lost_overflow);
57 return;
58 }
59
60 event_buffer[buffer_pos] = value;
61 if (++buffer_pos == buffer_size - buffer_watershed) {
62 atomic_set(&buffer_ready, 1);
63 wake_up(&buffer_wait);
64 }
65}
66
67
68/* Wake up the waiting process if any. This happens
69 * on "echo 0 >/dev/oprofile/enable" so the daemon
70 * processes the data remaining in the event buffer.
71 */
72void wake_up_buffer_waiter(void)
73{
Markus Armbruster59cc1852006-06-25 05:47:33 -070074 mutex_lock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 atomic_set(&buffer_ready, 1);
76 wake_up(&buffer_wait);
Markus Armbruster59cc1852006-06-25 05:47:33 -070077 mutex_unlock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070078}
79
Robert Richter6a180372008-10-16 15:01:40 +020080
Linus Torvalds1da177e2005-04-16 15:20:36 -070081int alloc_event_buffer(void)
82{
Jiri Kosina4dfc8962007-03-28 18:12:34 +020083 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -070084
Jiri Kosina4dfc8962007-03-28 18:12:34 +020085 spin_lock_irqsave(&oprofilefs_lock, flags);
Robert Richterbd2172f2008-12-16 16:19:54 +010086 buffer_size = oprofile_buffer_size;
87 buffer_watershed = oprofile_buffer_watershed;
Jiri Kosina4dfc8962007-03-28 18:12:34 +020088 spin_unlock_irqrestore(&oprofilefs_lock, flags);
Robert Richter6a180372008-10-16 15:01:40 +020089
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 if (buffer_watershed >= buffer_size)
91 return -EINVAL;
Robert Richter6a180372008-10-16 15:01:40 +020092
Robert Richterc0868932009-10-09 03:17:44 +020093 buffer_pos = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 event_buffer = vmalloc(sizeof(unsigned long) * buffer_size);
95 if (!event_buffer)
Robert Richterc0868932009-10-09 03:17:44 +020096 return -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -070097
Robert Richterc0868932009-10-09 03:17:44 +020098 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -070099}
100
101
102void free_event_buffer(void)
103{
David Rientjes066b3aa2009-09-09 15:02:33 +0200104 mutex_lock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 vfree(event_buffer);
Robert Richterc0868932009-10-09 03:17:44 +0200106 buffer_pos = 0;
Carl Lovef4156d12008-08-11 17:25:43 +1000107 event_buffer = NULL;
David Rientjes066b3aa2009-09-09 15:02:33 +0200108 mutex_unlock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109}
110
Robert Richter6a180372008-10-16 15:01:40 +0200111
Robert Richter25ad2912008-09-05 17:12:36 +0200112static int event_buffer_open(struct inode *inode, struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113{
114 int err = -EPERM;
115
116 if (!capable(CAP_SYS_ADMIN))
117 return -EPERM;
118
Nick Piggincae042a2008-10-23 16:25:54 +0200119 if (test_and_set_bit_lock(0, &buffer_opened))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 return -EBUSY;
121
122 /* Register as a user of dcookies
123 * to ensure they persist for the lifetime of
124 * the open event file
125 */
126 err = -EINVAL;
127 file->private_data = dcookie_register();
128 if (!file->private_data)
129 goto out;
Robert Richter6a180372008-10-16 15:01:40 +0200130
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 if ((err = oprofile_setup()))
132 goto fail;
133
134 /* NB: the actual start happens from userspace
135 * echo 1 >/dev/oprofile/enable
136 */
Robert Richter6a180372008-10-16 15:01:40 +0200137
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 return 0;
139
140fail:
141 dcookie_unregister(file->private_data);
142out:
Nick Piggincae042a2008-10-23 16:25:54 +0200143 __clear_bit_unlock(0, &buffer_opened);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 return err;
145}
146
147
Robert Richter25ad2912008-09-05 17:12:36 +0200148static int event_buffer_release(struct inode *inode, struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149{
150 oprofile_stop();
151 oprofile_shutdown();
152 dcookie_unregister(file->private_data);
153 buffer_pos = 0;
154 atomic_set(&buffer_ready, 0);
Nick Piggincae042a2008-10-23 16:25:54 +0200155 __clear_bit_unlock(0, &buffer_opened);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 return 0;
157}
158
159
Robert Richter25ad2912008-09-05 17:12:36 +0200160static ssize_t event_buffer_read(struct file *file, char __user *buf,
161 size_t count, loff_t *offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162{
163 int retval = -EINVAL;
164 size_t const max = buffer_size * sizeof(unsigned long);
165
166 /* handling partial reads is more trouble than it's worth */
167 if (count != max || *offset)
168 return -EINVAL;
169
170 wait_event_interruptible(buffer_wait, atomic_read(&buffer_ready));
171
172 if (signal_pending(current))
173 return -EINTR;
174
175 /* can't currently happen */
176 if (!atomic_read(&buffer_ready))
177 return -EAGAIN;
178
Markus Armbruster59cc1852006-06-25 05:47:33 -0700179 mutex_lock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180
Robert Richterc0868932009-10-09 03:17:44 +0200181 /* May happen if the buffer is freed during pending reads. */
David Rientjes066b3aa2009-09-09 15:02:33 +0200182 if (!event_buffer) {
183 retval = -EINTR;
184 goto out;
185 }
186
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187 atomic_set(&buffer_ready, 0);
188
189 retval = -EFAULT;
190
191 count = buffer_pos * sizeof(unsigned long);
Robert Richter6a180372008-10-16 15:01:40 +0200192
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 if (copy_to_user(buf, event_buffer, count))
194 goto out;
195
196 retval = count;
197 buffer_pos = 0;
Robert Richter6a180372008-10-16 15:01:40 +0200198
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199out:
Markus Armbruster59cc1852006-06-25 05:47:33 -0700200 mutex_unlock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 return retval;
202}
Robert Richter6a180372008-10-16 15:01:40 +0200203
Arjan van de Vend54b1fd2007-02-12 00:55:34 -0800204const struct file_operations event_buffer_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 .open = event_buffer_open,
206 .release = event_buffer_release,
207 .read = event_buffer_read,
208};