Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /** |
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> | |
c59ede7b | 18 | #include <linux/capability.h> |
1da177e4 LT |
19 | #include <linux/dcookies.h> |
20 | #include <linux/fs.h> | |
21 | #include <asm/uaccess.h> | |
6a18037d | 22 | |
1da177e4 LT |
23 | #include "oprof.h" |
24 | #include "event_buffer.h" | |
25 | #include "oprofile_stats.h" | |
26 | ||
59cc185a | 27 | DEFINE_MUTEX(buffer_mutex); |
6a18037d | 28 | |
1da177e4 LT |
29 | static unsigned long buffer_opened; |
30 | static DECLARE_WAIT_QUEUE_HEAD(buffer_wait); | |
25ad2913 | 31 | static unsigned long *event_buffer; |
1da177e4 LT |
32 | static unsigned long buffer_size; |
33 | static unsigned long buffer_watershed; | |
34 | static size_t buffer_pos; | |
59cc185a | 35 | /* atomic_t because wait_event checks it outside of buffer_mutex */ |
1da177e4 LT |
36 | static atomic_t buffer_ready = ATOMIC_INIT(0); |
37 | ||
c0868934 RR |
38 | /* |
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. | |
1da177e4 LT |
43 | */ |
44 | void add_event_entry(unsigned long value) | |
45 | { | |
066b3aa8 | 46 | /* |
c0868934 RR |
47 | * This shouldn't happen since all workqueues or handlers are |
48 | * canceled or flushed before the event buffer is freed. | |
066b3aa8 | 49 | */ |
c0868934 RR |
50 | if (!event_buffer) { |
51 | WARN_ON_ONCE(1); | |
066b3aa8 | 52 | return; |
c0868934 | 53 | } |
066b3aa8 | 54 | |
1da177e4 LT |
55 | 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 | */ | |
72 | void wake_up_buffer_waiter(void) | |
73 | { | |
59cc185a | 74 | mutex_lock(&buffer_mutex); |
1da177e4 LT |
75 | atomic_set(&buffer_ready, 1); |
76 | wake_up(&buffer_wait); | |
59cc185a | 77 | mutex_unlock(&buffer_mutex); |
1da177e4 LT |
78 | } |
79 | ||
6a18037d | 80 | |
1da177e4 LT |
81 | int alloc_event_buffer(void) |
82 | { | |
4dfc896e | 83 | unsigned long flags; |
1da177e4 | 84 | |
2d21a29f | 85 | raw_spin_lock_irqsave(&oprofilefs_lock, flags); |
bd2172f5 RR |
86 | buffer_size = oprofile_buffer_size; |
87 | buffer_watershed = oprofile_buffer_watershed; | |
2d21a29f | 88 | raw_spin_unlock_irqrestore(&oprofilefs_lock, flags); |
6a18037d | 89 | |
1da177e4 LT |
90 | if (buffer_watershed >= buffer_size) |
91 | return -EINVAL; | |
6a18037d | 92 | |
c0868934 | 93 | buffer_pos = 0; |
1da177e4 LT |
94 | event_buffer = vmalloc(sizeof(unsigned long) * buffer_size); |
95 | if (!event_buffer) | |
c0868934 | 96 | return -ENOMEM; |
1da177e4 | 97 | |
c0868934 | 98 | return 0; |
1da177e4 LT |
99 | } |
100 | ||
101 | ||
102 | void free_event_buffer(void) | |
103 | { | |
066b3aa8 | 104 | mutex_lock(&buffer_mutex); |
1da177e4 | 105 | vfree(event_buffer); |
c0868934 | 106 | buffer_pos = 0; |
f4156d1c | 107 | event_buffer = NULL; |
066b3aa8 | 108 | mutex_unlock(&buffer_mutex); |
1da177e4 LT |
109 | } |
110 | ||
6a18037d | 111 | |
25ad2913 | 112 | static int event_buffer_open(struct inode *inode, struct file *file) |
1da177e4 LT |
113 | { |
114 | int err = -EPERM; | |
115 | ||
116 | if (!capable(CAP_SYS_ADMIN)) | |
117 | return -EPERM; | |
118 | ||
cae042a7 | 119 | if (test_and_set_bit_lock(0, &buffer_opened)) |
1da177e4 LT |
120 | 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; | |
6a18037d | 130 | |
1da177e4 LT |
131 | if ((err = oprofile_setup())) |
132 | goto fail; | |
133 | ||
134 | /* NB: the actual start happens from userspace | |
135 | * echo 1 >/dev/oprofile/enable | |
136 | */ | |
6a18037d | 137 | |
729419f0 | 138 | return nonseekable_open(inode, file); |
1da177e4 LT |
139 | |
140 | fail: | |
141 | dcookie_unregister(file->private_data); | |
142 | out: | |
cae042a7 | 143 | __clear_bit_unlock(0, &buffer_opened); |
1da177e4 LT |
144 | return err; |
145 | } | |
146 | ||
147 | ||
25ad2913 | 148 | static int event_buffer_release(struct inode *inode, struct file *file) |
1da177e4 LT |
149 | { |
150 | oprofile_stop(); | |
151 | oprofile_shutdown(); | |
152 | dcookie_unregister(file->private_data); | |
153 | buffer_pos = 0; | |
154 | atomic_set(&buffer_ready, 0); | |
cae042a7 | 155 | __clear_bit_unlock(0, &buffer_opened); |
1da177e4 LT |
156 | return 0; |
157 | } | |
158 | ||
159 | ||
25ad2913 RR |
160 | static ssize_t event_buffer_read(struct file *file, char __user *buf, |
161 | size_t count, loff_t *offset) | |
1da177e4 LT |
162 | { |
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 | ||
59cc185a | 179 | mutex_lock(&buffer_mutex); |
1da177e4 | 180 | |
c0868934 | 181 | /* May happen if the buffer is freed during pending reads. */ |
066b3aa8 DR |
182 | if (!event_buffer) { |
183 | retval = -EINTR; | |
184 | goto out; | |
185 | } | |
186 | ||
1da177e4 LT |
187 | atomic_set(&buffer_ready, 0); |
188 | ||
189 | retval = -EFAULT; | |
190 | ||
191 | count = buffer_pos * sizeof(unsigned long); | |
6a18037d | 192 | |
1da177e4 LT |
193 | if (copy_to_user(buf, event_buffer, count)) |
194 | goto out; | |
195 | ||
196 | retval = count; | |
197 | buffer_pos = 0; | |
6a18037d | 198 | |
1da177e4 | 199 | out: |
59cc185a | 200 | mutex_unlock(&buffer_mutex); |
1da177e4 LT |
201 | return retval; |
202 | } | |
6a18037d | 203 | |
d54b1fdb | 204 | const struct file_operations event_buffer_fops = { |
1da177e4 LT |
205 | .open = event_buffer_open, |
206 | .release = event_buffer_release, | |
207 | .read = event_buffer_read, | |
729419f0 | 208 | .llseek = no_llseek, |
1da177e4 | 209 | }; |