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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> | |
22 | ||
23 | #include "oprof.h" | |
24 | #include "event_buffer.h" | |
25 | #include "oprofile_stats.h" | |
26 | ||
59cc185a | 27 | DEFINE_MUTEX(buffer_mutex); |
1da177e4 LT |
28 | |
29 | static unsigned long buffer_opened; | |
30 | static DECLARE_WAIT_QUEUE_HEAD(buffer_wait); | |
31 | static unsigned long * event_buffer; | |
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 | ||
38 | /* Add an entry to the event buffer. When we | |
39 | * get near to the end we wake up the process | |
40 | * sleeping on the read() of the file. | |
41 | */ | |
42 | void add_event_entry(unsigned long value) | |
43 | { | |
44 | if (buffer_pos == buffer_size) { | |
45 | atomic_inc(&oprofile_stats.event_lost_overflow); | |
46 | return; | |
47 | } | |
48 | ||
49 | event_buffer[buffer_pos] = value; | |
50 | if (++buffer_pos == buffer_size - buffer_watershed) { | |
51 | atomic_set(&buffer_ready, 1); | |
52 | wake_up(&buffer_wait); | |
53 | } | |
54 | } | |
55 | ||
56 | ||
57 | /* Wake up the waiting process if any. This happens | |
58 | * on "echo 0 >/dev/oprofile/enable" so the daemon | |
59 | * processes the data remaining in the event buffer. | |
60 | */ | |
61 | void wake_up_buffer_waiter(void) | |
62 | { | |
59cc185a | 63 | mutex_lock(&buffer_mutex); |
1da177e4 LT |
64 | atomic_set(&buffer_ready, 1); |
65 | wake_up(&buffer_wait); | |
59cc185a | 66 | mutex_unlock(&buffer_mutex); |
1da177e4 LT |
67 | } |
68 | ||
69 | ||
70 | int alloc_event_buffer(void) | |
71 | { | |
72 | int err = -ENOMEM; | |
73 | ||
74 | spin_lock(&oprofilefs_lock); | |
75 | buffer_size = fs_buffer_size; | |
76 | buffer_watershed = fs_buffer_watershed; | |
77 | spin_unlock(&oprofilefs_lock); | |
78 | ||
79 | if (buffer_watershed >= buffer_size) | |
80 | return -EINVAL; | |
81 | ||
82 | event_buffer = vmalloc(sizeof(unsigned long) * buffer_size); | |
83 | if (!event_buffer) | |
84 | goto out; | |
85 | ||
86 | err = 0; | |
87 | out: | |
88 | return err; | |
89 | } | |
90 | ||
91 | ||
92 | void free_event_buffer(void) | |
93 | { | |
94 | vfree(event_buffer); | |
95 | } | |
96 | ||
97 | ||
98 | static int event_buffer_open(struct inode * inode, struct file * file) | |
99 | { | |
100 | int err = -EPERM; | |
101 | ||
102 | if (!capable(CAP_SYS_ADMIN)) | |
103 | return -EPERM; | |
104 | ||
105 | if (test_and_set_bit(0, &buffer_opened)) | |
106 | return -EBUSY; | |
107 | ||
108 | /* Register as a user of dcookies | |
109 | * to ensure they persist for the lifetime of | |
110 | * the open event file | |
111 | */ | |
112 | err = -EINVAL; | |
113 | file->private_data = dcookie_register(); | |
114 | if (!file->private_data) | |
115 | goto out; | |
116 | ||
117 | if ((err = oprofile_setup())) | |
118 | goto fail; | |
119 | ||
120 | /* NB: the actual start happens from userspace | |
121 | * echo 1 >/dev/oprofile/enable | |
122 | */ | |
123 | ||
124 | return 0; | |
125 | ||
126 | fail: | |
127 | dcookie_unregister(file->private_data); | |
128 | out: | |
129 | clear_bit(0, &buffer_opened); | |
130 | return err; | |
131 | } | |
132 | ||
133 | ||
134 | static int event_buffer_release(struct inode * inode, struct file * file) | |
135 | { | |
136 | oprofile_stop(); | |
137 | oprofile_shutdown(); | |
138 | dcookie_unregister(file->private_data); | |
139 | buffer_pos = 0; | |
140 | atomic_set(&buffer_ready, 0); | |
141 | clear_bit(0, &buffer_opened); | |
142 | return 0; | |
143 | } | |
144 | ||
145 | ||
146 | static ssize_t event_buffer_read(struct file * file, char __user * buf, | |
147 | size_t count, loff_t * offset) | |
148 | { | |
149 | int retval = -EINVAL; | |
150 | size_t const max = buffer_size * sizeof(unsigned long); | |
151 | ||
152 | /* handling partial reads is more trouble than it's worth */ | |
153 | if (count != max || *offset) | |
154 | return -EINVAL; | |
155 | ||
156 | wait_event_interruptible(buffer_wait, atomic_read(&buffer_ready)); | |
157 | ||
158 | if (signal_pending(current)) | |
159 | return -EINTR; | |
160 | ||
161 | /* can't currently happen */ | |
162 | if (!atomic_read(&buffer_ready)) | |
163 | return -EAGAIN; | |
164 | ||
59cc185a | 165 | mutex_lock(&buffer_mutex); |
1da177e4 LT |
166 | |
167 | atomic_set(&buffer_ready, 0); | |
168 | ||
169 | retval = -EFAULT; | |
170 | ||
171 | count = buffer_pos * sizeof(unsigned long); | |
172 | ||
173 | if (copy_to_user(buf, event_buffer, count)) | |
174 | goto out; | |
175 | ||
176 | retval = count; | |
177 | buffer_pos = 0; | |
178 | ||
179 | out: | |
59cc185a | 180 | mutex_unlock(&buffer_mutex); |
1da177e4 LT |
181 | return retval; |
182 | } | |
183 | ||
184 | struct file_operations event_buffer_fops = { | |
185 | .open = event_buffer_open, | |
186 | .release = event_buffer_release, | |
187 | .read = event_buffer_read, | |
188 | }; |