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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> |
18 | #include <linux/capability.h> |
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 | |
27 | DEFINE_MUTEX(buffer_mutex); |
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; |
35 | /* atomic_t because wait_event checks it outside of buffer_mutex */ |
36 | static atomic_t buffer_ready = ATOMIC_INIT(0); |
37 | |
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. |
43 | */ |
44 | void add_event_entry(unsigned long value) |
45 | { |
46 | /* |
47 | * This shouldn't happen since all workqueues or handlers are |
48 | * canceled or flushed before the event buffer is freed. |
49 | */ |
50 | if (!event_buffer) { |
51 | WARN_ON_ONCE(1); |
52 | return; |
53 | } |
54 | |
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 | { |
74 | mutex_lock(&buffer_mutex); |
75 | atomic_set(&buffer_ready, 1); |
76 | wake_up(&buffer_wait); |
77 | mutex_unlock(&buffer_mutex); |
78 | } |
79 | |
80 | |
81 | int alloc_event_buffer(void) |
82 | { |
83 | unsigned long flags; |
84 | |
85 | raw_spin_lock_irqsave(&oprofilefs_lock, flags); |
86 | buffer_size = oprofile_buffer_size; |
87 | buffer_watershed = oprofile_buffer_watershed; |
88 | raw_spin_unlock_irqrestore(&oprofilefs_lock, flags); |
89 | |
90 | if (buffer_watershed >= buffer_size) |
91 | return -EINVAL; |
92 | |
93 | buffer_pos = 0; |
94 | event_buffer = vmalloc(sizeof(unsigned long) * buffer_size); |
95 | if (!event_buffer) |
96 | return -ENOMEM; |
97 | |
98 | return 0; |
99 | } |
100 | |
101 | |
102 | void free_event_buffer(void) |
103 | { |
104 | mutex_lock(&buffer_mutex); |
105 | vfree(event_buffer); |
106 | buffer_pos = 0; |
107 | event_buffer = NULL; |
108 | mutex_unlock(&buffer_mutex); |
109 | } |
110 | |
111 | |
112 | static int event_buffer_open(struct inode *inode, struct file *file) |
113 | { |
114 | int err = -EPERM; |
115 | |
116 | if (!capable(CAP_SYS_ADMIN)) |
117 | return -EPERM; |
118 | |
119 | if (test_and_set_bit_lock(0, &buffer_opened)) |
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; |
130 | |
131 | if ((err = oprofile_setup())) |
132 | goto fail; |
133 | |
134 | /* NB: the actual start happens from userspace |
135 | * echo 1 >/dev/oprofile/enable |
136 | */ |
137 | |
138 | return nonseekable_open(inode, file); |
139 | |
140 | fail: |
141 | dcookie_unregister(file->private_data); |
142 | out: |
143 | __clear_bit_unlock(0, &buffer_opened); |
144 | return err; |
145 | } |
146 | |
147 | |
148 | static int event_buffer_release(struct inode *inode, struct file *file) |
149 | { |
150 | oprofile_stop(); |
151 | oprofile_shutdown(); |
152 | dcookie_unregister(file->private_data); |
153 | buffer_pos = 0; |
154 | atomic_set(&buffer_ready, 0); |
155 | __clear_bit_unlock(0, &buffer_opened); |
156 | return 0; |
157 | } |
158 | |
159 | |
160 | static ssize_t event_buffer_read(struct file *file, char __user *buf, |
161 | size_t count, loff_t *offset) |
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 | |
179 | mutex_lock(&buffer_mutex); |
180 | |
181 | /* May happen if the buffer is freed during pending reads. */ |
182 | if (!event_buffer) { |
183 | retval = -EINTR; |
184 | goto out; |
185 | } |
186 | |
187 | atomic_set(&buffer_ready, 0); |
188 | |
189 | retval = -EFAULT; |
190 | |
191 | count = buffer_pos * sizeof(unsigned long); |
192 | |
193 | if (copy_to_user(buf, event_buffer, count)) |
194 | goto out; |
195 | |
196 | retval = count; |
197 | buffer_pos = 0; |
198 | |
199 | out: |
200 | mutex_unlock(&buffer_mutex); |
201 | return retval; |
202 | } |
203 | |
204 | const struct file_operations event_buffer_fops = { |
205 | .open = event_buffer_open, |
206 | .release = event_buffer_release, |
207 | .read = event_buffer_read, |
208 | .llseek = no_llseek, |
209 | }; |
210 |
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