1 /*
2 * seq_buf.c
3 *
4 * Copyright (C) 2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
5 *
6 * The seq_buf is a handy tool that allows you to pass a descriptor around
7 * to a buffer that other functions can write to. It is similar to the
8 * seq_file functionality but has some differences.
9 *
10 * To use it, the seq_buf must be initialized with seq_buf_init().
11 * This will set up the counters within the descriptor. You can call
12 * seq_buf_init() more than once to reset the seq_buf to start
13 * from scratch.
14 */
15 #include <linux/uaccess.h>
16 #include <linux/seq_file.h>
17 #include <linux/seq_buf.h>
18
19 /**
20 * seq_buf_can_fit - can the new data fit in the current buffer?
21 * @s: the seq_buf descriptor
22 * @len: The length to see if it can fit in the current buffer
23 *
24 * Returns true if there's enough unused space in the seq_buf buffer
25 * to fit the amount of new data according to @len.
26 */
seq_buf_can_fit(struct seq_buf * s,size_t len)27 static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
28 {
29 return s->len + len <= s->size;
30 }
31
32 /**
33 * seq_buf_print_seq - move the contents of seq_buf into a seq_file
34 * @m: the seq_file descriptor that is the destination
35 * @s: the seq_buf descriptor that is the source.
36 *
37 * Returns zero on success, non zero otherwise
38 */
seq_buf_print_seq(struct seq_file * m,struct seq_buf * s)39 int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
40 {
41 unsigned int len = seq_buf_used(s);
42
43 return seq_write(m, s->buffer, len);
44 }
45
46 /**
47 * seq_buf_vprintf - sequence printing of information.
48 * @s: seq_buf descriptor
49 * @fmt: printf format string
50 * @args: va_list of arguments from a printf() type function
51 *
52 * Writes a vnprintf() format into the sequencce buffer.
53 *
54 * Returns zero on success, -1 on overflow.
55 */
seq_buf_vprintf(struct seq_buf * s,const char * fmt,va_list args)56 int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)
57 {
58 int len;
59
60 WARN_ON(s->size == 0);
61
62 if (s->len < s->size) {
63 len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
64 if (s->len + len < s->size) {
65 s->len += len;
66 return 0;
67 }
68 }
69 seq_buf_set_overflow(s);
70 return -1;
71 }
72
73 /**
74 * seq_buf_printf - sequence printing of information
75 * @s: seq_buf descriptor
76 * @fmt: printf format string
77 *
78 * Writes a printf() format into the sequence buffer.
79 *
80 * Returns zero on success, -1 on overflow.
81 */
seq_buf_printf(struct seq_buf * s,const char * fmt,...)82 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...)
83 {
84 va_list ap;
85 int ret;
86
87 va_start(ap, fmt);
88 ret = seq_buf_vprintf(s, fmt, ap);
89 va_end(ap);
90
91 return ret;
92 }
93
94 #ifdef CONFIG_BINARY_PRINTF
95 /**
96 * seq_buf_bprintf - Write the printf string from binary arguments
97 * @s: seq_buf descriptor
98 * @fmt: The format string for the @binary arguments
99 * @binary: The binary arguments for @fmt.
100 *
101 * When recording in a fast path, a printf may be recorded with just
102 * saving the format and the arguments as they were passed to the
103 * function, instead of wasting cycles converting the arguments into
104 * ASCII characters. Instead, the arguments are saved in a 32 bit
105 * word array that is defined by the format string constraints.
106 *
107 * This function will take the format and the binary array and finish
108 * the conversion into the ASCII string within the buffer.
109 *
110 * Returns zero on success, -1 on overflow.
111 */
seq_buf_bprintf(struct seq_buf * s,const char * fmt,const u32 * binary)112 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
113 {
114 unsigned int len = seq_buf_buffer_left(s);
115 int ret;
116
117 WARN_ON(s->size == 0);
118
119 if (s->len < s->size) {
120 ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
121 if (s->len + ret < s->size) {
122 s->len += ret;
123 return 0;
124 }
125 }
126 seq_buf_set_overflow(s);
127 return -1;
128 }
129 #endif /* CONFIG_BINARY_PRINTF */
130
131 /**
132 * seq_buf_puts - sequence printing of simple string
133 * @s: seq_buf descriptor
134 * @str: simple string to record
135 *
136 * Copy a simple string into the sequence buffer.
137 *
138 * Returns zero on success, -1 on overflow
139 */
seq_buf_puts(struct seq_buf * s,const char * str)140 int seq_buf_puts(struct seq_buf *s, const char *str)
141 {
142 unsigned int len = strlen(str);
143
144 WARN_ON(s->size == 0);
145
146 /* Add 1 to len for the trailing null byte which must be there */
147 len += 1;
148
149 if (seq_buf_can_fit(s, len)) {
150 memcpy(s->buffer + s->len, str, len);
151 /* Don't count the trailing null byte against the capacity */
152 s->len += len - 1;
153 return 0;
154 }
155 seq_buf_set_overflow(s);
156 return -1;
157 }
158
159 /**
160 * seq_buf_putc - sequence printing of simple character
161 * @s: seq_buf descriptor
162 * @c: simple character to record
163 *
164 * Copy a single character into the sequence buffer.
165 *
166 * Returns zero on success, -1 on overflow
167 */
seq_buf_putc(struct seq_buf * s,unsigned char c)168 int seq_buf_putc(struct seq_buf *s, unsigned char c)
169 {
170 WARN_ON(s->size == 0);
171
172 if (seq_buf_can_fit(s, 1)) {
173 s->buffer[s->len++] = c;
174 return 0;
175 }
176 seq_buf_set_overflow(s);
177 return -1;
178 }
179
180 /**
181 * seq_buf_putmem - write raw data into the sequenc buffer
182 * @s: seq_buf descriptor
183 * @mem: The raw memory to copy into the buffer
184 * @len: The length of the raw memory to copy (in bytes)
185 *
186 * There may be cases where raw memory needs to be written into the
187 * buffer and a strcpy() would not work. Using this function allows
188 * for such cases.
189 *
190 * Returns zero on success, -1 on overflow
191 */
seq_buf_putmem(struct seq_buf * s,const void * mem,unsigned int len)192 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
193 {
194 WARN_ON(s->size == 0);
195
196 if (seq_buf_can_fit(s, len)) {
197 memcpy(s->buffer + s->len, mem, len);
198 s->len += len;
199 return 0;
200 }
201 seq_buf_set_overflow(s);
202 return -1;
203 }
204
205 #define MAX_MEMHEX_BYTES 8U
206 #define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)
207
208 /**
209 * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
210 * @s: seq_buf descriptor
211 * @mem: The raw memory to write its hex ASCII representation of
212 * @len: The length of the raw memory to copy (in bytes)
213 *
214 * This is similar to seq_buf_putmem() except instead of just copying the
215 * raw memory into the buffer it writes its ASCII representation of it
216 * in hex characters.
217 *
218 * Returns zero on success, -1 on overflow
219 */
seq_buf_putmem_hex(struct seq_buf * s,const void * mem,unsigned int len)220 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
221 unsigned int len)
222 {
223 unsigned char hex[HEX_CHARS];
224 const unsigned char *data = mem;
225 unsigned int start_len;
226 int i, j;
227
228 WARN_ON(s->size == 0);
229
230 BUILD_BUG_ON(MAX_MEMHEX_BYTES * 2 >= HEX_CHARS);
231
232 while (len) {
233 start_len = min(len, MAX_MEMHEX_BYTES);
234 #ifdef __BIG_ENDIAN
235 for (i = 0, j = 0; i < start_len; i++) {
236 #else
237 for (i = start_len-1, j = 0; i >= 0; i--) {
238 #endif
239 hex[j++] = hex_asc_hi(data[i]);
240 hex[j++] = hex_asc_lo(data[i]);
241 }
242 if (WARN_ON_ONCE(j == 0 || j/2 > len))
243 break;
244
245 /* j increments twice per loop */
246 hex[j++] = ' ';
247
248 seq_buf_putmem(s, hex, j);
249 if (seq_buf_has_overflowed(s))
250 return -1;
251
252 len -= start_len;
253 data += start_len;
254 }
255 return 0;
256 }
257
258 /**
259 * seq_buf_path - copy a path into the sequence buffer
260 * @s: seq_buf descriptor
261 * @path: path to write into the sequence buffer.
262 * @esc: set of characters to escape in the output
263 *
264 * Write a path name into the sequence buffer.
265 *
266 * Returns the number of written bytes on success, -1 on overflow
267 */
268 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
269 {
270 char *buf;
271 size_t size = seq_buf_get_buf(s, &buf);
272 int res = -1;
273
274 WARN_ON(s->size == 0);
275
276 if (size) {
277 char *p = d_path(path, buf, size);
278 if (!IS_ERR(p)) {
279 char *end = mangle_path(buf, p, esc);
280 if (end)
281 res = end - buf;
282 }
283 }
284 seq_buf_commit(s, res);
285
286 return res;
287 }
288
289 /**
290 * seq_buf_to_user - copy the squence buffer to user space
291 * @s: seq_buf descriptor
292 * @ubuf: The userspace memory location to copy to
293 * @cnt: The amount to copy
294 *
295 * Copies the sequence buffer into the userspace memory pointed to
296 * by @ubuf. It starts from the last read position (@s->readpos)
297 * and writes up to @cnt characters or till it reaches the end of
298 * the content in the buffer (@s->len), which ever comes first.
299 *
300 * On success, it returns a positive number of the number of bytes
301 * it copied.
302 *
303 * On failure it returns -EBUSY if all of the content in the
304 * sequence has been already read, which includes nothing in the
305 * sequence (@s->len == @s->readpos).
306 *
307 * Returns -EFAULT if the copy to userspace fails.
308 */
309 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
310 {
311 int len;
312 int ret;
313
314 if (!cnt)
315 return 0;
316
317 if (s->len <= s->readpos)
318 return -EBUSY;
319
320 len = seq_buf_used(s) - s->readpos;
321 if (cnt > len)
322 cnt = len;
323 ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
324 if (ret == cnt)
325 return -EFAULT;
326
327 cnt -= ret;
328
329 s->readpos += cnt;
330 return cnt;
331 }
332