1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * seq_buf.c
4 *
5 * Copyright (C) 2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
6 *
7 * The seq_buf is a handy tool that allows you to pass a descriptor around
8 * to a buffer that other functions can write to. It is similar to the
9 * seq_file functionality but has some differences.
10 *
11 * To use it, the seq_buf must be initialized with seq_buf_init().
12 * This will set up the counters within the descriptor. You can call
13 * seq_buf_init() more than once to reset the seq_buf to start
14 * from scratch.
15 */
16 #include <linux/uaccess.h>
17 #include <linux/seq_file.h>
18 #include <linux/seq_buf.h>
19
20 /**
21 * seq_buf_can_fit - can the new data fit in the current buffer?
22 * @s: the seq_buf descriptor
23 * @len: The length to see if it can fit in the current buffer
24 *
25 * Returns true if there's enough unused space in the seq_buf buffer
26 * to fit the amount of new data according to @len.
27 */
28 static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
29 {
30 return s->len + len <= s->size;
31 }
32
33 /**
34 * seq_buf_print_seq - move the contents of seq_buf into a seq_file
35 * @m: the seq_file descriptor that is the destination
36 * @s: the seq_buf descriptor that is the source.
37 *
38 * Returns zero on success, non zero otherwise
39 */
40 int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
41 {
42 unsigned int len = seq_buf_used(s);
43
44 return seq_write(m, s->buffer, len);
45 }
46
47 /**
48 * seq_buf_vprintf - sequence printing of information.
49 * @s: seq_buf descriptor
50 * @fmt: printf format string
51 * @args: va_list of arguments from a printf() type function
52 *
53 * Writes a vnprintf() format into the sequencce buffer.
54 *
55 * Returns zero on success, -1 on overflow.
56 */
57 int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)
58 {
59 int len;
60
61 WARN_ON(s->size == 0);
62
63 if (s->len < s->size) {
64 len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
65 if (s->len + len < s->size) {
66 s->len += len;
67 return 0;
68 }
69 }
70 seq_buf_set_overflow(s);
71 return -1;
72 }
73
74 /**
75 * seq_buf_printf - sequence printing of information
76 * @s: seq_buf descriptor
77 * @fmt: printf format string
78 *
79 * Writes a printf() format into the sequence buffer.
80 *
81 * Returns zero on success, -1 on overflow.
82 */
83 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...)
84 {
85 va_list ap;
86 int ret;
87
88 va_start(ap, fmt);
89 ret = seq_buf_vprintf(s, fmt, ap);
90 va_end(ap);
91
92 return ret;
93 }
94
95 #ifdef CONFIG_BINARY_PRINTF
96 /**
97 * seq_buf_bprintf - Write the printf string from binary arguments
98 * @s: seq_buf descriptor
99 * @fmt: The format string for the @binary arguments
100 * @binary: The binary arguments for @fmt.
101 *
102 * When recording in a fast path, a printf may be recorded with just
103 * saving the format and the arguments as they were passed to the
104 * function, instead of wasting cycles converting the arguments into
105 * ASCII characters. Instead, the arguments are saved in a 32 bit
106 * word array that is defined by the format string constraints.
107 *
108 * This function will take the format and the binary array and finish
109 * the conversion into the ASCII string within the buffer.
110 *
111 * Returns zero on success, -1 on overflow.
112 */
113 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
114 {
115 unsigned int len = seq_buf_buffer_left(s);
116 int ret;
117
118 WARN_ON(s->size == 0);
119
120 if (s->len < s->size) {
121 ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
122 if (s->len + ret < s->size) {
123 s->len += ret;
124 return 0;
125 }
126 }
127 seq_buf_set_overflow(s);
128 return -1;
129 }
130 #endif /* CONFIG_BINARY_PRINTF */
131
132 /**
133 * seq_buf_puts - sequence printing of simple string
134 * @s: seq_buf descriptor
135 * @str: simple string to record
136 *
137 * Copy a simple string into the sequence buffer.
138 *
139 * Returns zero on success, -1 on overflow
140 */
141 int seq_buf_puts(struct seq_buf *s, const char *str)
142 {
143 size_t len = strlen(str);
144
145 WARN_ON(s->size == 0);
146
147 /* Add 1 to len for the trailing null byte which must be there */
148 len += 1;
149
150 if (seq_buf_can_fit(s, len)) {
151 memcpy(s->buffer + s->len, str, len);
152 /* Don't count the trailing null byte against the capacity */
153 s->len += len - 1;
154 return 0;
155 }
156 seq_buf_set_overflow(s);
157 return -1;
158 }
159
160 /**
161 * seq_buf_putc - sequence printing of simple character
162 * @s: seq_buf descriptor
163 * @c: simple character to record
164 *
165 * Copy a single character into the sequence buffer.
166 *
167 * Returns zero on success, -1 on overflow
168 */
169 int seq_buf_putc(struct seq_buf *s, unsigned char c)
170 {
171 WARN_ON(s->size == 0);
172
173 if (seq_buf_can_fit(s, 1)) {
174 s->buffer[s->len++] = c;
175 return 0;
176 }
177 seq_buf_set_overflow(s);
178 return -1;
179 }
180
181 /**
182 * seq_buf_putmem - write raw data into the sequenc buffer
183 * @s: seq_buf descriptor
184 * @mem: The raw memory to copy into the buffer
185 * @len: The length of the raw memory to copy (in bytes)
186 *
187 * There may be cases where raw memory needs to be written into the
188 * buffer and a strcpy() would not work. Using this function allows
189 * for such cases.
190 *
191 * Returns zero on success, -1 on overflow
192 */
193 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
194 {
195 WARN_ON(s->size == 0);
196
197 if (seq_buf_can_fit(s, len)) {
198 memcpy(s->buffer + s->len, mem, len);
199 s->len += len;
200 return 0;
201 }
202 seq_buf_set_overflow(s);
203 return -1;
204 }
205
206 #define MAX_MEMHEX_BYTES 8U
207 #define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)
208
209 /**
210 * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
211 * @s: seq_buf descriptor
212 * @mem: The raw memory to write its hex ASCII representation of
213 * @len: The length of the raw memory to copy (in bytes)
214 *
215 * This is similar to seq_buf_putmem() except instead of just copying the
216 * raw memory into the buffer it writes its ASCII representation of it
217 * in hex characters.
218 *
219 * Returns zero on success, -1 on overflow
220 */
221 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
222 unsigned int len)
223 {
224 unsigned char hex[HEX_CHARS];
225 const unsigned char *data = mem;
226 unsigned int start_len;
227 int i, j;
228
229 WARN_ON(s->size == 0);
230
231 while (len) {
232 start_len = min(len, HEX_CHARS - 1);
233 #ifdef __BIG_ENDIAN
234 for (i = 0, j = 0; i < start_len; i++) {
235 #else
236 for (i = start_len-1, j = 0; i >= 0; i--) {
237 #endif
238 hex[j++] = hex_asc_hi(data[i]);
239 hex[j++] = hex_asc_lo(data[i]);
240 }
241 if (WARN_ON_ONCE(j == 0 || j/2 > len))
242 break;
243
244 /* j increments twice per loop */
245 len -= j / 2;
246 hex[j++] = ' ';
247
248 seq_buf_putmem(s, hex, j);
249 if (seq_buf_has_overflowed(s))
250 return -1;
251 }
252 return 0;
253 }
254
255 /**
256 * seq_buf_path - copy a path into the sequence buffer
257 * @s: seq_buf descriptor
258 * @path: path to write into the sequence buffer.
259 * @esc: set of characters to escape in the output
260 *
261 * Write a path name into the sequence buffer.
262 *
263 * Returns the number of written bytes on success, -1 on overflow
264 */
265 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
266 {
267 char *buf;
268 size_t size = seq_buf_get_buf(s, &buf);
269 int res = -1;
270
271 WARN_ON(s->size == 0);
272
273 if (size) {
274 char *p = d_path(path, buf, size);
275 if (!IS_ERR(p)) {
276 char *end = mangle_path(buf, p, esc);
277 if (end)
278 res = end - buf;
279 }
280 }
281 seq_buf_commit(s, res);
282
283 return res;
284 }
285
286 /**
287 * seq_buf_to_user - copy the squence buffer to user space
288 * @s: seq_buf descriptor
289 * @ubuf: The userspace memory location to copy to
290 * @cnt: The amount to copy
291 *
292 * Copies the sequence buffer into the userspace memory pointed to
293 * by @ubuf. It starts from the last read position (@s->readpos)
294 * and writes up to @cnt characters or till it reaches the end of
295 * the content in the buffer (@s->len), which ever comes first.
296 *
297 * On success, it returns a positive number of the number of bytes
298 * it copied.
299 *
300 * On failure it returns -EBUSY if all of the content in the
301 * sequence has been already read, which includes nothing in the
302 * sequence (@s->len == @s->readpos).
303 *
304 * Returns -EFAULT if the copy to userspace fails.
305 */
306 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
307 {
308 int len;
309 int ret;
310
311 if (!cnt)
312 return 0;
313
314 len = seq_buf_used(s);
315
316 if (len <= s->readpos)
317 return -EBUSY;
318
319 len -= s->readpos;
320 if (cnt > len)
321 cnt = len;
322 ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
323 if (ret == cnt)
324 return -EFAULT;
325
326 cnt -= ret;
327
328 s->readpos += cnt;
329 return cnt;
330 }