xref: /linux/lib/seq_buf.c (revision ab52c59103002b49f2455371e4b9c56ba3ef1781)
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 
17 #include <linux/bug.h>
18 #include <linux/err.h>
19 #include <linux/export.h>
20 #include <linux/hex.h>
21 #include <linux/minmax.h>
22 #include <linux/printk.h>
23 #include <linux/seq_buf.h>
24 #include <linux/seq_file.h>
25 #include <linux/sprintf.h>
26 #include <linux/string.h>
27 #include <linux/types.h>
28 #include <linux/uaccess.h>
29 
30 /**
31  * seq_buf_can_fit - can the new data fit in the current buffer?
32  * @s: the seq_buf descriptor
33  * @len: The length to see if it can fit in the current buffer
34  *
35  * Returns: true if there's enough unused space in the seq_buf buffer
36  * to fit the amount of new data according to @len.
37  */
38 static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
39 {
40 	return s->len + len <= s->size;
41 }
42 
43 /**
44  * seq_buf_print_seq - move the contents of seq_buf into a seq_file
45  * @m: the seq_file descriptor that is the destination
46  * @s: the seq_buf descriptor that is the source.
47  *
48  * Returns: zero on success, non-zero otherwise.
49  */
50 int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
51 {
52 	unsigned int len = seq_buf_used(s);
53 
54 	return seq_write(m, s->buffer, len);
55 }
56 
57 /**
58  * seq_buf_vprintf - sequence printing of information.
59  * @s: seq_buf descriptor
60  * @fmt: printf format string
61  * @args: va_list of arguments from a printf() type function
62  *
63  * Writes a vnprintf() format into the sequence buffer.
64  *
65  * Returns: zero on success, -1 on overflow.
66  */
67 int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)
68 {
69 	int len;
70 
71 	WARN_ON(s->size == 0);
72 
73 	if (s->len < s->size) {
74 		len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
75 		if (s->len + len < s->size) {
76 			s->len += len;
77 			return 0;
78 		}
79 	}
80 	seq_buf_set_overflow(s);
81 	return -1;
82 }
83 
84 /**
85  * seq_buf_printf - sequence printing of information
86  * @s: seq_buf descriptor
87  * @fmt: printf format string
88  *
89  * Writes a printf() format into the sequence buffer.
90  *
91  * Returns: zero on success, -1 on overflow.
92  */
93 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...)
94 {
95 	va_list ap;
96 	int ret;
97 
98 	va_start(ap, fmt);
99 	ret = seq_buf_vprintf(s, fmt, ap);
100 	va_end(ap);
101 
102 	return ret;
103 }
104 EXPORT_SYMBOL_GPL(seq_buf_printf);
105 
106 /**
107  * seq_buf_do_printk - printk() seq_buf line by line
108  * @s: seq_buf descriptor
109  * @lvl: printk level
110  *
111  * printk()-s a multi-line sequential buffer line by line. The function
112  * makes sure that the buffer in @s is NUL-terminated and safe to read
113  * as a string.
114  */
115 void seq_buf_do_printk(struct seq_buf *s, const char *lvl)
116 {
117 	const char *start, *lf;
118 
119 	if (s->size == 0 || s->len == 0)
120 		return;
121 
122 	start = seq_buf_str(s);
123 	while ((lf = strchr(start, '\n'))) {
124 		int len = lf - start + 1;
125 
126 		printk("%s%.*s", lvl, len, start);
127 		start = ++lf;
128 	}
129 
130 	/* No trailing LF */
131 	if (start < s->buffer + s->len)
132 		printk("%s%s\n", lvl, start);
133 }
134 EXPORT_SYMBOL_GPL(seq_buf_do_printk);
135 
136 #ifdef CONFIG_BINARY_PRINTF
137 /**
138  * seq_buf_bprintf - Write the printf string from binary arguments
139  * @s: seq_buf descriptor
140  * @fmt: The format string for the @binary arguments
141  * @binary: The binary arguments for @fmt.
142  *
143  * When recording in a fast path, a printf may be recorded with just
144  * saving the format and the arguments as they were passed to the
145  * function, instead of wasting cycles converting the arguments into
146  * ASCII characters. Instead, the arguments are saved in a 32 bit
147  * word array that is defined by the format string constraints.
148  *
149  * This function will take the format and the binary array and finish
150  * the conversion into the ASCII string within the buffer.
151  *
152  * Returns: zero on success, -1 on overflow.
153  */
154 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
155 {
156 	unsigned int len = seq_buf_buffer_left(s);
157 	int ret;
158 
159 	WARN_ON(s->size == 0);
160 
161 	if (s->len < s->size) {
162 		ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
163 		if (s->len + ret < s->size) {
164 			s->len += ret;
165 			return 0;
166 		}
167 	}
168 	seq_buf_set_overflow(s);
169 	return -1;
170 }
171 #endif /* CONFIG_BINARY_PRINTF */
172 
173 /**
174  * seq_buf_puts - sequence printing of simple string
175  * @s: seq_buf descriptor
176  * @str: simple string to record
177  *
178  * Copy a simple string into the sequence buffer.
179  *
180  * Returns: zero on success, -1 on overflow.
181  */
182 int seq_buf_puts(struct seq_buf *s, const char *str)
183 {
184 	size_t len = strlen(str);
185 
186 	WARN_ON(s->size == 0);
187 
188 	/* Add 1 to len for the trailing null byte which must be there */
189 	len += 1;
190 
191 	if (seq_buf_can_fit(s, len)) {
192 		memcpy(s->buffer + s->len, str, len);
193 		/* Don't count the trailing null byte against the capacity */
194 		s->len += len - 1;
195 		return 0;
196 	}
197 	seq_buf_set_overflow(s);
198 	return -1;
199 }
200 EXPORT_SYMBOL_GPL(seq_buf_puts);
201 
202 /**
203  * seq_buf_putc - sequence printing of simple character
204  * @s: seq_buf descriptor
205  * @c: simple character to record
206  *
207  * Copy a single character into the sequence buffer.
208  *
209  * Returns: zero on success, -1 on overflow.
210  */
211 int seq_buf_putc(struct seq_buf *s, unsigned char c)
212 {
213 	WARN_ON(s->size == 0);
214 
215 	if (seq_buf_can_fit(s, 1)) {
216 		s->buffer[s->len++] = c;
217 		return 0;
218 	}
219 	seq_buf_set_overflow(s);
220 	return -1;
221 }
222 EXPORT_SYMBOL_GPL(seq_buf_putc);
223 
224 /**
225  * seq_buf_putmem - write raw data into the sequence buffer
226  * @s: seq_buf descriptor
227  * @mem: The raw memory to copy into the buffer
228  * @len: The length of the raw memory to copy (in bytes)
229  *
230  * There may be cases where raw memory needs to be written into the
231  * buffer and a strcpy() would not work. Using this function allows
232  * for such cases.
233  *
234  * Returns: zero on success, -1 on overflow.
235  */
236 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
237 {
238 	WARN_ON(s->size == 0);
239 
240 	if (seq_buf_can_fit(s, len)) {
241 		memcpy(s->buffer + s->len, mem, len);
242 		s->len += len;
243 		return 0;
244 	}
245 	seq_buf_set_overflow(s);
246 	return -1;
247 }
248 
249 #define MAX_MEMHEX_BYTES	8U
250 #define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)
251 
252 /**
253  * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
254  * @s: seq_buf descriptor
255  * @mem: The raw memory to write its hex ASCII representation of
256  * @len: The length of the raw memory to copy (in bytes)
257  *
258  * This is similar to seq_buf_putmem() except instead of just copying the
259  * raw memory into the buffer it writes its ASCII representation of it
260  * in hex characters.
261  *
262  * Returns: zero on success, -1 on overflow.
263  */
264 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
265 		       unsigned int len)
266 {
267 	unsigned char hex[HEX_CHARS];
268 	const unsigned char *data = mem;
269 	unsigned int start_len;
270 	int i, j;
271 
272 	WARN_ON(s->size == 0);
273 
274 	BUILD_BUG_ON(MAX_MEMHEX_BYTES * 2 >= HEX_CHARS);
275 
276 	while (len) {
277 		start_len = min(len, MAX_MEMHEX_BYTES);
278 #ifdef __BIG_ENDIAN
279 		for (i = 0, j = 0; i < start_len; i++) {
280 #else
281 		for (i = start_len-1, j = 0; i >= 0; i--) {
282 #endif
283 			hex[j++] = hex_asc_hi(data[i]);
284 			hex[j++] = hex_asc_lo(data[i]);
285 		}
286 		if (WARN_ON_ONCE(j == 0 || j/2 > len))
287 			break;
288 
289 		/* j increments twice per loop */
290 		hex[j++] = ' ';
291 
292 		seq_buf_putmem(s, hex, j);
293 		if (seq_buf_has_overflowed(s))
294 			return -1;
295 
296 		len -= start_len;
297 		data += start_len;
298 	}
299 	return 0;
300 }
301 
302 /**
303  * seq_buf_path - copy a path into the sequence buffer
304  * @s: seq_buf descriptor
305  * @path: path to write into the sequence buffer.
306  * @esc: set of characters to escape in the output
307  *
308  * Write a path name into the sequence buffer.
309  *
310  * Returns: the number of written bytes on success, -1 on overflow.
311  */
312 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
313 {
314 	char *buf;
315 	size_t size = seq_buf_get_buf(s, &buf);
316 	int res = -1;
317 
318 	WARN_ON(s->size == 0);
319 
320 	if (size) {
321 		char *p = d_path(path, buf, size);
322 		if (!IS_ERR(p)) {
323 			char *end = mangle_path(buf, p, esc);
324 			if (end)
325 				res = end - buf;
326 		}
327 	}
328 	seq_buf_commit(s, res);
329 
330 	return res;
331 }
332 
333 /**
334  * seq_buf_to_user - copy the sequence buffer to user space
335  * @s: seq_buf descriptor
336  * @ubuf: The userspace memory location to copy to
337  * @start: The first byte in the buffer to copy
338  * @cnt: The amount to copy
339  *
340  * Copies the sequence buffer into the userspace memory pointed to
341  * by @ubuf. It starts from @start and writes up to @cnt characters
342  * or until it reaches the end of the content in the buffer (@s->len),
343  * whichever comes first.
344  *
345  * Returns:
346  * On success, it returns a positive number of the number of bytes
347  * it copied.
348  *
349  * On failure it returns -EBUSY if all of the content in the
350  * sequence has been already read, which includes nothing in the
351  * sequence (@s->len == @start).
352  *
353  * Returns -EFAULT if the copy to userspace fails.
354  */
355 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, size_t start, int cnt)
356 {
357 	int len;
358 	int ret;
359 
360 	if (!cnt)
361 		return 0;
362 
363 	len = seq_buf_used(s);
364 
365 	if (len <= start)
366 		return -EBUSY;
367 
368 	len -= start;
369 	if (cnt > len)
370 		cnt = len;
371 	ret = copy_to_user(ubuf, s->buffer + start, cnt);
372 	if (ret == cnt)
373 		return -EFAULT;
374 
375 	return cnt - ret;
376 }
377 
378 /**
379  * seq_buf_hex_dump - print formatted hex dump into the sequence buffer
380  * @s: seq_buf descriptor
381  * @prefix_str: string to prefix each line with;
382  *  caller supplies trailing spaces for alignment if desired
383  * @prefix_type: controls whether prefix of an offset, address, or none
384  *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)
385  * @rowsize: number of bytes to print per line; must be 16 or 32
386  * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
387  * @buf: data blob to dump
388  * @len: number of bytes in the @buf
389  * @ascii: include ASCII after the hex output
390  *
391  * Function is an analogue of print_hex_dump() and thus has similar interface.
392  *
393  * linebuf size is maximal length for one line.
394  * 32 * 3 - maximum bytes per line, each printed into 2 chars + 1 for
395  *	separating space
396  * 2 - spaces separating hex dump and ASCII representation
397  * 32 - ASCII representation
398  * 1 - terminating '\0'
399  *
400  * Returns: zero on success, -1 on overflow.
401  */
402 int seq_buf_hex_dump(struct seq_buf *s, const char *prefix_str, int prefix_type,
403 		     int rowsize, int groupsize,
404 		     const void *buf, size_t len, bool ascii)
405 {
406 	const u8 *ptr = buf;
407 	int i, linelen, remaining = len;
408 	unsigned char linebuf[32 * 3 + 2 + 32 + 1];
409 	int ret;
410 
411 	if (rowsize != 16 && rowsize != 32)
412 		rowsize = 16;
413 
414 	for (i = 0; i < len; i += rowsize) {
415 		linelen = min(remaining, rowsize);
416 		remaining -= rowsize;
417 
418 		hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
419 				   linebuf, sizeof(linebuf), ascii);
420 
421 		switch (prefix_type) {
422 		case DUMP_PREFIX_ADDRESS:
423 			ret = seq_buf_printf(s, "%s%p: %s\n",
424 			       prefix_str, ptr + i, linebuf);
425 			break;
426 		case DUMP_PREFIX_OFFSET:
427 			ret = seq_buf_printf(s, "%s%.8x: %s\n",
428 					     prefix_str, i, linebuf);
429 			break;
430 		default:
431 			ret = seq_buf_printf(s, "%s%s\n", prefix_str, linebuf);
432 			break;
433 		}
434 		if (ret)
435 			return ret;
436 	}
437 	return 0;
438 }
439