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