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 */
 28static 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 */
 40int 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 */
 57int 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 */
 83int 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 */
113int 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 */
141int seq_buf_puts(struct seq_buf *s, const char *str)
142{
143	unsigned int len = strlen(str);
144
145	WARN_ON(s->size == 0);
146
147	if (seq_buf_can_fit(s, len)) {
148		memcpy(s->buffer + s->len, str, len);
149		s->len += len;
150		return 0;
151	}
152	seq_buf_set_overflow(s);
153	return -1;
154}
155
156/**
157 * seq_buf_putc - sequence printing of simple character
158 * @s: seq_buf descriptor
159 * @c: simple character to record
160 *
161 * Copy a single character into the sequence buffer.
162 *
163 * Returns zero on success, -1 on overflow
164 */
165int seq_buf_putc(struct seq_buf *s, unsigned char c)
166{
167	WARN_ON(s->size == 0);
168
169	if (seq_buf_can_fit(s, 1)) {
170		s->buffer[s->len++] = c;
171		return 0;
172	}
173	seq_buf_set_overflow(s);
174	return -1;
175}
176
177/**
178 * seq_buf_putmem - write raw data into the sequenc buffer
179 * @s: seq_buf descriptor
180 * @mem: The raw memory to copy into the buffer
181 * @len: The length of the raw memory to copy (in bytes)
182 *
183 * There may be cases where raw memory needs to be written into the
184 * buffer and a strcpy() would not work. Using this function allows
185 * for such cases.
186 *
187 * Returns zero on success, -1 on overflow
188 */
189int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
190{
191	WARN_ON(s->size == 0);
192
193	if (seq_buf_can_fit(s, len)) {
194		memcpy(s->buffer + s->len, mem, len);
195		s->len += len;
196		return 0;
197	}
198	seq_buf_set_overflow(s);
199	return -1;
200}
201
202#define MAX_MEMHEX_BYTES	8U
203#define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)
204
205/**
206 * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
207 * @s: seq_buf descriptor
208 * @mem: The raw memory to write its hex ASCII representation of
209 * @len: The length of the raw memory to copy (in bytes)
210 *
211 * This is similar to seq_buf_putmem() except instead of just copying the
212 * raw memory into the buffer it writes its ASCII representation of it
213 * in hex characters.
214 *
215 * Returns zero on success, -1 on overflow
216 */
217int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
218		       unsigned int len)
219{
220	unsigned char hex[HEX_CHARS];
221	const unsigned char *data = mem;
222	unsigned int start_len;
223	int i, j;
224
225	WARN_ON(s->size == 0);
226
227	while (len) {
228		start_len = min(len, HEX_CHARS - 1);
229#ifdef __BIG_ENDIAN
230		for (i = 0, j = 0; i < start_len; i++) {
231#else
232		for (i = start_len-1, j = 0; i >= 0; i--) {
233#endif
234			hex[j++] = hex_asc_hi(data[i]);
235			hex[j++] = hex_asc_lo(data[i]);
236		}
237		if (WARN_ON_ONCE(j == 0 || j/2 > len))
238			break;
239
240		/* j increments twice per loop */
241		len -= j / 2;
242		hex[j++] = ' ';
243
244		seq_buf_putmem(s, hex, j);
245		if (seq_buf_has_overflowed(s))
246			return -1;
247	}
248	return 0;
249}
250
251/**
252 * seq_buf_path - copy a path into the sequence buffer
253 * @s: seq_buf descriptor
254 * @path: path to write into the sequence buffer.
255 * @esc: set of characters to escape in the output
256 *
257 * Write a path name into the sequence buffer.
258 *
259 * Returns the number of written bytes on success, -1 on overflow
260 */
261int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
262{
263	char *buf;
264	size_t size = seq_buf_get_buf(s, &buf);
265	int res = -1;
266
267	WARN_ON(s->size == 0);
268
269	if (size) {
270		char *p = d_path(path, buf, size);
271		if (!IS_ERR(p)) {
272			char *end = mangle_path(buf, p, esc);
273			if (end)
274				res = end - buf;
275		}
276	}
277	seq_buf_commit(s, res);
278
279	return res;
280}
281
282/**
283 * seq_buf_to_user - copy the squence buffer to user space
284 * @s: seq_buf descriptor
285 * @ubuf: The userspace memory location to copy to
286 * @cnt: The amount to copy
287 *
288 * Copies the sequence buffer into the userspace memory pointed to
289 * by @ubuf. It starts from the last read position (@s->readpos)
290 * and writes up to @cnt characters or till it reaches the end of
291 * the content in the buffer (@s->len), which ever comes first.
292 *
293 * On success, it returns a positive number of the number of bytes
294 * it copied.
295 *
296 * On failure it returns -EBUSY if all of the content in the
297 * sequence has been already read, which includes nothing in the
298 * sequence (@s->len == @s->readpos).
299 *
300 * Returns -EFAULT if the copy to userspace fails.
301 */
302int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
303{
304	int len;
305	int ret;
306
307	if (!cnt)
308		return 0;
309
310	len = seq_buf_used(s);
311
312	if (len <= s->readpos)
313		return -EBUSY;
314
315	len -= s->readpos;
316	if (cnt > len)
317		cnt = len;
318	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
319	if (ret == cnt)
320		return -EFAULT;
321
322	cnt -= ret;
323
324	s->readpos += cnt;
325	return cnt;
326}