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 */
 27static 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 */
 39int 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 */
 56int 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 */
 82int 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 */
112int 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 */
140int 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	if (seq_buf_can_fit(s, len)) {
147		memcpy(s->buffer + s->len, str, len);
148		s->len += len;
149		return 0;
150	}
151	seq_buf_set_overflow(s);
152	return -1;
153}
154
155/**
156 * seq_buf_putc - sequence printing of simple character
157 * @s: seq_buf descriptor
158 * @c: simple character to record
159 *
160 * Copy a single character into the sequence buffer.
161 *
162 * Returns zero on success, -1 on overflow
163 */
164int seq_buf_putc(struct seq_buf *s, unsigned char c)
165{
166	WARN_ON(s->size == 0);
167
168	if (seq_buf_can_fit(s, 1)) {
169		s->buffer[s->len++] = c;
170		return 0;
171	}
172	seq_buf_set_overflow(s);
173	return -1;
174}
175
176/**
177 * seq_buf_putmem - write raw data into the sequenc buffer
178 * @s: seq_buf descriptor
179 * @mem: The raw memory to copy into the buffer
180 * @len: The length of the raw memory to copy (in bytes)
181 *
182 * There may be cases where raw memory needs to be written into the
183 * buffer and a strcpy() would not work. Using this function allows
184 * for such cases.
185 *
186 * Returns zero on success, -1 on overflow
187 */
188int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
189{
190	WARN_ON(s->size == 0);
191
192	if (seq_buf_can_fit(s, len)) {
193		memcpy(s->buffer + s->len, mem, len);
194		s->len += len;
195		return 0;
196	}
197	seq_buf_set_overflow(s);
198	return -1;
199}
200
201#define MAX_MEMHEX_BYTES	8U
202#define HEX_CHARS		(MAX_MEMHEX_BYTES*2 + 1)
203
204/**
205 * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
206 * @s: seq_buf descriptor
207 * @mem: The raw memory to write its hex ASCII representation of
208 * @len: The length of the raw memory to copy (in bytes)
209 *
210 * This is similar to seq_buf_putmem() except instead of just copying the
211 * raw memory into the buffer it writes its ASCII representation of it
212 * in hex characters.
213 *
214 * Returns zero on success, -1 on overflow
215 */
216int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
217		       unsigned int len)
218{
219	unsigned char hex[HEX_CHARS];
220	const unsigned char *data = mem;
221	unsigned int start_len;
222	int i, j;
223
224	WARN_ON(s->size == 0);
225
226	while (len) {
227		start_len = min(len, HEX_CHARS - 1);
228#ifdef __BIG_ENDIAN
229		for (i = 0, j = 0; i < start_len; i++) {
230#else
231		for (i = start_len-1, j = 0; i >= 0; i--) {
232#endif
233			hex[j++] = hex_asc_hi(data[i]);
234			hex[j++] = hex_asc_lo(data[i]);
235		}
236		if (WARN_ON_ONCE(j == 0 || j/2 > len))
237			break;
238
239		/* j increments twice per loop */
240		len -= j / 2;
241		hex[j++] = ' ';
242
243		seq_buf_putmem(s, hex, j);
244		if (seq_buf_has_overflowed(s))
245			return -1;
246	}
247	return 0;
248}
249
250/**
251 * seq_buf_path - copy a path into the sequence buffer
252 * @s: seq_buf descriptor
253 * @path: path to write into the sequence buffer.
254 * @esc: set of characters to escape in the output
255 *
256 * Write a path name into the sequence buffer.
257 *
258 * Returns the number of written bytes on success, -1 on overflow
259 */
260int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
261{
262	char *buf;
263	size_t size = seq_buf_get_buf(s, &buf);
264	int res = -1;
265
266	WARN_ON(s->size == 0);
267
268	if (size) {
269		char *p = d_path(path, buf, size);
270		if (!IS_ERR(p)) {
271			char *end = mangle_path(buf, p, esc);
272			if (end)
273				res = end - buf;
274		}
275	}
276	seq_buf_commit(s, res);
277
278	return res;
279}
280
281/**
282 * seq_buf_to_user - copy the squence buffer to user space
283 * @s: seq_buf descriptor
284 * @ubuf: The userspace memory location to copy to
285 * @cnt: The amount to copy
286 *
287 * Copies the sequence buffer into the userspace memory pointed to
288 * by @ubuf. It starts from the last read position (@s->readpos)
289 * and writes up to @cnt characters or till it reaches the end of
290 * the content in the buffer (@s->len), which ever comes first.
291 *
292 * On success, it returns a positive number of the number of bytes
293 * it copied.
294 *
295 * On failure it returns -EBUSY if all of the content in the
296 * sequence has been already read, which includes nothing in the
297 * sequence (@s->len == @s->readpos).
298 *
299 * Returns -EFAULT if the copy to userspace fails.
300 */
301int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
302{
303	int len;
304	int ret;
305
306	if (!cnt)
307		return 0;
308
309	len = seq_buf_used(s);
310
311	if (len <= s->readpos)
312		return -EBUSY;
313
314	len -= s->readpos;
315	if (cnt > len)
316		cnt = len;
317	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
318	if (ret == cnt)
319		return -EFAULT;
320
321	cnt -= ret;
322
323	s->readpos += cnt;
324	return cnt;
325}