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Linux/lib/seq_buf.c

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  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 }
331 

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