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Linux/lib/seq_buf.c

  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  */
 27 static 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  */
 39 int 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  */
 56 int 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  */
 82 int 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  */
112 int 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  */
140 int 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  */
164 int 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  */
188 int 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  */
216 int 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  */
260 int 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  */
301 int 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 }
326 

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