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 (seq_buf_can_fit(s, len)) { 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 /** 95 * seq_buf_bitmask - write a bitmask array in its ASCII representation 96 * @s: seq_buf descriptor 97 * @maskp: points to an array of unsigned longs that represent a bitmask 98 * @nmaskbits: The number of bits that are valid in @maskp 99 * 100 * Writes a ASCII representation of a bitmask string into @s. 101 * 102 * Returns zero on success, -1 on overflow. 103 */ 104 int seq_buf_bitmask(struct seq_buf *s, const unsigned long *maskp, 105 int nmaskbits) 106 { 107 unsigned int len = seq_buf_buffer_left(s); 108 int ret; 109 110 WARN_ON(s->size == 0); 111 112 /* 113 * Note, because bitmap_scnprintf() only returns the number of bytes 114 * written and not the number that would be written, we use the last 115 * byte of the buffer to let us know if we overflowed. There's a small 116 * chance that the bitmap could have fit exactly inside the buffer, but 117 * it's not that critical if that does happen. 118 */ 119 if (len > 1) { 120 ret = bitmap_scnprintf(s->buffer + s->len, len, maskp, nmaskbits); 121 if (ret < len) { 122 s->len += ret; 123 return 0; 124 } 125 } 126 seq_buf_set_overflow(s); 127 return -1; 128 } 129 130 #ifdef CONFIG_BINARY_PRINTF 131 /** 132 * seq_buf_bprintf - Write the printf string from binary arguments 133 * @s: seq_buf descriptor 134 * @fmt: The format string for the @binary arguments 135 * @binary: The binary arguments for @fmt. 136 * 137 * When recording in a fast path, a printf may be recorded with just 138 * saving the format and the arguments as they were passed to the 139 * function, instead of wasting cycles converting the arguments into 140 * ASCII characters. Instead, the arguments are saved in a 32 bit 141 * word array that is defined by the format string constraints. 142 * 143 * This function will take the format and the binary array and finish 144 * the conversion into the ASCII string within the buffer. 145 * 146 * Returns zero on success, -1 on overflow. 147 */ 148 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary) 149 { 150 unsigned int len = seq_buf_buffer_left(s); 151 int ret; 152 153 WARN_ON(s->size == 0); 154 155 if (s->len < s->size) { 156 ret = bstr_printf(s->buffer + s->len, len, fmt, binary); 157 if (seq_buf_can_fit(s, ret)) { 158 s->len += ret; 159 return 0; 160 } 161 } 162 seq_buf_set_overflow(s); 163 return -1; 164 } 165 #endif /* CONFIG_BINARY_PRINTF */ 166 167 /** 168 * seq_buf_puts - sequence printing of simple string 169 * @s: seq_buf descriptor 170 * @str: simple string to record 171 * 172 * Copy a simple string into the sequence buffer. 173 * 174 * Returns zero on success, -1 on overflow 175 */ 176 int seq_buf_puts(struct seq_buf *s, const char *str) 177 { 178 unsigned int len = strlen(str); 179 180 WARN_ON(s->size == 0); 181 182 if (seq_buf_can_fit(s, len)) { 183 memcpy(s->buffer + s->len, str, len); 184 s->len += len; 185 return 0; 186 } 187 seq_buf_set_overflow(s); 188 return -1; 189 } 190 191 /** 192 * seq_buf_putc - sequence printing of simple character 193 * @s: seq_buf descriptor 194 * @c: simple character to record 195 * 196 * Copy a single character into the sequence buffer. 197 * 198 * Returns zero on success, -1 on overflow 199 */ 200 int seq_buf_putc(struct seq_buf *s, unsigned char c) 201 { 202 WARN_ON(s->size == 0); 203 204 if (seq_buf_can_fit(s, 1)) { 205 s->buffer[s->len++] = c; 206 return 0; 207 } 208 seq_buf_set_overflow(s); 209 return -1; 210 } 211 212 /** 213 * seq_buf_putmem - write raw data into the sequenc buffer 214 * @s: seq_buf descriptor 215 * @mem: The raw memory to copy into the buffer 216 * @len: The length of the raw memory to copy (in bytes) 217 * 218 * There may be cases where raw memory needs to be written into the 219 * buffer and a strcpy() would not work. Using this function allows 220 * for such cases. 221 * 222 * Returns zero on success, -1 on overflow 223 */ 224 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len) 225 { 226 WARN_ON(s->size == 0); 227 228 if (seq_buf_can_fit(s, len)) { 229 memcpy(s->buffer + s->len, mem, len); 230 s->len += len; 231 return 0; 232 } 233 seq_buf_set_overflow(s); 234 return -1; 235 } 236 237 #define MAX_MEMHEX_BYTES 8U 238 #define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1) 239 240 /** 241 * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex 242 * @s: seq_buf descriptor 243 * @mem: The raw memory to write its hex ASCII representation of 244 * @len: The length of the raw memory to copy (in bytes) 245 * 246 * This is similar to seq_buf_putmem() except instead of just copying the 247 * raw memory into the buffer it writes its ASCII representation of it 248 * in hex characters. 249 * 250 * Returns zero on success, -1 on overflow 251 */ 252 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem, 253 unsigned int len) 254 { 255 unsigned char hex[HEX_CHARS]; 256 const unsigned char *data = mem; 257 unsigned int start_len; 258 int i, j; 259 260 WARN_ON(s->size == 0); 261 262 while (len) { 263 start_len = min(len, HEX_CHARS - 1); 264 #ifdef __BIG_ENDIAN 265 for (i = 0, j = 0; i < start_len; i++) { 266 #else 267 for (i = start_len-1, j = 0; i >= 0; i--) { 268 #endif 269 hex[j++] = hex_asc_hi(data[i]); 270 hex[j++] = hex_asc_lo(data[i]); 271 } 272 if (WARN_ON_ONCE(j == 0 || j/2 > len)) 273 break; 274 275 /* j increments twice per loop */ 276 len -= j / 2; 277 hex[j++] = ' '; 278 279 seq_buf_putmem(s, hex, j); 280 if (seq_buf_has_overflowed(s)) 281 return -1; 282 } 283 return 0; 284 } 285 286 /** 287 * seq_buf_path - copy a path into the sequence buffer 288 * @s: seq_buf descriptor 289 * @path: path to write into the sequence buffer. 290 * @esc: set of characters to escape in the output 291 * 292 * Write a path name into the sequence buffer. 293 * 294 * Returns the number of written bytes on success, -1 on overflow 295 */ 296 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc) 297 { 298 char *buf; 299 size_t size = seq_buf_get_buf(s, &buf); 300 int res = -1; 301 302 WARN_ON(s->size == 0); 303 304 if (size) { 305 char *p = d_path(path, buf, size); 306 if (!IS_ERR(p)) { 307 char *end = mangle_path(buf, p, esc); 308 if (end) 309 res = end - buf; 310 } 311 } 312 seq_buf_commit(s, res); 313 314 return res; 315 } 316 317 /** 318 * seq_buf_to_user - copy the squence buffer to user space 319 * @s: seq_buf descriptor 320 * @ubuf: The userspace memory location to copy to 321 * @cnt: The amount to copy 322 * 323 * Copies the sequence buffer into the userspace memory pointed to 324 * by @ubuf. It starts from the last read position (@s->readpos) 325 * and writes up to @cnt characters or till it reaches the end of 326 * the content in the buffer (@s->len), which ever comes first. 327 * 328 * On success, it returns a positive number of the number of bytes 329 * it copied. 330 * 331 * On failure it returns -EBUSY if all of the content in the 332 * sequence has been already read, which includes nothing in the 333 * sequence (@s->len == @s->readpos). 334 * 335 * Returns -EFAULT if the copy to userspace fails. 336 */ 337 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt) 338 { 339 int len; 340 int ret; 341 342 if (!cnt) 343 return 0; 344 345 if (s->len <= s->readpos) 346 return -EBUSY; 347 348 len = seq_buf_used(s) - s->readpos; 349 if (cnt > len) 350 cnt = len; 351 ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt); 352 if (ret == cnt) 353 return -EFAULT; 354 355 cnt -= ret; 356 357 s->readpos += cnt; 358 return cnt; 359 } 360