lib/seq_buf.c

   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 EXPORT_SYMBOL_GPL(seq_buf_printf);
  95
  96 #ifdef CONFIG_BINARY_PRINTF
  97 /**
  98  * seq_buf_bprintf - Write the printf string from binary arguments
  99  * @s: seq_buf descriptor
 100  * @fmt: The format string for the @binary arguments
 101  * @binary: The binary arguments for @fmt.
 102  *
 103  * When recording in a fast path, a printf may be recorded with just
 104  * saving the format and the arguments as they were passed to the
 105  * function, instead of wasting cycles converting the arguments into
 106  * ASCII characters. Instead, the arguments are saved in a 32 bit
 107  * word array that is defined by the format string constraints.
 108  *
 109  * This function will take the format and the binary array and finish
 110  * the conversion into the ASCII string within the buffer.
 111  *
 112  * Returns zero on success, -1 on overflow.
 113  */
 114 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
 115 {
 116         unsigned int len = seq_buf_buffer_left(s);
 117         int ret;
 118
 119         WARN_ON(s->size == 0);
 120
 121         if (s->len < s->size) {
 122                 ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
 123                 if (s->len + ret < s->size) {
 124                         s->len += ret;
 125                         return 0;
 126                 }
 127         }
 128         seq_buf_set_overflow(s);
 129         return -1;
 130 }
 131 #endif /* CONFIG_BINARY_PRINTF */
 132
 133 /**
 134  * seq_buf_puts - sequence printing of simple string
 135  * @s: seq_buf descriptor
 136  * @str: simple string to record
 137  *
 138  * Copy a simple string into the sequence buffer.
 139  *
 140  * Returns zero on success, -1 on overflow
 141  */
 142 int seq_buf_puts(struct seq_buf *s, const char *str)
 143 {
 144         size_t len = strlen(str);
 145
 146         WARN_ON(s->size == 0);
 147
 148         /* Add 1 to len for the trailing null byte which must be there */
 149         len += 1;
 150
 151         if (seq_buf_can_fit(s, len)) {
 152                 memcpy(s->buffer + s->len, str, len);
 153                 /* Don't count the trailing null byte against the capacity */
 154                 s->len += len - 1;
 155                 return 0;
 156         }
 157         seq_buf_set_overflow(s);
 158         return -1;
 159 }
 160
 161 /**
 162  * seq_buf_putc - sequence printing of simple character
 163  * @s: seq_buf descriptor
 164  * @c: simple character to record
 165  *
 166  * Copy a single character into the sequence buffer.
 167  *
 168  * Returns zero on success, -1 on overflow
 169  */
 170 int seq_buf_putc(struct seq_buf *s, unsigned char c)
 171 {
 172         WARN_ON(s->size == 0);
 173
 174         if (seq_buf_can_fit(s, 1)) {
 175                 s->buffer[s->len++] = c;
 176                 return 0;
 177         }
 178         seq_buf_set_overflow(s);
 179         return -1;
 180 }
 181
 182 /**
 183  * seq_buf_putmem - write raw data into the sequenc buffer
 184  * @s: seq_buf descriptor
 185  * @mem: The raw memory to copy into the buffer
 186  * @len: The length of the raw memory to copy (in bytes)
 187  *
 188  * There may be cases where raw memory needs to be written into the
 189  * buffer and a strcpy() would not work. Using this function allows
 190  * for such cases.
 191  *
 192  * Returns zero on success, -1 on overflow
 193  */
 194 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
 195 {
 196         WARN_ON(s->size == 0);
 197
 198         if (seq_buf_can_fit(s, len)) {
 199                 memcpy(s->buffer + s->len, mem, len);
 200                 s->len += len;
 201                 return 0;
 202         }
 203         seq_buf_set_overflow(s);
 204         return -1;
 205 }
 206
 207 #define MAX_MEMHEX_BYTES        8U
 208 #define HEX_CHARS               (MAX_MEMHEX_BYTES*2 + 1)
 209
 210 /**
 211  * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
 212  * @s: seq_buf descriptor
 213  * @mem: The raw memory to write its hex ASCII representation of
 214  * @len: The length of the raw memory to copy (in bytes)
 215  *
 216  * This is similar to seq_buf_putmem() except instead of just copying the
 217  * raw memory into the buffer it writes its ASCII representation of it
 218  * in hex characters.
 219  *
 220  * Returns zero on success, -1 on overflow
 221  */
 222 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
 223                        unsigned int len)
 224 {
 225         unsigned char hex[HEX_CHARS];
 226         const unsigned char *data = mem;
 227         unsigned int start_len;
 228         int i, j;
 229
 230         WARN_ON(s->size == 0);
 231
 232         while (len) {
 233                 start_len = min(len, HEX_CHARS - 1);
 234 #ifdef __BIG_ENDIAN
 235                 for (i = 0, j = 0; i < start_len; i++) {
 236 #else
 237                 for (i = start_len-1, j = 0; i >= 0; i--) {
 238 #endif
 239                         hex[j++] = hex_asc_hi(data[i]);
 240                         hex[j++] = hex_asc_lo(data[i]);
 241                 }
 242                 if (WARN_ON_ONCE(j == 0 || j/2 > len))
 243                         break;
 244
 245                 /* j increments twice per loop */
 246                 len -= j / 2;
 247                 hex[j++] = ' ';
 248
 249                 seq_buf_putmem(s, hex, j);
 250                 if (seq_buf_has_overflowed(s))
 251                         return -1;
 252         }
 253         return 0;
 254 }
 255
 256 /**
 257  * seq_buf_path - copy a path into the sequence buffer
 258  * @s: seq_buf descriptor
 259  * @path: path to write into the sequence buffer.
 260  * @esc: set of characters to escape in the output
 261  *
 262  * Write a path name into the sequence buffer.
 263  *
 264  * Returns the number of written bytes on success, -1 on overflow
 265  */
 266 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
 267 {
 268         char *buf;
 269         size_t size = seq_buf_get_buf(s, &buf);
 270         int res = -1;
 271
 272         WARN_ON(s->size == 0);
 273
 274         if (size) {
 275                 char *p = d_path(path, buf, size);
 276                 if (!IS_ERR(p)) {
 277                         char *end = mangle_path(buf, p, esc);
 278                         if (end)
 279                                 res = end - buf;
 280                 }
 281         }
 282         seq_buf_commit(s, res);
 283
 284         return res;
 285 }
 286
 287 /**
 288  * seq_buf_to_user - copy the squence buffer to user space
 289  * @s: seq_buf descriptor
 290  * @ubuf: The userspace memory location to copy to
 291  * @cnt: The amount to copy
 292  *
 293  * Copies the sequence buffer into the userspace memory pointed to
 294  * by @ubuf. It starts from the last read position (@s->readpos)
 295  * and writes up to @cnt characters or till it reaches the end of
 296  * the content in the buffer (@s->len), which ever comes first.
 297  *
 298  * On success, it returns a positive number of the number of bytes
 299  * it copied.
 300  *
 301  * On failure it returns -EBUSY if all of the content in the
 302  * sequence has been already read, which includes nothing in the
 303  * sequence (@s->len == @s->readpos).
 304  *
 305  * Returns -EFAULT if the copy to userspace fails.
 306  */
 307 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
 308 {
 309         int len;
 310         int ret;
 311
 312         if (!cnt)
 313                 return 0;
 314
 315         len = seq_buf_used(s);
 316
 317         if (len <= s->readpos)
 318                 return -EBUSY;
 319
 320         len -= s->readpos;
 321         if (cnt > len)
 322                 cnt = len;
 323         ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
 324         if (ret == cnt)
 325                 return -EFAULT;
 326
 327         cnt -= ret;
 328
 329         s->readpos += cnt;
 330         return cnt;
 331 }
 332
 333 /**
 334  * seq_buf_hex_dump - print formatted hex dump into the sequence buffer
 335  * @s: seq_buf descriptor
 336  * @prefix_str: string to prefix each line with;
 337  *  caller supplies trailing spaces for alignment if desired
 338  * @prefix_type: controls whether prefix of an offset, address, or none
 339  *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)
 340  * @rowsize: number of bytes to print per line; must be 16 or 32
 341  * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
 342  * @buf: data blob to dump
 343  * @len: number of bytes in the @buf
 344  * @ascii: include ASCII after the hex output
 345  *
 346  * Function is an analogue of print_hex_dump() and thus has similar interface.
 347  *
 348  * linebuf size is maximal length for one line.
 349  * 32 * 3 - maximum bytes per line, each printed into 2 chars + 1 for
 350  *      separating space
 351  * 2 - spaces separating hex dump and ascii representation
 352  * 32 - ascii representation
 353  * 1 - terminating '\0'
 354  *
 355  * Returns zero on success, -1 on overflow
 356  */
 357 int seq_buf_hex_dump(struct seq_buf *s, const char *prefix_str, int prefix_type,
 358                      int rowsize, int groupsize,
 359                      const void *buf, size_t len, bool ascii)
 360 {
 361         const u8 *ptr = buf;
 362         int i, linelen, remaining = len;
 363         unsigned char linebuf[32 * 3 + 2 + 32 + 1];
 364         int ret;
 365
 366         if (rowsize != 16 && rowsize != 32)
 367                 rowsize = 16;
 368
 369         for (i = 0; i < len; i += rowsize) {
 370                 linelen = min(remaining, rowsize);
 371                 remaining -= rowsize;
 372
 373                 hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
 374                                    linebuf, sizeof(linebuf), ascii);
 375
 376                 switch (prefix_type) {
 377                 case DUMP_PREFIX_ADDRESS:
 378                         ret = seq_buf_printf(s, "%s%p: %s\n",
 379                                prefix_str, ptr + i, linebuf);
 380                         break;
 381                 case DUMP_PREFIX_OFFSET:
 382                         ret = seq_buf_printf(s, "%s%.8x: %s\n",
 383                                              prefix_str, i, linebuf);
 384                         break;
 385                 default:
 386                         ret = seq_buf_printf(s, "%s%s\n", prefix_str, linebuf);
 387                         break;
 388                 }
 389                 if (ret)
 390                         return ret;
 391         }
 392         return 0;
 393 }