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
  17 #include <linux/bug.h>
  18 #include <linux/err.h>
  19 #include <linux/export.h>
  20 #include <linux/hex.h>
  21 #include <linux/minmax.h>
  22 #include <linux/printk.h>
  23 #include <linux/seq_buf.h>
  24 #include <linux/seq_file.h>
  25 #include <linux/sprintf.h>
  26 #include <linux/string.h>
  27 #include <linux/types.h>
  28 #include <linux/uaccess.h>
  29
  30 /**
  31  * seq_buf_can_fit - can the new data fit in the current buffer?
  32  * @s: the seq_buf descriptor
  33  * @len: The length to see if it can fit in the current buffer
  34  *
  35  * Returns: true if there's enough unused space in the seq_buf buffer
  36  * to fit the amount of new data according to @len.
  37  */
  38 static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
  39 {
  40         return s->len + len <= s->size;
  41 }
  42
  43 /**
  44  * seq_buf_print_seq - move the contents of seq_buf into a seq_file
  45  * @m: the seq_file descriptor that is the destination
  46  * @s: the seq_buf descriptor that is the source.
  47  *
  48  * Returns: zero on success, non-zero otherwise.
  49  */
  50 int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s)
  51 {
  52         unsigned int len = seq_buf_used(s);
  53
  54         return seq_write(m, s->buffer, len);
  55 }
  56
  57 /**
  58  * seq_buf_vprintf - sequence printing of information.
  59  * @s: seq_buf descriptor
  60  * @fmt: printf format string
  61  * @args: va_list of arguments from a printf() type function
  62  *
  63  * Writes a vnprintf() format into the sequence buffer.
  64  *
  65  * Returns: zero on success, -1 on overflow.
  66  */
  67 int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)
  68 {
  69         int len;
  70
  71         WARN_ON(s->size == 0);
  72
  73         if (s->len < s->size) {
  74                 len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
  75                 if (s->len + len < s->size) {
  76                         s->len += len;
  77                         return 0;
  78                 }
  79         }
  80         seq_buf_set_overflow(s);
  81         return -1;
  82 }
  83
  84 /**
  85  * seq_buf_printf - sequence printing of information
  86  * @s: seq_buf descriptor
  87  * @fmt: printf format string
  88  *
  89  * Writes a printf() format into the sequence buffer.
  90  *
  91  * Returns: zero on success, -1 on overflow.
  92  */
  93 int seq_buf_printf(struct seq_buf *s, const char *fmt, ...)
  94 {
  95         va_list ap;
  96         int ret;
  97
  98         va_start(ap, fmt);
  99         ret = seq_buf_vprintf(s, fmt, ap);
 100         va_end(ap);
 101
 102         return ret;
 103 }
 104 EXPORT_SYMBOL_GPL(seq_buf_printf);
 105
 106 /**
 107  * seq_buf_do_printk - printk() seq_buf line by line
 108  * @s: seq_buf descriptor
 109  * @lvl: printk level
 110  *
 111  * printk()-s a multi-line sequential buffer line by line. The function
 112  * makes sure that the buffer in @s is NUL-terminated and safe to read
 113  * as a string.
 114  */
 115 void seq_buf_do_printk(struct seq_buf *s, const char *lvl)
 116 {
 117         const char *start, *lf;
 118
 119         if (s->size == 0 || s->len == 0)
 120                 return;
 121
 122         start = seq_buf_str(s);
 123         while ((lf = strchr(start, '\n'))) {
 124                 int len = lf - start + 1;
 125
 126                 printk("%s%.*s", lvl, len, start);
 127                 start = ++lf;
 128         }
 129
 130         /* No trailing LF */
 131         if (start < s->buffer + s->len)
 132                 printk("%s%s\n", lvl, start);
 133 }
 134 EXPORT_SYMBOL_GPL(seq_buf_do_printk);
 135
 136 #ifdef CONFIG_BINARY_PRINTF
 137 /**
 138  * seq_buf_bprintf - Write the printf string from binary arguments
 139  * @s: seq_buf descriptor
 140  * @fmt: The format string for the @binary arguments
 141  * @binary: The binary arguments for @fmt.
 142  *
 143  * When recording in a fast path, a printf may be recorded with just
 144  * saving the format and the arguments as they were passed to the
 145  * function, instead of wasting cycles converting the arguments into
 146  * ASCII characters. Instead, the arguments are saved in a 32 bit
 147  * word array that is defined by the format string constraints.
 148  *
 149  * This function will take the format and the binary array and finish
 150  * the conversion into the ASCII string within the buffer.
 151  *
 152  * Returns: zero on success, -1 on overflow.
 153  */
 154 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
 155 {
 156         unsigned int len = seq_buf_buffer_left(s);
 157         int ret;
 158
 159         WARN_ON(s->size == 0);
 160
 161         if (s->len < s->size) {
 162                 ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
 163                 if (s->len + ret < s->size) {
 164                         s->len += ret;
 165                         return 0;
 166                 }
 167         }
 168         seq_buf_set_overflow(s);
 169         return -1;
 170 }
 171 #endif /* CONFIG_BINARY_PRINTF */
 172
 173 /**
 174  * seq_buf_puts - sequence printing of simple string
 175  * @s: seq_buf descriptor
 176  * @str: simple string to record
 177  *
 178  * Copy a simple string into the sequence buffer.
 179  *
 180  * Returns: zero on success, -1 on overflow.
 181  */
 182 int seq_buf_puts(struct seq_buf *s, const char *str)
 183 {
 184         size_t len = strlen(str);
 185
 186         WARN_ON(s->size == 0);
 187
 188         /* Add 1 to len for the trailing null byte which must be there */
 189         len += 1;
 190
 191         if (seq_buf_can_fit(s, len)) {
 192                 memcpy(s->buffer + s->len, str, len);
 193                 /* Don't count the trailing null byte against the capacity */
 194                 s->len += len - 1;
 195                 return 0;
 196         }
 197         seq_buf_set_overflow(s);
 198         return -1;
 199 }
 200 EXPORT_SYMBOL_GPL(seq_buf_puts);
 201
 202 /**
 203  * seq_buf_putc - sequence printing of simple character
 204  * @s: seq_buf descriptor
 205  * @c: simple character to record
 206  *
 207  * Copy a single character into the sequence buffer.
 208  *
 209  * Returns: zero on success, -1 on overflow.
 210  */
 211 int seq_buf_putc(struct seq_buf *s, unsigned char c)
 212 {
 213         WARN_ON(s->size == 0);
 214
 215         if (seq_buf_can_fit(s, 1)) {
 216                 s->buffer[s->len++] = c;
 217                 return 0;
 218         }
 219         seq_buf_set_overflow(s);
 220         return -1;
 221 }
 222 EXPORT_SYMBOL_GPL(seq_buf_putc);
 223
 224 /**
 225  * seq_buf_putmem - write raw data into the sequence buffer
 226  * @s: seq_buf descriptor
 227  * @mem: The raw memory to copy into the buffer
 228  * @len: The length of the raw memory to copy (in bytes)
 229  *
 230  * There may be cases where raw memory needs to be written into the
 231  * buffer and a strcpy() would not work. Using this function allows
 232  * for such cases.
 233  *
 234  * Returns: zero on success, -1 on overflow.
 235  */
 236 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
 237 {
 238         WARN_ON(s->size == 0);
 239
 240         if (seq_buf_can_fit(s, len)) {
 241                 memcpy(s->buffer + s->len, mem, len);
 242                 s->len += len;
 243                 return 0;
 244         }
 245         seq_buf_set_overflow(s);
 246         return -1;
 247 }
 248
 249 #define MAX_MEMHEX_BYTES        8U
 250 #define HEX_CHARS               (MAX_MEMHEX_BYTES*2 + 1)
 251
 252 /**
 253  * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
 254  * @s: seq_buf descriptor
 255  * @mem: The raw memory to write its hex ASCII representation of
 256  * @len: The length of the raw memory to copy (in bytes)
 257  *
 258  * This is similar to seq_buf_putmem() except instead of just copying the
 259  * raw memory into the buffer it writes its ASCII representation of it
 260  * in hex characters.
 261  *
 262  * Returns: zero on success, -1 on overflow.
 263  */
 264 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
 265                        unsigned int len)
 266 {
 267         unsigned char hex[HEX_CHARS];
 268         const unsigned char *data = mem;
 269         unsigned int start_len;
 270         int i, j;
 271
 272         WARN_ON(s->size == 0);
 273
 274         BUILD_BUG_ON(MAX_MEMHEX_BYTES * 2 >= HEX_CHARS);
 275
 276         while (len) {
 277                 start_len = min(len, MAX_MEMHEX_BYTES);
 278 #ifdef __BIG_ENDIAN
 279                 for (i = 0, j = 0; i < start_len; i++) {
 280 #else
 281                 for (i = start_len-1, j = 0; i >= 0; i--) {
 282 #endif
 283                         hex[j++] = hex_asc_hi(data[i]);
 284                         hex[j++] = hex_asc_lo(data[i]);
 285                 }
 286                 if (WARN_ON_ONCE(j == 0 || j/2 > len))
 287                         break;
 288
 289                 /* j increments twice per loop */
 290                 hex[j++] = ' ';
 291
 292                 seq_buf_putmem(s, hex, j);
 293                 if (seq_buf_has_overflowed(s))
 294                         return -1;
 295
 296                 len -= start_len;
 297                 data += start_len;
 298         }
 299         return 0;
 300 }
 301
 302 /**
 303  * seq_buf_path - copy a path into the sequence buffer
 304  * @s: seq_buf descriptor
 305  * @path: path to write into the sequence buffer.
 306  * @esc: set of characters to escape in the output
 307  *
 308  * Write a path name into the sequence buffer.
 309  *
 310  * Returns: the number of written bytes on success, -1 on overflow.
 311  */
 312 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
 313 {
 314         char *buf;
 315         size_t size = seq_buf_get_buf(s, &buf);
 316         int res = -1;
 317
 318         WARN_ON(s->size == 0);
 319
 320         if (size) {
 321                 char *p = d_path(path, buf, size);
 322                 if (!IS_ERR(p)) {
 323                         char *end = mangle_path(buf, p, esc);
 324                         if (end)
 325                                 res = end - buf;
 326                 }
 327         }
 328         seq_buf_commit(s, res);
 329
 330         return res;
 331 }
 332
 333 /**
 334  * seq_buf_to_user - copy the sequence buffer to user space
 335  * @s: seq_buf descriptor
 336  * @ubuf: The userspace memory location to copy to
 337  * @start: The first byte in the buffer to copy
 338  * @cnt: The amount to copy
 339  *
 340  * Copies the sequence buffer into the userspace memory pointed to
 341  * by @ubuf. It starts from @start and writes up to @cnt characters
 342  * or until it reaches the end of the content in the buffer (@s->len),
 343  * whichever comes first.
 344  *
 345  * Returns:
 346  * On success, it returns a positive number of the number of bytes
 347  * it copied.
 348  *
 349  * On failure it returns -EBUSY if all of the content in the
 350  * sequence has been already read, which includes nothing in the
 351  * sequence (@s->len == @start).
 352  *
 353  * Returns -EFAULT if the copy to userspace fails.
 354  */
 355 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, size_t start, int cnt)
 356 {
 357         int len;
 358         int ret;
 359
 360         if (!cnt)
 361                 return 0;
 362
 363         len = seq_buf_used(s);
 364
 365         if (len <= start)
 366                 return -EBUSY;
 367
 368         len -= start;
 369         if (cnt > len)
 370                 cnt = len;
 371         ret = copy_to_user(ubuf, s->buffer + start, cnt);
 372         if (ret == cnt)
 373                 return -EFAULT;
 374
 375         return cnt - ret;
 376 }
 377
 378 /**
 379  * seq_buf_hex_dump - print formatted hex dump into the sequence buffer
 380  * @s: seq_buf descriptor
 381  * @prefix_str: string to prefix each line with;
 382  *  caller supplies trailing spaces for alignment if desired
 383  * @prefix_type: controls whether prefix of an offset, address, or none
 384  *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)
 385  * @rowsize: number of bytes to print per line; must be 16 or 32
 386  * @groupsize: number of bytes to print at a time (1, 2, 4, 8; default = 1)
 387  * @buf: data blob to dump
 388  * @len: number of bytes in the @buf
 389  * @ascii: include ASCII after the hex output
 390  *
 391  * Function is an analogue of print_hex_dump() and thus has similar interface.
 392  *
 393  * linebuf size is maximal length for one line.
 394  * 32 * 3 - maximum bytes per line, each printed into 2 chars + 1 for
 395  *      separating space
 396  * 2 - spaces separating hex dump and ASCII representation
 397  * 32 - ASCII representation
 398  * 1 - terminating '\0'
 399  *
 400  * Returns: zero on success, -1 on overflow.
 401  */
 402 int seq_buf_hex_dump(struct seq_buf *s, const char *prefix_str, int prefix_type,
 403                      int rowsize, int groupsize,
 404                      const void *buf, size_t len, bool ascii)
 405 {
 406         const u8 *ptr = buf;
 407         int i, linelen, remaining = len;
 408         unsigned char linebuf[32 * 3 + 2 + 32 + 1];
 409         int ret;
 410
 411         if (rowsize != 16 && rowsize != 32)
 412                 rowsize = 16;
 413
 414         for (i = 0; i < len; i += rowsize) {
 415                 linelen = min(remaining, rowsize);
 416                 remaining -= rowsize;
 417
 418                 hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
 419                                    linebuf, sizeof(linebuf), ascii);
 420
 421                 switch (prefix_type) {
 422                 case DUMP_PREFIX_ADDRESS:
 423                         ret = seq_buf_printf(s, "%s%p: %s\n",
 424                                prefix_str, ptr + i, linebuf);
 425                         break;
 426                 case DUMP_PREFIX_OFFSET:
 427                         ret = seq_buf_printf(s, "%s%.8x: %s\n",
 428                                              prefix_str, i, linebuf);
 429                         break;
 430                 default:
 431                         ret = seq_buf_printf(s, "%s%s\n", prefix_str, linebuf);
 432                         break;
 433                 }
 434                 if (ret)
 435                         return ret;
 436         }
 437         return 0;
 438 }