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 (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 }