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         /* Add 1 to len for the trailing null byte which must be there */
 147         len += 1;
 148
 149         if (seq_buf_can_fit(s, len)) {
 150                 memcpy(s->buffer + s->len, str, len);
 151                 /* Don't count the trailing null byte against the capacity */
 152                 s->len += len - 1;
 153                 return 0;
 154         }
 155         seq_buf_set_overflow(s);
 156         return -1;
 157 }
 158
 159 /**
 160  * seq_buf_putc - sequence printing of simple character
 161  * @s: seq_buf descriptor
 162  * @c: simple character to record
 163  *
 164  * Copy a single character into the sequence buffer.
 165  *
 166  * Returns zero on success, -1 on overflow
 167  */
 168 int seq_buf_putc(struct seq_buf *s, unsigned char c)
 169 {
 170         WARN_ON(s->size == 0);
 171
 172         if (seq_buf_can_fit(s, 1)) {
 173                 s->buffer[s->len++] = c;
 174                 return 0;
 175         }
 176         seq_buf_set_overflow(s);
 177         return -1;
 178 }
 179
 180 /**
 181  * seq_buf_putmem - write raw data into the sequenc buffer
 182  * @s: seq_buf descriptor
 183  * @mem: The raw memory to copy into the buffer
 184  * @len: The length of the raw memory to copy (in bytes)
 185  *
 186  * There may be cases where raw memory needs to be written into the
 187  * buffer and a strcpy() would not work. Using this function allows
 188  * for such cases.
 189  *
 190  * Returns zero on success, -1 on overflow
 191  */
 192 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
 193 {
 194         WARN_ON(s->size == 0);
 195
 196         if (seq_buf_can_fit(s, len)) {
 197                 memcpy(s->buffer + s->len, mem, len);
 198                 s->len += len;
 199                 return 0;
 200         }
 201         seq_buf_set_overflow(s);
 202         return -1;
 203 }
 204
 205 #define MAX_MEMHEX_BYTES        8U
 206 #define HEX_CHARS               (MAX_MEMHEX_BYTES*2 + 1)
 207
 208 /**
 209  * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
 210  * @s: seq_buf descriptor
 211  * @mem: The raw memory to write its hex ASCII representation of
 212  * @len: The length of the raw memory to copy (in bytes)
 213  *
 214  * This is similar to seq_buf_putmem() except instead of just copying the
 215  * raw memory into the buffer it writes its ASCII representation of it
 216  * in hex characters.
 217  *
 218  * Returns zero on success, -1 on overflow
 219  */
 220 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
 221                        unsigned int len)
 222 {
 223         unsigned char hex[HEX_CHARS];
 224         const unsigned char *data = mem;
 225         unsigned int start_len;
 226         int i, j;
 227
 228         WARN_ON(s->size == 0);
 229
 230         while (len) {
 231                 start_len = min(len, HEX_CHARS - 1);
 232 #ifdef __BIG_ENDIAN
 233                 for (i = 0, j = 0; i < start_len; i++) {
 234 #else
 235                 for (i = start_len-1, j = 0; i >= 0; i--) {
 236 #endif
 237                         hex[j++] = hex_asc_hi(data[i]);
 238                         hex[j++] = hex_asc_lo(data[i]);
 239                 }
 240                 if (WARN_ON_ONCE(j == 0 || j/2 > len))
 241                         break;
 242
 243                 /* j increments twice per loop */
 244                 len -= j / 2;
 245                 hex[j++] = ' ';
 246
 247                 seq_buf_putmem(s, hex, j);
 248                 if (seq_buf_has_overflowed(s))
 249                         return -1;
 250         }
 251         return 0;
 252 }
 253
 254 /**
 255  * seq_buf_path - copy a path into the sequence buffer
 256  * @s: seq_buf descriptor
 257  * @path: path to write into the sequence buffer.
 258  * @esc: set of characters to escape in the output
 259  *
 260  * Write a path name into the sequence buffer.
 261  *
 262  * Returns the number of written bytes on success, -1 on overflow
 263  */
 264 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
 265 {
 266         char *buf;
 267         size_t size = seq_buf_get_buf(s, &buf);
 268         int res = -1;
 269
 270         WARN_ON(s->size == 0);
 271
 272         if (size) {
 273                 char *p = d_path(path, buf, size);
 274                 if (!IS_ERR(p)) {
 275                         char *end = mangle_path(buf, p, esc);
 276                         if (end)
 277                                 res = end - buf;
 278                 }
 279         }
 280         seq_buf_commit(s, res);
 281
 282         return res;
 283 }
 284
 285 /**
 286  * seq_buf_to_user - copy the squence buffer to user space
 287  * @s: seq_buf descriptor
 288  * @ubuf: The userspace memory location to copy to
 289  * @cnt: The amount to copy
 290  *
 291  * Copies the sequence buffer into the userspace memory pointed to
 292  * by @ubuf. It starts from the last read position (@s->readpos)
 293  * and writes up to @cnt characters or till it reaches the end of
 294  * the content in the buffer (@s->len), which ever comes first.
 295  *
 296  * On success, it returns a positive number of the number of bytes
 297  * it copied.
 298  *
 299  * On failure it returns -EBUSY if all of the content in the
 300  * sequence has been already read, which includes nothing in the
 301  * sequence (@s->len == @s->readpos).
 302  *
 303  * Returns -EFAULT if the copy to userspace fails.
 304  */
 305 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
 306 {
 307         int len;
 308         int ret;
 309
 310         if (!cnt)
 311                 return 0;
 312
 313         len = seq_buf_used(s);
 314
 315         if (len <= s->readpos)
 316                 return -EBUSY;
 317
 318         len -= s->readpos;
 319         if (cnt > len)
 320                 cnt = len;
 321         ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
 322         if (ret == cnt)
 323                 return -EFAULT;
 324
 325         cnt -= ret;
 326
 327         s->readpos += cnt;
 328         return cnt;
 329 }