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