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
  95 #ifdef CONFIG_BINARY_PRINTF
  96 /**
  97  * seq_buf_bprintf - Write the printf string from binary arguments
  98  * @s: seq_buf descriptor
  99  * @fmt: The format string for the @binary arguments
 100  * @binary: The binary arguments for @fmt.
 101  *
 102  * When recording in a fast path, a printf may be recorded with just
 103  * saving the format and the arguments as they were passed to the
 104  * function, instead of wasting cycles converting the arguments into
 105  * ASCII characters. Instead, the arguments are saved in a 32 bit
 106  * word array that is defined by the format string constraints.
 107  *
 108  * This function will take the format and the binary array and finish
 109  * the conversion into the ASCII string within the buffer.
 110  *
 111  * Returns zero on success, -1 on overflow.
 112  */
 113 int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)
 114 {
 115         unsigned int len = seq_buf_buffer_left(s);
 116         int ret;
 117
 118         WARN_ON(s->size == 0);
 119
 120         if (s->len < s->size) {
 121                 ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
 122                 if (s->len + ret < s->size) {
 123                         s->len += ret;
 124                         return 0;
 125                 }
 126         }
 127         seq_buf_set_overflow(s);
 128         return -1;
 129 }
 130 #endif /* CONFIG_BINARY_PRINTF */
 131
 132 /**
 133  * seq_buf_puts - sequence printing of simple string
 134  * @s: seq_buf descriptor
 135  * @str: simple string to record
 136  *
 137  * Copy a simple string into the sequence buffer.
 138  *
 139  * Returns zero on success, -1 on overflow
 140  */
 141 int seq_buf_puts(struct seq_buf *s, const char *str)
 142 {
 143         size_t len = strlen(str);
 144
 145         WARN_ON(s->size == 0);
 146
 147         /* Add 1 to len for the trailing null byte which must be there */
 148         len += 1;
 149
 150         if (seq_buf_can_fit(s, len)) {
 151                 memcpy(s->buffer + s->len, str, len);
 152                 /* Don't count the trailing null byte against the capacity */
 153                 s->len += len - 1;
 154                 return 0;
 155         }
 156         seq_buf_set_overflow(s);
 157         return -1;
 158 }
 159
 160 /**
 161  * seq_buf_putc - sequence printing of simple character
 162  * @s: seq_buf descriptor
 163  * @c: simple character to record
 164  *
 165  * Copy a single character into the sequence buffer.
 166  *
 167  * Returns zero on success, -1 on overflow
 168  */
 169 int seq_buf_putc(struct seq_buf *s, unsigned char c)
 170 {
 171         WARN_ON(s->size == 0);
 172
 173         if (seq_buf_can_fit(s, 1)) {
 174                 s->buffer[s->len++] = c;
 175                 return 0;
 176         }
 177         seq_buf_set_overflow(s);
 178         return -1;
 179 }
 180
 181 /**
 182  * seq_buf_putmem - write raw data into the sequenc buffer
 183  * @s: seq_buf descriptor
 184  * @mem: The raw memory to copy into the buffer
 185  * @len: The length of the raw memory to copy (in bytes)
 186  *
 187  * There may be cases where raw memory needs to be written into the
 188  * buffer and a strcpy() would not work. Using this function allows
 189  * for such cases.
 190  *
 191  * Returns zero on success, -1 on overflow
 192  */
 193 int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
 194 {
 195         WARN_ON(s->size == 0);
 196
 197         if (seq_buf_can_fit(s, len)) {
 198                 memcpy(s->buffer + s->len, mem, len);
 199                 s->len += len;
 200                 return 0;
 201         }
 202         seq_buf_set_overflow(s);
 203         return -1;
 204 }
 205
 206 #define MAX_MEMHEX_BYTES        8U
 207 #define HEX_CHARS               (MAX_MEMHEX_BYTES*2 + 1)
 208
 209 /**
 210  * seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
 211  * @s: seq_buf descriptor
 212  * @mem: The raw memory to write its hex ASCII representation of
 213  * @len: The length of the raw memory to copy (in bytes)
 214  *
 215  * This is similar to seq_buf_putmem() except instead of just copying the
 216  * raw memory into the buffer it writes its ASCII representation of it
 217  * in hex characters.
 218  *
 219  * Returns zero on success, -1 on overflow
 220  */
 221 int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
 222                        unsigned int len)
 223 {
 224         unsigned char hex[HEX_CHARS];
 225         const unsigned char *data = mem;
 226         unsigned int start_len;
 227         int i, j;
 228
 229         WARN_ON(s->size == 0);
 230
 231         while (len) {
 232                 start_len = min(len, HEX_CHARS - 1);
 233 #ifdef __BIG_ENDIAN
 234                 for (i = 0, j = 0; i < start_len; i++) {
 235 #else
 236                 for (i = start_len-1, j = 0; i >= 0; i--) {
 237 #endif
 238                         hex[j++] = hex_asc_hi(data[i]);
 239                         hex[j++] = hex_asc_lo(data[i]);
 240                 }
 241                 if (WARN_ON_ONCE(j == 0 || j/2 > len))
 242                         break;
 243
 244                 /* j increments twice per loop */
 245                 len -= j / 2;
 246                 hex[j++] = ' ';
 247
 248                 seq_buf_putmem(s, hex, j);
 249                 if (seq_buf_has_overflowed(s))
 250                         return -1;
 251         }
 252         return 0;
 253 }
 254
 255 /**
 256  * seq_buf_path - copy a path into the sequence buffer
 257  * @s: seq_buf descriptor
 258  * @path: path to write into the sequence buffer.
 259  * @esc: set of characters to escape in the output
 260  *
 261  * Write a path name into the sequence buffer.
 262  *
 263  * Returns the number of written bytes on success, -1 on overflow
 264  */
 265 int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
 266 {
 267         char *buf;
 268         size_t size = seq_buf_get_buf(s, &buf);
 269         int res = -1;
 270
 271         WARN_ON(s->size == 0);
 272
 273         if (size) {
 274                 char *p = d_path(path, buf, size);
 275                 if (!IS_ERR(p)) {
 276                         char *end = mangle_path(buf, p, esc);
 277                         if (end)
 278                                 res = end - buf;
 279                 }
 280         }
 281         seq_buf_commit(s, res);
 282
 283         return res;
 284 }
 285
 286 /**
 287  * seq_buf_to_user - copy the squence buffer to user space
 288  * @s: seq_buf descriptor
 289  * @ubuf: The userspace memory location to copy to
 290  * @cnt: The amount to copy
 291  *
 292  * Copies the sequence buffer into the userspace memory pointed to
 293  * by @ubuf. It starts from the last read position (@s->readpos)
 294  * and writes up to @cnt characters or till it reaches the end of
 295  * the content in the buffer (@s->len), which ever comes first.
 296  *
 297  * On success, it returns a positive number of the number of bytes
 298  * it copied.
 299  *
 300  * On failure it returns -EBUSY if all of the content in the
 301  * sequence has been already read, which includes nothing in the
 302  * sequence (@s->len == @s->readpos).
 303  *
 304  * Returns -EFAULT if the copy to userspace fails.
 305  */
 306 int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
 307 {
 308         int len;
 309         int ret;
 310
 311         if (!cnt)
 312                 return 0;
 313
 314         len = seq_buf_used(s);
 315
 316         if (len <= s->readpos)
 317                 return -EBUSY;
 318
 319         len -= s->readpos;
 320         if (cnt > len)
 321                 cnt = len;
 322         ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
 323         if (ret == cnt)
 324                 return -EFAULT;
 325
 326         cnt -= ret;
 327
 328         s->readpos += cnt;
 329         return cnt;
 330 }