fs/read_write.c

   1 /*
   2  *  linux/fs/read_write.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/types.h>
   8 #include <linux/errno.h>
   9 #include <linux/stat.h>
  10 #include <linux/kernel.h>
  11 #include <linux/sched.h>
  12 #include <linux/fcntl.h>
  13 #include <linux/file.h>
  14 #include <linux/mm.h>
  15 #include <linux/uio.h>
  16 #include <linux/malloc.h>
  17 #include <linux/smp.h>
  18 #include <linux/smp_lock.h>
  19 #include <linux/limits.h>
  20
  21 #include <asm/uaccess.h>
  22
  23 static loff_t default_llseek(struct file *file, loff_t offset, int origin)
  24 {
  25         long long retval;
  26
  27         switch (origin) {
  28                 case 2:
  29                         offset += file->f_dentry->d_inode->i_size;
  30                         break;
  31                 case 1:
  32                         offset += file->f_pos;
  33         }
  34         retval = -EINVAL;
  35         if (offset >= 0) {
  36                 if (offset != file->f_pos) {
  37                         file->f_pos = offset;
  38                         file->f_reada = 0;
  39                         file->f_version = ++event;
  40                 }
  41                 retval = offset;
  42         }
  43         return retval;
  44 }
  45
  46 static inline loff_t llseek(struct file *file, loff_t offset, int origin)
  47 {
  48         loff_t (*fn)(struct file *, loff_t, int);
  49
  50         fn = default_llseek;
  51         if (file->f_op && file->f_op->llseek)
  52                 fn = file->f_op->llseek;
  53         return fn(file, offset, origin);
  54 }
  55
  56 asmlinkage off_t sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
  57 {
  58         off_t retval;
  59         struct file * file;
  60         struct dentry * dentry;
  61         struct inode * inode;
  62
  63         lock_kernel();
  64         retval = -EBADF;
  65         file = fget(fd);
  66         if (!file)
  67                 goto bad;
  68         /* N.B. Shouldn't this be ENOENT?? */
  69         if (!(dentry = file->f_dentry) ||
  70             !(inode = dentry->d_inode))
  71                 goto out_putf;
  72         retval = -EINVAL;
  73         if (origin <= 2)
  74                 retval = llseek(file, offset, origin);
  75 out_putf:
  76         fput(file);
  77 bad:
  78         unlock_kernel();
  79         return retval;
  80 }
  81
  82 #if !defined(__alpha__)
  83 asmlinkage int sys_llseek(unsigned int fd, unsigned long offset_high,
  84                           unsigned long offset_low, loff_t * result,
  85                           unsigned int origin)
  86 {
  87         int retval;
  88         struct file * file;
  89         struct dentry * dentry;
  90         struct inode * inode;
  91         loff_t offset;
  92
  93         lock_kernel();
  94         retval = -EBADF;
  95         file = fget(fd);
  96         if (!file)
  97                 goto bad;
  98         /* N.B. Shouldn't this be ENOENT?? */
  99         if (!(dentry = file->f_dentry) ||
 100             !(inode = dentry->d_inode))
 101                 goto out_putf;
 102         retval = -EINVAL;
 103         if (origin > 2)
 104                 goto out_putf;
 105
 106         offset = llseek(file, ((loff_t) offset_high << 32) | offset_low,
 107                         origin);
 108
 109         retval = (int)offset;
 110         if (offset >= 0) {
 111                 retval = -EFAULT;
 112                 if (!copy_to_user(result, &offset, sizeof(offset)))
 113                         retval = 0;
 114         }
 115 out_putf:
 116         fput(file);
 117 bad:
 118         unlock_kernel();
 119         return retval;
 120 }
 121 #endif
 122
 123 asmlinkage ssize_t sys_read(unsigned int fd, char * buf, size_t count)
 124 {
 125         ssize_t ret;
 126         struct file * file;
 127         ssize_t (*read)(struct file *, char *, size_t, loff_t *);
 128
 129         lock_kernel();
 130
 131         ret = -EBADF;
 132         file = fget(fd);
 133         if (!file)
 134                 goto bad_file;
 135         if (!(file->f_mode & FMODE_READ))
 136                 goto out;
 137         ret = locks_verify_area(FLOCK_VERIFY_READ, file->f_dentry->d_inode,
 138                                 file, file->f_pos, count);
 139         if (ret)
 140                 goto out;
 141         ret = -EINVAL;
 142         if (!file->f_op || !(read = file->f_op->read))
 143                 goto out;
 144         ret = read(file, buf, count, &file->f_pos);
 145 out:
 146         fput(file);
 147 bad_file:
 148         unlock_kernel();
 149         return ret;
 150 }
 151
 152 asmlinkage ssize_t sys_write(unsigned int fd, const char * buf, size_t count)
 153 {
 154         ssize_t ret;
 155         struct file * file;
 156         struct inode * inode;
 157         ssize_t (*write)(struct file *, const char *, size_t, loff_t *);
 158
 159         lock_kernel();
 160
 161         ret = -EBADF;
 162         file = fget(fd);
 163         if (!file)
 164                 goto bad_file;
 165         if (!(file->f_mode & FMODE_WRITE))
 166                 goto out;
 167         inode = file->f_dentry->d_inode;
 168         ret = locks_verify_area(FLOCK_VERIFY_WRITE, inode, file,
 169                                 file->f_pos, count);
 170         if (ret)
 171                 goto out;
 172         ret = -EINVAL;
 173         if (!file->f_op || !(write = file->f_op->write))
 174                 goto out;
 175
 176         down(&inode->i_sem);
 177         ret = write(file, buf, count, &file->f_pos);
 178         up(&inode->i_sem);
 179 out:
 180         fput(file);
 181 bad_file:
 182         unlock_kernel();
 183         return ret;
 184 }
 185
 186
 187 static ssize_t do_readv_writev(int type, struct file *file,
 188                                const struct iovec * vector,
 189                                unsigned long count)
 190 {
 191         typedef ssize_t (*io_fn_t)(struct file *, char *, size_t, loff_t *);
 192
 193         size_t tot_len;
 194         struct iovec iovstack[UIO_FASTIOV];
 195         struct iovec *iov=iovstack;
 196         ssize_t ret, i;
 197         io_fn_t fn;
 198         struct inode *inode;
 199
 200         /*
 201          * First get the "struct iovec" from user memory and
 202          * verify all the pointers
 203          */
 204         ret = 0;
 205         if (!count)
 206                 goto out_nofree;
 207         ret = -EINVAL;
 208         if (count > UIO_MAXIOV)
 209                 goto out_nofree;
 210         if (count > UIO_FASTIOV) {
 211                 ret = -ENOMEM;
 212                 iov = kmalloc(count*sizeof(struct iovec), GFP_KERNEL);
 213                 if (!iov)
 214                         goto out_nofree;
 215         }
 216         ret = -EFAULT;
 217         if (copy_from_user(iov, vector, count*sizeof(*vector)))
 218                 goto out;
 219
 220         tot_len = 0;
 221         for (i = 0 ; i < count ; i++)
 222                 tot_len += iov[i].iov_len;
 223
 224         inode = file->f_dentry->d_inode;
 225         ret = locks_verify_area((type == VERIFY_READ
 226                                  ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE),
 227                                 inode, file, file->f_pos, tot_len);
 228         if (ret) goto out;
 229
 230         /*
 231          * Then do the actual IO.  Note that sockets need to be handled
 232          * specially as they have atomicity guarantees and can handle
 233          * iovec's natively
 234          */
 235         if (inode->i_sock) {
 236                 ret = sock_readv_writev(type,inode,file,iov,count,tot_len);
 237                 goto out;
 238         }
 239
 240         ret = -EINVAL;
 241         if (!file->f_op)
 242                 goto out;
 243
 244         /* VERIFY_WRITE actually means a read, as we write to user space */
 245         fn = file->f_op->read;
 246         if (type == VERIFY_READ)
 247                 fn = (io_fn_t) file->f_op->write;
 248
 249         ret = 0;
 250         vector = iov;
 251         while (count > 0) {
 252                 void * base;
 253                 size_t len;
 254                 ssize_t nr;
 255
 256                 base = vector->iov_base;
 257                 len = vector->iov_len;
 258                 vector++;
 259                 count--;
 260
 261                 nr = fn(file, base, len, &file->f_pos);
 262
 263                 if (nr < 0) {
 264                         if (!ret) ret = nr;
 265                         break;
 266                 }
 267                 ret += nr;
 268                 if (nr != len)
 269                         break;
 270         }
 271
 272 out:
 273         if (iov != iovstack)
 274                 kfree(iov);
 275 out_nofree:
 276         return ret;
 277 }
 278
 279 asmlinkage ssize_t sys_readv(unsigned long fd, const struct iovec * vector,
 280                              unsigned long count)
 281 {
 282         struct file * file;
 283         ssize_t ret;
 284
 285         lock_kernel();
 286
 287         ret = -EBADF;
 288         file = fget(fd);
 289         if (!file)
 290                 goto bad_file;
 291         if (file->f_mode & FMODE_READ)
 292                 ret = do_readv_writev(VERIFY_WRITE, file, vector, count);
 293         fput(file);
 294
 295 bad_file:
 296         unlock_kernel();
 297         return ret;
 298 }
 299
 300 asmlinkage ssize_t sys_writev(unsigned long fd, const struct iovec * vector,
 301                               unsigned long count)
 302 {
 303         struct file * file;
 304         ssize_t ret;
 305
 306         lock_kernel();
 307
 308         ret = -EBADF;
 309         file = fget(fd);
 310         if (!file)
 311                 goto bad_file;
 312         if (file->f_mode & FMODE_WRITE) {
 313                 down(&file->f_dentry->d_inode->i_sem);
 314                 ret = do_readv_writev(VERIFY_READ, file, vector, count);
 315                 up(&file->f_dentry->d_inode->i_sem);
 316         }
 317         fput(file);
 318
 319 bad_file:
 320         unlock_kernel();
 321         return ret;
 322 }
 323
 324 /* From the Single Unix Spec: pread & pwrite act like lseek to pos + op +
 325    lseek back to original location.  They fail just like lseek does on
 326    non-seekable files.  */
 327
 328 asmlinkage ssize_t sys_pread(unsigned int fd, char * buf,
 329                              size_t count, loff_t pos)
 330 {
 331         ssize_t ret;
 332         struct file * file;
 333         ssize_t (*read)(struct file *, char *, size_t, loff_t *);
 334
 335         lock_kernel();
 336
 337         ret = -EBADF;
 338         file = fget(fd);
 339         if (!file)
 340                 goto bad_file;
 341         if (!(file->f_mode & FMODE_READ))
 342                 goto out;
 343         ret = locks_verify_area(FLOCK_VERIFY_READ, file->f_dentry->d_inode,
 344                                 file, pos, count);
 345         if (ret)
 346                 goto out;
 347         ret = -EINVAL;
 348         if (!file->f_op || !(read = file->f_op->read))
 349                 goto out;
 350         if (pos < 0)
 351                 goto out;
 352         ret = read(file, buf, count, &pos);
 353 out:
 354         fput(file);
 355 bad_file:
 356         unlock_kernel();
 357         return ret;
 358 }
 359
 360 asmlinkage ssize_t sys_pwrite(unsigned int fd, const char * buf,
 361                               size_t count, loff_t pos)
 362 {
 363         ssize_t ret;
 364         struct file * file;
 365         ssize_t (*write)(struct file *, const char *, size_t, loff_t *);
 366
 367         lock_kernel();
 368
 369         ret = -EBADF;
 370         file = fget(fd);
 371         if (!file)
 372                 goto bad_file;
 373         if (!(file->f_mode & FMODE_WRITE))
 374                 goto out;
 375         ret = locks_verify_area(FLOCK_VERIFY_WRITE, file->f_dentry->d_inode,
 376                                 file, pos, count);
 377         if (ret)
 378                 goto out;
 379         ret = -EINVAL;
 380         if (!file->f_op || !(write = file->f_op->write))
 381                 goto out;
 382         if (pos < 0)
 383                 goto out;
 384
 385         down(&file->f_dentry->d_inode->i_sem);
 386         ret = write(file, buf, count, &pos);
 387         up(&file->f_dentry->d_inode->i_sem);
 388
 389 out:
 390         fput(file);
 391 bad_file:
 392         unlock_kernel();
 393         return ret;
 394 }