fdisk/llseek.c

   1 /*
   2  * llseek.c -- stub calling the llseek system call
   3  *
   4  * Copyright (C) 1994 Remy Card.  This file may be redistributed
   5  * under the terms of the GNU Public License.
   6  */
   7
   8 #include <sys/types.h>
   9
  10 #include <errno.h>
  11 #include <unistd.h>
  12
  13 extern long long ext2_llseek (unsigned int, long long, unsigned int);
  14
  15 #ifdef __linux__
  16
  17 #ifdef HAVE_LLSEEK
  18 #include <syscall.h>
  19
  20 #else   /* HAVE_LLSEEK */
  21
  22 #if defined(__alpha__) || defined(__ia64__) || defined(__s390x__)
  23
  24 #define my_llseek lseek
  25
  26 #else
  27 #include <linux/unistd.h>       /* for __NR__llseek */
  28
  29 static int _llseek (unsigned int, unsigned long,
  30                    unsigned long, long long *, unsigned int);
  31
  32 #ifdef __NR__llseek
  33
  34 static _syscall5(int,_llseek,unsigned int,fd,unsigned long,offset_high,
  35                  unsigned long, offset_low,long long *,result,
  36                  unsigned int, origin)
  37
  38 #else
  39
  40 /* no __NR__llseek on compilation machine - might give it explicitly */
  41 static int _llseek (unsigned int fd, unsigned long oh,
  42                     unsigned long ol, long long *result,
  43                     unsigned int origin) {
  44         errno = ENOSYS;
  45         return -1;
  46 }
  47
  48 #endif
  49
  50 static long long my_llseek (unsigned int fd, long long offset,
  51                 unsigned int origin)
  52 {
  53         long long result;
  54         int retval;
  55
  56         retval = _llseek (fd, ((unsigned long long) offset) >> 32,
  57                         ((unsigned long long) offset) & 0xffffffff,
  58                         &result, origin);
  59         return (retval == -1 ? (long long) retval : result);
  60 }
  61
  62 #endif /* __alpha__ */
  63
  64 #endif  /* HAVE_LLSEEK */
  65
  66 long long ext2_llseek (unsigned int fd, long long offset,
  67                          unsigned int origin)
  68 {
  69         long long result;
  70         static int do_compat = 0;
  71
  72         if (!do_compat) {
  73                 result = my_llseek (fd, offset, origin);
  74                 if (!(result == -1 && errno == ENOSYS))
  75                         return result;
  76
  77                 /*
  78                  * Just in case this code runs on top of an old kernel
  79                  * which does not support the llseek system call
  80                  */
  81                 do_compat = 1;
  82                 /*
  83                  * Now try ordinary lseek.
  84                  */
  85         }
  86
  87         if ((sizeof(off_t) >= sizeof(long long)) ||
  88             (offset < ((long long) 1 << ((sizeof(off_t)*8) -1))))
  89                 return lseek(fd, (off_t) offset, origin);
  90
  91         errno = EINVAL;
  92         return -1;
  93 }
  94
  95 #else /* !linux */
  96
  97 long long ext2_llseek (unsigned int fd, long long offset,
  98                          unsigned int origin)
  99 {
 100         if ((sizeof(off_t) < sizeof(long long)) &&
 101             (offset >= ((long long) 1 << ((sizeof(off_t)*8) -1)))) {
 102                 errno = EINVAL;
 103                 return -1;
 104         }
 105         return lseek (fd, (off_t) offset, origin);
 106 }
 107
 108 #endif  /* linux */
 109
 110