granicus.if.org Git - strace/blob - lseek.c

   1 #include "defs.h"
   2
   3 #include "xlat/whence_codes.h"
   4
   5 /* Linux kernel has exactly one version of lseek:
   6  * fs/read_write.c::SYSCALL_DEFINE3(lseek, unsigned, fd, off_t, offset, unsigned, origin)
   7  * In kernel, off_t is always the same as (kernel's) long
   8  * (see include/uapi/asm-generic/posix_types.h),
   9  * which means that on x32 we need to use tcp->ext_arg[N] to get offset argument.
  10  * Use test/x32_lseek.c to test lseek decoding.
  11  */
  12 #if defined(LINUX_MIPSN32) || defined(X32)
  13 SYS_FUNC(lseek)
  14 {
  15         long long offset;
  16         int whence;
  17
  18         if (entering(tcp)) {
  19                 printfd(tcp, tcp->u_arg[0]);
  20                 offset = tcp->ext_arg[1];
  21                 whence = tcp->u_arg[2];
  22                 if (whence == SEEK_SET)
  23                         tprintf(", %llu, ", offset);
  24                 else
  25                         tprintf(", %lld, ", offset);
  26                 printxval(whence_codes, whence, "SEEK_???");
  27         }
  28         return RVAL_LUDECIMAL;
  29 }
  30 #else
  31 SYS_FUNC(lseek)
  32 {
  33         long offset;
  34         int whence;
  35
  36         if (entering(tcp)) {
  37                 printfd(tcp, tcp->u_arg[0]);
  38                 offset = tcp->u_arg[1];
  39                 whence = tcp->u_arg[2];
  40                 if (whence == SEEK_SET)
  41                         tprintf(", %lu, ", offset);
  42                 else
  43                         tprintf(", %ld, ", offset);
  44                 printxval(whence_codes, whence, "SEEK_???");
  45         }
  46         return RVAL_UDECIMAL;
  47 }
  48 #endif
  49
  50 /* llseek syscall takes explicitly two ulong arguments hi, lo,
  51  * rather than one 64-bit argument for which LONG_LONG works
  52  * appropriate for the native byte order.
  53  *
  54  * See kernel's fs/read_write.c::SYSCALL_DEFINE5(llseek, ...)
  55  *
  56  * hi,lo are "unsigned longs" and combined exactly this way in kernel:
  57  * ((loff_t) hi << 32) | lo
  58  * Note that for architectures with kernel's long wider than userspace long
  59  * (such as x32), combining code will use *kernel's*, i.e. *wide* longs
  60  * for hi and lo. We would need to use tcp->ext_arg[N] on x32...
  61  * ...however, x32 (and x86_64) does not _have_ llseek syscall as such.
  62  */
  63 SYS_FUNC(llseek)
  64 {
  65         if (entering(tcp)) {
  66                 printfd(tcp, tcp->u_arg[0]);
  67                 if (tcp->u_arg[4] == SEEK_SET)
  68                         tprintf(", %llu, ",
  69                                 ((long long) tcp->u_arg[1]) << 32 |
  70                                 (unsigned long long) (unsigned) tcp->u_arg[2]);
  71                 else
  72                         tprintf(", %lld, ",
  73                                 ((long long) tcp->u_arg[1]) << 32 |
  74                                 (unsigned long long) (unsigned) tcp->u_arg[2]);
  75         }
  76         else {
  77                 long long off;
  78                 if (syserror(tcp) || umove(tcp, tcp->u_arg[3], &off) < 0)
  79                         tprintf("%#lx, ", tcp->u_arg[3]);
  80                 else
  81                         tprintf("[%llu], ", off);
  82                 printxval(whence_codes, tcp->u_arg[4], "SEEK_???");
  83         }
  84         return 0;
  85 }