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         printfd(tcp, tcp->u_arg[0]);
  19 # ifdef X32
  20         /* tcp->ext_arg is not initialized for i386 personality */
  21         if (current_personality == 1)
  22                 offset = tcp->u_arg[1];
  23         else
  24 # endif
  25         offset = tcp->ext_arg[1];
  26         whence = tcp->u_arg[2];
  27         if (whence == SEEK_SET)
  28                 tprintf(", %llu, ", offset);
  29         else
  30                 tprintf(", %lld, ", offset);
  31         printxval(whence_codes, whence, "SEEK_???");
  32
  33         return RVAL_DECODED | RVAL_LUDECIMAL;
  34 }
  35 #else
  36 SYS_FUNC(lseek)
  37 {
  38         long offset;
  39         int whence;
  40
  41         printfd(tcp, tcp->u_arg[0]);
  42         offset = tcp->u_arg[1];
  43         whence = tcp->u_arg[2];
  44         if (whence == SEEK_SET)
  45                 tprintf(", %lu, ", offset);
  46         else
  47                 tprintf(", %ld, ", offset);
  48         printxval(whence_codes, whence, "SEEK_???");
  49
  50         return RVAL_DECODED | RVAL_UDECIMAL;
  51 }
  52 #endif
  53
  54 /* llseek syscall takes explicitly two ulong arguments hi, lo,
  55  * rather than one 64-bit argument for which LONG_LONG works
  56  * appropriate for the native byte order.
  57  *
  58  * See kernel's fs/read_write.c::SYSCALL_DEFINE5(llseek, ...)
  59  *
  60  * hi,lo are "unsigned longs" and combined exactly this way in kernel:
  61  * ((loff_t) hi << 32) | lo
  62  * Note that for architectures with kernel's long wider than userspace long
  63  * (such as x32), combining code will use *kernel's*, i.e. *wide* longs
  64  * for hi and lo. We would need to use tcp->ext_arg[N] on x32...
  65  * ...however, x32 (and x86_64) does not _have_ llseek syscall as such.
  66  */
  67 SYS_FUNC(llseek)
  68 {
  69         if (entering(tcp)) {
  70                 printfd(tcp, tcp->u_arg[0]);
  71                 if (tcp->u_arg[4] == SEEK_SET)
  72                         tprintf(", %llu, ",
  73                                 ((long long) tcp->u_arg[1]) << 32 |
  74                                 (unsigned long long) (unsigned) tcp->u_arg[2]);
  75                 else
  76                         tprintf(", %lld, ",
  77                                 ((long long) tcp->u_arg[1]) << 32 |
  78                                 (unsigned long long) (unsigned) tcp->u_arg[2]);
  79         } else {
  80                 printnum_int64(tcp, tcp->u_arg[3], "%" PRIu64);
  81                 tprints(", ");
  82                 printxval(whence_codes, tcp->u_arg[4], "SEEK_???");
  83         }
  84         return 0;
  85 }