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 int
  14 sys_lseek(struct tcb *tcp)
  15 {
  16         long long offset;
  17         int whence;
  18
  19         if (entering(tcp)) {
  20                 printfd(tcp, tcp->u_arg[0]);
  21                 offset = tcp->ext_arg[1];
  22                 whence = tcp->u_arg[2];
  23                 if (whence == SEEK_SET)
  24                         tprintf(", %llu, ", offset);
  25                 else
  26                         tprintf(", %lld, ", offset);
  27                 printxval(whence_codes, whence, "SEEK_???");
  28         }
  29         return RVAL_LUDECIMAL;
  30 }
  31 #else
  32 int
  33 sys_lseek(struct tcb *tcp)
  34 {
  35         long offset;
  36         int whence;
  37
  38         if (entering(tcp)) {
  39                 printfd(tcp, tcp->u_arg[0]);
  40                 offset = tcp->u_arg[1];
  41                 whence = tcp->u_arg[2];
  42                 if (whence == SEEK_SET)
  43                         tprintf(", %lu, ", offset);
  44                 else
  45                         tprintf(", %ld, ", offset);
  46                 printxval(whence_codes, whence, "SEEK_???");
  47         }
  48         return RVAL_UDECIMAL;
  49 }
  50 #endif
  51
  52 /* llseek syscall takes explicitly two ulong arguments hi, lo,
  53  * rather than one 64-bit argument for which LONG_LONG works
  54  * appropriate for the native byte order.
  55  *
  56  * See kernel's fs/read_write.c::SYSCALL_DEFINE5(llseek, ...)
  57  *
  58  * hi,lo are "unsigned longs" and combined exactly this way in kernel:
  59  * ((loff_t) hi << 32) | lo
  60  * Note that for architectures with kernel's long wider than userspace long
  61  * (such as x32), combining code will use *kernel's*, i.e. *wide* longs
  62  * for hi and lo. We would need to use tcp->ext_arg[N] on x32...
  63  * ...however, x32 (and x86_64) does not _have_ llseek syscall as such.
  64  */
  65 int
  66 sys_llseek(struct tcb *tcp)
  67 {
  68         if (entering(tcp)) {
  69                 printfd(tcp, tcp->u_arg[0]);
  70                 if (tcp->u_arg[4] == SEEK_SET)
  71                         tprintf(", %llu, ",
  72                                 ((long long) tcp->u_arg[1]) << 32 |
  73                                 (unsigned long long) (unsigned) tcp->u_arg[2]);
  74                 else
  75                         tprintf(", %lld, ",
  76                                 ((long long) tcp->u_arg[1]) << 32 |
  77                                 (unsigned long long) (unsigned) tcp->u_arg[2]);
  78         }
  79         else {
  80                 long long off;
  81                 if (syserror(tcp) || umove(tcp, tcp->u_arg[3], &off) < 0)
  82                         tprintf("%#lx, ", tcp->u_arg[3]);
  83                 else
  84                         tprintf("[%llu], ", off);
  85                 printxval(whence_codes, tcp->u_arg[4], "SEEK_???");
  86         }
  87         return 0;
  88 }