1  /*
       2   * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
       3   * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
       4   * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
       5   * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
       6   * Copyright (c) 2002-2005 Roland McGrath <roland@redhat.com>
       7   * Copyright (c) 2009 Andreas Schwab <schwab@redhat.com>
       8   * Copyright (c) 2012 H.J. Lu <hongjiu.lu@intel.com>
       9   * Copyright (c) 2013 Denys Vlasenko <vda.linux@googlemail.com>
      10   * Copyright (c) 2014-2016 Dmitry V. Levin <ldv@strace.io>
      11   * Copyright (c) 2014-2021 The strace developers.
      12   * All rights reserved.
      13   *
      14   * SPDX-License-Identifier: LGPL-2.1-or-later
      15   */
      16  
      17  #include "defs.h"
      18  
      19  #include "xlat/whence_codes.h"
      20  
      21  /* Linux kernel has exactly one version of lseek:
      22   * fs/read_write.c::SYSCALL_DEFINE3(lseek, unsigned, fd, off_t, offset, unsigned, origin)
      23   * In kernel, off_t is always the same as (kernel's) long
      24   * (see include/uapi/asm-generic/posix_types.h).
      25   * Use test/x32_lseek.c to test lseek decoding.
      26   */
      27  SYS_FUNC(lseek)
      28  {
      29  	/* fd */
      30  	printfd(tcp, tcp->u_arg[0]);
      31  	tprint_arg_next();
      32  
      33  	kernel_long_t offset;
      34  
      35  #ifndef current_klongsize
      36  	if (current_klongsize < sizeof(kernel_long_t)) {
      37  		offset = (int) tcp->u_arg[1];
      38  	} else
      39  #endif /* !current_klongsize */
      40  	{
      41  		offset = tcp->u_arg[1];
      42  	}
      43  
      44  	/* offset */
      45  	PRINT_VAL_D(offset);
      46  	tprint_arg_next();
      47  
      48  	/* whence */
      49  	printxval(whence_codes, tcp->u_arg[2], "SEEK_???");
      50  
      51  	return RVAL_DECODED;
      52  }
      53  
      54  /* llseek syscall takes explicitly two ulong arguments hi, lo,
      55   * rather than one 64-bit argument for which ULONG_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.
      65   */
      66  SYS_FUNC(llseek)
      67  {
      68  	if (entering(tcp)) {
      69  		/* fd */
      70  		printfd(tcp, tcp->u_arg[0]);
      71  		tprint_arg_next();
      72  
      73  		long long offset = ((long long) tcp->u_arg[1] << 32) |
      74  				   ((long long) tcp->u_arg[2]);
      75  
      76  		/* offset */
      77  		PRINT_VAL_D(offset);
      78  		tprint_arg_next();
      79  	} else {
      80  		/* result */
      81  		printnum_int64(tcp, tcp->u_arg[3], "%" PRIu64);
      82  		tprint_arg_next();
      83  
      84  		/* whence */
      85  		printxval(whence_codes, tcp->u_arg[4], "SEEK_???");
      86  	}
      87  	return 0;
      88  }