1 /* Linux lseek implementation, 32 bits off_t.
2    Copyright (C) 2016-2021 Free Software Foundation, Inc.
3    This file is part of the GNU C Library.
4 
5    The GNU C Library is free software; you can redistribute it and/or
6    modify it under the terms of the GNU Lesser General Public
7    License as published by the Free Software Foundation; either
8    version 2.1 of the License, or (at your option) any later version.
9 
10    The GNU C Library is distributed in the hope that it will be useful,
11    but WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13    Lesser General Public License for more details.
14 
15    You should have received a copy of the GNU Lesser General Public
16    License along with the GNU C Library.  If not, see
17    <https://www.gnu.org/licenses/>.  */
18 
19 #include <unistd.h>
20 #include <stdint.h>
21 #include <sys/types.h>
22 #include <sysdep.h>
23 #include <errno.h>
24 
25 #ifndef __OFF_T_MATCHES_OFF64_T
26 
27 /* Test for overflows of structures where we ask the kernel to fill them
28    in with standard 64-bit syscalls but return them through APIs that
29    only expose the low 32 bits of some fields.  */
30 
lseek_overflow(loff_t res)31 static inline off_t lseek_overflow (loff_t res)
32 {
33   off_t retval = (off_t) res;
34   if (retval == res)
35     return retval;
36 
37   __set_errno (EOVERFLOW);
38   return (off_t) -1;
39 }
40 
41 off_t
__lseek(int fd,off_t offset,int whence)42 __lseek (int fd, off_t offset, int whence)
43 {
44 # ifdef __NR__llseek
45   loff_t res;
46   int rc = INLINE_SYSCALL_CALL (_llseek, fd,
47 				(long) (((uint64_t) (offset)) >> 32),
48 				(long) offset, &res, whence);
49   return rc ?: lseek_overflow (res);
50 # else
51   return INLINE_SYSCALL_CALL (lseek, fd, offset, whence);
52 # endif
53 }
54 libc_hidden_def (__lseek)
55 weak_alias (__lseek, lseek)
56 strong_alias (__lseek, __libc_lseek)
57 #endif /* __OFF_T_MATCHES_OFF64_T  */
58