1/* Get directory entries. Linux non-LFS version.
2 Copyright (C) 1993-2018 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 <http://www.gnu.org/licenses/>. */
18
19#include <dirent.h>
20
21#if !_DIRENT_MATCHES_DIRENT64
22
23# include <unistd.h>
24# include <string.h>
25# include <errno.h>
26
27# ifndef DIRENT_SET_DP_INO
28# define DIRENT_SET_DP_INO(dp, value) (dp)->d_ino = (value)
29# endif
30
31/* Pack the dirent64 struct down into 32-bit offset/inode fields, and
32 ensure that no overflow occurs. */
33ssize_t
34__getdents (int fd, char *buf, size_t nbytes)
35{
36 union
37 {
38 /* For !_DIRENT_MATCHES_DIRENT64 kernel 'linux_dirent64' has the same
39 layout of 'struct dirent64'. */
40 struct dirent64 k;
41 struct dirent u;
42 char b[1];
43 } *kbuf = (void *) buf, *outp, *inp;
44 size_t kbytes = nbytes;
45 off64_t last_offset = -1;
46 ssize_t retval;
47
48# define size_diff (offsetof (struct dirent64, d_name) \
49 - offsetof (struct dirent, d_name))
50 char kbuftmp[sizeof (struct dirent) + size_diff];
51 if (nbytes <= sizeof (struct dirent))
52 kbuf = (void*) kbuftmp;
53
54 retval = INLINE_SYSCALL_CALL (getdents64, fd, kbuf, kbytes);
55 if (retval == -1)
56 return -1;
57
58 /* These two pointers might alias the same memory buffer.
59 Standard C requires that we always use the same type for them,
60 so we must use the union type. */
61 inp = kbuf;
62 outp = (void *) buf;
63
64 while (&inp->b < &kbuf->b + retval)
65 {
66 const size_t alignment = _Alignof (struct dirent);
67 /* Since inp->k.d_reclen is already aligned for the kernel
68 structure this may compute a value that is bigger
69 than necessary. */
70 size_t old_reclen = inp->k.d_reclen;
71 size_t new_reclen = ((old_reclen - size_diff + alignment - 1)
72 & ~(alignment - 1));
73
74 /* Copy the data out of the old structure into temporary space.
75 Then copy the name, which may overlap if BUF == KBUF. */
76 const uint64_t d_ino = inp->k.d_ino;
77 const int64_t d_off = inp->k.d_off;
78 const uint8_t d_type = inp->k.d_type;
79
80 memmove (outp->u.d_name, inp->k.d_name,
81 old_reclen - offsetof (struct dirent64, d_name));
82
83 /* Now we have copied the data from INP and access only OUTP. */
84
85 DIRENT_SET_DP_INO (&outp->u, d_ino);
86 outp->u.d_off = d_off;
87 if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)
88 && outp->u.d_ino != d_ino)
89 || (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)
90 && outp->u.d_off != d_off))
91 {
92 /* Overflow. If there was at least one entry before this one,
93 return them without error, otherwise signal overflow. */
94 if (last_offset != -1)
95 {
96 __lseek64 (fd, last_offset, SEEK_SET);
97 return outp->b - buf;
98 }
99 return INLINE_SYSCALL_ERROR_RETURN_VALUE (EOVERFLOW);
100 }
101
102 last_offset = d_off;
103 outp->u.d_reclen = new_reclen;
104 outp->u.d_type = d_type;
105
106 inp = (void *) inp + old_reclen;
107 outp = (void *) outp + new_reclen;
108 }
109
110 return outp->b - buf;
111}
112
113# undef DIRENT_SET_DP_INO
114
115#endif /* _DIRENT_MATCHES_DIRENT64 */
116