1/* Get directory entries. Linux non-LFS version.
2 Copyright (C) 1993-2021 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 <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, void *buf0, size_t nbytes)
35{
36 char *buf = buf0;
37
38 union
39 {
40 /* For !_DIRENT_MATCHES_DIRENT64 kernel 'linux_dirent64' has the same
41 layout of 'struct dirent64'. */
42 struct dirent64 k;
43 struct dirent u;
44 char b[1];
45 } *kbuf = (void *) buf, *outp, *inp;
46 size_t kbytes = nbytes;
47 off64_t last_offset = -1;
48 ssize_t retval;
49
50# define size_diff (offsetof (struct dirent64, d_name) \
51 - offsetof (struct dirent, d_name))
52 char kbuftmp[sizeof (struct dirent) + size_diff];
53 if (nbytes <= sizeof (struct dirent))
54 kbuf = (void*) kbuftmp;
55
56 retval = INLINE_SYSCALL_CALL (getdents64, fd, kbuf, kbytes);
57 if (retval == -1)
58 return -1;
59
60 /* These two pointers might alias the same memory buffer.
61 Standard C requires that we always use the same type for them,
62 so we must use the union type. */
63 inp = kbuf;
64 outp = (void *) buf;
65
66 while (&inp->b < &kbuf->b + retval)
67 {
68 const size_t alignment = _Alignof (struct dirent);
69 /* Since inp->k.d_reclen is already aligned for the kernel
70 structure this may compute a value that is bigger
71 than necessary. */
72 size_t old_reclen = inp->k.d_reclen;
73 size_t new_reclen = ((old_reclen - size_diff + alignment - 1)
74 & ~(alignment - 1));
75
76 /* Copy the data out of the old structure into temporary space.
77 Then copy the name, which may overlap if BUF == KBUF. */
78 const uint64_t d_ino = inp->k.d_ino;
79 const int64_t d_off = inp->k.d_off;
80 const uint8_t d_type = inp->k.d_type;
81
82 memmove (outp->u.d_name, inp->k.d_name,
83 old_reclen - offsetof (struct dirent64, d_name));
84
85 /* Now we have copied the data from INP and access only OUTP. */
86
87 DIRENT_SET_DP_INO (&outp->u, d_ino);
88 outp->u.d_off = d_off;
89 if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)
90 && outp->u.d_ino != d_ino)
91 || (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)
92 && outp->u.d_off != d_off))
93 {
94 /* Overflow. If there was at least one entry before this one,
95 return them without error, otherwise signal overflow. */
96 if (last_offset != -1)
97 {
98 __lseek64 (fd, last_offset, SEEK_SET);
99 return outp->b - buf;
100 }
101 return INLINE_SYSCALL_ERROR_RETURN_VALUE (EOVERFLOW);
102 }
103
104 last_offset = d_off;
105 outp->u.d_reclen = new_reclen;
106 outp->u.d_type = d_type;
107
108 inp = (void *) inp + old_reclen;
109 outp = (void *) outp + new_reclen;
110 }
111
112 return outp->b - buf;
113}
114
115# undef DIRENT_SET_DP_INO
116
117#endif /* _DIRENT_MATCHES_DIRENT64 */
118