1/* Get directory entries. Linux LFS version.
2 Copyright (C) 1997-2019 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 <string.h>
20#include <dirent.h>
21#include <errno.h>
22
23/* The kernel struct linux_dirent64 matches the 'struct getdents64' type. */
24ssize_t
25__getdents64 (int fd, char *buf, size_t nbytes)
26{
27 return INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
28}
29
30#if _DIRENT_MATCHES_DIRENT64
31strong_alias (__getdents64, __getdents)
32#else
33# include <shlib-compat.h>
34
35# if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
36# include <olddirent.h>
37# include <unistd.h>
38
39static ssize_t
40handle_overflow (int fd, __off64_t offset, ssize_t count)
41{
42 /* If this is the first entry in the buffer, we can report the
43 error. */
44 if (offset == 0)
45 {
46 __set_errno (EOVERFLOW);
47 return -1;
48 }
49
50 /* Otherwise, seek to the overflowing entry, so that the next call
51 will report the error, and return the data read so far. */
52 if (__lseek64 (fd, offset, SEEK_SET) != 0)
53 return -1;
54 return count;
55}
56
57ssize_t
58__old_getdents64 (int fd, char *buf, size_t nbytes)
59{
60 /* We do not move the individual directory entries. This is only
61 possible if the target type (struct __old_dirent64) is smaller
62 than the source type. */
63 _Static_assert (offsetof (struct __old_dirent64, d_name)
64 <= offsetof (struct dirent64, d_name),
65 "__old_dirent64 is larger than dirent64");
66 _Static_assert (__alignof__ (struct __old_dirent64)
67 <= __alignof__ (struct dirent64),
68 "alignment of __old_dirent64 is larger than dirent64");
69
70 ssize_t retval = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
71 if (retval > 0)
72 {
73 /* This is the marker for the first entry. Offset 0 is reserved
74 for the first entry (see rewinddir). Here, we use it as a
75 marker for the first entry in the buffer. We never actually
76 seek to offset 0 because handle_overflow reports the error
77 directly, so it does not matter that the offset is incorrect
78 if entries have been read from the descriptor before (so that
79 the descriptor is not actually at offset 0). */
80 __off64_t previous_offset = 0;
81
82 char *p = buf;
83 char *end = buf + retval;
84 while (p < end)
85 {
86 struct dirent64 *source = (struct dirent64 *) p;
87
88 /* Copy out the fixed-size data. */
89 __ino_t ino = source->d_ino;
90 __off64_t offset = source->d_off;
91 unsigned int reclen = source->d_reclen;
92 unsigned char type = source->d_type;
93
94 /* Check for ino_t overflow. */
95 if (__glibc_unlikely (ino != source->d_ino))
96 return handle_overflow (fd, previous_offset, p - buf);
97
98 /* Convert to the target layout. Use a separate struct and
99 memcpy to side-step aliasing issues. */
100 struct __old_dirent64 result;
101 result.d_ino = ino;
102 result.d_off = offset;
103 result.d_reclen = reclen;
104 result.d_type = type;
105
106 /* Write the fixed-sized part of the result to the
107 buffer. */
108 size_t result_name_offset = offsetof (struct __old_dirent64, d_name);
109 memcpy (p, &result, result_name_offset);
110
111 /* Adjust the position of the name if necessary. Copy
112 everything until the end of the record, including the
113 terminating NUL byte. */
114 if (result_name_offset != offsetof (struct dirent64, d_name))
115 memmove (p + result_name_offset, source->d_name,
116 reclen - offsetof (struct dirent64, d_name));
117
118 p += reclen;
119 previous_offset = offset;
120 }
121 }
122 return retval;
123}
124# endif /* SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2) */
125#endif /* _DIRENT_MATCHES_DIRENT64 */
126