1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
/* Copyright (C) 1993, 1995-2003, 2004, 2006, 2007, 2011
This file is part of the GNU C Library.
Simplified from sysdeps/unix/sysv/linux/getdents.c.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<http://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <assert.h>
#include <errno.h>
#include <dirent.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sysdep.h>
#include <sys/syscall.h>
/* Pack the dirent64 struct down into 32-bit offset/inode fields, and
ensure that no overflow occurs. */
ssize_t
__getdents (int fd, char *buf, size_t nbytes)
{
union
{
struct dirent64 k; /* Kernel structure. */
struct dirent u;
char b[1];
} *kbuf = (void *) buf, *outp, *inp;
size_t kbytes = nbytes;
off64_t last_offset = -1;
ssize_t retval;
const size_t size_diff = (offsetof (struct dirent64, d_name)
- offsetof (struct dirent, d_name));
if (nbytes <= sizeof (struct dirent))
{
kbytes = nbytes + offsetof (struct dirent64, d_name)
- offsetof (struct dirent, d_name);
kbuf = __alloca(kbytes);
}
retval = INLINE_SYSCALL (getdents64, 3, fd, kbuf, kbytes);
if (retval == -1)
return -1;
/* These two pointers might alias the same memory buffer.
Standard C requires that we always use the same type for them,
so we must use the union type. */
inp = kbuf;
outp = (void *) buf;
while (&inp->b < &kbuf->b + retval)
{
const size_t alignment = __alignof__ (struct dirent);
/* Since inp->k.d_reclen is already aligned for the kernel
structure this may compute a value that is bigger
than necessary. */
size_t old_reclen = inp->k.d_reclen;
size_t new_reclen = ((old_reclen - size_diff + alignment - 1)
& ~(alignment - 1));
/* Copy the data out of the old structure into temporary space.
Then copy the name, which may overlap if BUF == KBUF. */
const uint64_t d_ino = inp->k.d_ino;
const int64_t d_off = inp->k.d_off;
const uint8_t d_type = inp->k.d_type;
memmove (outp->u.d_name, inp->k.d_name,
old_reclen - offsetof (struct dirent64, d_name));
/* Now we have copied the data from INP and access only OUTP. */
outp->u.d_ino = d_ino;
outp->u.d_off = d_off;
if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)
&& outp->u.d_ino != d_ino)
|| (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)
&& outp->u.d_off != d_off))
{
/* Overflow. If there was at least one entry before this one,
return them without error, otherwise signal overflow. */
if (last_offset != -1)
{
__lseek64 (fd, last_offset, SEEK_SET);
return outp->b - buf;
}
__set_errno (EOVERFLOW);
return -1;
}
last_offset = d_off;
outp->u.d_reclen = new_reclen;
outp->u.d_type = d_type;
inp = (void *) inp + old_reclen;
outp = (void *) outp + new_reclen;
}
return outp->b - buf;
}
|
