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6ec2e0f5 SDJ |
1 | /* Create /proc/self/fd-related names for subfiles of open directories. |
2 | ||
5e8754f9 | 3 | Copyright (C) 2006, 2009-2016 Free Software Foundation, Inc. |
6ec2e0f5 SDJ |
4 | |
5 | This program is free software: you can redistribute it and/or modify | |
6 | it under the terms of the GNU General Public License as published by | |
7 | the Free Software Foundation; either version 3 of the License, or | |
8 | (at your option) any later version. | |
9 | ||
10 | This program 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 | |
13 | GNU General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU General Public License | |
5e8754f9 | 16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
6ec2e0f5 SDJ |
17 | |
18 | /* Written by Paul Eggert. */ | |
19 | ||
20 | #include <config.h> | |
21 | ||
22 | #include "openat-priv.h" | |
23 | ||
24 | #include <sys/types.h> | |
25 | #include <sys/stat.h> | |
26 | #include <fcntl.h> | |
27 | ||
28 | #include <stdio.h> | |
29 | #include <stdlib.h> | |
30 | #include <string.h> | |
31 | #include <unistd.h> | |
32 | ||
33 | #ifdef __KLIBC__ | |
34 | # include <InnoTekLIBC/backend.h> | |
35 | #endif | |
36 | ||
37 | #include "intprops.h" | |
38 | ||
39 | /* Set BUF to the name of the subfile of the directory identified by | |
40 | FD, where the subfile is named FILE. If successful, return BUF if | |
41 | the result fits in BUF, dynamically allocated memory otherwise. | |
42 | Return NULL (setting errno) on error. */ | |
43 | char * | |
44 | openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file) | |
45 | { | |
46 | char *result = buf; | |
47 | int dirlen; | |
48 | ||
49 | /* Make sure the caller gets ENOENT when appropriate. */ | |
50 | if (!*file) | |
51 | { | |
52 | buf[0] = '\0'; | |
53 | return buf; | |
54 | } | |
55 | ||
56 | #ifndef __KLIBC__ | |
57 | # define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/" | |
58 | { | |
59 | enum { | |
60 | PROC_SELF_FD_DIR_SIZE_BOUND | |
61 | = (sizeof PROC_SELF_FD_FORMAT - (sizeof "%d" - 1) | |
62 | + INT_STRLEN_BOUND (int)) | |
63 | }; | |
64 | ||
65 | static int proc_status = 0; | |
66 | if (! proc_status) | |
67 | { | |
68 | /* Set PROC_STATUS to a positive value if /proc/self/fd is | |
69 | reliable, and a negative value otherwise. Solaris 10 | |
70 | /proc/self/fd mishandles "..", and any file name might expand | |
71 | to ".." after symbolic link expansion, so avoid /proc/self/fd | |
72 | if it mishandles "..". Solaris 10 has openat, but this | |
73 | problem is exhibited on code that built on Solaris 8 and | |
74 | running on Solaris 10. */ | |
75 | ||
76 | int proc_self_fd = open ("/proc/self/fd", | |
77 | O_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK); | |
78 | if (proc_self_fd < 0) | |
79 | proc_status = -1; | |
80 | else | |
81 | { | |
82 | /* Detect whether /proc/self/fd/%i/../fd exists, where %i is the | |
83 | number of a file descriptor open on /proc/self/fd. On Linux, | |
84 | that name resolves to /proc/self/fd, which was opened above. | |
85 | However, on Solaris, it may resolve to /proc/self/fd/fd, which | |
86 | cannot exist, since all names in /proc/self/fd are numeric. */ | |
87 | char dotdot_buf[PROC_SELF_FD_DIR_SIZE_BOUND + sizeof "../fd" - 1]; | |
88 | sprintf (dotdot_buf, PROC_SELF_FD_FORMAT "../fd", proc_self_fd); | |
89 | proc_status = access (dotdot_buf, F_OK) ? -1 : 1; | |
90 | close (proc_self_fd); | |
91 | } | |
92 | } | |
93 | ||
94 | if (proc_status < 0) | |
95 | return NULL; | |
96 | else | |
97 | { | |
98 | size_t bufsize = PROC_SELF_FD_DIR_SIZE_BOUND + strlen (file); | |
99 | if (OPENAT_BUFFER_SIZE < bufsize) | |
100 | { | |
101 | result = malloc (bufsize); | |
102 | if (! result) | |
103 | return NULL; | |
104 | } | |
105 | ||
106 | dirlen = sprintf (result, PROC_SELF_FD_FORMAT, fd); | |
107 | } | |
108 | } | |
109 | #else | |
110 | /* OS/2 kLIBC provides a function to retrieve a path from a fd. */ | |
111 | { | |
112 | char dir[_MAX_PATH]; | |
113 | size_t bufsize; | |
114 | ||
115 | if (__libc_Back_ioFHToPath (fd, dir, sizeof dir)) | |
116 | return NULL; | |
117 | ||
118 | dirlen = strlen (dir); | |
119 | bufsize = dirlen + 1 + strlen (file) + 1; /* 1 for '/', 1 for null */ | |
120 | if (OPENAT_BUFFER_SIZE < bufsize) | |
121 | { | |
122 | result = malloc (bufsize); | |
123 | if (! result) | |
124 | return NULL; | |
125 | } | |
126 | ||
127 | strcpy (result, dir); | |
128 | result[dirlen++] = '/'; | |
129 | } | |
130 | #endif | |
131 | ||
132 | strcpy (result + dirlen, file); | |
133 | return result; | |
134 | } |