1 | /* Return a range of open file descriptors. |
2 | Copyright (C) 2021-2024 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 <errno.h> |
20 | #include <fcntl.h> |
21 | #include <support/support.h> |
22 | #include <support/check.h> |
23 | #include <support/xunistd.h> |
24 | #include <stdlib.h> |
25 | #include <sys/resource.h> |
26 | |
27 | static void |
28 | increase_nofile (void) |
29 | { |
30 | struct rlimit rl; |
31 | if (getrlimit (RLIMIT_NOFILE, rlimits: &rl) == -1) |
32 | FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m" ); |
33 | |
34 | rl.rlim_cur += 128; |
35 | |
36 | if (setrlimit (RLIMIT_NOFILE, rlimits: &rl) == 1) |
37 | FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m" ); |
38 | } |
39 | |
40 | static int |
41 | open_dev_null (int flags, mode_t mode) |
42 | { |
43 | int fd = open64 (file: "/dev/null" , oflag: flags, mode); |
44 | if (fd >= 0) |
45 | return fd; |
46 | |
47 | if (fd < 0 && errno != EMFILE) |
48 | FAIL_EXIT1 ("open64 (\"/dev/null\", 0x%x, 0%o): %m" , flags, mode); |
49 | |
50 | increase_nofile (); |
51 | |
52 | return xopen (path: "/dev/null" , flags, mode); |
53 | } |
54 | |
55 | struct range |
56 | { |
57 | int lowfd; |
58 | size_t len; |
59 | }; |
60 | |
61 | struct range_list |
62 | { |
63 | size_t total; |
64 | size_t used; |
65 | struct range *ranges; |
66 | }; |
67 | |
68 | static void |
69 | range_init (struct range_list *r) |
70 | { |
71 | r->total = 8; |
72 | r->used = 0; |
73 | r->ranges = xmalloc (n: r->total * sizeof (struct range)); |
74 | } |
75 | |
76 | static void |
77 | range_add (struct range_list *r, int lowfd, size_t len) |
78 | { |
79 | if (r->used == r->total) |
80 | { |
81 | r->total *= 2; |
82 | r->ranges = xrealloc (o: r->ranges, n: r->total * sizeof (struct range)); |
83 | } |
84 | r->ranges[r->used].lowfd = lowfd; |
85 | r->ranges[r->used].len = len; |
86 | r->used++; |
87 | } |
88 | |
89 | static void |
90 | range_close (struct range_list *r) |
91 | { |
92 | for (size_t i = 0; i < r->used; i++) |
93 | { |
94 | int minfd = r->ranges[i].lowfd; |
95 | int maxfd = r->ranges[i].lowfd + r->ranges[i].len; |
96 | for (int fd = minfd; fd < maxfd; fd++) |
97 | xclose (fd); |
98 | } |
99 | free (ptr: r->ranges); |
100 | } |
101 | |
102 | int |
103 | support_open_dev_null_range (int num, int flags, mode_t mode) |
104 | { |
105 | /* We keep track of the ranges that hit an already opened descriptor, so |
106 | we close them after we get a working range. */ |
107 | struct range_list rl; |
108 | range_init (r: &rl); |
109 | |
110 | int lowfd = open_dev_null (flags, mode); |
111 | int prevfd = lowfd; |
112 | while (true) |
113 | { |
114 | int i = 1; |
115 | for (; i < num; i++) |
116 | { |
117 | int fd = open_dev_null (flags, mode); |
118 | if (fd != lowfd + i) |
119 | { |
120 | range_add (r: &rl, lowfd, len: prevfd - lowfd + 1); |
121 | |
122 | prevfd = lowfd = fd; |
123 | break; |
124 | } |
125 | prevfd = fd; |
126 | } |
127 | if (i == num) |
128 | break; |
129 | } |
130 | |
131 | range_close (r: &rl); |
132 | |
133 | return lowfd; |
134 | } |
135 | |