]>
Commit | Line | Data |
---|---|---|
f3d05ee6 CB |
1 | /* liblxcapi |
2 | * | |
3 | * Copyright © 2017 Christian Brauner <christian.brauner@ubuntu.com>. | |
4 | * Copyright © 2017 Canonical Ltd. | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2, as | |
8 | * published by the Free Software Foundation. | |
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 along | |
16 | * with this program; if not, write to the Free Software Foundation, Inc., | |
17 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 | */ | |
19 | ||
d38dd64a CB |
20 | #ifndef _GNU_SOURCE |
21 | #define _GNU_SOURCE 1 | |
22 | #endif | |
f3d05ee6 CB |
23 | #define __STDC_FORMAT_MACROS |
24 | #include <errno.h> | |
25 | #include <inttypes.h> | |
26 | #include <stdbool.h> | |
27 | #include <stdio.h> | |
28 | #include <stdlib.h> | |
29 | #include <string.h> | |
f3d05ee6 | 30 | #include <sys/mman.h> |
d38dd64a | 31 | #include <unistd.h> |
f3d05ee6 | 32 | |
d38dd64a | 33 | #include "config.h" |
f3d05ee6 | 34 | #include "ringbuf.h" |
6a886ddf | 35 | #include "syscall_wrappers.h" |
f3d05ee6 CB |
36 | #include "utils.h" |
37 | ||
38 | int lxc_ringbuf_create(struct lxc_ringbuf *buf, size_t size) | |
39 | { | |
40 | char *tmp; | |
41 | int ret; | |
42 | int memfd = -1; | |
43 | ||
44 | buf->size = size; | |
45 | buf->r_off = 0; | |
46 | buf->w_off = 0; | |
47 | ||
48 | /* verify that we are at least given the multiple of a page size */ | |
49 | if (buf->size % lxc_getpagesize()) | |
50 | return -EINVAL; | |
51 | ||
52 | buf->addr = mmap(NULL, buf->size * 2, PROT_NONE, | |
53 | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); | |
54 | if (buf->addr == MAP_FAILED) | |
55 | return -EINVAL; | |
56 | ||
57 | memfd = memfd_create(".lxc_ringbuf", MFD_CLOEXEC); | |
58 | if (memfd < 0) { | |
709384a0 CB |
59 | char template[] = P_tmpdir "/.lxc_ringbuf_XXXXXX"; |
60 | ||
f3d05ee6 CB |
61 | if (errno != ENOSYS) |
62 | goto on_error; | |
63 | ||
709384a0 | 64 | memfd = lxc_make_tmpfile(template, true); |
f3d05ee6 CB |
65 | } |
66 | if (memfd < 0) | |
67 | goto on_error; | |
68 | ||
69 | ret = ftruncate(memfd, buf->size); | |
70 | if (ret < 0) | |
71 | goto on_error; | |
72 | ||
73 | tmp = mmap(buf->addr, buf->size, PROT_READ | PROT_WRITE, | |
74 | MAP_FIXED | MAP_SHARED, memfd, 0); | |
75 | if (tmp == MAP_FAILED || tmp != buf->addr) | |
76 | goto on_error; | |
77 | ||
78 | tmp = mmap(buf->addr + buf->size, buf->size, PROT_READ | PROT_WRITE, | |
79 | MAP_FIXED | MAP_SHARED, memfd, 0); | |
80 | if (tmp == MAP_FAILED || tmp != (buf->addr + buf->size)) | |
81 | goto on_error; | |
82 | ||
83 | close(memfd); | |
84 | ||
85 | return 0; | |
86 | ||
87 | on_error: | |
88 | lxc_ringbuf_release(buf); | |
89 | if (memfd >= 0) | |
90 | close(memfd); | |
91 | return -1; | |
92 | } | |
93 | ||
94 | void lxc_ringbuf_move_read_addr(struct lxc_ringbuf *buf, size_t len) | |
95 | { | |
96 | buf->r_off += len; | |
97 | ||
98 | if (buf->r_off < buf->size) | |
99 | return; | |
100 | ||
101 | /* wrap around */ | |
102 | buf->r_off -= buf->size; | |
103 | buf->w_off -= buf->size; | |
104 | } | |
105 | ||
106 | /** | |
107 | * lxc_ringbuf_write - write a message to the ringbuffer | |
108 | * - The size of the message should never be greater than the size of the whole | |
109 | * ringbuffer. | |
110 | * - The write method will always succeed i.e. it will always advance the r_off | |
111 | * if it detects that there's not enough space available to write the | |
112 | * message. | |
113 | */ | |
114 | int lxc_ringbuf_write(struct lxc_ringbuf *buf, const char *msg, size_t len) | |
115 | { | |
116 | char *w_addr; | |
117 | uint64_t free; | |
118 | ||
119 | /* sanity check: a write should never exceed the ringbuffer's total size */ | |
120 | if (len > buf->size) | |
121 | return -EFBIG; | |
122 | ||
123 | free = lxc_ringbuf_free(buf); | |
124 | ||
125 | /* not enough space left so advance read address */ | |
126 | if (len > free) | |
127 | lxc_ringbuf_move_read_addr(buf, len); | |
128 | w_addr = lxc_ringbuf_get_write_addr(buf); | |
129 | memcpy(w_addr, msg, len); | |
130 | lxc_ringbuf_move_write_addr(buf, len); | |
131 | return 0; | |
132 | } | |
133 | ||
134 | int lxc_ringbuf_read(struct lxc_ringbuf *buf, char *out, size_t *len) | |
135 | { | |
136 | uint64_t used; | |
137 | ||
138 | /* there's nothing to read */ | |
139 | if (buf->r_off == buf->w_off) | |
140 | return -ENODATA; | |
141 | ||
142 | /* read maximum amount available */ | |
143 | used = lxc_ringbuf_used(buf); | |
144 | if (used < *len) | |
145 | *len = used; | |
146 | ||
147 | /* copy data to reader but don't advance addr */ | |
148 | memcpy(out, lxc_ringbuf_get_read_addr(buf), *len); | |
149 | out[*len - 1] = '\0'; | |
150 | return 0; | |
151 | } |