path: root/util-linux/mkswap.c (plain)
blob: 954a1948dc4b3eb46ef812ef703c2bce99d03fdb

1	/* vi: set sw=4 ts=4: */
2	/* mkswap.c - format swap device (Linux v1 only)
3	*
4	* Copyright 2006 Rob Landley <rob@landley.net>
5	*
6	* Licensed under GPLv2, see file LICENSE in this source tree.
7	*/
8	//config:config MKSWAP
9	//config: bool "mkswap"
10	//config: default y
11	//config: help
12	//config: The mkswap utility is used to configure a file or disk partition as
13	//config: Linux swap space. This allows Linux to use the entire file or
14	//config: partition as if it were additional RAM, which can greatly increase
15	//config: the capability of low-memory machines. This additional memory is
16	//config: much slower than real RAM, but can be very helpful at preventing your
17	//config: applications being killed by the Linux out of memory (OOM) killer.
18	//config: Once you have created swap space using 'mkswap' you need to enable
19	//config: the swap space using the 'swapon' utility.
20	//config:
21	//config:config FEATURE_MKSWAP_UUID
22	//config: bool "UUID support"
23	//config: default y
24	//config: depends on MKSWAP
25	//config: help
26	//config: Generate swap spaces with universally unique identifiers.
27
28	//applet:IF_MKSWAP(APPLET(mkswap, BB_DIR_SBIN, BB_SUID_DROP))
29
30	//kbuild:lib-$(CONFIG_MKSWAP) += mkswap.o
31
32	//usage:#define mkswap_trivial_usage
33	//usage: "[-L LBL] BLOCKDEV [KBYTES]"
34	//usage:#define mkswap_full_usage "\n\n"
35	//usage: "Prepare BLOCKDEV to be used as swap partition\n"
36	//usage: "\n -L LBL Label"
37
38	#include "libbb.h"
39	#include "common_bufsiz.h"
40
41	#if ENABLE_SELINUX
42	static void mkswap_selinux_setcontext(int fd, const char *path)
43	{
44	struct stat stbuf;
45
46	if (!is_selinux_enabled())
47	return;
48
49	xfstat(fd, &stbuf, path);
50	if (S_ISREG(stbuf.st_mode)) {
51	security_context_t newcon;
52	security_context_t oldcon = NULL;
53	context_t context;
54
55	if (fgetfilecon(fd, &oldcon) < 0) {
56	if (errno != ENODATA)
57	goto error;
58	if (matchpathcon(path, stbuf.st_mode, &oldcon) < 0)
59	goto error;
60	}
61	context = context_new(oldcon);
62	if (!context || context_type_set(context, "swapfile_t"))
63	goto error;
64	newcon = context_str(context);
65	if (!newcon)
66	goto error;
67	/* fsetfilecon_raw is hidden */
68	if (strcmp(oldcon, newcon) != 0 && fsetfilecon(fd, newcon) < 0)
69	goto error;
70	if (ENABLE_FEATURE_CLEAN_UP) {
71	context_free(context);
72	freecon(oldcon);
73	}
74	}
75	return;
76	error:
77	bb_perror_msg_and_die("SELinux relabeling failed");
78	}
79	#else
80	# define mkswap_selinux_setcontext(fd, path) ((void)0)
81	#endif
82
83	/* from Linux 2.6.23 */
84	/*
85	* Magic header for a swap area. ... Note that the first
86	* kilobyte is reserved for boot loader or disk label stuff.
87	*/
88	struct swap_header_v1 {
89	/* char bootbits[1024]; Space for disklabel etc. */
90	uint32_t version; /* second kbyte, word 0 */
91	uint32_t last_page; /* 1 */
92	uint32_t nr_badpages; /* 2 */
93	char sws_uuid[16]; /* 3,4,5,6 */
94	char sws_volume[16]; /* 7,8,9,10 */
95	uint32_t padding[117]; /* 11..127 */
96	uint32_t badpages[1]; /* 128 */
97	/* total 129 32-bit words in 2nd kilobyte */
98	} FIX_ALIASING;
99
100	#define NWORDS 129
101	#define hdr ((struct swap_header_v1*)bb_common_bufsiz1)
102	#define INIT_G() do { setup_common_bufsiz(); } while (0)
103
104	struct BUG_sizes {
105	char swap_header_v1_wrong[sizeof(*hdr) != (NWORDS * 4) ? -1 : 1];
106	char bufsiz1_is_too_small[COMMON_BUFSIZE < (NWORDS * 4) ? -1 : 1];
107	};
108
109	/* Stored without terminating NUL */
110	static const char SWAPSPACE2[sizeof("SWAPSPACE2")-1] ALIGN1 = "SWAPSPACE2";
111
112	int mkswap_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
113	int mkswap_main(int argc UNUSED_PARAM, char **argv)
114	{
115	int fd;
116	unsigned pagesize;
117	off_t len;
118	const char *label = "";
119
120	INIT_G();
121
122	opt_complementary = "-1"; /* at least one param */
123	/* TODO: -p PAGESZ, -U UUID */
124	getopt32(argv, "L:", &label);
125	argv += optind;
126
127	fd = xopen(argv[0], O_WRONLY);
128
129	/* Figure out how big the device is */
130	len = get_volume_size_in_bytes(fd, argv[1], 1024, /*extend:*/ 1);
131	pagesize = getpagesize();
132	len -= pagesize;
133
134	/* Announce our intentions */
135	printf("Setting up swapspace version 1, size = %"OFF_FMT"u bytes\n", len);
136	mkswap_selinux_setcontext(fd, argv[0]);
137
138	/* hdr is zero-filled so far. Clear the first kbyte, or else
139	* mkswap-ing former FAT partition does NOT erase its signature.
140	*
141	* util-linux-ng 2.17.2 claims to erase it only if it does not see
142	* a partition table and is not run on whole disk. -f forces it.
143	*/
144	xwrite(fd, hdr, 1024);
145
146	/* Fill the header. */
147	hdr->version = 1;
148	hdr->last_page = (uoff_t)len / pagesize;
149
150	if (ENABLE_FEATURE_MKSWAP_UUID) {
151	char uuid_string[32];
152	generate_uuid((void*)hdr->sws_uuid);
153	bin2hex(uuid_string, hdr->sws_uuid, 16);
154	/* f.e. UUID=dfd9c173-be52-4d27-99a5-c34c6c2ff55f */
155	printf("UUID=%.8s" "-%.4s-%.4s-%.4s-%.12s\n",
156	uuid_string,
157	uuid_string+8,
158	uuid_string+8+4,
159	uuid_string+8+4+4,
160	uuid_string+8+4+4+4
161	);
162	}
163	safe_strncpy(hdr->sws_volume, label, 16);
164
165	/* Write the header. Sync to disk because some kernel versions check
166	* signature on disk (not in cache) during swapon. */
167	xwrite(fd, hdr, NWORDS * 4);
168	xlseek(fd, pagesize - 10, SEEK_SET);
169	xwrite(fd, SWAPSPACE2, 10);
170	fsync(fd);
171
172	if (ENABLE_FEATURE_CLEAN_UP)
173	close(fd);
174
175	return 0;
176	}
177