1 /* vi: set sw=4 ts=4: */
2 /* mkswap.c - format swap device (Linux v1 only)
4 * Copyright 2006 Rob Landley <rob@landley.net>
6 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
11 static void mkswap_selinux_setcontext(int fd, const char *path)
15 if (!is_selinux_enabled())
18 if (fstat(fd, &stbuf) < 0)
19 bb_perror_msg_and_die("fstat failed");
20 if (S_ISREG(stbuf.st_mode)) {
21 security_context_t newcon;
22 security_context_t oldcon = NULL;
25 if (fgetfilecon(fd, &oldcon) < 0) {
28 if (matchpathcon(path, stbuf.st_mode, &oldcon) < 0)
31 context = context_new(oldcon);
32 if (!context || context_type_set(context, "swapfile_t"))
34 newcon = context_str(context);
37 /* fsetfilecon_raw is hidden */
38 if (strcmp(oldcon, newcon) != 0 && fsetfilecon(fd, newcon) < 0)
40 if (ENABLE_FEATURE_CLEAN_UP) {
41 context_free(context);
47 bb_perror_msg_and_die("SELinux relabeling failed");
50 # define mkswap_selinux_setcontext(fd, path) ((void)0)
53 #if ENABLE_FEATURE_MKSWAP_UUID
54 static void mkswap_generate_uuid(uint8_t *buf)
56 /* http://www.ietf.org/rfc/rfc4122.txt
57 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
58 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
60 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
61 * | time_mid | time_hi_and_version |
62 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
63 * |clk_seq_and_variant | node (0-1) |
64 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
66 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
67 * IOW, uuid has this layout:
68 * uint32_t time_low (big endian)
69 * uint16_t time_mid (big endian)
70 * uint16_t time_hi_and_version (big endian)
71 * version is a 4-bit field:
73 * 2 DCE Security, with embedded POSIX UIDs
75 * 4 Randomly generated
76 * 5 Name-based (SHA-1)
77 * uint16_t clk_seq_and_variant (big endian)
78 * variant is a 3-bit field:
79 * 0xx Reserved, NCS backward compatibility
80 * 10x The variant specified in rfc4122
81 * 110 Reserved, Microsoft backward compatibility
82 * 111 Reserved for future definition
85 * For version 4, these bits are set/cleared:
86 * time_hi_and_version & 0x0fff | 0x4000
87 * clk_seq_and_variant & 0x3fff | 0x8000
93 i = open("/dev/urandom", O_RDONLY);
98 /* Paranoia. /dev/urandom may be missing.
99 * rand() is guaranteed to generate at least [0, 2^15) range,
100 * but lowest bits in some libc are not so "random". */
101 srand(monotonic_us());
104 for (i = 0; i < 16; i++)
105 buf[i] ^= rand() >> 5;
113 buf[4 + 2 ] = (buf[4 + 2 ] & 0x0f) | 0x40;
115 buf[4 + 2 + 2] = (buf[4 + 2 + 2] & 0x3f) | 0x80;
117 bin2hex(uuid_string, (void*) buf, 16);
118 /* f.e. UUID=dfd9c173-be52-4d27-99a5-c34c6c2ff55f */
119 printf("UUID=%.8s" "-%.4s-%.4s-%.4s-%.12s\n",
128 # define mkswap_generate_uuid(buf) ((void)0)
131 #if 0 /* from Linux 2.6.23 */
133 * Magic header for a swap area. The first part of the union is
134 * what the swap magic looks like for the old (limited to 128MB)
135 * swap area format, the second part of the union adds - in the
136 * old reserved area - some extra information. Note that the first
137 * kilobyte is reserved for boot loader or disk label stuff...
141 char reserved[PAGE_SIZE - 10];
142 char magic[10]; /* SWAP-SPACE or SWAPSPACE2 */
145 char bootbits[1024]; /* Space for disklabel etc. */
146 __u32 version; /* second kbyte, word 0 */
147 __u32 last_page; /* 1 */
148 __u32 nr_badpages; /* 2 */
149 unsigned char sws_uuid[16]; /* 3,4,5,6 */
150 unsigned char sws_volume[16]; /* 7,8,9,10 */
151 __u32 padding[117]; /* 11..127 */
152 __u32 badpages[1]; /* 128, total 129 32-bit words */
158 #define hdr ((uint32_t*)(&bb_common_bufsiz1))
160 struct BUG_bufsiz1_is_too_small {
161 char BUG_bufsiz1_is_too_small[COMMON_BUFSIZE < (NWORDS * 4) ? -1 : 1];
164 /* Stored without terminating NUL */
165 static const char SWAPSPACE2[sizeof("SWAPSPACE2")-1] ALIGN1 = "SWAPSPACE2";
167 int mkswap_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
168 int mkswap_main(int argc, char **argv)
173 // No options supported.
175 if (argc != 2) bb_show_usage();
177 // Figure out how big the device is and announce our intentions.
179 fd = xopen(argv[1], O_RDWR);
180 /* fdlength was reported to be unreliable - use seek */
181 len = xlseek(fd, 0, SEEK_END);
183 xlseek(fd, 0, SEEK_SET);
185 pagesize = getpagesize();
186 printf("Setting up swapspace version 1, size = %"OFF_FMT"u bytes\n",
188 mkswap_selinux_setcontext(fd, argv[1]);
190 // Make a header. hdr is zero-filled so far...
192 hdr[1] = (len / pagesize) - 1;
193 mkswap_generate_uuid((void*) &hdr[3]);
195 // Write the header. Sync to disk because some kernel versions check
196 // signature on disk (not in cache) during swapon.
197 xlseek(fd, 1024, SEEK_SET);
198 xwrite(fd, hdr, NWORDS * 4);
199 xlseek(fd, pagesize - 10, SEEK_SET);
200 xwrite(fd, SWAPSPACE2, 10);
203 if (ENABLE_FEATURE_CLEAN_UP) close(fd);