LXR busybox/util-linux/mkswap.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * mkswap.c - format swap device (Linux v1 only)
   4 *
   5 * Copyright 2006 Rob Landley <rob@landley.net>
   6 *
   7 * Licensed under GPLv2, see file LICENSE in this source tree.
   8 */
   9//config:config MKSWAP
  10//config:       bool "mkswap (6.3 kb)"
  11//config:       default y
  12//config:       help
  13//config:       The mkswap utility is used to configure a file or disk partition as
  14//config:       Linux swap space. This allows Linux to use the entire file or
  15//config:       partition as if it were additional RAM, which can greatly increase
  16//config:       the capability of low-memory machines. This additional memory is
  17//config:       much slower than real RAM, but can be very helpful at preventing your
  18//config:       applications being killed by the Linux out of memory (OOM) killer.
  19//config:       Once you have created swap space using 'mkswap' you need to enable
  20//config:       the swap space using the 'swapon' utility.
  21//config:
  22//config:config FEATURE_MKSWAP_UUID
  23//config:       bool "UUID support"
  24//config:       default y
  25//config:       depends on MKSWAP
  26//config:       help
  27//config:       Generate swap spaces with universally unique identifiers.
  28
  29//applet:IF_MKSWAP(APPLET(mkswap, BB_DIR_SBIN, BB_SUID_DROP))
  30
  31//kbuild:lib-$(CONFIG_MKSWAP) += mkswap.o
  32
  33//usage:#define mkswap_trivial_usage
  34//usage:       "[-L LBL] BLOCKDEV [KBYTES]"
  35//usage:#define mkswap_full_usage "\n\n"
  36//usage:       "Prepare BLOCKDEV to be used as swap partition\n"
  37//usage:     "\n        -L LBL  Label"
  38
  39#include "libbb.h"
  40#include "common_bufsiz.h"
  41
  42#if ENABLE_SELINUX
  43static void mkswap_selinux_setcontext(int fd, const char *path)
  44{
  45        struct stat stbuf;
  46
  47        if (!is_selinux_enabled())
  48                return;
  49
  50        xfstat(fd, &stbuf, path);
  51        if (S_ISREG(stbuf.st_mode)) {
  52                security_context_t newcon;
  53                security_context_t oldcon = NULL;
  54                context_t context;
  55
  56                if (fgetfilecon(fd, &oldcon) < 0) {
  57                        if (errno != ENODATA)
  58                                goto error;
  59                        if (matchpathcon(path, stbuf.st_mode, &oldcon) < 0)
  60                                goto error;
  61                }
  62                context = context_new(oldcon);
  63                if (!context || context_type_set(context, "swapfile_t"))
  64                        goto error;
  65                newcon = context_str(context);
  66                if (!newcon)
  67                        goto error;
  68                /* fsetfilecon_raw is hidden */
  69                if (strcmp(oldcon, newcon) != 0 && fsetfilecon(fd, newcon) < 0)
  70                        goto error;
  71                if (ENABLE_FEATURE_CLEAN_UP) {
  72                        context_free(context);
  73                        freecon(oldcon);
  74                }
  75        }
  76        return;
  77 error:
  78        bb_perror_msg_and_die("SELinux relabeling failed");
  79}
  80#else
  81# define mkswap_selinux_setcontext(fd, path) ((void)0)
  82#endif
  83
  84/* from Linux 2.6.23 */
  85/*
  86 * Magic header for a swap area. ... Note that the first
  87 * kilobyte is reserved for boot loader or disk label stuff.
  88 */
  89struct swap_header_v1 {
  90/*      char     bootbits[1024];    Space for disklabel etc. */
  91        uint32_t version;        /* second kbyte, word 0 */
  92        uint32_t last_page;      /* 1 */
  93        uint32_t nr_badpages;    /* 2 */
  94        char     sws_uuid[16];   /* 3,4,5,6 */
  95        char     sws_volume[16]; /* 7,8,9,10 */
  96        uint32_t padding[117];   /* 11..127 */
  97        uint32_t badpages[1];    /* 128 */
  98        /* total 129 32-bit words in 2nd kilobyte */
  99} FIX_ALIASING;
 100
 101#define NWORDS 129
 102#define hdr ((struct swap_header_v1*)bb_common_bufsiz1)
 103#define INIT_G() do { setup_common_bufsiz(); } while (0)
 104
 105struct BUG_sizes {
 106        char swap_header_v1_wrong[sizeof(*hdr)  != (NWORDS * 4) ? -1 : 1];
 107        char bufsiz1_is_too_small[COMMON_BUFSIZE < (NWORDS * 4) ? -1 : 1];
 108};
 109
 110/* Stored without terminating NUL */
 111static const char SWAPSPACE2[sizeof("SWAPSPACE2")-1] ALIGN1 = "SWAPSPACE2";
 112
 113int mkswap_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 114int mkswap_main(int argc UNUSED_PARAM, char **argv)
 115{
 116        int fd;
 117        unsigned pagesize;
 118        off_t len;
 119        const char *label = "";
 120
 121        INIT_G();
 122
 123        /* TODO: -p PAGESZ, -U UUID */
 124        getopt32(argv, "^" "L:" "\0" "-1"/*at least one arg*/, &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