LXR busybox/klibc-utils/resume.c

   1/*
   2 * Copyright (c) 2017 Denys Vlasenko <vda.linux@googlemail.com>
   3 *
   4 * Licensed under GPLv2, see file LICENSE in this source tree.
   5 */
   6//config:config RESUME
   7//config:       bool "resume (3.2 kb)"
   8//config:       default y
   9//config:       help
  10//config:       Resume from saved "suspend-to-disk" image
  11
  12//applet:IF_RESUME(APPLET_NOEXEC(resume, resume, BB_DIR_BIN, BB_SUID_DROP, resume))
  13
  14//kbuild:lib-$(CONFIG_RESUME) += resume.o
  15
  16#include "libbb.h"
  17
  18/* This is a NOEXEC applet. Be very careful! */
  19
  20/* name_to_dev_t() in klibc-utils supports extended device name formats,
  21 * apart from the usual case where /dev/NAME already exists.
  22 *
  23 * - device number in hexadecimal represents itself (in dev_t layout).
  24 * - device number in major:minor decimal represents itself.
  25 * - if block device (or partition) with this name is found in sysfs.
  26 * - if /dev/ prefix is not given, it is assumed.
  27 *
  28 * klibc-utils also recognizes these, but they don't work
  29 * for "resume" tool purposes (thus we don't support them (yet?)):
  30 * - /dev/nfs
  31 * - /dev/ram (alias to /dev/ram0)
  32 * - /dev/mtd
  33 */
  34static dev_t name_to_dev_t(const char *devname)
  35{
  36        char devfile[sizeof(int)*3 * 2 + 4];
  37        char *sysname;
  38        unsigned major_num, minor_num;
  39        struct stat st;
  40        int r;
  41
  42        if (strncmp(devname, "/dev/", 5) != 0) {
  43                char *cptr;
  44
  45                cptr = strchr(devname, ':');
  46                if (cptr) {
  47                        /* Colon-separated decimal device number? */
  48                        *cptr = '\0';
  49                        major_num = bb_strtou(devname, NULL, 10);
  50                        if (!errno)
  51                                minor_num = bb_strtou(cptr + 1, NULL, 10);
  52                        *cptr = ':';
  53                        if (!errno)
  54                                return makedev(major_num, minor_num);
  55                } else {
  56                        /* Hexadecimal device number? */
  57                        dev_t res = (dev_t) bb_strtoul(devname, NULL, 16);
  58                        if (!errno)
  59                                return res;
  60                }
  61
  62                devname = xasprintf("/dev/%s", devname);
  63        }
  64        /* Now devname is always "/dev/FOO" */
  65
  66        if (stat(devname, &st) == 0 && S_ISBLK(st.st_mode))
  67                return st.st_rdev;
  68
  69        /* Full blockdevs as well as partitions may be visible
  70         * in /sys/class/block/ even if /dev is not populated.
  71         */
  72        sysname = xasprintf("/sys/class/block/%s/dev", devname + 5);
  73        r = open_read_close(sysname, devfile, sizeof(devfile) - 1);
  74        //free(sysname);
  75        if (r > 0) {
  76                devfile[r] = '\0';
  77                if (sscanf(devfile, "%u:%u", &major_num, &minor_num) == 2) {
  78                        return makedev(major_num, minor_num);
  79                }
  80        }
  81
  82        return (dev_t) 0;
  83}
  84
  85//usage:#define resume_trivial_usage
  86//usage:       "BLOCKDEV [OFFSET]"
  87//usage:#define resume_full_usage "\n"
  88//usage:   "\n""Restore system state from 'suspend-to-disk' data in BLOCKDEV"
  89
  90int resume_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  91int resume_main(int argc UNUSED_PARAM, char **argv)
  92{
  93        unsigned long long ofs;
  94        dev_t resume_device;
  95        char *s;
  96        int fd;
  97
  98        argv++;
  99        if (!argv[0])
 100                bb_show_usage();
 101
 102        resume_device = name_to_dev_t(argv[0]);
 103        if (major(resume_device) == 0) {
 104                bb_error_msg_and_die("invalid resume device: %s", argv[0]);
 105        }
 106
 107        ofs = (argv[1] ? xstrtoull(argv[1], 0) : 0);
 108        /* Old kernels have no /sys/power/resume_offset, set it only if necessary */
 109        if (ofs != 0) {
 110                fd = xopen("/sys/power/resume_offset", O_WRONLY);
 111                s = xasprintf("%llu", ofs);
 112                xwrite_str(fd, s);
 113        }
 114
 115        fd = xopen("/sys/power/resume", O_WRONLY);
 116        s = xasprintf("%u:%u", major(resume_device), minor(resume_device));
 117
 118        xwrite_str(fd, s);
 119        /* if write() returns, resume did not succeed */
 120
 121        return EXIT_FAILURE; /* klibc-utils exits -1 aka 255 */
 122}
 123