116 lines
3.1 KiB
C
116 lines
3.1 KiB
C
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/*
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* Copyright (c) 2017 Denys Vlasenko <vda.linux@googlemail.com>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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//config:config RESUME
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//config: bool "resume"
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//config: default y
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//config: help
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//config: Resume from saved "suspend-to-disk" image
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//applet:IF_RESUME(APPLET_NOEXEC(resume, resume, BB_DIR_BIN, BB_SUID_DROP, resume))
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//kbuild:lib-$(CONFIG_RESUME) += resume.o
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#include "libbb.h"
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/* This is a NOEXEC applet. Be very careful! */
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/* name_to_dev_t() in klibc-utils supports extended device name formats,
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* apart from the usual case where /dev/NAME already exists.
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*
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* - device number in hexadecimal represents itself (in dev_t layout).
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* - device number in major:minor decimal represents itself.
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* - if block device (or partition) with this name is found in sysfs.
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* - if /dev/ prefix is not given, it is assumed.
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*
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* klibc-utils also recognizes these, but they don't work
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* for "resume" tool purposes (thus we don't support them (yet?)):
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* - /dev/nfs
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* - /dev/ram (alias to /dev/ram0)
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* - /dev/mtd
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*/
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static dev_t name_to_dev_t(const char *devname)
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{
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char devfile[sizeof(int)*3 * 2 + 4];
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char *sysname;
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unsigned major_num, minor_num;
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struct stat st;
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int r;
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if (strncmp(devname, "/dev/", 5) != 0) {
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char *cptr;
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cptr = strchr(devname, ':');
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if (cptr) {
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/* Colon-separated decimal device number? */
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*cptr = '\0';
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major_num = bb_strtou(devname, NULL, 10);
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if (!errno)
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minor_num = bb_strtou(cptr + 1, NULL, 10);
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*cptr = ':';
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if (!errno)
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return makedev(major_num, minor_num);
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} else {
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/* Hexadecimal device number? */
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dev_t res = (dev_t) bb_strtoul(devname, NULL, 16);
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if (!errno)
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return res;
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}
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devname = xasprintf("/dev/%s", devname);
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}
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/* Now devname is always "/dev/FOO" */
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if (stat(devname, &st) == 0 && S_ISBLK(st.st_mode))
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return st.st_rdev;
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/* Full blockdevs as well as partitions may be visible
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* in /sys/class/block/ even if /dev is not populated.
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*/
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sysname = xasprintf("/sys/class/block/%s/dev", devname + 5);
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r = open_read_close(sysname, devfile, sizeof(devfile) - 1);
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//free(sysname);
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if (r > 0) {
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devfile[r] = '\0';
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if (sscanf(devfile, "%u:%u", &major_num, &minor_num) == 2) {
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return makedev(major_num, minor_num);
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}
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}
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return (dev_t) 0;
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}
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//usage:#define resume_trivial_usage
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//usage: "BLOCKDEV [OFFSET]"
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//usage:#define resume_full_usage "\n"
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//usage: "\n""Restore system state from 'suspend-to-disk' data in BLOCKDEV"
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int resume_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int resume_main(int argc UNUSED_PARAM, char **argv)
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{
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unsigned long long ofs;
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dev_t resume_device;
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char *s;
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int fd;
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argv++;
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if (!argv[0])
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bb_show_usage();
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resume_device = name_to_dev_t(argv[0]);
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if (major(resume_device) == 0) {
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bb_error_msg_and_die("invalid resume device: %s", argv[0]);
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}
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ofs = (argv[1] ? xstrtoull(argv[1], 0) : 0);
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fd = xopen("/sys/power/resume", O_WRONLY);
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s = xasprintf("%u:%u:%llu", major(resume_device), minor(resume_device), ofs);
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xwrite_str(fd, s);
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/* if write() returns, resume did not succeed */
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return EXIT_FAILURE; /* klibc-utils exits -1 aka 255 */
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}
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