a2ea3b2fc8
This adds a small tool that may be used to look into OS images, and mount them to any place. This is mostly a friendlier version of test-dissect-image.c. I am not sure this should really become a proper command of systemd, hence for now do not install it into bindir, but simply libexecdir. This tool is already pretty useful since you can mount image files with it, honouring the various partitions correctly. I figure this is going to become more interesting if the dissctor learns luks and verity support.
167 lines
4.6 KiB
C
167 lines
4.6 KiB
C
/***
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This file is part of systemd.
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Copyright 2016 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <fcntl.h>
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#include <linux/loop.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "loop-util.h"
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int loop_device_make(int fd, int open_flags, LoopDevice **ret) {
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const struct loop_info64 info = {
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.lo_flags = LO_FLAGS_AUTOCLEAR|LO_FLAGS_PARTSCAN|(open_flags == O_RDONLY ? LO_FLAGS_READ_ONLY : 0),
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};
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_cleanup_close_ int control = -1, loop = -1;
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_cleanup_free_ char *loopdev = NULL;
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struct stat st;
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LoopDevice *d;
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int nr;
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assert(fd >= 0);
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assert(ret);
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assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
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if (fstat(fd, &st) < 0)
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return -errno;
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if (S_ISBLK(st.st_mode)) {
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int copy;
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/* If this is already a block device, store a copy of the fd as it is */
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copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
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if (copy < 0)
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return -errno;
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d = new0(LoopDevice, 1);
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if (!d)
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return -ENOMEM;
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*d = (LoopDevice) {
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.fd = copy,
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.nr = -1,
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};
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*ret = d;
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return 0;
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}
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if (!S_ISREG(st.st_mode))
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return -EINVAL;
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control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
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if (control < 0)
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return -errno;
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nr = ioctl(control, LOOP_CTL_GET_FREE);
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if (nr < 0)
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return -errno;
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if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
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return -ENOMEM;
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loop = open(loopdev, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
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if (loop < 0)
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return -errno;
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if (ioctl(loop, LOOP_SET_FD, fd) < 0)
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return -errno;
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if (ioctl(loop, LOOP_SET_STATUS64, &info) < 0)
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return -errno;
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d = new(LoopDevice, 1);
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if (!d)
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return -ENOMEM;
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*d = (LoopDevice) {
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.fd = loop,
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.node = loopdev,
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.nr = nr,
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};
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loop = -1;
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loopdev = NULL;
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*ret = d;
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return (*ret)->fd;
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}
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int loop_device_make_by_path(const char *path, int open_flags, LoopDevice **ret) {
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_cleanup_close_ int fd = -1;
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assert(path);
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assert(ret);
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assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
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fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
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if (fd < 0)
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return -errno;
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return loop_device_make(fd, open_flags, ret);
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}
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LoopDevice* loop_device_unref(LoopDevice *d) {
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if (!d)
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return NULL;
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if (d->fd >= 0) {
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if (d->nr >= 0 && !d->relinquished) {
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if (ioctl(d->fd, LOOP_CLR_FD) < 0)
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log_debug_errno(errno, "Failed to clear loop device: %m");
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}
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safe_close(d->fd);
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}
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if (d->nr >= 0 && !d->relinquished) {
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_cleanup_close_ int control = -1;
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control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
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if (control < 0)
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log_debug_errno(errno, "Failed to open loop control device: %m");
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else {
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if (ioctl(control, LOOP_CTL_REMOVE, d->nr) < 0)
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log_debug_errno(errno, "Failed to remove loop device: %m");
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}
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}
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free(d->node);
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free(d);
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return NULL;
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}
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void loop_device_relinquish(LoopDevice *d) {
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assert(d);
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/* Don't attempt to clean up the loop device anymore from this point on. Leave the clean-ing up to the kernel
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* itself, using the loop device "auto-clear" logic we already turned on when creating the device. */
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d->relinquished = true;
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}
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