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dissect: add small "systemd-dissect" tool as wrapper around dissect-image.c 

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.
This commit is contained in:
Lennart Poettering 2016-12-02 19:32:09 +01:00
parent 9f3c7fc1ad
commit a2ea3b2fc8
6 changed files with 234 additions and 3 deletions
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1
.gitignore vendored
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@ -67,6 +67,7 @@
/systemd-debug-generator
/systemd-delta
/systemd-detect-virt
/systemd-dissect
/systemd-escape
/systemd-export
/systemd-firstboot

12
Makefile.am
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@ -404,6 +404,11 @@ rootlibexec_PROGRAMS = \
systemd-socket-proxyd \
systemd-update-done
if HAVE_BLKID
rootlibexec_PROGRAMS += \
systemd-dissect
endif
if HAVE_UTMP
rootlibexec_PROGRAMS += \
systemd-update-utmp
@ -3073,6 +3078,13 @@ systemd_notify_SOURCES = \
systemd_notify_LDADD = \
libsystemd-shared.la
# ------------------------------------------------------------------------------
systemd_dissect_SOURCES = \
src/dissect/dissect.c
systemd_dissect_LDADD = \
libsystemd-shared.la
# ------------------------------------------------------------------------------
systemd_path_SOURCES = \
src/path/path.c

1
src/dissect/Makefile Symbolic link
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@ -0,0 +1 @@
../Makefile

206
src/dissect/dissect.c Normal file
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@ -0,0 +1,206 @@
/***
This file is part of systemd.
Copyright 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <fcntl.h>
#include <stdio.h>
#include <getopt.h>
#include "architecture.h"
#include "dissect-image.h"
#include "log.h"
#include "loop-util.h"
#include "string-util.h"
#include "util.h"
static enum {
ACTION_DISSECT,
ACTION_MOUNT,
} arg_action = ACTION_DISSECT;
static const char *arg_image = NULL;
static const char *arg_path = NULL;
static bool arg_read_only = false;
static void help(void) {
printf("%s [OPTIONS...] IMAGE\n"
"%s [OPTIONS...] --mount IMAGE PATH\n"
"Dissect a file system OS image.\n\n"
" -h --help Show this help\n"
" --version Show package version\n"
" -m --mount Mount the image to the specified directory\n"
" -r --read-only Mount read-only\n",
program_invocation_short_name,
program_invocation_short_name);
}
static int parse_argv(int argc, char *argv[]) {
enum {
ARG_VERSION = 0x100,
};
static const struct option options[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, ARG_VERSION },
{ "mount", no_argument, NULL, 'm' },
{ "read-only", no_argument, NULL, 'r' },
{}
};
int c;
assert(argc >= 0);
assert(argv);
while ((c = getopt_long(argc, argv, "hmr", options, NULL)) >= 0) {
switch (c) {
case 'h':
help();
return 0;
case ARG_VERSION:
return version();
case 'm':
arg_action = ACTION_MOUNT;
break;
case 'r':
arg_read_only = true;
break;
case '?':
return -EINVAL;
default:
assert_not_reached("Unhandled option");
}
}
switch (arg_action) {
case ACTION_DISSECT:
if (optind + 1 != argc) {
log_error("Expected a file path as only argument.");
return -EINVAL;
}
arg_image = argv[optind];
arg_read_only = true;
break;
case ACTION_MOUNT:
if (optind + 2 != argc) {
log_error("Expected a file path and mount point path as only arguments.");
return -EINVAL;
}
arg_image = argv[optind];
arg_path = argv[optind + 1];
break;
default:
assert_not_reached("Unknown action.");
}
return 1;
}
int main(int argc, char *argv[]) {
_cleanup_(loop_device_unrefp) LoopDevice *d = NULL;
_cleanup_(dissected_image_unrefp) DissectedImage *m = NULL;
int r;
log_parse_environment();
log_open();
r = parse_argv(argc, argv);
if (r <= 0)
goto finish;
r = loop_device_make_by_path(arg_image, arg_read_only ? O_RDONLY : O_RDWR, &d);
if (r < 0) {
log_error_errno(r, "Failed to set up loopback device: %m");
goto finish;
}
r = dissect_image(d->fd, &m);
if (r == -ENOPKG) {
log_error_errno(r, "Couldn't identify a suitable partition table or file system in %s.", arg_image);
goto finish;
}
if (r < 0) {
log_error_errno(r, "Failed to dissect image: %m");
goto finish;
}
switch (arg_action) {
case ACTION_DISSECT: {
unsigned i;
for (i = 0; i < _PARTITION_DESIGNATOR_MAX; i++) {
DissectedPartition *p = m->partitions + i;
if (!p->found)
continue;
printf("Found %s '%s' partition",
p->rw ? "writable" : "read-only",
partition_designator_to_string(i));
if (p->fstype)
printf(" of type %s", p->fstype);
if (p->architecture != _ARCHITECTURE_INVALID)
printf(" for %s", architecture_to_string(p->architecture));
if (p->partno >= 0)
printf(" on partition #%i", p->partno);
if (p->node)
printf(" (%s)", p->node);
putchar('\n');
}
break;
}
case ACTION_MOUNT:
r = dissected_image_mount(m, arg_path,
(arg_read_only ? DISSECTED_IMAGE_READ_ONLY : 0) |
DISSECTED_IMAGE_DISCARD_ON_LOOP);
if (r < 0) {
log_error_errno(r, "Failed to mount image: %m");
goto finish;
}
loop_device_relinquish(d);
break;
default:
assert_not_reached("Unknown action.");
}
finish:
return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}

13
src/shared/loop-util.c
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@ -129,7 +129,7 @@ LoopDevice* loop_device_unref(LoopDevice *d) {
if (d->fd >= 0) {
if (d->nr >= 0) {
if (d->nr >= 0 && !d->relinquished) {
if (ioctl(d->fd, LOOP_CLR_FD) < 0)
log_debug_errno(errno, "Failed to clear loop device: %m");
@ -138,7 +138,7 @@ LoopDevice* loop_device_unref(LoopDevice *d) {
safe_close(d->fd);
}
if (d->nr >= 0) {
if (d->nr >= 0 && !d->relinquished) {
_cleanup_close_ int control = -1;
control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
@ -155,3 +155,12 @@ LoopDevice* loop_device_unref(LoopDevice *d) {
return NULL;
}
void loop_device_relinquish(LoopDevice *d) {
assert(d);
/* Don't attempt to clean up the loop device anymore from this point on. Leave the clean-ing up to the kernel
* itself, using the loop device "auto-clear" logic we already turned on when creating the device. */
d->relinquished = true;
}

4
src/shared/loop-util.h
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@ -29,11 +29,13 @@ struct LoopDevice {
int fd;
int nr;
char *node;
bool relinquished;
};
int loop_device_make(int fd, int open_flags, LoopDevice **ret);
int loop_device_make_by_path(const char *path, int open_flags, LoopDevice **ret);
LoopDevice* loop_device_unref(LoopDevice *d);
DEFINE_TRIVIAL_CLEANUP_FUNC(LoopDevice*, loop_device_unref);
void loop_device_relinquish(LoopDevice *d);