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Diffstat (limited to '')
| -rw-r--r-- | lib/utils_loop.c | 271 |
1 files changed, 271 insertions, 0 deletions
diff --git a/lib/utils_loop.c b/lib/utils_loop.c new file mode 100644 index 0000000..9f6d307 --- /dev/null +++ b/lib/utils_loop.c @@ -0,0 +1,271 @@ +/* + * loopback block device utilities + * + * Copyright (C) 2009-2019 Red Hat, Inc. All rights reserved. + * Copyright (C) 2009-2019 Milan Broz + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include <stdlib.h> +#include <string.h> +#include <stdio.h> +#include <unistd.h> +#include <fcntl.h> +#include <errno.h> +#include <limits.h> +#include <sys/ioctl.h> +#include <sys/stat.h> +#include <sys/types.h> +#ifdef HAVE_SYS_SYSMACROS_H +# include <sys/sysmacros.h> /* for major, minor */ +#endif +#include <linux/loop.h> + +#include "utils_loop.h" + +#define LOOP_DEV_MAJOR 7 + +#ifndef LO_FLAGS_AUTOCLEAR +#define LO_FLAGS_AUTOCLEAR 4 +#endif + +#ifndef LOOP_CTL_GET_FREE +#define LOOP_CTL_GET_FREE 0x4C82 +#endif + +#ifndef LOOP_SET_CAPACITY +#define LOOP_SET_CAPACITY 0x4C07 +#endif + +static char *crypt_loop_get_device_old(void) +{ + char dev[20]; + int i, loop_fd; + struct loop_info64 lo64 = {0}; + + for (i = 0; i < 256; i++) { + sprintf(dev, "/dev/loop%d", i); + + loop_fd = open(dev, O_RDONLY); + if (loop_fd < 0) + return NULL; + + if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) && + errno == ENXIO) { + close(loop_fd); + return strdup(dev); + } + close(loop_fd); + } + + return NULL; +} + +static char *crypt_loop_get_device(void) +{ + char dev[64]; + int i, loop_fd; + struct stat st; + + loop_fd = open("/dev/loop-control", O_RDONLY); + if (loop_fd < 0) + return crypt_loop_get_device_old(); + + i = ioctl(loop_fd, LOOP_CTL_GET_FREE); + if (i < 0) { + close(loop_fd); + return NULL; + } + close(loop_fd); + + if (sprintf(dev, "/dev/loop%d", i) < 0) + return NULL; + + if (stat(dev, &st) || !S_ISBLK(st.st_mode)) + return NULL; + + return strdup(dev); +} + +int crypt_loop_attach(char **loop, const char *file, int offset, + int autoclear, int *readonly) +{ + struct loop_info64 lo64 = {0}; + char *lo_file_name; + int loop_fd = -1, file_fd = -1, r = 1; + + *loop = NULL; + + file_fd = open(file, (*readonly ? O_RDONLY : O_RDWR) | O_EXCL); + if (file_fd < 0 && (errno == EROFS || errno == EACCES) && !*readonly) { + *readonly = 1; + file_fd = open(file, O_RDONLY | O_EXCL); + } + if (file_fd < 0) + goto out; + + while (loop_fd < 0) { + *loop = crypt_loop_get_device(); + if (!*loop) + goto out; + + loop_fd = open(*loop, *readonly ? O_RDONLY : O_RDWR); + if (loop_fd < 0) + goto out; + + if (ioctl(loop_fd, LOOP_SET_FD, file_fd) < 0) { + if (errno != EBUSY) + goto out; + free(*loop); + *loop = NULL; + + close(loop_fd); + loop_fd = -1; + } + } + + lo_file_name = (char*)lo64.lo_file_name; + lo_file_name[LO_NAME_SIZE-1] = '\0'; + strncpy(lo_file_name, file, LO_NAME_SIZE-1); + lo64.lo_offset = offset; + if (autoclear) + lo64.lo_flags |= LO_FLAGS_AUTOCLEAR; + + if (ioctl(loop_fd, LOOP_SET_STATUS64, &lo64) < 0) { + (void)ioctl(loop_fd, LOOP_CLR_FD, 0); + goto out; + } + + /* Verify that autoclear is really set */ + if (autoclear) { + memset(&lo64, 0, sizeof(lo64)); + if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0 || + !(lo64.lo_flags & LO_FLAGS_AUTOCLEAR)) { + (void)ioctl(loop_fd, LOOP_CLR_FD, 0); + goto out; + } + } + + r = 0; +out: + if (r && loop_fd >= 0) + close(loop_fd); + if (file_fd >= 0) + close(file_fd); + if (r && *loop) { + free(*loop); + *loop = NULL; + } + return r ? -1 : loop_fd; +} + +int crypt_loop_detach(const char *loop) +{ + int loop_fd = -1, r = 1; + + loop_fd = open(loop, O_RDONLY); + if (loop_fd < 0) + return 1; + + if (!ioctl(loop_fd, LOOP_CLR_FD, 0)) + r = 0; + + close(loop_fd); + return r; +} + +int crypt_loop_resize(const char *loop) +{ + int loop_fd = -1, r = 1; + + loop_fd = open(loop, O_RDONLY); + if (loop_fd < 0) + return 1; + + if (!ioctl(loop_fd, LOOP_SET_CAPACITY, 0)) + r = 0; + + close(loop_fd); + return r; +} + +static char *_ioctl_backing_file(const char *loop) +{ + struct loop_info64 lo64 = {0}; + int loop_fd; + + loop_fd = open(loop, O_RDONLY); + if (loop_fd < 0) + return NULL; + + if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0) { + close(loop_fd); + return NULL; + } + + lo64.lo_file_name[LO_NAME_SIZE-2] = '*'; + lo64.lo_file_name[LO_NAME_SIZE-1] = 0; + + close(loop_fd); + + return strdup((char*)lo64.lo_file_name); +} + +static char *_sysfs_backing_file(const char *loop) +{ + struct stat st; + char buf[PATH_MAX]; + size_t len; + int fd; + + if (stat(loop, &st) || !S_ISBLK(st.st_mode)) + return NULL; + + snprintf(buf, sizeof(buf), "/sys/dev/block/%d:%d/loop/backing_file", + major(st.st_rdev), minor(st.st_rdev)); + + fd = open(buf, O_RDONLY); + if (fd < 0) + return NULL; + + len = read(fd, buf, PATH_MAX); + close(fd); + if (len < 2) + return NULL; + + buf[len - 1] = '\0'; + return strdup(buf); +} + +char *crypt_loop_backing_file(const char *loop) +{ + char *bf = _sysfs_backing_file(loop); + return bf ?: _ioctl_backing_file(loop); +} + +int crypt_loop_device(const char *loop) +{ + struct stat st; + + if (!loop) + return 0; + + if (stat(loop, &st) || !S_ISBLK(st.st_mode) || + major(st.st_rdev) != LOOP_DEV_MAJOR) + return 0; + + return 1; +} |