445 lines
12 KiB
C
445 lines
12 KiB
C
|
// SPDX-License-Identifier: GPL-2.0
|
||
|
|
/*
|
||
|
|
* Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
|
||
|
|
* that.
|
||
|
|
*/
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <errno.h>
|
||
|
|
#include <string.h>
|
||
|
|
#include <arpa/inet.h>
|
||
|
|
#include <endian.h>
|
||
|
|
#include "cow.h"
|
||
|
|
#include "cow_sys.h"
|
||
|
|
|
||
|
|
#define PATH_LEN_V1 256
|
||
|
|
|
||
|
|
/* unsigned time_t works until year 2106 */
|
||
|
|
typedef __u32 time32_t;
|
||
|
|
|
||
|
|
struct cow_header_v1 {
|
||
|
|
__s32 magic;
|
||
|
|
__s32 version;
|
||
|
|
char backing_file[PATH_LEN_V1];
|
||
|
|
time32_t mtime;
|
||
|
|
__u64 size;
|
||
|
|
__s32 sectorsize;
|
||
|
|
} __attribute__((packed));
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
|
||
|
|
* case other systems have different values for MAXPATHLEN.
|
||
|
|
*
|
||
|
|
* The same must hold for V2 - we want file format compatibility, not anything
|
||
|
|
* else.
|
||
|
|
*/
|
||
|
|
#define PATH_LEN_V3 4096
|
||
|
|
#define PATH_LEN_V2 PATH_LEN_V3
|
||
|
|
|
||
|
|
struct cow_header_v2 {
|
||
|
|
__u32 magic;
|
||
|
|
__u32 version;
|
||
|
|
char backing_file[PATH_LEN_V2];
|
||
|
|
time32_t mtime;
|
||
|
|
__u64 size;
|
||
|
|
__s32 sectorsize;
|
||
|
|
} __attribute__((packed));
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Changes from V2 -
|
||
|
|
* PATH_LEN_V3 as described above
|
||
|
|
* Explicitly specify field bit lengths for systems with different
|
||
|
|
* lengths for the usual C types. Not sure whether char or
|
||
|
|
* time_t should be changed, this can be changed later without
|
||
|
|
* breaking compatibility
|
||
|
|
* Add alignment field so that different alignments can be used for the
|
||
|
|
* bitmap and data
|
||
|
|
* Add cow_format field to allow for the possibility of different ways
|
||
|
|
* of specifying the COW blocks. For now, the only value is 0,
|
||
|
|
* for the traditional COW bitmap.
|
||
|
|
* Move the backing_file field to the end of the header. This allows
|
||
|
|
* for the possibility of expanding it into the padding required
|
||
|
|
* by the bitmap alignment.
|
||
|
|
* The bitmap and data portions of the file will be aligned as specified
|
||
|
|
* by the alignment field. This is to allow COW files to be
|
||
|
|
* put on devices with restrictions on access alignments, such as
|
||
|
|
* /dev/raw, with a 512 byte alignment restriction. This also
|
||
|
|
* allows the data to be more aligned more strictly than on
|
||
|
|
* sector boundaries. This is needed for ubd-mmap, which needs
|
||
|
|
* the data to be page aligned.
|
||
|
|
* Fixed (finally!) the rounding bug
|
||
|
|
*/
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Until Dec2005, __attribute__((packed)) was left out from the below
|
||
|
|
* definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
|
||
|
|
* align size to 8-byte alignment. This shifted all fields above (no padding
|
||
|
|
* was present on 32-bit, no other padding was added).
|
||
|
|
*
|
||
|
|
* However, this _can be detected_: it means that cow_format (always 0 until
|
||
|
|
* now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
|
||
|
|
* impossible to find 4 zeros. -bb */
|
||
|
|
|
||
|
|
struct cow_header_v3 {
|
||
|
|
__u32 magic;
|
||
|
|
__u32 version;
|
||
|
|
__u32 mtime;
|
||
|
|
__u64 size;
|
||
|
|
__u32 sectorsize;
|
||
|
|
__u32 alignment;
|
||
|
|
__u32 cow_format;
|
||
|
|
char backing_file[PATH_LEN_V3];
|
||
|
|
} __attribute__((packed));
|
||
|
|
|
||
|
|
/* This is the broken layout used by some 64-bit binaries. */
|
||
|
|
struct cow_header_v3_broken {
|
||
|
|
__u32 magic;
|
||
|
|
__u32 version;
|
||
|
|
__s64 mtime;
|
||
|
|
__u64 size;
|
||
|
|
__u32 sectorsize;
|
||
|
|
__u32 alignment;
|
||
|
|
__u32 cow_format;
|
||
|
|
char backing_file[PATH_LEN_V3];
|
||
|
|
};
|
||
|
|
|
||
|
|
/* COW format definitions - for now, we have only the usual COW bitmap */
|
||
|
|
#define COW_BITMAP 0
|
||
|
|
|
||
|
|
union cow_header {
|
||
|
|
struct cow_header_v1 v1;
|
||
|
|
struct cow_header_v2 v2;
|
||
|
|
struct cow_header_v3 v3;
|
||
|
|
struct cow_header_v3_broken v3_b;
|
||
|
|
};
|
||
|
|
|
||
|
|
#define COW_MAGIC 0x4f4f4f4d /* MOOO */
|
||
|
|
#define COW_VERSION 3
|
||
|
|
|
||
|
|
#define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
|
||
|
|
#define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
|
||
|
|
|
||
|
|
void cow_sizes(int version, __u64 size, int sectorsize, int align,
|
||
|
|
int bitmap_offset, unsigned long *bitmap_len_out,
|
||
|
|
int *data_offset_out)
|
||
|
|
{
|
||
|
|
if (version < 3) {
|
||
|
|
*bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
|
||
|
|
|
||
|
|
*data_offset_out = bitmap_offset + *bitmap_len_out;
|
||
|
|
*data_offset_out = (*data_offset_out + sectorsize - 1) /
|
||
|
|
sectorsize;
|
||
|
|
*data_offset_out *= sectorsize;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
*bitmap_len_out = DIV_ROUND(size, sectorsize);
|
||
|
|
*bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
|
||
|
|
|
||
|
|
*data_offset_out = bitmap_offset + *bitmap_len_out;
|
||
|
|
*data_offset_out = ROUND_UP(*data_offset_out, align);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
static int absolutize(char *to, int size, char *from)
|
||
|
|
{
|
||
|
|
char save_cwd[256], *slash;
|
||
|
|
int remaining;
|
||
|
|
|
||
|
|
if (getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
|
||
|
|
cow_printf("absolutize : unable to get cwd - errno = %d\n",
|
||
|
|
errno);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
slash = strrchr(from, '/');
|
||
|
|
if (slash != NULL) {
|
||
|
|
*slash = '\0';
|
||
|
|
if (chdir(from)) {
|
||
|
|
*slash = '/';
|
||
|
|
cow_printf("absolutize : Can't cd to '%s' - "
|
||
|
|
"errno = %d\n", from, errno);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
*slash = '/';
|
||
|
|
if (getcwd(to, size) == NULL) {
|
||
|
|
cow_printf("absolutize : unable to get cwd of '%s' - "
|
||
|
|
"errno = %d\n", from, errno);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
remaining = size - strlen(to);
|
||
|
|
if (strlen(slash) + 1 > remaining) {
|
||
|
|
cow_printf("absolutize : unable to fit '%s' into %d "
|
||
|
|
"chars\n", from, size);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
strcat(to, slash);
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
if (strlen(save_cwd) + 1 + strlen(from) + 1 > size) {
|
||
|
|
cow_printf("absolutize : unable to fit '%s' into %d "
|
||
|
|
"chars\n", from, size);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
strcpy(to, save_cwd);
|
||
|
|
strcat(to, "/");
|
||
|
|
strcat(to, from);
|
||
|
|
}
|
||
|
|
if (chdir(save_cwd)) {
|
||
|
|
cow_printf("absolutize : Can't cd to '%s' - "
|
||
|
|
"errno = %d\n", save_cwd, errno);
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
int write_cow_header(char *cow_file, int fd, char *backing_file,
|
||
|
|
int sectorsize, int alignment, unsigned long long *size)
|
||
|
|
{
|
||
|
|
struct cow_header_v3 *header;
|
||
|
|
long long modtime;
|
||
|
|
int err;
|
||
|
|
|
||
|
|
err = cow_seek_file(fd, 0);
|
||
|
|
if (err < 0) {
|
||
|
|
cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
err = -ENOMEM;
|
||
|
|
header = cow_malloc(sizeof(*header));
|
||
|
|
if (header == NULL) {
|
||
|
|
cow_printf("write_cow_header - failed to allocate COW V3 "
|
||
|
|
"header\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
header->magic = htobe32(COW_MAGIC);
|
||
|
|
header->version = htobe32(COW_VERSION);
|
||
|
|
|
||
|
|
err = -EINVAL;
|
||
|
|
if (strlen(backing_file) > sizeof(header->backing_file) - 1) {
|
||
|
|
/* Below, %zd is for a size_t value */
|
||
|
|
cow_printf("Backing file name \"%s\" is too long - names are "
|
||
|
|
"limited to %zd characters\n", backing_file,
|
||
|
|
sizeof(header->backing_file) - 1);
|
||
|
|
goto out_free;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (absolutize(header->backing_file, sizeof(header->backing_file),
|
||
|
|
backing_file))
|
||
|
|
goto out_free;
|
||
|
|
|
||
|
|
err = os_file_modtime(header->backing_file, &modtime);
|
||
|
|
if (err < 0) {
|
||
|
|
cow_printf("write_cow_header - backing file '%s' mtime "
|
||
|
|
"request failed, err = %d\n", header->backing_file,
|
||
|
|
-err);
|
||
|
|
goto out_free;
|
||
|
|
}
|
||
|
|
|
||
|
|
err = cow_file_size(header->backing_file, size);
|
||
|
|
if (err < 0) {
|
||
|
|
cow_printf("write_cow_header - couldn't get size of "
|
||
|
|
"backing file '%s', err = %d\n",
|
||
|
|
header->backing_file, -err);
|
||
|
|
goto out_free;
|
||
|
|
}
|
||
|
|
|
||
|
|
header->mtime = htobe32(modtime);
|
||
|
|
header->size = htobe64(*size);
|
||
|
|
header->sectorsize = htobe32(sectorsize);
|
||
|
|
header->alignment = htobe32(alignment);
|
||
|
|
header->cow_format = COW_BITMAP;
|
||
|
|
|
||
|
|
err = cow_write_file(fd, header, sizeof(*header));
|
||
|
|
if (err != sizeof(*header)) {
|
||
|
|
cow_printf("write_cow_header - write of header to "
|
||
|
|
"new COW file '%s' failed, err = %d\n", cow_file,
|
||
|
|
-err);
|
||
|
|
goto out_free;
|
||
|
|
}
|
||
|
|
err = 0;
|
||
|
|
out_free:
|
||
|
|
cow_free(header);
|
||
|
|
out:
|
||
|
|
return err;
|
||
|
|
}
|
||
|
|
|
||
|
|
int file_reader(__u64 offset, char *buf, int len, void *arg)
|
||
|
|
{
|
||
|
|
int fd = *((int *) arg);
|
||
|
|
|
||
|
|
return pread(fd, buf, len, offset);
|
||
|
|
}
|
||
|
|
|
||
|
|
/* XXX Need to sanity-check the values read from the header */
|
||
|
|
|
||
|
|
int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
|
||
|
|
__u32 *version_out, char **backing_file_out,
|
||
|
|
long long *mtime_out, unsigned long long *size_out,
|
||
|
|
int *sectorsize_out, __u32 *align_out,
|
||
|
|
int *bitmap_offset_out)
|
||
|
|
{
|
||
|
|
union cow_header *header;
|
||
|
|
char *file;
|
||
|
|
int err, n;
|
||
|
|
unsigned long version, magic;
|
||
|
|
|
||
|
|
header = cow_malloc(sizeof(*header));
|
||
|
|
if (header == NULL) {
|
||
|
|
cow_printf("read_cow_header - Failed to allocate header\n");
|
||
|
|
return -ENOMEM;
|
||
|
|
}
|
||
|
|
err = -EINVAL;
|
||
|
|
n = (*reader)(0, (char *) header, sizeof(*header), arg);
|
||
|
|
if (n < offsetof(typeof(header->v1), backing_file)) {
|
||
|
|
cow_printf("read_cow_header - short header\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
magic = header->v1.magic;
|
||
|
|
if (magic == COW_MAGIC)
|
||
|
|
version = header->v1.version;
|
||
|
|
else if (magic == be32toh(COW_MAGIC))
|
||
|
|
version = be32toh(header->v1.version);
|
||
|
|
/* No error printed because the non-COW case comes through here */
|
||
|
|
else goto out;
|
||
|
|
|
||
|
|
*version_out = version;
|
||
|
|
|
||
|
|
if (version == 1) {
|
||
|
|
if (n < sizeof(header->v1)) {
|
||
|
|
cow_printf("read_cow_header - failed to read V1 "
|
||
|
|
"header\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
*mtime_out = header->v1.mtime;
|
||
|
|
*size_out = header->v1.size;
|
||
|
|
*sectorsize_out = header->v1.sectorsize;
|
||
|
|
*bitmap_offset_out = sizeof(header->v1);
|
||
|
|
*align_out = *sectorsize_out;
|
||
|
|
file = header->v1.backing_file;
|
||
|
|
}
|
||
|
|
else if (version == 2) {
|
||
|
|
if (n < sizeof(header->v2)) {
|
||
|
|
cow_printf("read_cow_header - failed to read V2 "
|
||
|
|
"header\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
*mtime_out = be32toh(header->v2.mtime);
|
||
|
|
*size_out = be64toh(header->v2.size);
|
||
|
|
*sectorsize_out = be32toh(header->v2.sectorsize);
|
||
|
|
*bitmap_offset_out = sizeof(header->v2);
|
||
|
|
*align_out = *sectorsize_out;
|
||
|
|
file = header->v2.backing_file;
|
||
|
|
}
|
||
|
|
/* This is very subtle - see above at union cow_header definition */
|
||
|
|
else if (version == 3 && (*((int*)header->v3.backing_file) != 0)) {
|
||
|
|
if (n < sizeof(header->v3)) {
|
||
|
|
cow_printf("read_cow_header - failed to read V3 "
|
||
|
|
"header\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
*mtime_out = be32toh(header->v3.mtime);
|
||
|
|
*size_out = be64toh(header->v3.size);
|
||
|
|
*sectorsize_out = be32toh(header->v3.sectorsize);
|
||
|
|
*align_out = be32toh(header->v3.alignment);
|
||
|
|
if (*align_out == 0) {
|
||
|
|
cow_printf("read_cow_header - invalid COW header, "
|
||
|
|
"align == 0\n");
|
||
|
|
}
|
||
|
|
*bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
|
||
|
|
file = header->v3.backing_file;
|
||
|
|
}
|
||
|
|
else if (version == 3) {
|
||
|
|
cow_printf("read_cow_header - broken V3 file with"
|
||
|
|
" 64-bit layout - recovering content.\n");
|
||
|
|
|
||
|
|
if (n < sizeof(header->v3_b)) {
|
||
|
|
cow_printf("read_cow_header - failed to read V3 "
|
||
|
|
"header\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* this was used until Dec2005 - 64bits are needed to represent
|
||
|
|
* 2106+. I.e. we can safely do this truncating cast.
|
||
|
|
*
|
||
|
|
* Additionally, we must use be32toh() instead of be64toh(), since
|
||
|
|
* the program used to use the former (tested - I got mtime
|
||
|
|
* mismatch "0 vs whatever").
|
||
|
|
*
|
||
|
|
* Ever heard about bug-to-bug-compatibility ? ;-) */
|
||
|
|
*mtime_out = (time32_t) be32toh(header->v3_b.mtime);
|
||
|
|
|
||
|
|
*size_out = be64toh(header->v3_b.size);
|
||
|
|
*sectorsize_out = be32toh(header->v3_b.sectorsize);
|
||
|
|
*align_out = be32toh(header->v3_b.alignment);
|
||
|
|
if (*align_out == 0) {
|
||
|
|
cow_printf("read_cow_header - invalid COW header, "
|
||
|
|
"align == 0\n");
|
||
|
|
}
|
||
|
|
*bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
|
||
|
|
file = header->v3_b.backing_file;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
cow_printf("read_cow_header - invalid COW version\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
err = -ENOMEM;
|
||
|
|
*backing_file_out = cow_strdup(file);
|
||
|
|
if (*backing_file_out == NULL) {
|
||
|
|
cow_printf("read_cow_header - failed to allocate backing "
|
||
|
|
"file\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
err = 0;
|
||
|
|
out:
|
||
|
|
cow_free(header);
|
||
|
|
return err;
|
||
|
|
}
|
||
|
|
|
||
|
|
int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
|
||
|
|
int alignment, int *bitmap_offset_out,
|
||
|
|
unsigned long *bitmap_len_out, int *data_offset_out)
|
||
|
|
{
|
||
|
|
unsigned long long size, offset;
|
||
|
|
char zero = 0;
|
||
|
|
int err;
|
||
|
|
|
||
|
|
err = write_cow_header(cow_file, fd, backing_file, sectorsize,
|
||
|
|
alignment, &size);
|
||
|
|
if (err)
|
||
|
|
goto out;
|
||
|
|
|
||
|
|
*bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
|
||
|
|
cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
|
||
|
|
bitmap_len_out, data_offset_out);
|
||
|
|
|
||
|
|
offset = *data_offset_out + size - sizeof(zero);
|
||
|
|
err = cow_seek_file(fd, offset);
|
||
|
|
if (err < 0) {
|
||
|
|
cow_printf("cow bitmap lseek failed : err = %d\n", -err);
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* does not really matter how much we write it is just to set EOF
|
||
|
|
* this also sets the entire COW bitmap
|
||
|
|
* to zero without having to allocate it
|
||
|
|
*/
|
||
|
|
err = cow_write_file(fd, &zero, sizeof(zero));
|
||
|
|
if (err != sizeof(zero)) {
|
||
|
|
cow_printf("Write of bitmap to new COW file '%s' failed, "
|
||
|
|
"err = %d\n", cow_file, -err);
|
||
|
|
if (err >= 0)
|
||
|
|
err = -EINVAL;
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
out:
|
||
|
|
return err;
|
||
|
|
}
|