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