diff options
Diffstat (limited to 'kernel/arch/um/drivers/cow_user.c')
| -rw-r--r-- | kernel/arch/um/drivers/cow_user.c | 443 |
1 files changed, 443 insertions, 0 deletions
diff --git a/kernel/arch/um/drivers/cow_user.c b/kernel/arch/um/drivers/cow_user.c new file mode 100644 index 000000000..0ee9cc6cc --- /dev/null +++ b/kernel/arch/um/drivers/cow_user.c @@ -0,0 +1,443 @@ +/* + * Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com) + * Licensed under the GPL + */ + +/* + * _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 + +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; + unsigned 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, + time_t *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 + * 2038+. 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; +} |