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Diff VHD creation: change plat_data_space to store the number of bytes, not the number of sectors. This is counter to the VHD spec, but it's what Hyper-V, VPC, VirtualBox do.

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This commit is contained in:
Stephen McKinney
2020-11-07 02:09:35 -06:00
parent 4546b616f6
commit 4c6ffbd14b
1 changed files with 17 additions and 11 deletions
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28
src/minivhd_create.c
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@@ -92,7 +92,7 @@ static int mvhd_gen_par_loc(MVHDSparseHeader* header,
int rv = 0;
char* par_filename;
size_t par_fn_len;
char rel_path[MVHD_MAX_PATH_BYTES] = {0};
char rel_path[MVHD_MAX_PATH_BYTES] = {0};
char child_dir[MVHD_MAX_PATH_BYTES] = {0};
size_t child_dir_len;
if (strlen(child_path) < sizeof child_dir) {
@@ -110,18 +110,18 @@ static int mvhd_gen_par_loc(MVHDSparseHeader* header,
*err = MVHD_ERR_PATH_LEN;
rv = -1;
goto end;
}
}
/* We have our paths, now store the parent filename directly in the sparse header. */
int outlen = sizeof header->par_utf16_name;
int outlen = sizeof header->par_utf16_name;
int utf_ret;
utf_ret = UTF8ToUTF16BE((unsigned char*)header->par_utf16_name, &outlen, (const unsigned char*)par_filename, (int*)&par_fn_len);
utf_ret = UTF8ToUTF16BE((unsigned char*)header->par_utf16_name, &outlen, (const unsigned char*)par_filename, (int*)&par_fn_len);
if (utf_ret < 0) {
mvhd_set_encoding_err(utf_ret, (int*)err);
rv = -1;
goto end;
}
/* And encode the paths to UTF16-LE */
/* And encode the paths to UTF16-LE */
size_t par_path_len = strlen(par_path);
outlen = sizeof *w2ku_path_buff * MVHD_MAX_PATH_CHARS;
utf_ret = UTF8ToUTF16LE((unsigned char*)w2ku_path_buff, &outlen, (const unsigned char*)par_path, (int*)&par_path_len);
@@ -131,7 +131,7 @@ static int mvhd_gen_par_loc(MVHDSparseHeader* header,
goto end;
}
int w2ku_len = utf_ret;
outlen = sizeof *w2ru_path_buff * MVHD_MAX_PATH_CHARS;
outlen = sizeof *w2ru_path_buff * MVHD_MAX_PATH_CHARS;
utf_ret = UTF8ToUTF16LE((unsigned char*)w2ru_path_buff, &outlen, (const unsigned char*)rel_path, (int*)&rel_len);
if (utf_ret < 0) {
mvhd_set_encoding_err(utf_ret, (int*)err);
@@ -144,14 +144,20 @@ static int mvhd_gen_par_loc(MVHDSparseHeader* header,
* This is the information needed to find the paths saved elsewhere
* in the VHD image
*/
/* Note about the plat_data_space field: The VHD spec says this field stores the number of sectors needed to store the locator path.
* However, Hyper-V and VPC store the number of bytes, not the number of sectors, and will refuse to open VHDs which have the
* number of sectors in this field.
* See https://stackoverflow.com/questions/40760181/mistake-in-virtual-hard-disk-image-format-specification
*/
header->par_loc_entry[0].plat_code = MVHD_DIF_LOC_W2KU;
header->par_loc_entry[0].plat_data_len = (uint32_t)w2ku_len;
header->par_loc_entry[0].plat_data_offset = (uint64_t)start_offset;
header->par_loc_entry[0].plat_data_space = (header->par_loc_entry[0].plat_data_len / MVHD_SECTOR_SIZE) + 1;
header->par_loc_entry[0].plat_data_space = ((header->par_loc_entry[0].plat_data_len / MVHD_SECTOR_SIZE) + 1) * MVHD_SECTOR_SIZE;
header->par_loc_entry[1].plat_code = MVHD_DIF_LOC_W2RU;
header->par_loc_entry[1].plat_data_len = (uint32_t)w2ru_len;
header->par_loc_entry[1].plat_data_offset = (uint64_t)start_offset + ((uint64_t)header->par_loc_entry[0].plat_data_space * MVHD_SECTOR_SIZE);
header->par_loc_entry[1].plat_data_space = (header->par_loc_entry[1].plat_data_len / MVHD_SECTOR_SIZE) + 1;
header->par_loc_entry[1].plat_data_offset = (uint64_t)start_offset + ((uint64_t)header->par_loc_entry[0].plat_data_space);
header->par_loc_entry[1].plat_data_space = ((header->par_loc_entry[1].plat_data_len / MVHD_SECTOR_SIZE) + 1) * MVHD_SECTOR_SIZE;
goto end;
end:
@@ -357,7 +363,7 @@ static MVHDMeta* mvhd_create_sparse_diff(const char* path, const char* par_path,
/* Fill the space required for location data with zero */
uint8_t empty_sect[MVHD_SECTOR_SIZE] = {0};
for (int i = 0; i < 2; i++) {
for (uint32_t j = 0; j < vhdm->sparse.par_loc_entry[i].plat_data_space; j++) {
for (uint32_t j = 0; j < (vhdm->sparse.par_loc_entry[i].plat_data_space / MVHD_SECTOR_SIZE); j++) {
fwrite(empty_sect, sizeof empty_sect, 1, f);
}
}
@@ -367,7 +373,7 @@ static MVHDMeta* mvhd_create_sparse_diff(const char* path, const char* par_path,
mvhd_fseeko64(f, vhdm->sparse.par_loc_entry[1].plat_data_offset, SEEK_SET);
fwrite(w2ru_path_buff, vhdm->sparse.par_loc_entry[1].plat_data_len, 1, f);
/* and reset the file position to continue */
mvhd_fseeko64(f, vhdm->sparse.par_loc_entry[1].plat_data_offset + ((uint64_t)(vhdm->sparse.par_loc_entry[1].plat_data_space) * MVHD_SECTOR_SIZE), SEEK_SET);
mvhd_fseeko64(f, vhdm->sparse.par_loc_entry[1].plat_data_offset + vhdm->sparse.par_loc_entry[1].plat_data_space, SEEK_SET);
mvhd_write_empty_sectors(f, 5);
}
/* And finish with the footer */