From patchwork Wed Mar 6 14:48:33 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Cody X-Patchwork-Id: 225518 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id BC5052C02C1 for ; Thu, 7 Mar 2013 01:51:22 +1100 (EST) Received: from localhost ([::1]:45529 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDFgf-0006zb-2U for incoming@patchwork.ozlabs.org; Wed, 06 Mar 2013 09:51:21 -0500 Received: from eggs.gnu.org ([208.118.235.92]:54165) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDFe8-0003LB-Jg for qemu-devel@nongnu.org; Wed, 06 Mar 2013 09:48:51 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UDFe1-0002g8-Hb for qemu-devel@nongnu.org; Wed, 06 Mar 2013 09:48:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:19488) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UDFe1-0002g3-Ag for qemu-devel@nongnu.org; Wed, 06 Mar 2013 09:48:37 -0500 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r26EmaIf024131 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 6 Mar 2013 09:48:36 -0500 Received: from localhost (ovpn-112-42.phx2.redhat.com [10.3.112.42]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r26EmYfs005524 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 6 Mar 2013 09:48:35 -0500 From: Jeff Cody To: qemu-devel@nongnu.org Date: Wed, 6 Mar 2013 09:48:33 -0500 Message-Id: In-Reply-To: References: X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, sw@weilnetz.de, stefanha@redhat.com Subject: [Qemu-devel] [PATCH 6/7] block: add header update capability for VHDX images. X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org This adds the ability to update the headers in a VHDX image, including generating a new MS-compatible GUID, and checksum. Signed-off-by: Jeff Cody --- block/vhdx.c | 165 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 163 insertions(+), 2 deletions(-) diff --git a/block/vhdx.c b/block/vhdx.c index 97775d2..13d1e7f 100644 --- a/block/vhdx.c +++ b/block/vhdx.c @@ -27,6 +27,11 @@ le16_to_cpus(&(guid)->data2); \ le16_to_cpus(&(guid)->data3); } while (0) +#define cpu_to_leguids(guid) do { \ + cpu_to_le32s(&(guid)->data1); \ + cpu_to_le16s(&(guid)->data2); \ + cpu_to_le16s(&(guid)->data3); } while (0) + /* Several metadata and region table data entries are identified by * guids in a MS-specific GUID format. */ @@ -160,11 +165,35 @@ typedef struct BDRVVHDXState { vhdx_bat_entry *bat; uint64_t bat_offset; + ms_guid session_guid; + + vhdx_parent_locator_header parent_header; vhdx_parent_locator_entry *parent_entries; } BDRVVHDXState; +/* Calculates new checksum. + * + * Zero is substituted during crc calculation for the original crc field + * crc_offset: byte offset in buf of the buffer crc + * buf: buffer pointer + * size: size of buffer (must be > crc_offset+4) + */ +static uint32_t vhdx_update_checksum(uint8_t *buf, size_t size, int crc_offset) +{ + uint32_t crc; + + assert(buf != NULL); + assert(size > (crc_offset+4)); + + memset(buf+crc_offset, 0, sizeof(crc)); + crc = crc32c(0xffffffff, buf, size); + memcpy(buf+crc_offset, &crc, sizeof(crc)); + + return crc; +} + /* Validates the checksum of the buffer, with an in-place CRC. * * Zero is substituted during crc calculation for the original crc field, @@ -198,6 +227,33 @@ static bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset) } /* + * This generates a UUID that is compliant with the MS GUIDs used + * in the VHDX spec (and elsewhere). + * + * We can do this with uuid_generate if uuid.h is present, + * however not all systems have uuid and the generation is + * pretty straightforward for the DCE + random usage case + * + */ +static void vhdx_guid_generate(ms_guid *guid) +{ + assert(guid != NULL); + + int i; + + guid->data1 = g_random_int(); + guid->data2 = g_random_int_range(0, 0xffff); + guid->data3 = g_random_int_range(0, 0x0fff); + guid->data3 |= 0x4000; /* denotes random algorithm */ + + guid->data4[0] = g_random_int_range(0, 0x3f); + guid->data4[0] |= 0x80; /* denotes DCE type */ + for (i = 1; i < sizeof(guid->data4); i++) { + guid->data4[i] = g_random_int_range(0, 0xff); + } +} + +/* * Per the MS VHDX Specification, for every VHDX file: * - The header section is fixed size - 1 MB * - The header section is always the first "object" @@ -236,6 +292,107 @@ static void vhdx_header_le_import(vhdx_header *h) le64_to_cpus(&h->log_offset); } +/* All VHDX structures on disk are little endian */ +static void vhdx_header_le_export(vhdx_header *orig_h, vhdx_header *new_h) +{ + assert(orig_h != NULL); + assert(new_h != NULL); + + new_h->signature = cpu_to_le32(orig_h->signature); + new_h->checksum = cpu_to_le32(orig_h->checksum); + new_h->sequence_number = cpu_to_le64(orig_h->sequence_number); + + memcpy(&new_h->file_write_guid, &orig_h->file_write_guid, sizeof(ms_guid)); + memcpy(&new_h->data_write_guid, &orig_h->data_write_guid, sizeof(ms_guid)); + memcpy(&new_h->log_guid, &orig_h->log_guid, sizeof(ms_guid)); + + cpu_to_leguids(&new_h->file_write_guid); + cpu_to_leguids(&new_h->data_write_guid); + cpu_to_leguids(&new_h->log_guid); + + new_h->log_version = cpu_to_le16(orig_h->log_version); + new_h->version = cpu_to_le16(orig_h->version); + new_h->log_length = cpu_to_le32(orig_h->log_length); + new_h->log_offset = cpu_to_le64(orig_h->log_offset); +} + +/* Update the VHDX headers + * + * This follows the VHDX spec procedures for header updates. + * + * - non-current header is updated with largest sequence number + */ +static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s, bool rw) +{ + int ret = 0; + int hdr_idx = 0; + uint64_t header_offset = VHDX_HEADER1_OFFSET; + + vhdx_header *active_header; + vhdx_header *inactive_header; + vhdx_header header_le; + uint8_t *buffer; + + /* operate on the non-current header */ + if (s->curr_header == 0) { + hdr_idx = 1; + header_offset = VHDX_HEADER2_OFFSET; + } + + active_header = s->headers[s->curr_header]; + inactive_header = s->headers[hdr_idx]; + + inactive_header->sequence_number = active_header->sequence_number + 1; + + /* a new file guid must be generate before any file write, including + * headers */ + memcpy(&inactive_header->file_write_guid, &s->session_guid, + sizeof(ms_guid)); + + /* a new data guid only needs to be generate before any guest-visisble + * writes, so update it if the image is opened r/w. */ + if (rw) { + vhdx_guid_generate(&inactive_header->data_write_guid); + } + + /* the header checksum is not over just the packed size of vhdx_header, + * but rather over the entire 'reserved' range for the header, which is + * 4KB (VHDX_HEADER_SIZE). */ + + buffer = g_malloc(VHDX_HEADER_SIZE); + /* we can't assume the extra reserved bytes are 0 */ + ret = bdrv_pread(bs->file, header_offset, buffer, VHDX_HEADER_SIZE); + if (ret < 0) { + goto fail; + } + /* overwrite the actual vhdx_header portion */ + memcpy(buffer, inactive_header, sizeof(vhdx_header)); + inactive_header->checksum = vhdx_update_checksum(buffer, + VHDX_HEADER_SIZE, 4); + vhdx_header_le_export(inactive_header, &header_le); + bdrv_pwrite_sync(bs->file, header_offset, &header_le, sizeof(vhdx_header)); + s->curr_header = hdr_idx; + +fail: + g_free(buffer); + return ret; +} + +/* + * The VHDX spec calls for header updates to be performed twice, so that both + * the current and non-current header have valid info + */ +static int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s, bool rw) +{ + int ret; + + ret = vhdx_update_header(bs, s, rw); + if (ret < 0) { + return ret; + } + ret = vhdx_update_header(bs, s, rw); + return ret; +} /* opens the specified header block from the VHDX file header section */ static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s) @@ -628,6 +785,11 @@ static int vhdx_open(BlockDriverState *bs, int flags) qemu_co_mutex_init(&s->lock); + /* This is used for any header updates, for the file_write_guid. + * The spec dictates that a new value should be used for the first + * header update */ + vhdx_guid_generate(&s->session_guid); + ret = vhdx_parse_header(bs, s); if (ret) { goto fail; @@ -664,8 +826,7 @@ static int vhdx_open(BlockDriverState *bs, int flags) } if (flags & BDRV_O_RDWR) { - ret = -ENOTSUP; - goto fail; + vhdx_update_headers(bs, s, false); } /* TODO: differencing files, write */