[libvirt] [PATCH 4/4] Support for probing qed image metadata

Implement getBackingStore() for QED images. The header format is defined in the QED spec: http://wiki.qemu.org/Features/QED . Signed-off-by: Adam Litke <agl(a)us.ibm.com&gt; Acked-by: Eric Blake <eblake(a)redhat.com&gt; Cc: Stefan Hajnoczi <stefan.hajnoczi(a)uk.ibm.com&gt; Cc: Anthony Liguori <aliguori(a)linux.vnet.ibm.com&gt; --- src/util/storage_file.c | 78 +++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 76 insertions(+), 2 deletions(-) diff --git a/src/util/storage_file.c b/src/util/storage_file.c index 89c2cbe..9d97066 100644 --- a/src/util/storage_file.c +++ b/src/util/storage_file.c @@ -89,6 +89,8 @@ static int qcow2GetBackingStore(char **, int *, const unsigned char *, size_t); static int vmdk4GetBackingStore(char **, int *, const unsigned char *, size_t); +static int +qedGetBackingStore(char **, int *, const unsigned char *, size_t); #define QCOWX_HDR_VERSION (4) #define QCOWX_HDR_BACKING_FILE_OFFSET (QCOWX_HDR_VERSION+4) @@ -104,7 +106,12 @@ static int vmdk4GetBackingStore(char **, int *, #define QCOW2_HDR_EXTENSION_END 0 #define QCOW2_HDR_EXTENSION_BACKING_FORMAT 0xE2792ACA -#define QED_HDR_IMAGE_SIZE (4+4+4+4+8+8+8) +#define QED_HDR_FEATURES_OFFSET (4+4+4+4) +#define QED_HDR_IMAGE_SIZE (QED_HDR_FEATURES_OFFSET+8+8+8+8) +#define QED_HDR_BACKING_FILE_OFFSET (QED_HDR_IMAGE_SIZE+8) +#define QED_HDR_BACKING_FILE_SIZE (QED_HDR_BACKING_FILE_OFFSET+4) +#define QED_F_BACKING_FILE 0x01 +#define QED_F_BACKING_FORMAT_NO_PROBE 0x04 /* VMDK needs at least this to find backing store, * other formats need less */ @@ -157,7 +164,7 @@ static struct FileTypeInfo const fileTypeInfo[] = { /* http://wiki.qemu.org/Features/QED */ "QED\0", NULL, LV_LITTLE_ENDIAN, -1, -1, - QED_HDR_IMAGE_SIZE, 8, 1, -1, NULL, + QED_HDR_IMAGE_SIZE, 8, 1, -1, qedGetBackingStore, }, [VIR_STORAGE_FILE_VMDK] = { "KDMV", NULL, @@ -417,6 +424,73 @@ cleanup: return ret; } +static unsigned long +qedGetHeaderUL(const unsigned char *loc) +{ + return ( ((unsigned long)loc[3] << 24) + | ((unsigned long)loc[2] << 16) + | ((unsigned long)loc[1] << 8) + | ((unsigned long)loc[0] << 0)); +} + +static unsigned long long +qedGetHeaderULL(const unsigned char *loc) +{ + return ( ((unsigned long)loc[7] << 56) + | ((unsigned long)loc[6] << 48) + | ((unsigned long)loc[5] << 40) + | ((unsigned long)loc[4] << 32) + | ((unsigned long)loc[3] << 24) + | ((unsigned long)loc[2] << 16) + | ((unsigned long)loc[1] << 8) + | ((unsigned long)loc[0] << 0)); +} + +static int +qedGetBackingStore(char **res, + int *format, + const unsigned char *buf, + size_t buf_size) +{ + unsigned long long flags; + unsigned long offset, size; + + *res = NULL; + /* Check if this image has a backing file */ + if (buf_size < QED_HDR_FEATURES_OFFSET+8) + return BACKING_STORE_INVALID; + flags = qedGetHeaderULL(buf + QED_HDR_FEATURES_OFFSET); + if (!(flags & QED_F_BACKING_FILE)) + return BACKING_STORE_OK; + + /* Parse the backing file */ + if (buf_size < QED_HDR_BACKING_FILE_OFFSET+8) + return BACKING_STORE_INVALID; + offset = qedGetHeaderUL(buf + QED_HDR_BACKING_FILE_OFFSET); + if (offset > buf_size) + return BACKING_STORE_INVALID; + size = qedGetHeaderUL(buf + QED_HDR_BACKING_FILE_SIZE); + if (size == 0) + return BACKING_STORE_OK; + if (offset + size > buf_size || offset + size < offset) + return BACKING_STORE_INVALID; + if (VIR_ALLOC_N(*res, size + 1) < 0) { + virReportOOMError(); + return BACKING_STORE_ERROR; + } + memcpy(*res, buf + offset, size); + (*res)[size] = '\0'; + + if (format) { + if (flags & QED_F_BACKING_FORMAT_NO_PROBE) + *format = VIR_STORAGE_FILE_RAW; + else + *format = VIR_STORAGE_FILE_AUTO_SAFE; + } + + return BACKING_STORE_OK; +} + /** * Return an absolute path corresponding to PATH, which is absolute or relative * to the directory containing BASE_FILE, or NULL on error -- 1.7.3.2.164.g6f10c