Re: [libvirt] [PATCH 2/2] 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 .

+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 (size + 1 == 0) + 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 = virStorageFileFormatTypeFromString("raw"); + else + *format = VIR_STORAGE_FILE_AUTO; + } + + return BACKING_STORE_OK; +}