On 02/16/2017 03:43 AM, Igor Mammedov wrote:
>> +++ b/hw/acpi/bios-linker-loader.c
>> @@ -78,6 +78,21 @@ struct BiosLinkerLoaderEntry {
>> uint32_t length;
>> } cksum;
>>
>> + /*
>> + * COMMAND_WRITE_POINTER - write the fw_cfg file (originating from
>> + * @dest_file) at @wr_pointer.offset, by adding a pointer to
>> + * @src_offset within the table originating from @src_file.
>> + * 1,2,4 or 8 byte unsigned addition is used depending on
>> + * @wr_pointer.size.
>> + */
>> + struct {
>> + char dest_file[BIOS_LINKER_LOADER_FILESZ];
>> + char src_file[BIOS_LINKER_LOADER_FILESZ];
>> + uint32_t dst_offset;
>> + uint32_t src_offset;
>> + uint8_t size;
>> + } wr_pointer;
>> +
>> /* padding */
>> char pad[124];
> Shouldn't padding be reduced by 4 bytes to keep
> sizeof(BiosLinkerLoaderEntry) the same as before patch,
> so that old bios would be able to skip this unknown command
> and read the next at the right offset?No, because you are in the middle of a union rather than a struct (the outer BiosLinkerLoaderEntry struct size is determined by the largest member of the union, which is 'char pad[124]'; the new wr_pointer addition to the union does not change the size of the union). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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