Re: [PATCH v2 10/14] platform/x86/intel/ifs: Add metadata validation

Dave Hansen
2022-11-11T18:49:01Z

On 11/11/22 10:39, Borislav Petkov wrote:
>> +struct meta_data {
>> + unsigned int meta_type; // metadata type
>> + unsigned int meta_size; // size of this entire struct including hdrs.
>> + unsigned int test_type; // IFS test type
>> + unsigned int fusa_info; // Fusa info
>> + unsigned int total_images; // Total number of images
>> + unsigned int current_image; // Current Image #
>> + unsigned int total_chunks; // Total number of chunks in this image
>> + unsigned int starting_chunk; // Starting chunk number in this image
>> + unsigned int size_per_chunk; // size of each chunk
>> + unsigned int chunks_per_stride; // number of chunks in a stride
>> + unsigned int reserved[54]; // Align to 256 bytes for chunk alignment.
> That looks weird.
>
> __packed and __aligned doesn't work?

... and don't we try to use fixed-size typed in hardware structures,
like u32?

There are also much nicer ways to do this:

union meta_data {
struct {
u32 meta_type; // metadata type
u32 meta_size; // size of ...
};
u8 padding[IFS_CHUNK_ALIGNMENT];
}

That doesn't have any magic linkage between the magic "54" (times 4) and
IFS_CHUNK_ALIGNMENT. It makes the compiler do the hard work for you.

Voila, you have a union that's always IFS_CHUNK_ALIGNMENT in size, No
magic 54's necessary.