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

[Dave Hansen <dave.hansen@intel.com>]

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.