Re: [PATCH v5 06/10] platform/x86/intel/ifs: Authenticate and copy to secured memory

Thomas Gleixner
2022-05-04T10:48:49Z

On Thu, Apr 28 2022 at 08:38, Tony Luck wrote:
> The IFS image contains hashes that will be used to authenticate the ifs
> test chunks. First, use WRMSR to copy the hashes and enumerate the number
> of test chunks, chunk size and the maximum number of cores that can run
> scan test simultaneously.
>
> Next, use WRMSR to authenticate each and every scan test chunk which is
> also stored in the IFS image. The CPU will check if the test chunks match

s/also// ?

> +
> +/* MSR_CHUNKS_AUTH_STATUS bit fields */
> +union ifs_chunks_auth_status {
> + u64 data;
> + struct {
> + u32 valid_chunks :8;
> + u32 total_chunks :8;
> + u32 rsvd1 :16;
> + u32 error_code :8;
> + u32 rsvd2 :24;
> + };
> +};
> +
> /**
> * struct ifs_data - attributes related to intel IFS driver
> * @integrity_cap_bit - MSR_INTEGRITY_CAPS bit enumerating this test
> + * @loaded_version: stores the currently loaded ifs image version.
> + * @loaded: If a valid test binary has been loaded into the memory
> + * @loading_error: Error occurred on another CPU while loading image
> + * @valid_chunks: number of chunks which could be validated.
> */
> struct ifs_data {
> int integrity_cap_bit;
> + int loaded_version;
> + bool loaded;
> + bool loading_error;
> + int valid_chunks;

The above struct is nicely tabular. Can we have that here too please?

> +/*
> + * IFS requires scan chunks authenticated per each socket in the platform.
> + * Once the test chunk is authenticated, it is automatically copied to secured memory
> + * and proceed the authentication for the next chunk.
> + */
> +static int scan_chunks_sanity_check(struct device *dev)
> +{
> + int metadata_size, curr_pkg, cpu, ret = -ENOMEM;
> + struct ifs_data *ifsd = ifs_get_data(dev);
> + bool *package_authenticated;
> + char *test_ptr;
> +
> + package_authenticated = kcalloc(topology_max_packages(), sizeof(bool), GFP_KERNEL);
> + if (!package_authenticated)
> + return ret;
> +
> + metadata_size = ifs_header_ptr->metadata_size;
> +
> + /* Spec says that if the Meta Data Size = 0 then it should be treated as 2000 */
> + if (metadata_size == 0)
> + metadata_size = 2000;
> +
> + /* Scan chunk start must be 256 byte aligned */
> + if ((metadata_size + IFS_HEADER_SIZE) % 256) {
> + dev_err(dev, "Scan pattern offset within the binary is not 256 byte aligned\n");
> + return -EINVAL;
> + }
> +
> + test_ptr = (char *)ifs_header_ptr + IFS_HEADER_SIZE + metadata_size;
> + ifsd->loading_error = false;
> +
> + ifs_test_image_ptr = (u64)test_ptr;
> + ifsd->loaded_version = ifs_header_ptr->blob_revision;
> +
> + /* copy the scan hash and authenticate per package */
> + cpus_read_lock();
> + for_each_online_cpu(cpu) {
> + curr_pkg = topology_physical_package_id(cpu);
> + if (package_authenticated[curr_pkg])
> + continue;
> + package_authenticated[curr_pkg] = 1;

Setting the authenticated indicator _before_ actually doing the
authentication is just wrong. It does not matter in this case, but it's
still making my eyes bleed.

> + ret = smp_call_function_single(cpu, copy_hashes_authenticate_chunks,
> + dev, 1);

Why has this to be a smp function call? Just because it's conveniant?
This is nothing urgent and no hotpath, so this really can use
queue_work_on().

Thanks,

tglx