* Dov Murik (dovmu...@linux.ibm.com) wrote:
> In sev_add_kernel_loader_hashes, the sizes of structs are known at
> compile-time, so calculate needed padding at compile-time.
>
> No functional change intended.
>
> Signed-off-by: Dov Murik <dovmu...@linux.ibm.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> target/i386/sev.c | 28 ++++++++++++++++++----------
> 1 file changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index a20ddb545e..c09de9c6f0 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -109,9 +109,19 @@ typedef struct QEMU_PACKED SevHashTable {
> SevHashTableEntry cmdline;
> SevHashTableEntry initrd;
> SevHashTableEntry kernel;
> - uint8_t padding[];
> } SevHashTable;
>
> +/*
> + * Data encrypted by sev_encrypt_flash() must be padded to a multiple of
> + * 16 bytes.
> + */
> +typedef struct QEMU_PACKED PaddedSevHashTable {
> + SevHashTable ht;
> + uint8_t padding[ROUND_UP(sizeof(SevHashTable), 16) -
> sizeof(SevHashTable)];
> +} PaddedSevHashTable;
> +
> +QEMU_BUILD_BUG_ON(sizeof(PaddedSevHashTable) % 16 != 0);
> +
> static SevGuestState *sev_guest;
> static Error *sev_mig_blocker;
>
> @@ -1196,19 +1206,19 @@ bool
> sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
> uint8_t *data;
> SevHashTableDescriptor *area;
> SevHashTable *ht;
> + PaddedSevHashTable *padded_ht;
> uint8_t cmdline_hash[HASH_SIZE];
> uint8_t initrd_hash[HASH_SIZE];
> uint8_t kernel_hash[HASH_SIZE];
> uint8_t *hashp;
> size_t hash_len = HASH_SIZE;
> - int aligned_len = ROUND_UP(sizeof(SevHashTable), 16);
>
> if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
> warn_report("SEV: kernel specified but OVMF has no hash table guid");
> return false;
> }
> area = (SevHashTableDescriptor *)data;
> - if (!area->base || area->size < aligned_len) {
> + if (!area->base || area->size < sizeof(PaddedSevHashTable)) {
> warn_report("SEV: OVMF's hashes table area is invalid (base=0x%x
> size=0x%x)",
> area->base, area->size);
> return false;
> @@ -1253,7 +1263,8 @@ bool
> sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
> * Populate the hashes table in the guest's memory at the OVMF-designated
> * area for the SEV hashes table
> */
> - ht = qemu_map_ram_ptr(NULL, area->base);
> + padded_ht = qemu_map_ram_ptr(NULL, area->base);
> + ht = &padded_ht->ht;
>
> ht->guid = sev_hash_table_header_guid;
> ht->len = sizeof(*ht);
> @@ -1270,13 +1281,10 @@ bool
> sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
> ht->kernel.len = sizeof(ht->kernel);
> memcpy(ht->kernel.hash, kernel_hash, sizeof(ht->kernel.hash));
>
> - /* When calling sev_encrypt_flash, the length has to be 16 byte aligned
> */
> - if (aligned_len != ht->len) {
> - /* zero the excess data so the measurement can be reliably
> calculated */
> - memset(ht->padding, 0, aligned_len - ht->len);
> - }
> + /* zero the excess data so the measurement can be reliably calculated */
> + memset(padded_ht->padding, 0, sizeof(padded_ht->padding));
>
> - if (sev_encrypt_flash((uint8_t *)ht, aligned_len, errp) < 0) {
> + if (sev_encrypt_flash((uint8_t *)padded_ht, sizeof(*padded_ht), errp) <
> 0) {
> return false;
> }
>
> --
> 2.25.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
