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[PULL 5/6] target/i386/sev: Perform padding calculations at compile-time
From: |
Daniel P . Berrangé |
Subject: |
[PULL 5/6] target/i386/sev: Perform padding calculations at compile-time |
Date: |
Thu, 18 Nov 2021 13:35:31 +0000 |
From: Dov Murik <dovmurik@linux.ibm.com>
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 <dovmurik@linux.ibm.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Daniel P. Berrangé <berrange@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 d11b512361..4fd258a570 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -110,9 +110,19 @@ 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;
@@ -1216,12 +1226,12 @@ 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);
/*
* Only add the kernel hashes if the sev-guest configuration explicitly
@@ -1237,7 +1247,7 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext
*ctx, Error **errp)
return false;
}
area = (SevHashTableDescriptor *)data;
- if (!area->base || area->size < aligned_len) {
+ if (!area->base || area->size < sizeof(PaddedSevHashTable)) {
error_setg(errp, "SEV: guest firmware hashes table area is invalid "
"(base=0x%x size=0x%x)", area->base, area->size);
return false;
@@ -1282,7 +1292,8 @@ 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);
@@ -1299,13 +1310,10 @@ 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;
}
--
2.31.1
- [PULL 0/6 for-6.2] AMD SEV patches, Daniel P . Berrangé, 2021/11/18
- [PULL 1/6] qapi/qom, target/i386: sev-guest: Introduce kernel-hashes=on|off option, Daniel P . Berrangé, 2021/11/18
- [PULL 2/6] target/i386/sev: Add kernel hashes only if sev-guest.kernel-hashes=on, Daniel P . Berrangé, 2021/11/18
- [PULL 4/6] target/i386/sev: Fail when invalid hashes table area detected, Daniel P . Berrangé, 2021/11/18
- [PULL 3/6] target/i386/sev: Rephrase error message when no hashes table in guest firmware, Daniel P . Berrangé, 2021/11/18
- [PULL 5/6] target/i386/sev: Perform padding calculations at compile-time,
Daniel P . Berrangé <=
- [PULL 6/6] target/i386/sev: Replace qemu_map_ram_ptr with address_space_map, Daniel P . Berrangé, 2021/11/18
- Re: [PULL 0/6 for-6.2] AMD SEV patches, Richard Henderson, 2021/11/18