From: Dov Murik <dovmurik@linux.ibm.com>
To: qemu-devel@nongnu.org
Cc: "Tom Lendacky" <thomas.lendacky@amd.com>,
"Ashish Kalra" <ashish.kalra@amd.com>,
"Brijesh Singh" <brijesh.singh@amd.com>,
"Eduardo Habkost" <ehabkost@redhat.com>,
"James Bottomley" <jejb@linux.ibm.com>,
"Marcelo Tosatti" <mtosatti@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Dov Murik" <dovmurik@linux.ibm.com>,
"Tobin Feldman-Fitzthum" <tobin@linux.ibm.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: [PATCH 3/3] sev/i386: Perform padding calculations at compile-time
Date: Mon, 1 Nov 2021 10:21:36 +0000 [thread overview]
Message-ID: <20211101102136.1706421-4-dovmurik@linux.ibm.com> (raw)
In-Reply-To: <20211101102136.1706421-1-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>
---
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
next prev parent reply other threads:[~2021-11-01 10:23 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 10:21 [PATCH 0/3] SEV: fixes for -kernel launch with incompatible OVMF Dov Murik
2021-11-01 10:21 ` [PATCH 1/3] sev/i386: Allow launching with -kernel if no OVMF hashes table found Dov Murik
2021-11-01 14:25 ` Tom Lendacky
2021-11-01 17:56 ` Dov Murik
2021-11-03 16:02 ` Daniel P. Berrangé
2021-11-04 18:18 ` Dr. David Alan Gilbert
2021-11-04 18:22 ` Daniel P. Berrangé
2021-11-05 7:41 ` Dov Murik
2021-11-01 10:21 ` [PATCH 2/3] sev/i386: Warn if using -kernel with invalid OVMF hashes table area Dov Murik
2021-11-02 12:36 ` Dr. David Alan Gilbert
2021-11-02 12:56 ` Dov Murik
2021-11-02 18:38 ` Dr. David Alan Gilbert
2021-11-02 19:00 ` Philippe Mathieu-Daudé
2021-11-03 16:07 ` Daniel P. Berrangé
2021-11-05 7:52 ` Dov Murik
2021-11-01 10:21 ` Dov Murik [this message]
2021-11-02 11:36 ` [PATCH 3/3] sev/i386: Perform padding calculations at compile-time Dr. David Alan Gilbert
2021-11-02 11:50 ` Dov Murik
2021-11-03 14:49 ` Philippe Mathieu-Daudé
2021-11-02 10:52 ` [PATCH 0/3] SEV: fixes for -kernel launch with incompatible OVMF Brijesh Singh
2021-11-02 13:22 ` Dov Murik
2021-11-02 14:48 ` Brijesh Singh
2021-11-03 14:08 ` Dr. David Alan Gilbert
2021-11-03 15:44 ` Brijesh Singh
2021-11-05 7:38 ` Dov Murik
2021-11-05 18:32 ` Dov Murik
2021-11-08 21:22 ` Brijesh Singh
2021-11-09 7:34 ` Dov Murik
2021-11-03 16:10 ` Daniel P. Berrangé
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