drivers/smmstore: Implement SMMSTORE version 2

SMMSTORE version 2 is a complete redesign of the current driver. It is
not backwards-compatible with version 1, and only one version can be
used at a time.

Key features:
* Uses a fixed communication buffer instead of writing to arbitrary
  memory addresses provided by untrusted ring0 code.
* Gives the caller full control over the used data format.
* Splits the store into smaller chunks to allow fault tolerant updates.
* Doesn't provide feedback about the actual read/written bytes, just
  returns error or success in registers.
* Returns an error if the requested operation would overflow the
  communication buffer.

Separate the SMMSTORE into 64 KiB blocks that can individually be
read/written/erased. To be used by payloads that implement a
FaultTolerant Variable store like TianoCore.

The implementation has been tested against EDK2 master.

An example EDK2 implementation can be found here:
https://github.com/9elements/edk2-1/commit/eb1127744a3a5d5c8ac4e8eb76f07e79c736dbe2

Change-Id: I25e49d184135710f3e6dd1ad3bed95de950fe057
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Christian Walter <christian.walter@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40520
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>

1 files changed, 90 insertions, 4 deletions

diff --git a/src/include/smmstore.h b/src/include/smmstore.h
index ff0b72001a..2c37ca39b9 100644
--- a/src/include/smmstore.h
+++ b/src/include/smmstore.h
@@ -10,10 +10,18 @@
 #define SMMSTORE_RET_FAILURE 1
 #define SMMSTORE_RET_UNSUPPORTED 2
 
+/* Version 1 */
 #define SMMSTORE_CMD_CLEAR 1
 #define SMMSTORE_CMD_READ 2
 #define SMMSTORE_CMD_APPEND 3
 
+/* Version 2 */
+#define SMMSTORE_CMD_INIT 4
+#define SMMSTORE_CMD_RAW_READ 5
+#define SMMSTORE_CMD_RAW_WRITE 6
+#define SMMSTORE_CMD_RAW_CLEAR 7
+
+/* Version 1 */
 struct smmstore_params_read {
 	void *buf;
 	ssize_t bufsize;
@@ -26,12 +34,90 @@ struct smmstore_params_append {
 	size_t valsize;
 };
 
-/* SMM responder */
+/* Version 2 */
+/*
+ * The Version 2 protocol separates the SMMSTORE into 64KiB blocks, each
+ * of which can be read/written/cleared in an independent manner. The
+ * data format isn't specified. See documentation page for more details.
+ */
+
+#define SMM_BLOCK_SIZE (64 * KiB)
+
+/*
+ * Sets the communication buffer to use for read and write operations.
+ */
+struct smmstore_params_init {
+	uint32_t com_buffer;
+	uint32_t com_buffer_size;
+} __packed;
+
+/*
+ * Returns the number of blocks the SMMSTORE supports and their size.
+ * For EDK2 this should be at least two blocks with 64 KiB each.
+ * The mmap_addr is set the memory mapped physical address of the SMMSTORE.
+ */
+struct smmstore_params_info {
+	uint32_t num_blocks;
+	uint32_t block_size;
+	uint32_t mmap_addr;
+} __packed;
+
+/*
+ * Reads a chunk of raw data with size @bufsize from the block specified by
+ * @block_id starting at @bufoffset.
+ * The read data is placed in memory pointed to by @buf.
+ *
+ * @block_id must be less than num_blocks
+ * @bufoffset + @bufsize must be less than block_size
+ */
+struct smmstore_params_raw_write {
+	uint32_t bufsize;
+	uint32_t bufoffset;
+	uint32_t block_id;
+} __packed;
+
+/*
+ * Writes a chunk of raw data with size @bufsize to the block specified by
+ * @block_id starting at @bufoffset.
+ *
+ * @block_id must be less than num_blocks
+ * @bufoffset + @bufsize must be less than block_size
+ */
+struct smmstore_params_raw_read {
+	uint32_t bufsize;
+	uint32_t bufoffset;
+	uint32_t block_id;
+} __packed;
+
+/*
+ * Erases the specified block.
+ *
+ * @block_id must be less than num_blocks
+ */
+struct smmstore_params_raw_clear {
+	uint32_t block_id;
+} __packed;
+
+
+/* SMM handler */
 uint32_t smmstore_exec(uint8_t command, void *param);
 
-/* implementation */
+/* Implementation of Version 1 */
 int smmstore_read_region(void *buf, ssize_t *bufsize);
-int smmstore_append_data(void *key, uint32_t key_sz,
-	void *value, uint32_t value_sz);
+int smmstore_append_data(void *key, uint32_t key_sz, void *value, uint32_t value_sz);
 int smmstore_clear_region(void);
+
+/* Implementation of Version 2 */
+int smmstore_init(void *buf, size_t len);
+int smmstore_rawread_region(uint32_t block_id, uint32_t offset, uint32_t bufsize);
+int smmstore_rawwrite_region(uint32_t block_id, uint32_t offset, uint32_t bufsize);
+int smmstore_rawclear_region(uint32_t block_id);
+#if ENV_RAMSTAGE
+int smmstore_get_info(struct smmstore_params_info *info);
+#endif
+
+/* Advertise SMMSTORE v2 support */
+struct lb_header;
+void lb_smmstorev2(struct lb_header *header);
+
 #endif