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:
eb1127744a

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>

src/drivers/smmstore/Kconfig

@@ -6,6 +6,18 @@ config SMMSTORE
 	default y if PAYLOAD_TIANOCORE
 	select SPI_FLASH_SMM if BOOT_DEVICE_SPI_FLASH_RW_NOMMAP
 
+config SMMSTORE_V2
+	bool "Use version 2 of SMMSTORE API"
+	depends on SMMSTORE
+	default n
+	help
+	  Version 2 of SMMSTORE allows secure communication with SMM and
+	  makes no assumptions on the structure of the data stored within.
+	  It splits the store into chunks to allows fault tolerant writes.
+
+	  By using version 2 you cannot make use of software that expects
+	  a version 1 SMMSTORE.
+
 config SMMSTORE_IN_CBFS
 	bool
 	default n

src/drivers/smmstore/Makefile.inc

@@ -1,3 +1,4 @@
 ramstage-$(CONFIG_SMMSTORE) += store.c
+ramstage-$(CONFIG_SMMSTORE_V2) += ramstage.c
 
 smm-$(CONFIG_SMMSTORE) += store.c smi.c

src/drivers/smmstore/ramstage.c

@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <bootstate.h>
+#include <cpu/x86/smm.h>
+#include <commonlib/helpers.h>
+#include <commonlib/region.h>
+#include <console/console.h>
+#include <smmstore.h>
+#include <types.h>
+#include <cbmem.h>
+
+static struct smmstore_params_info info;
+
+void lb_smmstorev2(struct lb_header *header)
+{
+	struct lb_record *rec;
+	struct lb_smmstorev2 *store;
+	const struct cbmem_entry *e;
+
+	e = cbmem_entry_find(CBMEM_ID_SMM_COMBUFFER);
+	if (!e)
+		return;
+
+	rec = lb_new_record(header);
+	store = (struct lb_smmstorev2 *)rec;
+
+	store->tag = LB_TAG_SMMSTOREV2;
+	store->size = sizeof(*store);
+	store->com_buffer = (uintptr_t)cbmem_entry_start(e);
+	store->com_buffer_size = cbmem_entry_size(e);
+	store->mmap_addr = info.mmap_addr;
+	store->num_blocks = info.num_blocks;
+	store->block_size = info.block_size;
+	store->apm_cmd = APM_CNT_SMMSTORE;
+}
+
+static void init_store(void *unused)
+{
+	struct smmstore_params_init args;
+	uint32_t eax = ~0;
+	uint32_t ebx;
+
+	if (smmstore_get_info(&info) < 0) {
+		printk(BIOS_INFO, "SMMSTORE: Failed to get meta data\n");
+		return;
+	}
+
+	void *ptr = cbmem_add(CBMEM_ID_SMM_COMBUFFER, info.block_size);
+	if (!ptr) {
+		printk(BIOS_ERR, "SMMSTORE: Failed to add com buffer\n");
+		return;
+	}
+
+	args.com_buffer = (uintptr_t)ptr;
+	args.com_buffer_size = info.block_size;
+	ebx = (uintptr_t)&args;
+
+	printk(BIOS_INFO, "SMMSTORE: Setting up SMI handler\n");
+
+	/* Issue SMI using APM to update the com buffer and to lock the SMMSTORE */
+	__asm__ __volatile__ (
+		"outb %%al, %%dx"
+		: "=a" (eax)
+		: "a" ((SMMSTORE_CMD_INIT << 8) | APM_CNT_SMMSTORE),
+		  "b" (ebx),
+		  "d" (APM_CNT)
+		: "memory");
+
+	if (eax != SMMSTORE_RET_SUCCESS) {
+		printk(BIOS_ERR, "SMMSTORE: Failed to install com buffer\n");
+		return;
+	}
+}
+
+/* The SMI APM handler is installed at DEV_INIT phase */
+BOOT_STATE_INIT_ENTRY(BS_DEV_INIT, BS_ON_EXIT, init_store, NULL);

src/drivers/smmstore/smi.c

@@ -23,8 +23,7 @@ static int range_check(void *start, size_t size)
 	return 0;
 }
 
-/* Param is usually EBX, ret in EAX */
-uint32_t smmstore_exec(uint8_t command, void *param)
+static uint32_t smmstorev1_exec(uint8_t command, void *param)
 {
 	uint32_t ret = SMMSTORE_RET_FAILURE;
 
@@ -66,13 +65,89 @@ uint32_t smmstore_exec(uint8_t command, void *param)
 			ret = SMMSTORE_RET_SUCCESS;
 		break;
 	}
-
 	default:
 		printk(BIOS_DEBUG,
-			"Unknown SMM store command: 0x%02x\n", command);
+		       "Unknown SMM store v1 command: 0x%02x\n", command);
 		ret = SMMSTORE_RET_UNSUPPORTED;
 		break;
 	}
 
 	return ret;
 }
+
+static uint32_t smmstorev2_exec(uint8_t command, void *param)
+{
+	uint32_t ret = SMMSTORE_RET_FAILURE;
+
+	switch (command) {
+	case SMMSTORE_CMD_INIT: {
+		printk(BIOS_DEBUG, "Init SMM store\n");
+		struct smmstore_params_init *params = param;
+
+		if (range_check(params, sizeof(*params)) != 0)
+			break;
+
+		void *buf = (void *)(uintptr_t)params->com_buffer;
+
+		if (range_check(buf, params->com_buffer_size) != 0)
+			break;
+
+		if (smmstore_init(buf, params->com_buffer_size) == 0)
+			ret = SMMSTORE_RET_SUCCESS;
+		break;
+	}
+	case SMMSTORE_CMD_RAW_READ: {
+		printk(BIOS_DEBUG, "Raw read from SMM store, param = %p\n", param);
+		struct smmstore_params_raw_read *params = param;
+
+		if (range_check(params, sizeof(*params)) != 0)
+			break;
+
+		if (smmstore_rawread_region(params->block_id, params->bufoffset,
+					    params->bufsize) == 0)
+			ret = SMMSTORE_RET_SUCCESS;
+		break;
+	}
+	case SMMSTORE_CMD_RAW_WRITE: {
+		printk(BIOS_DEBUG, "Raw write to SMM store, param = %p\n", param);
+		struct smmstore_params_raw_write *params = param;
+
+		if (range_check(params, sizeof(*params)) != 0)
+			break;
+
+		if (smmstore_rawwrite_region(params->block_id, params->bufoffset,
+					     params->bufsize) == 0)
+			ret = SMMSTORE_RET_SUCCESS;
+		break;
+	}
+	case SMMSTORE_CMD_RAW_CLEAR: {
+		printk(BIOS_DEBUG, "Raw clear SMM store, param = %p\n", param);
+		struct smmstore_params_raw_clear *params = param;
+
+		if (range_check(params, sizeof(*params)) != 0)
+			break;
+
+		if (smmstore_rawclear_region(params->block_id) == 0)
+			ret = SMMSTORE_RET_SUCCESS;
+		break;
+	}
+	default:
+		printk(BIOS_DEBUG,
+			"Unknown SMM store v2 command: 0x%02x\n", command);
+		ret = SMMSTORE_RET_UNSUPPORTED;
+		break;
+	}
+
+	return ret;
+}
+
+uint32_t smmstore_exec(uint8_t command, void *param)
+{
+	if (!param)
+		return SMMSTORE_RET_FAILURE;
+
+	if (CONFIG(SMMSTORE_V2))
+		return smmstorev2_exec(command, param);
+	else
+		return smmstorev1_exec(command, param);
+}

src/drivers/smmstore/store.c

@@ -262,3 +262,200 @@ int smmstore_clear_region(void)
 
 	return 0;
 }
+
+
+/* Implementation of Version 2 */
+
+static bool store_initialized;
+static struct mem_region_device mdev_com_buf;
+
+static int smmstore_rdev_chain(struct region_device *rdev)
+{
+	if (!store_initialized)
+		return -1;
+
+	return rdev_chain_full(rdev, &mdev_com_buf.rdev);
+}
+
+/**
+ * Call once before using the store. In SMM this must be called through an
+ * APM SMI handler providing the communication buffer address and length.
+ */
+int smmstore_init(void *buf, size_t len)
+{
+	if (!buf || len < SMM_BLOCK_SIZE)
+		return -1;
+
+	if (store_initialized)
+		return -1;
+
+	mem_region_device_rw_init(&mdev_com_buf, buf, len);
+
+	store_initialized = true;
+
+	return 0;
+}
+
+#if ENV_RAMSTAGE
+/**
+ * Provide metadata for the coreboot tables.
+ * Must only be called in ramstage, but not in SMM.
+ */
+int smmstore_get_info(struct smmstore_params_info *out)
+{
+	struct region_device store;
+
+	if (lookup_store(&store) < 0) {
+		printk(BIOS_ERR, "smm store: lookup of store failed\n");
+		return -1;
+	}
+
+	if (!IS_ALIGNED(region_device_offset(&store), SMM_BLOCK_SIZE)) {
+		printk(BIOS_ERR, "smm store: store not aligned to block size\n");
+		return -1;
+	}
+
+	out->block_size = SMM_BLOCK_SIZE;
+	out->num_blocks = region_device_sz(&store) / SMM_BLOCK_SIZE;
+
+	/* FIXME: Broken EDK2 always assumes memory mapped Firmware Block Volumes */
+	out->mmap_addr = (uintptr_t)rdev_mmap_full(&store);
+
+	printk(BIOS_DEBUG, "smm store: %d # blocks with size 0x%x\n",
+	       out->num_blocks, out->block_size);
+
+	return 0;
+}
+#endif
+
+/* Returns -1 on error, 0 on success */
+static int lookup_block_in_store(struct region_device *store, uint32_t block_id)
+{
+	if (lookup_store(store) < 0) {
+		printk(BIOS_ERR, "smm store: lookup of store failed\n");
+		return -1;
+	}
+
+	if ((block_id * SMM_BLOCK_SIZE) >= region_device_sz(store)) {
+		printk(BIOS_ERR, "smm store: block ID out of range\n");
+		return -1;
+	}
+
+	return 0;
+}
+
+/* Returns NULL on error, pointer from rdev_mmap on success */
+static void *mmap_com_buf(struct region_device *com_buf, uint32_t offset, uint32_t bufsize)
+{
+	if (smmstore_rdev_chain(com_buf) < 0) {
+		printk(BIOS_ERR, "smm store: lookup of com buffer failed\n");
+		return NULL;
+	}
+
+	if (offset >= region_device_sz(com_buf)) {
+		printk(BIOS_ERR, "smm store: offset out of range\n");
+		return NULL;
+	}
+
+	void *ptr = rdev_mmap(com_buf, offset, bufsize);
+	if (!ptr)
+		printk(BIOS_ERR, "smm store: not enough space for new data\n");
+
+	return ptr;
+}
+
+/**
+ * Reads the specified block of the SMMSTORE and places it in the communication
+ * buffer.
+ * @param block_id The id of the block to operate on
+ * @param offset Offset within the block.
+ *               Must be smaller than the block size.
+ * @param bufsize Size of chunk to read within the block.
+ *                Must be smaller than the block size.
+
+ * @return Returns -1 on error, 0 on success.
+ */
+int smmstore_rawread_region(uint32_t block_id, uint32_t offset, uint32_t bufsize)
+{
+	struct region_device store;
+	struct region_device com_buf;
+
+	if (lookup_block_in_store(&store, block_id) < 0)
+		return -1;
+
+	void *ptr = mmap_com_buf(&com_buf, offset, bufsize);
+	if (!ptr)
+		return -1;
+
+	printk(BIOS_DEBUG, "smm store: reading %p block %d, offset=0x%x, size=%x\n",
+	       ptr, block_id, offset, bufsize);
+
+	ssize_t ret = rdev_readat(&store, ptr, block_id * SMM_BLOCK_SIZE + offset, bufsize);
+	rdev_munmap(&com_buf, ptr);
+	if (ret < 0)
+		return -1;
+
+	return 0;
+}
+
+/**
+ * Writes the specified block of the SMMSTORE by reading it from the communication
+ * buffer.
+ * @param block_id The id of the block to operate on
+ * @param offset Offset within the block.
+ *               Must be smaller than the block size.
+ * @param bufsize Size of chunk to read within the block.
+ *                Must be smaller than the block size.
+
+ * @return Returns -1 on error, 0 on success.
+ */
+int smmstore_rawwrite_region(uint32_t block_id, uint32_t offset, uint32_t bufsize)
+{
+	struct region_device store;
+	struct region_device com_buf;
+
+	if (lookup_block_in_store(&store, block_id) < 0)
+		return -1;
+
+	if (rdev_chain(&store, &store, block_id * SMM_BLOCK_SIZE + offset, bufsize)) {
+		printk(BIOS_ERR, "smm store: not enough space for new data\n");
+		return -1;
+	}
+
+	void *ptr = mmap_com_buf(&com_buf, offset, bufsize);
+	if (!ptr)
+		return -1;
+
+	printk(BIOS_DEBUG, "smm store: writing %p block %d, offset=0x%x, size=%x\n",
+	       ptr, block_id, offset, bufsize);
+
+	ssize_t ret = rdev_writeat(&store, ptr, 0, bufsize);
+	rdev_munmap(&com_buf, ptr);
+	if (ret < 0)
+		return -1;
+
+	return 0;
+}
+
+/**
+ * Erases the specified block of the SMMSTORE. The communication buffer remains untouched.
+ *
+ * @param block_id The id of the block to operate on
+ *
+ * @return Returns -1 on error, 0 on success.
+ */
+int smmstore_rawclear_region(uint32_t block_id)
+{
+	struct region_device store;
+
+	if (lookup_block_in_store(&store, block_id) < 0)
+		return -1;
+
+	ssize_t ret = rdev_eraseat(&store, block_id * SMM_BLOCK_SIZE, SMM_BLOCK_SIZE);
+	if (ret != SMM_BLOCK_SIZE) {
+		printk(BIOS_ERR, "smm store: erasing block failed\n");
+		return -1;
+	}
+
+	return 0;
+}