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, 76 insertions, 0 deletions

diff --git a/src/drivers/smmstore/ramstage.c b/src/drivers/smmstore/ramstage.c
new file mode 100644
index 0000000000..ef80e221bc
--- /dev/null
+++ b/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);