util: add smmstoretool for editing SMMSTORE

Offline SMMSTORE variable modification tool.  Can be used to
pre-configure ROM image or debug EFI state stored in a dump.

Change-Id: I6c1c06f1d0c39c13b5be76a3070f09b715aca6e0
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79080
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

util/smmstoretool/storage.c

@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "storage.h"
+
+#include <assert.h>
+#include <stdio.h>
+
+#include "fv.h"
+#include "utils.h"
+
+bool storage_open(const char store_file[], struct storage_t *storage, bool rw)
+{
+	storage->rw = rw;
+
+	storage->file = map_file(store_file, rw);
+	if (storage->file.start == NULL) {
+		fprintf(stderr, "Failed to load smm-store-file \"%s\"\n",
+			store_file);
+		return false;
+	}
+
+	bool auth_vars;
+	if (!fv_parse(storage->file, &storage->store_area, &auth_vars)) {
+		if (!rw) {
+			fprintf(stderr,
+				"Failed to find variable store in \"%s\"\n",
+				store_file);
+			goto error;
+		}
+
+		if (!fv_init(storage->file)) {
+			fprintf(stderr,
+				"Failed to create variable store in \"%s\"\n",
+				store_file);
+			goto error;
+		}
+
+		if (!fv_parse(storage->file, &storage->store_area, &auth_vars)) {
+			fprintf(stderr,
+				"Failed to parse newly formatted store in \"%s\"\n",
+				store_file);
+			goto error;
+		}
+
+		fprintf(stderr,
+			"Successfully created variable store in \"%s\"\n",
+			store_file);
+	}
+
+	storage->vs = vs_load(storage->store_area, auth_vars);
+	return true;
+
+error:
+	unmap_file(storage->file);
+	return false;
+}
+
+bool storage_write_back(struct storage_t *storage)
+{
+	assert(storage->rw && "Only RW storage can be updated.");
+
+	bool success = vs_store(&storage->vs, storage->store_area);
+	if (!success)
+		fprintf(stderr, "Failed to update variable store\n");
+	storage_drop(storage);
+	return success;
+}
+
+void storage_drop(struct storage_t *storage)
+{
+	unmap_file(storage->file);
+	vs_free(&storage->vs);
+}