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>

19 files changed, 1602 insertions, 0 deletions

diff --git a/util/README.md b/util/README.md
index 51c4068a6c..ec1c6bf7ce 100644
--- a/util/README.md
+++ b/util/README.md
@@ -133,6 +133,7 @@ from the local git repository for auditing or release `Bash`
 Does not show variants. `Shell`
 	* _ucode_h_to_bin.sh_ - Microcode conversion tool `Bash`
 	* _update_submodules_ - Check all submodules for updates `Bash`
+* __smmstoretool__ - Offline SMMSTORE variable modification tool `C`
 * __spdtool__ - Dumps SPD ROMs from a given blob to separate files
 using known patterns and reserved bits. Useful for analysing firmware
 that holds SPDs on boards that have soldered down DRAM. `python`
diff --git a/util/smmstoretool/.gitignore b/util/smmstoretool/.gitignore
new file mode 100644
index 0000000000..0cc355ef3e
--- /dev/null
+++ b/util/smmstoretool/.gitignore
@@ -0,0 +1 @@
+smmstoretool
diff --git a/util/smmstoretool/Makefile b/util/smmstoretool/Makefile
new file mode 100644
index 0000000000..78b77caa2d
--- /dev/null
+++ b/util/smmstoretool/Makefile
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+PRG  := smmstoretool
+TOP  ?= $(abspath ../..)
+ROOT := $(TOP)/src
+MDE  := $(ROOT)/vendorcode/intel/edk2/UDK2017/MdePkg/Include/
+
+CC      ?= $(CROSS_COMPILE)gcc
+HOSTCC  ?= $(CC)
+INSTALL ?= /usr/bin/env install
+PREFIX  ?= /usr/local
+
+HOSTCFLAGS ?= $(CFLAGS)
+HOSTCFLAGS += -Wall -Wextra -MMD -MP -O3
+HOSTCFLAGS += -I $(ROOT)/commonlib/bsd/include
+HOSTCFLAGS += -I $(ROOT)/vendorcode/intel/edk2/
+HOSTCFLAGS += -I $(MDE)
+
+HOSTLDFLAGS ?= $(LDFLAGS)
+
+MACHINE := $(shell uname -m)
+ifeq ($(MACHINE),x86_64)
+    HOSTCFLAGS += -I $(MDE)/X64
+else ifeq ($(patsubst i%86,Ia32,$(MACHINE)),Ia32)
+    HOSTCFLAGS += -I $(MDE)/Ia32
+else
+    $(error Unsupported machine: '$(MACHINE)')
+endif
+
+SRC := data.c fv.c guids.c main.c storage.c utils.c vs.c
+
+OBJ := $(SRC:.c=.o)
+DEP := $(SRC:.c=.o.d)
+
+.PHONY: all debug clean install
+
+all: $(PRG)
+
+debug: HOSTCFLAGS += -O0 -g
+debug: HOSTLDFLAGS += -g
+debug: all
+
+install: $(PRG)
+	$(INSTALL) -d $(DESTDIR)$(PREFIX)/bin/
+	$(INSTALL) $^ $(DESTDIR)$(PREFIX)/bin/
+
+clean:
+	-$(RM) $(PRG) $(OBJ) $(DEP)
+
+$(PRG): $(OBJ)
+	$(HOSTCC) -o $@ $^ $(HOSTLDFLAGS)
+
+%.o: %.c
+	$(HOSTCC) $(HOSTCFLAGS) -c -o $@ -MF $@.d $<
+
+-include $(DEP)
diff --git a/util/smmstoretool/data.c b/util/smmstoretool/data.c
new file mode 100644
index 0000000000..778bf8a6cb
--- /dev/null
+++ b/util/smmstoretool/data.c
@@ -0,0 +1,180 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "data.h"
+
+#include <ctype.h>
+#include <limits.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "utils.h"
+
+void print_data(const uint8_t data[], size_t data_size, enum data_type type)
+{
+	if (data_size == 0)
+		return;
+
+	switch (type) {
+	case DATA_TYPE_BOOL:
+		bool value = false;
+		for (size_t i = 0; i < data_size; ++i) {
+			if (data[i] != 0) {
+				value = true;
+				break;
+			}
+		}
+		printf("%s\n", value ? "true" : "false");
+		break;
+	case DATA_TYPE_UINT8:
+		if (data_size != 1) {
+			fprintf(stderr,
+				"warning: expected size of 1, got %zu\n",
+				data_size);
+		}
+
+		if (data_size >= 1)
+			printf("%u\n", *(uint8_t *)data);
+		break;
+	case DATA_TYPE_UINT16:
+		if (data_size != 2) {
+			fprintf(stderr,
+				"warning: expected size of 2, got %zu\n",
+				data_size);
+		}
+
+		if (data_size >= 2)
+			printf("%u\n", *(uint16_t *)data);
+		break;
+	case DATA_TYPE_UINT32:
+		if (data_size != 4) {
+			fprintf(stderr,
+				"warning: expected size of 4, got %zu\n",
+				data_size);
+		}
+
+		if (data_size >= 4)
+			printf("%u\n", *(uint32_t *)data);
+		break;
+	case DATA_TYPE_ASCII:
+		for (size_t i = 0; i < data_size; ++i) {
+			char c = data[i];
+			if (isprint(c))
+				printf("%c", c);
+		}
+		printf("\n");
+		break;
+	case DATA_TYPE_UNICODE:
+		char *chars = to_chars((const CHAR16 *)data, data_size);
+		printf("%s\n", chars);
+		free(chars);
+		break;
+	case DATA_TYPE_RAW:
+		fwrite(data, 1, data_size, stdout);
+		break;
+	}
+}
+
+static uint64_t parse_uint(const char source[],
+			   const char type[],
+			   unsigned long long max)
+{
+	char *end;
+	unsigned long long uint = strtoull(source, &end, /*base=*/0);
+	if (*end != '\0') {
+		fprintf(stderr, "Trailing characters in \"%s\": %s\n",
+			source, end);
+		return UINT64_MAX;
+	}
+	if (uint > max) {
+		fprintf(stderr, "Invalid %s value: %llu\n", type, uint);
+		return UINT64_MAX;
+	}
+
+	return uint;
+}
+
+void *make_data(const char source[], size_t *data_size, enum data_type type)
+{
+	switch (type) {
+	void *data;
+	bool boolean;
+	unsigned long long uint;
+
+	case DATA_TYPE_BOOL:
+		if (str_eq(source, "true")) {
+			boolean = true;
+		} else if (str_eq(source, "false")) {
+			boolean = false;
+		} else {
+			fprintf(stderr, "Invalid boolean value: \"%s\"\n",
+				source);
+			return NULL;
+		}
+
+		*data_size = 1;
+		data = xmalloc(*data_size);
+		*(uint8_t *)data = boolean;
+		return data;
+	case DATA_TYPE_UINT8:
+		uint = parse_uint(source, "uint8", UINT8_MAX);
+		if (uint == UINT64_MAX)
+			return NULL;
+
+		*data_size = 1;
+		data = xmalloc(*data_size);
+		*(uint8_t *)data = uint;
+		return data;
+	case DATA_TYPE_UINT16:
+		uint = parse_uint(source, "uint16", UINT16_MAX);
+		if (uint == UINT64_MAX)
+			return NULL;
+
+		*data_size = 2;
+		data = xmalloc(*data_size);
+		*(uint16_t *)data = uint;
+		return data;
+	case DATA_TYPE_UINT32:
+		uint = parse_uint(source, "uint32", UINT32_MAX);
+		if (uint == UINT64_MAX)
+			return NULL;
+
+		*data_size = 4;
+		data = xmalloc(*data_size);
+		*(uint32_t *)data = uint;
+		return data;
+	case DATA_TYPE_ASCII:
+		*data_size = strlen(source) + 1;
+		return strdup(source);
+	case DATA_TYPE_UNICODE:
+		return to_uchars(source, data_size);
+	case DATA_TYPE_RAW:
+		fprintf(stderr, "Raw data type is output only\n");
+		return NULL;
+	}
+
+	return NULL;
+}
+
+bool parse_data_type(const char str[], enum data_type *type)
+{
+	if (str_eq(str, "bool"))
+		*type = DATA_TYPE_BOOL;
+	else if (str_eq(str, "uint8"))
+		*type = DATA_TYPE_UINT8;
+	else if (str_eq(str, "uint16"))
+		*type = DATA_TYPE_UINT16;
+	else if (str_eq(str, "uint32"))
+		*type = DATA_TYPE_UINT32;
+	else if (str_eq(str, "ascii"))
+		*type = DATA_TYPE_ASCII;
+	else if (str_eq(str, "unicode"))
+		*type = DATA_TYPE_UNICODE;
+	else if (str_eq(str, "raw"))
+		*type = DATA_TYPE_RAW;
+	else
+		return false;
+
+	return true;
+}
diff --git a/util/smmstoretool/data.h b/util/smmstoretool/data.h
new file mode 100644
index 0000000000..13bd7bc4f4
--- /dev/null
+++ b/util/smmstoretool/data.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__DATA_H__
+#define SMMSTORETOOL__DATA_H__
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+enum data_type {
+	DATA_TYPE_BOOL,
+	DATA_TYPE_UINT8,
+	DATA_TYPE_UINT16,
+	DATA_TYPE_UINT32,
+	DATA_TYPE_ASCII,
+	DATA_TYPE_UNICODE,
+	DATA_TYPE_RAW,
+};
+
+void print_data(const uint8_t data[], size_t data_size, enum data_type type);
+
+void *make_data(const char source[], size_t *data_size, enum data_type type);
+
+bool parse_data_type(const char str[], enum data_type *type);
+
+#endif // SMMSTORETOOL__DATA_H__
diff --git a/util/smmstoretool/description.md b/util/smmstoretool/description.md
new file mode 100644
index 0000000000..c6f493f8cb
--- /dev/null
+++ b/util/smmstoretool/description.md
@@ -0,0 +1 @@
+Offline SMMSTORE variable modification tool `C`
diff --git a/util/smmstoretool/fv.c b/util/smmstoretool/fv.c
new file mode 100644
index 0000000000..c9d342e162
--- /dev/null
+++ b/util/smmstoretool/fv.c
@@ -0,0 +1,175 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "fv.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "udk2017.h"
+
+// The same as in `smmstore.h` header, which isn't in `commonlib`.
+#define SMM_BLOCK_SIZE (64*1024)
+
+static const EFI_GUID EfiVariableGuid = EFI_VARIABLE_GUID;
+
+static const EFI_GUID EfiAuthenticatedVariableGuid =
+	EFI_AUTHENTICATED_VARIABLE_GUID;
+
+static const EFI_GUID EfiSystemNvDataFvGuid = {
+	0xfff12b8d, 0x7696, 0x4c8b,
+	{ 0xa9, 0x85, 0x27, 0x47, 0x07, 0x5b, 0x4f, 0x50 }
+};
+
+static uint16_t calc_checksum(const uint16_t *hdr, size_t size)
+{
+	assert(size % 2 == 0 && "Header can't have odd length.");
+
+	uint16_t checksum = 0;
+	for (size_t i = 0; i < size / 2; ++i)
+		checksum += hdr[i];
+	return checksum;
+}
+
+bool
+fv_init(struct mem_range_t fv)
+{
+	if (fv.length % SMM_BLOCK_SIZE != 0) {
+		fprintf(stderr,
+			"Firmware Volume size is not a multiple of 64KiB\n");
+		return false;
+	}
+
+	memset(fv.start, 0xff, fv.length);
+
+	const EFI_FIRMWARE_VOLUME_HEADER vol_hdr = {
+		.FileSystemGuid = EfiSystemNvDataFvGuid,
+		.FvLength = fv.length,
+		.Signature = EFI_FVH_SIGNATURE,
+		.Attributes = EFI_FVB2_READ_ENABLED_CAP
+					| EFI_FVB2_READ_STATUS
+					| EFI_FVB2_WRITE_ENABLED_CAP
+					| EFI_FVB2_WRITE_STATUS
+					| EFI_FVB2_STICKY_WRITE
+					| EFI_FVB2_MEMORY_MAPPED
+					| EFI_FVB2_ERASE_POLARITY,
+		.HeaderLength = sizeof(vol_hdr)
+			      + sizeof(EFI_FV_BLOCK_MAP_ENTRY),
+		.Revision = EFI_FVH_REVISION,
+		.BlockMap[0] = {
+			.NumBlocks = fv.length / SMM_BLOCK_SIZE,
+			.Length = SMM_BLOCK_SIZE,
+		},
+	};
+
+	EFI_FIRMWARE_VOLUME_HEADER *vol_hdr_dst = (void *)fv.start;
+	*vol_hdr_dst = vol_hdr;
+	vol_hdr_dst->BlockMap[1].NumBlocks = 0;
+	vol_hdr_dst->BlockMap[1].Length = 0;
+
+	vol_hdr_dst->Checksum =
+		~calc_checksum((const void *)vol_hdr_dst, vol_hdr.HeaderLength);
+	++vol_hdr_dst->Checksum;
+
+	const VARIABLE_STORE_HEADER var_store_hdr = {
+		// Authentication-related fields will be filled with 0xff.
+		.Signature = EfiAuthenticatedVariableGuid,
+		// Actual size of the storage is block size, the rest is
+		// Fault Tolerant Write (FTW) space and the FTW spare space.
+		.Size = SMM_BLOCK_SIZE - vol_hdr.HeaderLength,
+		.Format = VARIABLE_STORE_FORMATTED,
+		.State = VARIABLE_STORE_HEALTHY,
+	};
+
+	VARIABLE_STORE_HEADER *var_store_hdr_dst =
+		(void *)(fv.start + vol_hdr.HeaderLength);
+	*var_store_hdr_dst = var_store_hdr;
+
+	return true;
+}
+
+static bool guid_eq(const EFI_GUID *lhs, const EFI_GUID *rhs)
+{
+	return memcmp(lhs, rhs, sizeof(*lhs)) == 0;
+}
+
+static bool check_fw_vol_hdr(const EFI_FIRMWARE_VOLUME_HEADER *hdr,
+			     size_t max_size)
+{
+	if (hdr->Revision != EFI_FVH_REVISION ||
+		hdr->Signature != EFI_FVH_SIGNATURE ||
+		hdr->FvLength > max_size ||
+		hdr->HeaderLength > max_size ||
+		hdr->HeaderLength % 2 != 0) {
+		fprintf(stderr, "No firmware volume header present\n");
+		return false;
+	}
+
+	if (!guid_eq(&hdr->FileSystemGuid, &EfiSystemNvDataFvGuid)) {
+		fprintf(stderr, "Firmware volume GUID non-compatible\n");
+		return false;
+	}
+
+	uint16_t checksum = calc_checksum((const void *)hdr, hdr->HeaderLength);
+	if (checksum != 0) {
+		fprintf(stderr,
+			"Firmware Volume checksum is non-zero: 0x%04X\n",
+			checksum);
+		return false;
+	}
+
+	return true;
+}
+
+static bool check_var_store_hdr(const VARIABLE_STORE_HEADER *hdr,
+				size_t max_size,
+				bool *auth_vars)
+{
+	*auth_vars = guid_eq(&hdr->Signature, &EfiAuthenticatedVariableGuid);
+	if (!*auth_vars && !guid_eq(&hdr->Signature, &EfiVariableGuid)) {
+		fprintf(stderr, "Variable store has unexpected GUID\n");
+		return false;
+	}
+
+	if (hdr->Size > max_size) {
+		fprintf(stderr, "Variable store size is too large: %zu > %zu\n",
+			(size_t)hdr->Size, max_size);
+		return false;
+	}
+
+	if (hdr->Format != VARIABLE_STORE_FORMATTED) {
+		fprintf(stderr, "Variable store is not formatted\n");
+		return false;
+	}
+
+	if (hdr->State != VARIABLE_STORE_HEALTHY) {
+		fprintf(stderr, "Variable store is not in a healthy state\n");
+		return false;
+	}
+
+	return true;
+}
+
+bool
+fv_parse(struct mem_range_t fv, struct mem_range_t *var_store, bool *auth_vars)
+{
+	const EFI_FIRMWARE_VOLUME_HEADER *vol_hdr = (void *)fv.start;
+	if (!check_fw_vol_hdr(vol_hdr, fv.length)) {
+		fprintf(stderr, "No valid firmware volume was found\n");
+		return false;
+	}
+
+	uint8_t *fw_vol_data = fv.start + vol_hdr->HeaderLength;
+	size_t volume_size = fv.length - vol_hdr->HeaderLength;
+	const VARIABLE_STORE_HEADER *var_store_hdr = (void *)fw_vol_data;
+	if (!check_var_store_hdr(var_store_hdr, volume_size, auth_vars)) {
+		fprintf(stderr, "No valid variable store was found");
+		return false;
+	}
+
+	var_store->start = fw_vol_data + sizeof(*var_store_hdr);
+	var_store->length = volume_size - sizeof(*var_store_hdr);
+	return true;
+}
diff --git a/util/smmstoretool/fv.h b/util/smmstoretool/fv.h
new file mode 100644
index 0000000000..b28db4cbf2
--- /dev/null
+++ b/util/smmstoretool/fv.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__FV_H__
+#define SMMSTORETOOL__FV_H__
+
+#include <stdbool.h>
+
+#include "utils.h"
+
+// Firmware volume is what's stored in SMMSTORE region of CBFS.  It wraps
+// variable store.
+
+bool fv_init(struct mem_range_t fv);
+
+bool fv_parse(struct mem_range_t fv,
+	      struct mem_range_t *var_store,
+	      bool *auth_vars);
+
+#endif // SMMSTORETOOL__FV_H__
diff --git a/util/smmstoretool/guids.c b/util/smmstoretool/guids.c
new file mode 100644
index 0000000000..4ba92b9798
--- /dev/null
+++ b/util/smmstoretool/guids.c
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "guids.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <commonlib/bsd/helpers.h>
+
+#include "udk2017.h"
+#include "utils.h"
+
+const struct guid_alias_t known_guids[] = {
+	{
+		"coreboot",
+		{
+			0xceae4c1d, 0x335b, 0x4685,
+			{ 0xa4, 0xa0, 0xfc, 0x4a, 0x94, 0xee, 0xa0, 0x85 }
+		},
+	},
+	{
+		"dasharo",
+		{
+			0xd15b327e, 0xff2d, 0x4fc1,
+			{ 0xab, 0xf6, 0xc1, 0x2b, 0xd0, 0x8c, 0x13, 0x59 }
+		},
+	},
+	{
+		"global",
+		{
+			0x8be4df61, 0x93ca, 0x11d2,
+			{ 0xaa, 0x0d, 0x00, 0xe0, 0x98, 0x03, 0x2b, 0x8c }
+		},
+	},
+	{
+		"microsoft",
+		{
+			0x77fa9abd, 0x0359, 0x4d32,
+			{ 0xbd, 0x60, 0x28, 0xf4, 0xe7, 0x8f, 0x78, 0x4b }
+		},
+	},
+};
+
+const int known_guid_count = ARRAY_SIZE(known_guids);
+
+char *format_guid(const EFI_GUID *guid, bool use_alias)
+{
+	if (use_alias) {
+		for (int i = 0; i < known_guid_count; ++i) {
+			const struct guid_alias_t *known_guid = &known_guids[i];
+			if (memcmp(&known_guid->guid, guid, sizeof(*guid)) == 0)
+				return strdup(known_guid->alias);
+		}
+	}
+
+	char *str = xmalloc(GUID_LEN + 1);
+	snprintf(str, GUID_LEN + 1,
+		 "%08x-%04x-%04x-%02x%02x%02x%02x%02x%02x%02x%02x",
+		 guid->Data1, guid->Data2, guid->Data3,
+		 guid->Data4[0], guid->Data4[1],
+		 guid->Data4[2], guid->Data4[3],
+		 guid->Data4[4], guid->Data4[5],
+		 guid->Data4[6], guid->Data4[7]);
+	return str;
+}
+
+bool parse_guid(const char str[], EFI_GUID *guid)
+{
+	for (int i = 0; i < known_guid_count; ++i) {
+		const struct guid_alias_t *known_guid = &known_guids[i];
+		if (str_eq(known_guid->alias, str)) {
+			*guid = known_guid->guid;
+			return true;
+		}
+	}
+
+	if (strlen(str) != GUID_LEN)
+		return false;
+
+	int n = sscanf(str,
+		       "%08x-%04hx-%04hx-"
+		       "%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx",
+		       &guid->Data1, &guid->Data2, &guid->Data3,
+		       &guid->Data4[0], &guid->Data4[1],
+		       &guid->Data4[2], &guid->Data4[3],
+		       &guid->Data4[4], &guid->Data4[5],
+		       &guid->Data4[6], &guid->Data4[7]);
+	return n == 11;
+}
diff --git a/util/smmstoretool/guids.h b/util/smmstoretool/guids.h
new file mode 100644
index 0000000000..b4dad1257a
--- /dev/null
+++ b/util/smmstoretool/guids.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__GUIDS_H__
+#define SMMSTORETOOL__GUIDS_H__
+
+#include <stdbool.h>
+
+#include "udk2017.h"
+
+#define GUID_LEN 35
+
+struct guid_alias_t {
+	const char *alias;
+	EFI_GUID guid;
+};
+
+extern const struct guid_alias_t known_guids[];
+
+extern const int known_guid_count;
+
+char *format_guid(const EFI_GUID *guid, bool use_alias);
+
+bool parse_guid(const char str[], EFI_GUID *guid);
+
+#endif // SMMSTORETOOL__GUIDS_H__
diff --git a/util/smmstoretool/main.c b/util/smmstoretool/main.c
new file mode 100644
index 0000000000..eff5d9c02b
--- /dev/null
+++ b/util/smmstoretool/main.c
@@ -0,0 +1,487 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <commonlib/bsd/helpers.h>
+
+#include "data.h"
+#include "guids.h"
+#include "storage.h"
+#include "udk2017.h"
+#include "vs.h"
+
+struct subcommand_t {
+	const char *name;
+	const char *description;
+	void (*print_help)(FILE *f, const struct subcommand_t *info);
+	int (*process)(int argc, char *argv[], const char store_file[]);
+};
+
+static void help_get(FILE *f, const struct subcommand_t *info);
+static void help_guids(FILE *f, const struct subcommand_t *info);
+static void help_help(FILE *f, const struct subcommand_t *info);
+static void help_list(FILE *f, const struct subcommand_t *info);
+static void help_remove(FILE *f, const struct subcommand_t *info);
+static void help_set(FILE *f, const struct subcommand_t *info);
+static int process_get(int argc, char *argv[], const char store_file[]);
+static int process_guids(int argc, char *argv[], const char store_file[]);
+static int process_help(int argc, char *argv[], const char store_file[]);
+static int process_list(int argc, char *argv[], const char store_file[]);
+static int process_remove(int argc, char *argv[], const char store_file[]);
+static int process_set(int argc, char *argv[], const char store_file[]);
+
+static const struct subcommand_t sub_commands[] = {
+	{
+		.name = "get",
+		.description = "display current value of a variable",
+		.print_help = &help_get,
+		.process = &process_get,
+	},
+	{
+		.name = "guids",
+		.description = "show GUID to alias mapping",
+		.print_help = &help_guids,
+		.process = &process_guids,
+	},
+	{
+		.name = "help",
+		.description = "provide built-in help",
+		.print_help = &help_help,
+		.process = &process_help,
+	},
+	{
+		.name = "list",
+		.description = "list variables present in the store",
+		.print_help = &help_list,
+		.process = &process_list,
+	},
+	{
+		.name = "remove",
+		.description = "remove a variable from the store",
+		.print_help = &help_remove,
+		.process = &process_remove,
+	},
+	{
+		.name = "set",
+		.description = "add or updates a variable in the store",
+		.print_help = &help_set,
+		.process = &process_set,
+	},
+};
+
+static const int sub_command_count = ARRAY_SIZE(sub_commands);
+
+static const char *USAGE_FMT = "Usage: %s smm-store-file sub-command\n"
+			       "       %s -h|--help\n";
+
+static const char *program_name;
+
+static void print_program_usage(void)
+{
+	fprintf(stderr, USAGE_FMT, program_name, program_name);
+	exit(EXIT_FAILURE);
+}
+
+static void print_sub_command_usage(const char sub_command[])
+{
+	fprintf(stderr, "\n");
+	fprintf(stderr, USAGE_FMT, program_name, program_name);
+	fprintf(stderr, "\n");
+
+	for (int i = 0; i < sub_command_count; ++i) {
+		const struct subcommand_t *cmd = &sub_commands[i];
+		if (!str_eq(cmd->name, sub_command))
+			continue;
+
+		cmd->print_help(stderr, cmd);
+		break;
+	}
+
+	exit(EXIT_FAILURE);
+}
+
+static void print_help(void)
+{
+	printf(USAGE_FMT, program_name, program_name);
+
+	printf("\n");
+	printf("Sub-commands:\n");
+	for (int i = 0; i < sub_command_count; ++i) {
+		const struct subcommand_t *cmd = &sub_commands[i];
+		printf(" * %-6s - %s\n", cmd->name, cmd->description);
+	}
+}
+
+static void print_types(FILE *f)
+{
+	fprintf(f, "Types and their values:\n");
+	fprintf(f, " * bool (true, false)\n");
+	fprintf(f, " * uint8 (0-255)\n");
+	fprintf(f, " * ascii (NUL-terminated)\n");
+	fprintf(f, " * unicode (widened and NUL-terminated)\n");
+	fprintf(f, " * raw (output only; raw bytes on output)\n");
+}
+
+static void help_set(FILE *f, const struct subcommand_t *info)
+{
+	fprintf(f, "Create or update a variable:\n");
+	fprintf(f, "  %s smm-store-file %s \\\n", program_name, info->name);
+	fprintf(f, "      -g vendor-guid \\\n");
+	fprintf(f, "      -n variable-name \\\n");
+	fprintf(f, "      -t variable-type \\\n");
+	fprintf(f, "      -v value\n");
+	fprintf(f, "\n");
+	print_types(f);
+}
+
+static int process_set(int argc, char *argv[], const char store_file[])
+{
+	const char *name = NULL;
+	const char *value = NULL;
+	const char *type_str = NULL;
+	const char *guid_str = NULL;
+	int opt;
+	while ((opt = getopt(argc, argv, "n:t:v:g:")) != -1) {
+		switch (opt) {
+		case 'n':
+			name = optarg;
+			break;
+		case 't':
+			type_str = optarg;
+			break;
+		case 'v':
+			value = optarg;
+			break;
+		case 'g':
+			guid_str = optarg;
+			break;
+
+		case '?': /* parsing error */
+			print_sub_command_usage(argv[0]);
+		}
+	}
+
+	if (argv[optind] != NULL) {
+		fprintf(stderr, "First unexpected positional argument: %s\n",
+			argv[optind]);
+		print_sub_command_usage(argv[0]);
+	}
+
+	if (name == NULL || value == NULL || type_str == NULL ||
+	    guid_str == NULL) {
+		fprintf(stderr, "All options are required\n");
+		print_sub_command_usage(argv[0]);
+	}
+
+	if (name[0] == '\0') {
+		fprintf(stderr, "Variable name can't be empty\n");
+		print_sub_command_usage(argv[0]);
+	}
+
+	EFI_GUID guid;
+	if (!parse_guid(guid_str, &guid)) {
+		fprintf(stderr, "Failed to parse GUID: %s\n", guid_str);
+		return EXIT_FAILURE;
+	}
+
+	enum data_type type;
+	if (!parse_data_type(type_str, &type)) {
+		fprintf(stderr, "Failed to parse type: %s\n", type_str);
+		return EXIT_FAILURE;
+	}
+
+	size_t data_size;
+	void *data = make_data(value, &data_size, type);
+	if (data == NULL) {
+		fprintf(stderr, "Failed to parse value \"%s\" as %s\n",
+			value, type_str);
+		return EXIT_FAILURE;
+	}
+
+	struct storage_t storage;
+	if (!storage_open(store_file, &storage, /*rw=*/true)) {
+		free(data);
+		return EXIT_FAILURE;
+	}
+
+	struct var_t *var = vs_find(&storage.vs, name, &guid);
+	if (var == NULL) {
+		var = vs_new_var(&storage.vs);
+		var->name = to_uchars(name, &var->name_size);
+		var->data = data;
+		var->data_size = data_size;
+		var->guid = guid;
+	} else {
+		free(var->data);
+		var->data = data;
+		var->data_size = data_size;
+	}
+
+	return storage_write_back(&storage) ? EXIT_SUCCESS : EXIT_FAILURE;
+}
+
+static void help_list(FILE *f, const struct subcommand_t *info)
+{
+	fprintf(f, "List variables in the store:\n");
+	fprintf(f, "  %s smm-store-file %s\n", program_name, info->name);
+}
+
+static int process_list(int argc, char *argv[], const char store_file[])
+{
+	if (argc != 1) {
+		fprintf(stderr, "Invalid invocation\n");
+		print_sub_command_usage(argv[0]);
+	}
+
+	struct storage_t storage;
+	if (!storage_open(store_file, &storage, /*rw=*/false))
+		return EXIT_FAILURE;
+
+	for (struct var_t *v = storage.vs.vars; v != NULL; v = v->next) {
+		char *name = to_chars(v->name, v->name_size);
+		char *guid = format_guid(&v->guid, /*use_alias=*/true);
+
+		printf("%-*s:%s (%zu %s)\n", GUID_LEN, guid, name, v->data_size,
+		       v->data_size == 1 ? "byte" : "bytes");
+
+		free(name);
+		free(guid);
+	}
+
+	storage_drop(&storage);
+	return EXIT_SUCCESS;
+}
+
+static void help_get(FILE *f, const struct subcommand_t *info)
+{
+	fprintf(f, "Read variable's value:\n");
+	fprintf(f, "  %s smm-store-file %s \\\n", program_name, info->name);
+	fprintf(f, "      -g vendor-guid \\\n");
+	fprintf(f, "      -n variable-name \\\n");
+	fprintf(f, "      -t variable-type\n");
+	fprintf(f, "\n");
+	print_types(f);
+}
+
+static int process_get(int argc, char *argv[], const char store_file[])
+{
+	const char *name = NULL;
+	const char *type_str = NULL;
+	const char *guid_str = NULL;
+	int opt;
+	while ((opt = getopt(argc, argv, "n:g:t:")) != -1) {
+		switch (opt) {
+		case 'n':
+			name = optarg;
+			break;
+		case 'g':
+			guid_str = optarg;
+			break;
+		case 't':
+			type_str = optarg;
+			break;
+
+		case '?': /* parsing error */
+			print_sub_command_usage(argv[0]);
+		}
+	}
+
+	if (name == NULL || type_str == NULL || guid_str == NULL) {
+		fprintf(stderr, "All options are required\n");
+		print_sub_command_usage(argv[0]);
+	}
+
+	EFI_GUID guid;
+	if (!parse_guid(guid_str, &guid)) {
+		fprintf(stderr, "Failed to parse GUID: %s\n", guid_str);
+		return EXIT_FAILURE;
+	}
+
+	enum data_type type;
+	if (!parse_data_type(type_str, &type)) {
+		fprintf(stderr, "Failed to parse type: %s\n", type_str);
+		return EXIT_FAILURE;
+	}
+
+	struct storage_t storage;
+	if (!storage_open(store_file, &storage, /*rw=*/false))
+		return EXIT_FAILURE;
+
+	int result = EXIT_SUCCESS;
+
+	struct var_t *var = vs_find(&storage.vs, name, &guid);
+	if (var == NULL) {
+		result = EXIT_FAILURE;
+		fprintf(stderr, "Couldn't find variable \"%s:%s\"\n",
+			guid_str, name);
+	} else if (var->data_size == 0) {
+		fprintf(stderr, "There is no data to show.\n");
+		result = EXIT_FAILURE;
+	} else {
+		print_data(var->data, var->data_size, type);
+	}
+
+	storage_drop(&storage);
+	return result;
+}
+
+static void help_help(FILE *f, const struct subcommand_t *info)
+{
+	fprintf(f, "Display generic help:\n");
+	fprintf(f, "  %s smm-store-file %s\n", program_name, info->name);
+	fprintf(f, "\n");
+	fprintf(f, "Display sub-command help:\n");
+	fprintf(f, "  %s smm-store-file %s sub-command\n",
+		program_name, info->name);
+}
+
+static int process_help(int argc, char *argv[], const char store_file[])
+{
+	(void)store_file;
+
+	if (argc == 1) {
+		print_help();
+		return EXIT_SUCCESS;
+	}
+
+	if (argc != 2) {
+		fprintf(stderr, "Invalid invocation\n");
+		print_sub_command_usage(argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	const char *sub_command = argv[1];
+
+	for (int i = 0; i < sub_command_count; ++i) {
+		const struct subcommand_t *cmd = &sub_commands[i];
+		if (!str_eq(cmd->name, sub_command))
+			continue;
+
+		cmd->print_help(stdout, cmd);
+		return EXIT_SUCCESS;
+	}
+
+	fprintf(stderr, "Unknown sub-command: %s\n", sub_command);
+	print_help();
+	return EXIT_FAILURE;
+}
+
+static void help_remove(FILE *f, const struct subcommand_t *info)
+{
+	fprintf(f, "Remove a variable:\n");
+	fprintf(f, "  %s smm-store-file %s \\\n", program_name, info->name);
+	fprintf(f, "      -g vendor-guid \\\n");
+	fprintf(f, "      -n variable-name\n");
+}
+
+static int process_remove(int argc, char *argv[], const char store_file[])
+{
+	const char *name = NULL;
+	const char *guid_str = NULL;
+	int opt;
+	while ((opt = getopt(argc, argv, "n:g:")) != -1) {
+		switch (opt) {
+		case 'n':
+			name = optarg;
+			break;
+		case 'g':
+			guid_str = optarg;
+			break;
+
+		case '?': /* parsing error */
+			print_sub_command_usage(argv[0]);
+		}
+	}
+
+	if (name == NULL || guid_str == NULL) {
+		fprintf(stderr, "All options are required\n");
+		print_sub_command_usage(argv[0]);
+	}
+
+	EFI_GUID guid;
+	if (!parse_guid(guid_str, &guid)) {
+		fprintf(stderr, "Failed to parse GUID: %s\n", guid_str);
+		return EXIT_FAILURE;
+	}
+
+	struct storage_t storage;
+	if (!storage_open(store_file, &storage, /*rw=*/true))
+		return EXIT_FAILURE;
+
+	int result = EXIT_SUCCESS;
+
+	struct var_t *var = vs_find(&storage.vs, name, &guid);
+	if (var == NULL) {
+		result = EXIT_FAILURE;
+		fprintf(stderr, "Couldn't find variable \"%s:%s\"\n",
+			guid_str, name);
+	} else {
+		vs_delete(&storage.vs, var);
+	}
+
+	storage_write_back(&storage);
+	return result;
+}
+
+static void help_guids(FILE *f, const struct subcommand_t *info)
+{
+	fprintf(f, "List recognized GUIDS:\n");
+	fprintf(f, "  %s smm-store-file %s\n", program_name, info->name);
+}
+
+static int process_guids(int argc, char *argv[], const char store_file[])
+{
+	(void)store_file;
+
+	if (argc != 1) {
+		fprintf(stderr, "Invalid invocation\n");
+		print_sub_command_usage(argv[0]);
+	}
+
+	for (int i = 0; i < known_guid_count; ++i) {
+		char *guid = format_guid(&known_guids[i].guid,
+					 /*use_alias=*/false);
+		printf("%-10s -> %s\n", known_guids[i].alias, guid);
+		free(guid);
+	}
+	return EXIT_SUCCESS;
+}
+
+int main(int argc, char *argv[])
+{
+	program_name = argv[0];
+
+	if (argc > 1 && (str_eq(argv[1], "-h") || str_eq(argv[1], "--help"))) {
+		print_help();
+		exit(EXIT_SUCCESS);
+	}
+
+	if (argc < 3)
+		print_program_usage();
+
+	const char *store_file = argv[1];
+	const char *sub_command = argv[2];
+
+	int sub_command_argc = argc - 2;
+	char **sub_command_argv = argv + 2;
+
+	for (int i = 0; i < sub_command_count; ++i) {
+		const struct subcommand_t *cmd = &sub_commands[i];
+		if (!str_eq(cmd->name, sub_command))
+			continue;
+
+		return cmd->process(sub_command_argc,
+				    sub_command_argv,
+				    store_file);
+	}
+
+	fprintf(stderr, "Unknown sub-command: %s\n", sub_command);
+	print_help();
+	return EXIT_FAILURE;
+}
diff --git a/util/smmstoretool/storage.c b/util/smmstoretool/storage.c
new file mode 100644
index 0000000000..abc6840b67
--- /dev/null
+++ b/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);
+}
diff --git a/util/smmstoretool/storage.h b/util/smmstoretool/storage.h
new file mode 100644
index 0000000000..eb5cb08fc5
--- /dev/null
+++ b/util/smmstoretool/storage.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__STORAGE_H__
+#define SMMSTORETOOL__STORAGE_H__
+
+#include "vs.h"
+#include "utils.h"
+
+struct storage_t {
+	bool rw;
+	struct mem_range_t file;
+	struct mem_range_t store_area;
+	struct var_store_t vs;
+};
+
+bool storage_open(const char store_file[], struct storage_t *storage, bool rw);
+
+bool storage_write_back(struct storage_t *storage);
+
+void storage_drop(struct storage_t *storage);
+
+#endif // SMMSTORETOOL__STORAGE_H__
diff --git a/util/smmstoretool/udk2017.h b/util/smmstoretool/udk2017.h
new file mode 100644
index 0000000000..5a4286a634
--- /dev/null
+++ b/util/smmstoretool/udk2017.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__UDK2017_H__
+#define SMMSTORETOOL__UDK2017_H__
+
+#include <UDK2017/MdePkg/Include/Uefi/UefiBaseType.h>
+#include <UDK2017/MdePkg/Include/Uefi/UefiMultiPhase.h>
+#include <UDK2017/MdePkg/Include/Pi/PiFirmwareVolume.h>
+#include <UDK2017/MdeModulePkg/Include/Guid/VariableFormat.h>
+
+/*
+ * ProcessorBind.h contains `#pragma GCC visibility push(hidden)` guarded by an
+ * identical condition, but there is no corresponding `pop` pragma. This can
+ * cause trouble for code following headers above including libc headers because
+ * linker suddenly considers declarations from them (e.g., `strcmp()`) to be
+ * hidden.
+ *
+ * In order to address this situation all UDK2017 headers used by this tool
+ * must be listed above and included indirectly through this header which
+ * restores default visibility.
+ *
+ * Mind that this issue appears only if the following conditions are satisfied
+ * and not all toolchains are configured to build position-independent code by
+ * default (as if -fpic or -fpie appears on compilation command-line).
+ */
+#if defined(__GNUC__) && defined(__pic__) && !defined(USING_LTO)
+#pragma GCC visibility pop
+#endif
+
+#endif // SMMSTORETOOL__UDK2017_H__
diff --git a/util/smmstoretool/utils.c b/util/smmstoretool/utils.c
new file mode 100644
index 0000000000..9f554e0501
--- /dev/null
+++ b/util/smmstoretool/utils.c
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "utils.h"
+
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void *xmalloc(size_t size)
+{
+	void *p = malloc(size);
+	if (p == NULL) {
+		fprintf(stderr, "Failed to allocate memory\n");
+		abort();
+	}
+	return p;
+}
+
+char *to_chars(const CHAR16 uchars[], size_t size)
+{
+	char *chars = xmalloc(size / 2 + 1);
+
+	const CHAR16 *from = uchars;
+	char *to = chars;
+	while (*from != 0) {
+		CHAR16 uc = *from++;
+		if (uc < CHAR_MAX)
+			*to++ = uc;
+		else
+			*to++ = '?';
+	}
+
+	// In case there was no terminating NUL.
+	if (to != chars && to[-1] != '\0')
+		*to = '\0';
+
+	return chars;
+}
+
+CHAR16 *to_uchars(const char chars[], size_t *size)
+{
+	*size = (strlen(chars) + 1) * 2;
+	CHAR16 *uchars = xmalloc(*size);
+
+	const char *from = chars;
+	CHAR16 *to = uchars;
+	while (*from != '\0')
+		*to++ = *from++;
+	*to = 0;
+
+	return uchars;
+}
+
+bool str_eq(const char lhs[], const char rhs[])
+{
+	return strcmp(lhs, rhs) == 0;
+}
+
+struct mem_range_t map_file(const char path[], bool rw)
+{
+	struct mem_range_t range = {0};
+
+	int open_flags = rw ? O_RDWR : O_RDONLY;
+	int mmap_flags = rw ? PROT_READ | PROT_WRITE : PROT_READ;
+
+	int fd = open(path, open_flags);
+	if (fd == -1) {
+		fprintf(stderr, "Failed to open(): %s\n", strerror(errno));
+		return range;
+	}
+
+	struct stat stat_buf;
+	if (fstat(fd, &stat_buf) != 0) {
+		(void)close(fd);
+		fprintf(stderr, "Failed to fstat(): %s\n", strerror(errno));
+		return range;
+	}
+
+	if (stat_buf.st_size == 0) {
+		(void)close(fd);
+		fprintf(stderr, "Can't map an empty \"%s\" file\n", path);
+		return range;
+	}
+
+	uint8_t *mem = mmap(/*addr=*/NULL, stat_buf.st_size, mmap_flags,
+			    MAP_SHARED | MAP_POPULATE, fd, /*offset=*/0);
+	(void)close(fd);
+	if (mem == MAP_FAILED) {
+		fprintf(stderr, "Failed to mmap(): %s\n", strerror(errno));
+		return range;
+	}
+
+	range.start = mem;
+	range.length = stat_buf.st_size;
+	return range;
+}
+
+void unmap_file(struct mem_range_t store)
+{
+	if (munmap(store.start, store.length) != 0)
+		fprintf(stderr, "Failed to munmap(): %s\n", strerror(errno));
+}
diff --git a/util/smmstoretool/utils.h b/util/smmstoretool/utils.h
new file mode 100644
index 0000000000..a1cefc1748
--- /dev/null
+++ b/util/smmstoretool/utils.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__UTILS_H__
+#define SMMSTORETOOL__UTILS_H__
+
+#include <stddef.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "udk2017.h"
+
+struct mem_range_t {
+	uint8_t *start;
+	size_t length;
+};
+
+void *xmalloc(size_t size);
+
+char *to_chars(const CHAR16 uchars[], size_t size);
+
+CHAR16 *to_uchars(const char chars[], size_t *size);
+
+bool str_eq(const char lhs[], const char rhs[]);
+
+struct mem_range_t map_file(const char path[], bool rw);
+
+void unmap_file(struct mem_range_t store);
+
+#endif // SMMSTORETOOL__UTILS_H__
diff --git a/util/smmstoretool/vs.c b/util/smmstoretool/vs.c
new file mode 100644
index 0000000000..a1167ca2de
--- /dev/null
+++ b/util/smmstoretool/vs.c
@@ -0,0 +1,232 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "vs.h"
+
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "udk2017.h"
+#include "utils.h"
+
+static size_t get_var_hdr_size(bool auth_vars)
+{
+	if (auth_vars)
+		return sizeof(AUTHENTICATED_VARIABLE_HEADER);
+	return sizeof(VARIABLE_HEADER);
+}
+
+struct var_store_t vs_load(struct mem_range_t vs_data, bool auth_vars)
+{
+	uint8_t *var_hdr = vs_data.start;
+
+	struct var_store_t vs = {
+		.auth_vars = auth_vars,
+		.vars = NULL,
+	};
+
+	struct var_t *last_var = NULL;
+
+	const size_t var_hdr_size = get_var_hdr_size(auth_vars);
+	while (var_hdr + var_hdr_size < vs_data.start + vs_data.length) {
+		uint16_t start_id;
+		uint8_t state;
+		struct var_t var = {0};
+		uint8_t *var_data = var_hdr;
+
+		if (auth_vars) {
+			const AUTHENTICATED_VARIABLE_HEADER *auth_hdr =
+				(void *)var_data;
+
+			start_id = auth_hdr->StartId;
+			state = auth_hdr->State;
+
+			var.reserved = auth_hdr->Reserved;
+			var.attrs = auth_hdr->Attributes;
+			var.name_size = auth_hdr->NameSize;
+			var.data_size = auth_hdr->DataSize;
+			var.guid = auth_hdr->VendorGuid;
+		} else {
+			const VARIABLE_HEADER *no_auth_hdr = (void *)var_data;
+
+			start_id = no_auth_hdr->StartId;
+			state = no_auth_hdr->State;
+
+			var.reserved = no_auth_hdr->Reserved;
+			var.attrs = no_auth_hdr->Attributes;
+			var.name_size = no_auth_hdr->NameSize;
+			var.data_size = no_auth_hdr->DataSize;
+			var.guid = no_auth_hdr->VendorGuid;
+		}
+
+		var_hdr += HEADER_ALIGN(var_hdr_size +
+					var.name_size +
+					var.data_size);
+
+		if (start_id != VARIABLE_DATA)
+			break;
+
+		if (state != VAR_ADDED)
+			continue;
+
+		if (var.data_size == UINT32_MAX ||
+		    var.name_size == UINT32_MAX ||
+		    var.attrs == UINT32_MAX)
+			continue;
+
+		CHAR16 *name = (void *)(var_data + var_hdr_size);
+		var.name = xmalloc(var.name_size);
+		memcpy(var.name, name, var.name_size);
+
+		uint8_t *data =
+			(void *)(var_data + var_hdr_size + var.name_size);
+		var.data = xmalloc(var.data_size);
+		memcpy(var.data, data, var.data_size);
+
+		struct var_t *var_node = xmalloc(sizeof(*var_node));
+		*var_node = var;
+		if (last_var != NULL)
+			last_var->next = var_node;
+		else if (vs.vars == NULL)
+			vs.vars = var_node;
+		last_var = var_node;
+	}
+
+	return vs;
+}
+
+static void store_var(const struct var_t *var, bool auth_vars, uint8_t *data)
+{
+	if (auth_vars) {
+		AUTHENTICATED_VARIABLE_HEADER hdr;
+		memset(&hdr, 0xff, sizeof(hdr));
+
+		hdr.StartId = VARIABLE_DATA;
+		hdr.State = VAR_ADDED;
+		hdr.Reserved = var->reserved;
+		hdr.Attributes = var->attrs;
+		hdr.VendorGuid = var->guid;
+		hdr.NameSize = var->name_size;
+		hdr.DataSize = var->data_size;
+
+		memcpy(data, &hdr, sizeof(hdr));
+		data += sizeof(hdr);
+	} else {
+		VARIABLE_HEADER hdr;
+		memset(&hdr, 0xff, sizeof(hdr));
+
+		hdr.StartId = VARIABLE_DATA;
+		hdr.State = VAR_ADDED;
+		hdr.Reserved = var->reserved;
+		hdr.Attributes = var->attrs;
+		hdr.VendorGuid = var->guid;
+		hdr.NameSize = var->name_size;
+		hdr.DataSize = var->data_size;
+
+		memcpy(data, &hdr, sizeof(hdr));
+		data += sizeof(hdr);
+	}
+
+	memcpy(data, var->name, var->name_size);
+	memcpy(data + var->name_size, var->data, var->data_size);
+}
+
+bool vs_store(struct var_store_t *vs, struct mem_range_t vs_data)
+{
+	uint8_t *out_data = vs_data.start;
+
+	const size_t var_hdr_size = get_var_hdr_size(vs->auth_vars);
+	for (struct var_t *var = vs->vars; var != NULL; var = var->next) {
+		const size_t var_size =
+			var_hdr_size + var->name_size + var->data_size;
+		if (out_data + var_size > vs_data.start + vs_data.length) {
+			fprintf(stderr,
+				"Not enough space to serialize Variable Store.\n");
+			return false;
+		}
+
+		store_var(var, vs->auth_vars, out_data);
+		out_data += HEADER_ALIGN(var_size);
+	}
+
+	// The rest is "uninitialized".
+	memset(out_data, 0xff, vs_data.length - (out_data - vs_data.start));
+
+	return true;
+}
+
+struct var_t *vs_new_var(struct var_store_t *vs)
+{
+	struct var_t *new_var = xmalloc(sizeof(*new_var));
+
+	memset(new_var, 0, sizeof(*new_var));
+	new_var->attrs = EFI_VARIABLE_NON_VOLATILE
+				   | EFI_VARIABLE_BOOTSERVICE_ACCESS
+				   | EFI_VARIABLE_RUNTIME_ACCESS;
+
+	struct var_t *var = vs->vars;
+	if (var == NULL) {
+		vs->vars = new_var;
+	} else {
+		while (var->next != NULL)
+			var = var->next;
+		var->next = new_var;
+	}
+
+	return new_var;
+}
+
+struct var_t *vs_find(struct var_store_t *vs,
+		      const char name[],
+		      const EFI_GUID *guid)
+{
+	size_t name_size;
+	CHAR16 *uchar_name = to_uchars(name, &name_size);
+
+	struct var_t *var;
+	for (var = vs->vars; var != NULL; var = var->next) {
+		if (var->name_size != name_size)
+			continue;
+		if (memcmp(var->name, uchar_name, name_size) != 0)
+			continue;
+		if (memcmp(&var->guid, guid, sizeof(*guid)) != 0)
+			continue;
+		break;
+	}
+
+	free(uchar_name);
+	return var;
+}
+
+static void free_var(struct var_t *var)
+{
+	free(var->name);
+	free(var->data);
+	free(var);
+}
+
+void vs_delete(struct var_store_t *vs, struct var_t *var)
+{
+	if (vs->vars == var) {
+		vs->vars = var->next;
+		free_var(var);
+		return;
+	}
+
+	for (struct var_t *v = vs->vars; v != NULL; v = v->next) {
+		if (v->next == var) {
+			v->next = var->next;
+			free_var(var);
+			return;
+		}
+	}
+}
+
+void vs_free(struct var_store_t *vs)
+{
+	for (struct var_t *next, *var = vs->vars; var != NULL; var = next) {
+		next = var->next;
+		free_var(var);
+	}
+}
diff --git a/util/smmstoretool/vs.h b/util/smmstoretool/vs.h
new file mode 100644
index 0000000000..2ac9e6c8b2
--- /dev/null
+++ b/util/smmstoretool/vs.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef SMMSTORETOOL__VS_H__
+#define SMMSTORETOOL__VS_H__
+
+#include <stdbool.h>
+
+#include "udk2017.h"
+#include "utils.h"
+
+// Variable store is part of firmware volume.  This unit doesn't deal with its
+// header only with data that follows.
+
+struct var_t {
+	uint8_t reserved;
+	uint32_t attrs;
+	EFI_GUID guid;
+	CHAR16 *name;
+	size_t name_size; // in bytes
+	uint8_t *data;
+	size_t data_size; // in bytes
+	struct var_t *next;
+};
+
+struct var_store_t {
+	struct var_t *vars;
+	bool auth_vars;
+};
+
+struct var_store_t vs_load(struct mem_range_t vs_data, bool auth_vars);
+
+bool vs_store(struct var_store_t *vs, struct mem_range_t vs_data);
+
+struct var_t *vs_new_var(struct var_store_t *vs);
+
+struct var_t *vs_find(struct var_store_t *vs,
+		      const char name[],
+		      const EFI_GUID *guid);
+
+void vs_delete(struct var_store_t *vs, struct var_t *var);
+
+void vs_free(struct var_store_t *vs);
+
+#endif // SMMSTORETOOL__VS_H__
diff --git a/util/util_readme/post_util.md b/util/util_readme/post_util.md
index 78519ad14c..892dc8a766 100644
--- a/util/util_readme/post_util.md
+++ b/util/util_readme/post_util.md
@@ -4,6 +4,7 @@
 * [cbfstool](util/cbfstool/index.md)
 * [ifdtool](util/ifdtool/index.md)
 * [intelp2m](util/intelp2m/index.md)
+* [smmstoretool](util/smmstoretool/index.md)
 
 ## Generated documentation