Merge tag 'efi-2026-03-14' of https://source.denx.de/u-boot/custodians/u-boot-efi into next

Pull request efi-2026-03-14

CI: https://source.denx.de/u-boot/custodians/u-boot-efi/-/pipelines/29512

UEFI:

* Require at least 128 KiB of stack space to use EFI sub-system.
* Avoid buffer overrun in efi_var_restore().
* Avoid superfluous variable store writes on unchanged data
* Implement SPI Flash store for EFI variables.
* Add an efidebug ecpt sub-command to display the ECPT table
  and a unit test for the command.

Others:

* Add missing include string.h to make exception command build again.
* lib: uuid: add EBBR 2.1 conformance profile GUID

9 files changed, 227 insertions, 12 deletions

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 579eed65880..b5f81e0ff53 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -15,6 +15,8 @@ config EFI_LOADER
 	# We need EFI_STUB_32BIT to be set on x86_32 with EFI_STUB
 	depends on !EFI_STUB || !X86 || X86_64 || EFI_STUB_32BIT
 	depends on !EFI_APP
+	# The EFI specification requires 128 KiB or more of stack space
+	depends on STACK_SIZE >= 0x20000
 	default y if !ARM || SYS_CPU = armv7 || SYS_CPU = armv8
 	select EFI
 	select CHARSET
@@ -124,6 +126,24 @@ config EFI_VARIABLE_FILE_STORE
 	  Select this option if you want non-volatile UEFI variables to be
 	  stored as file /ubootefi.var on the EFI system partition.
 
+config EFI_VARIABLE_SF_STORE
+	bool "Store non-volatile UEFI variables in SPI Flash"
+	depends on SPI_FLASH
+	help
+	  Select this option if you want non-volatile UEFI variables to be
+	  stored in SPI Flash.
+
+	  Define CONFIG_EFI_VARIABLE_SF_OFFSET as offset in SPI Flash to use as
+	  the storage for variables. CONFIG_EFI_VAR_BUF_SIZE defines the space
+	  needed.
+
+	  Note that SPI Flash devices have a limited number of program/erase
+	  cycles. Frequent updates to UEFI variables may cause excessive wear
+	  and can permanently damage the flash device, particularly on SPI NAND
+	  or low-end SPI NOR parts without wear leveling. This option should be
+	  used with care on such systems, and is not recommended for platforms
+	  where UEFI variables are updated frequently.
+
 config EFI_MM_COMM_TEE
 	bool "UEFI variables storage service via the trusted world"
 	depends on OPTEE
@@ -194,6 +214,21 @@ config FFA_SHARED_MM_BUF_ADDR
 	  the MM SP in secure world.
 	  It is assumed that the MM SP knows the address of the shared MM communication buffer.
 
+config EFI_VARIABLE_SF_OFFSET
+	hex "EFI variables in SPI flash offset"
+	depends on EFI_VARIABLE_SF_STORE
+	help
+	  Offset from the start of the SPI Flash where EFI variables will be stored.
+	  This should be aligned to the sector size of SPI Flash.
+
+config EFI_VARIABLE_SF_DEVICE_INDEX
+	int "Device Index for target SPI Flash"
+	depends on EFI_VARIABLE_SF_STORE
+	default 0
+	help
+	  The index of SPI Flash device used for storing EFI variables. This would be
+	  needed if there are more than 1 SPI Flash devices available to use.
+
 config EFI_VARIABLES_PRESEED
 	bool "Initial values for UEFI variables"
 	depends on !COMPILE_TEST
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index ca1775eb03b..d73ad43951b 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -54,6 +54,7 @@ obj-y += efi_variable_tee.o
 else
 obj-y += efi_variable.o
 obj-$(CONFIG_EFI_VARIABLE_FILE_STORE) += efi_var_file.o
+obj-$(CONFIG_EFI_VARIABLE_SF_STORE) += efi_var_sf.o
 obj-$(CONFIG_EFI_VARIABLES_PRESEED) += efi_var_seed.o
 endif
 obj-y += efi_watchdog.o
diff --git a/lib/efi_loader/efi_conformance.c b/lib/efi_loader/efi_conformance.c
index 2d31800ccb8..470141af483 100644
--- a/lib/efi_loader/efi_conformance.c
+++ b/lib/efi_loader/efi_conformance.c
@@ -12,7 +12,7 @@
 #include <efi_api.h>
 #include <malloc.h>
 
-static const efi_guid_t efi_ecpt_guid = EFI_CONFORMANCE_PROFILES_TABLE_GUID;
+const efi_guid_t efi_ecpt_guid = EFI_CONFORMANCE_PROFILES_TABLE_GUID;
 
 /**
  * efi_ecpt_register() - Install the ECPT system table.
diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
index 35eb6a77766..73d4097464c 100644
--- a/lib/efi_loader/efi_runtime.c
+++ b/lib/efi_loader/efi_runtime.c
@@ -210,6 +210,30 @@ void __efi_runtime efi_memcpy_runtime(void *dest, const void *src, size_t n)
 }
 
 /**
+ * efi_memcmp_runtime() - compare memory areas
+ *
+ * At runtime memcmp() is not available.
+ *
+ * @s1:		first memory area
+ * @s2:		second memory area
+ * @n:		number of bytes to compare
+ * Return:	0 if equal, negative if s1 < s2, positive if s1 > s2
+ */
+int __efi_runtime efi_memcmp_runtime(const void *s1, const void *s2, size_t n)
+{
+	const u8 *pos1 = s1;
+	const u8 *pos2 = s2;
+
+	for (; n; --n) {
+		if (*pos1 != *pos2)
+			return *pos1 - *pos2;
+		++pos1;
+		++pos2;
+	}
+	return 0;
+}
+
+/**
  * efi_update_table_header_crc32() - Update crc32 in table header
  *
  * @table:	EFI table
diff --git a/lib/efi_loader/efi_var_common.c b/lib/efi_loader/efi_var_common.c
index 5ea1688dca3..d63c2d1b1cd 100644
--- a/lib/efi_loader/efi_var_common.c
+++ b/lib/efi_loader/efi_var_common.c
@@ -497,6 +497,8 @@ efi_status_t efi_var_restore(struct efi_var_file *buf, bool safe)
 	efi_status_t ret;
 
 	if (buf->reserved || buf->magic != EFI_VAR_FILE_MAGIC ||
+	    buf->length > EFI_VAR_BUF_SIZE ||
+	    buf->length < sizeof(struct efi_var_file) ||
 	    buf->crc32 != crc32(0, (u8 *)buf->var,
 				buf->length - sizeof(struct efi_var_file))) {
 		log_err("Invalid EFI variables file\n");
@@ -524,7 +526,7 @@ efi_status_t efi_var_restore(struct efi_var_file *buf, bool safe)
 			continue;
 		ret = efi_var_mem_ins(var->name, &var->guid, var->attr,
 				      var->length, data, 0, NULL,
-				      var->time);
+				      var->time, NULL);
 		if (ret != EFI_SUCCESS)
 			log_err("Failed to set EFI variable %ls\n", var->name);
 	}
diff --git a/lib/efi_loader/efi_var_mem.c b/lib/efi_loader/efi_var_mem.c
index 31180df9e3a..8d5f99f4870 100644
--- a/lib/efi_loader/efi_var_mem.c
+++ b/lib/efi_loader/efi_var_mem.c
@@ -159,12 +159,39 @@ efi_status_t __efi_runtime efi_var_mem_ins(
 				const efi_guid_t *vendor, u32 attributes,
 				const efi_uintn_t size1, const void *data1,
 				const efi_uintn_t size2, const void *data2,
-				const u64 time)
+				const u64 time, bool *changep)
 {
 	u16 *data;
 	struct efi_var_entry *var;
 	u32 var_name_len;
 
+	if (changep)
+		*changep = true;
+
+	/*
+	 * If this is not an append (size2 == 0), check whether the variable
+	 * already exists with identical attributes and data. When nothing
+	 * changed we can skip the write and avoid superfluous erases.
+	 */
+	if (!size2 && changep) {
+		struct efi_var_entry *old;
+
+		old = efi_var_mem_find(vendor, variable_name, NULL);
+		if (old && old->attr == attributes &&
+		    old->length == size1 && old->time == time) {
+			u16 *old_data;
+
+			for (old_data = old->name; *old_data; ++old_data)
+				;
+			++old_data;
+
+			if (!efi_memcmp_runtime(old_data, data1, size1)) {
+				*changep = false;
+				return EFI_SUCCESS;
+			}
+		}
+	}
+
 	var = (struct efi_var_entry *)
 	      ((uintptr_t)efi_var_buf + efi_var_buf->length);
 	var_name_len = u16_strlen(variable_name) + 1;
diff --git a/lib/efi_loader/efi_var_sf.c b/lib/efi_loader/efi_var_sf.c
new file mode 100644
index 00000000000..6eae8d46464
--- /dev/null
+++ b/lib/efi_loader/efi_var_sf.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * SPI Flash interface for UEFI variables
+ *
+ * Copyright (c) 2023, Shantur Rathore
+ * Copyright (C) 2026, Advanced Micro Devices, Inc.
+ */
+
+#define LOG_CATEGORY LOGC_EFI
+
+#include <efi_loader.h>
+#include <efi_variable.h>
+#include <spi_flash.h>
+#include <dm.h>
+
+efi_status_t efi_var_to_storage(void)
+{
+	struct efi_var_file *buf;
+	struct spi_flash *flash;
+	struct udevice *sfdev;
+	efi_status_t ret;
+	size_t erase_len;
+	loff_t len;
+	int r;
+
+	ret = efi_var_collect(&buf, &len, EFI_VARIABLE_NON_VOLATILE);
+	if (ret != EFI_SUCCESS)
+		goto error;
+
+	if (len > EFI_VAR_BUF_SIZE) {
+		log_debug("EFI var buffer length more than target SPI Flash size\n");
+		ret = EFI_OUT_OF_RESOURCES;
+		goto error;
+	}
+
+	log_debug("Got buffer to write buf->len: %d\n", buf->length);
+
+	r = uclass_get_device(UCLASS_SPI_FLASH,
+			      CONFIG_EFI_VARIABLE_SF_DEVICE_INDEX, &sfdev);
+	if (r) {
+		ret = EFI_DEVICE_ERROR;
+		goto error;
+	}
+
+	flash = dev_get_uclass_priv(sfdev);
+	if (!flash) {
+		log_debug("Failed to get SPI Flash priv data\n");
+		ret = EFI_DEVICE_ERROR;
+		goto error;
+	}
+	erase_len = ALIGN(len, flash->sector_size);
+
+	r = spi_flash_erase_dm(sfdev, CONFIG_EFI_VARIABLE_SF_OFFSET,
+			       erase_len);
+	if (r) {
+		log_debug("Failed to erase SPI Flash\n");
+		ret = EFI_DEVICE_ERROR;
+		goto error;
+	}
+
+	r = spi_flash_write_dm(sfdev, CONFIG_EFI_VARIABLE_SF_OFFSET, len, buf);
+	if (r) {
+		log_debug("Failed to write to SPI Flash: %d\n", r);
+		ret = EFI_DEVICE_ERROR;
+	}
+
+error:
+	free(buf);
+	return ret;
+}
+
+efi_status_t efi_var_from_storage(void)
+{
+	struct efi_var_file *buf;
+	struct udevice *sfdev;
+	efi_status_t ret;
+	int r;
+
+	buf = calloc(1, EFI_VAR_BUF_SIZE);
+	if (!buf) {
+		log_err("Unable to allocate buffer\n");
+		return EFI_OUT_OF_RESOURCES;
+	}
+
+	r = uclass_get_device(UCLASS_SPI_FLASH,
+			      CONFIG_EFI_VARIABLE_SF_DEVICE_INDEX, &sfdev);
+	if (r) {
+		log_err("Failed to get SPI Flash device: %d\n", r);
+		ret = EFI_DEVICE_ERROR;
+		goto error;
+	}
+
+	r = spi_flash_read_dm(sfdev, CONFIG_EFI_VARIABLE_SF_OFFSET,
+			      EFI_VAR_BUF_SIZE, buf);
+	if (r) {
+		log_err("Failed to read from SPI Flash: %d\n", r);
+		ret = EFI_DEVICE_ERROR;
+		goto error;
+	}
+
+	if (efi_var_restore(buf, false) != EFI_SUCCESS) {
+		log_err("No valid EFI variables in SPI Flash\n");
+		ret = EFI_DEVICE_ERROR;
+		goto error;
+	}
+
+	ret = EFI_SUCCESS;
+error:
+	free(buf);
+	return ret;
+}
diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
index 8512bc20f11..9923936c1b5 100644
--- a/lib/efi_loader/efi_variable.c
+++ b/lib/efi_loader/efi_variable.c
@@ -277,6 +277,7 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
 	struct efi_var_entry *var;
 	efi_uintn_t ret;
 	bool append, delete;
+	bool changed = false;
 	u64 time = 0;
 	enum efi_auth_var_type var_type;
 
@@ -366,6 +367,7 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
 	if (delete) {
 		/* EFI_NOT_FOUND has been handled before */
 		attributes = var->attr;
+		changed = true;
 		ret = EFI_SUCCESS;
 	} else if (append && var) {
 		/*
@@ -380,15 +382,19 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
 		ret = efi_var_mem_ins(variable_name, vendor,
 				      attributes & ~EFI_VARIABLE_APPEND_WRITE,
 				      var->length, old_data, data_size, data,
-				      time);
+				      time, &changed);
 	} else {
 		ret = efi_var_mem_ins(variable_name, vendor, attributes,
-				      data_size, data, 0, NULL, time);
+				      data_size, data, 0, NULL, time,
+				      &changed);
 	}
 
 	if (ret != EFI_SUCCESS)
 		return ret;
 
+	if (!changed)
+		return EFI_SUCCESS;
+
 	efi_var_mem_del(var);
 
 	if (var_type == EFI_AUTH_VAR_PK)
@@ -396,10 +402,7 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
 	else
 		ret = EFI_SUCCESS;
 
-	/*
-	 * Write non-volatile EFI variables
-	 * TODO: check if a value change has occured to avoid superfluous writes
-	 */
+	/* Write non-volatile EFI variables to storage */
 	if (attributes & EFI_VARIABLE_NON_VOLATILE) {
 		if (IS_ENABLED(CONFIG_EFI_VARIABLE_NO_STORE))
 			return EFI_SUCCESS;
@@ -498,6 +501,7 @@ efi_set_variable_runtime(u16 *variable_name, const efi_guid_t *vendor,
 	struct efi_var_entry *var;
 	efi_uintn_t ret;
 	bool append, delete;
+	bool changed = false;
 	u64 time = 0;
 
 	if (!IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE))
@@ -549,6 +553,7 @@ efi_set_variable_runtime(u16 *variable_name, const efi_guid_t *vendor,
 	if (delete) {
 		/* EFI_NOT_FOUND has been handled before */
 		attributes = var->attr;
+		changed = true;
 		ret = EFI_SUCCESS;
 	} else if (append && var) {
 		u16 *old_data = (void *)((uintptr_t)var->name +
@@ -556,15 +561,19 @@ efi_set_variable_runtime(u16 *variable_name, const efi_guid_t *vendor,
 
 		ret = efi_var_mem_ins(variable_name, vendor, attributes,
 				      var->length, old_data, data_size, data,
-				      time);
+				      time, &changed);
 	} else {
 		ret = efi_var_mem_ins(variable_name, vendor, attributes,
-				      data_size, data, 0, NULL, time);
+				      data_size, data, 0, NULL, time,
+				      &changed);
 	}
 
 	if (ret != EFI_SUCCESS)
 		return ret;
-	/* We are always inserting new variables, get rid of the old copy */
+
+	if (!changed)
+		return EFI_SUCCESS;
+
 	efi_var_mem_del(var);
 
 	return EFI_SUCCESS;
diff --git a/lib/uuid.c b/lib/uuid.c
index 0a166320e07..3a666d0430d 100644
--- a/lib/uuid.c
+++ b/lib/uuid.c
@@ -254,6 +254,12 @@ static const struct {
 		NULL, "EFI Conformance Profiles Table",
 		EFI_CONFORMANCE_PROFILES_TABLE_GUID,
 	},
+#if CONFIG_IS_ENABLED(EFI_ECPT)
+	{
+		NULL, "EFI EBBR 2.1 Conformance Profile",
+		EFI_CONFORMANCE_PROFILE_EBBR_2_1_GUID,
+	},
+#endif
 #ifdef CONFIG_EFI_RISCV_BOOT_PROTOCOL
 	{
 		NULL, "RISC-V Boot",