From: "Ying-Chun Liu (PaulLiu)" <paul....@linaro.org>
Add EFI_SYSTEM_TABLE_POINTER structure for remote debugger to locate
the address of EFI_SYSTEM_TABLE.
This feature is described in UEFI SPEC version 2.10. Section 18.4.2.
The implementation ensures support for hardware-assisted debugging and
provides a standardized mechanism for debuggers to discover the EFI
system table.
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul....@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodi...@linaro.org>
Tested-by: Heinrich Schuchardt <xypron.g...@gmx.de>
Cc: Peter Robinson <pbrobin...@gmail.com>
Cc: Simon Glass <s...@chromium.org>
---
V2: add Kconfig options to turn on/off this feature.
V3: make efi_initialize_system_table_pointer() do the job as described.
V4: use efi_alloc_aligned_pages() for system_table_pointer.
V5: move the code into a separate module.
V6: Use macros to replace size_4MB
V7: Fix the code based on the review. Update license field.
V8: Fix pointer casting that causes qemu_arm_defconfig failed. Modify KConfig
so that more defconfigs enabled by default.
---
include/efi_api.h | 16 ++++++++++++
include/efi_loader.h | 2 ++
lib/efi_loader/Kconfig | 9 +++++++
lib/efi_loader/Makefile | 1 +
lib/efi_loader/efi_debug_support.c | 40 ++++++++++++++++++++++++++++++
lib/efi_loader/efi_setup.c | 7 ++++++
6 files changed, 75 insertions(+)
create mode 100644 lib/efi_loader/efi_debug_support.c
diff --git a/include/efi_api.h b/include/efi_api.h
index eb61eafa028..6c4c1a0cc7b 100644
--- a/include/efi_api.h
+++ b/include/efi_api.h
@@ -259,6 +259,22 @@ struct efi_capsule_result_variable_header {
efi_status_t capsule_status;
} __packed;
+/**
+ * struct efi_system_table_pointer - struct to store the pointer of system
+ * table.
+ * @signature: The signature of this struct.
+ * @efi_system_table_base: The physical address of System Table.
+ * @crc32: CRC32 checksum
+ *
+ * This struct is design for hardware debugger to search through memory to
+ * get the address of EFI System Table.
+ */
+struct efi_system_table_pointer {
+ u64 signature;
+ efi_physical_addr_t efi_system_table_base;
+ u32 crc32;
+};
+
struct efi_memory_range {
efi_physical_addr_t address;
u64 length;
diff --git a/include/efi_loader.h b/include/efi_loader.h
index 8f9f2bcf1cb..8f065244d8e 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -646,6 +646,8 @@ efi_status_t efi_tcg2_measure_dtb(void *dtb);
efi_status_t efi_root_node_register(void);
/* Called by bootefi to initialize runtime */
efi_status_t efi_initialize_system_table(void);
+/* Called by bootefi to initialize debug */
+efi_status_t efi_initialize_system_table_pointer(void);
/* efi_runtime_detach() - detach unimplemented runtime functions */
void efi_runtime_detach(void);
/* efi_convert_pointer() - convert pointer to virtual address */
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 7f02a83e2a2..621db8b5c79 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -71,6 +71,15 @@ config EFI_SECURE_BOOT
config EFI_SIGNATURE_SUPPORT
bool
+config EFI_DEBUG_SUPPORT
+ bool "EFI Debug Support"
+ default y if !HAS_BOARD_SIZE_LIMIT
+ help
+ Select this option if you want to setup the EFI Debug Support
+ Table and the EFI_SYSTEM_TABLE_POINTER which is used by the debug
+ agent or an external debugger to determine loaded image information
+ in a quiescent manner.
+
menu "UEFI services"
config EFI_GET_TIME
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index cf050e5385d..51ccf1cd87e 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -70,6 +70,7 @@ obj-$(CONFIG_EFI_RISCV_BOOT_PROTOCOL) += efi_riscv.o
obj-$(CONFIG_EFI_LOAD_FILE2_INITRD) += efi_load_initrd.o
obj-$(CONFIG_EFI_SIGNATURE_SUPPORT) += efi_signature.o
obj-$(CONFIG_EFI_ECPT) += efi_conformance.o
+obj-$(CONFIG_EFI_DEBUG_SUPPORT) += efi_debug_support.o
EFI_VAR_SEED_FILE := $(subst $\",,$(CONFIG_EFI_VAR_SEED_FILE))
$(obj)/efi_var_seed.o: $(srctree)/$(EFI_VAR_SEED_FILE)
diff --git a/lib/efi_loader/efi_debug_support.c
b/lib/efi_loader/efi_debug_support.c
new file mode 100644
index 00000000000..7dc5fa93af9
--- /dev/null
+++ b/lib/efi_loader/efi_debug_support.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * EFI debug support
+ *
+ * Copyright (c) 2025 Ying-Chun Liu, Linaro Ltd. <paul....@linaro.org>
+ */
+
+#include <efi_loader.h>
+#include <linux/sizes.h>
+#include <u-boot/crc.h>
+
+struct efi_system_table_pointer __efi_runtime_data * systab_pointer = NULL;
+
+/**
+ * efi_initialize_system_table_pointer() - Initialize system table pointer
+ *
+ * Return: status code
+ */
+efi_status_t efi_initialize_system_table_pointer(void)
+{
+ /* Allocate efi_system_table_pointer structure with 4MB alignment. */
+ systab_pointer = efi_alloc_aligned_pages(sizeof(struct
efi_system_table_pointer),
+ EFI_RUNTIME_SERVICES_DATA,
+ SZ_4M);
+
+ if (!systab_pointer) {
+ log_err("Installing EFI system table pointer failed\n");
+ return EFI_OUT_OF_RESOURCES;
+ }
+
+ memset(systab_pointer, 0, sizeof(struct efi_system_table_pointer));
+
+ systab_pointer->signature = EFI_SYSTEM_TABLE_SIGNATURE;
+ systab_pointer->efi_system_table_base = (uintptr_t)&systab;
+ systab_pointer->crc32 = crc32(0,
+ (const unsigned char *)systab_pointer,
+ sizeof(struct efi_system_table_pointer));
+
+ return EFI_SUCCESS;
+}
diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
index 48f91da5df7..78c5059256a 100644
--- a/lib/efi_loader/efi_setup.c
+++ b/lib/efi_loader/efi_setup.c
@@ -278,6 +278,13 @@ efi_status_t efi_init_obj_list(void)
if (ret != EFI_SUCCESS)
goto out;
+ /* Initialize system table pointer */
+ if (IS_ENABLED(CONFIG_EFI_DEBUG_SUPPORT)) {
+ ret = efi_initialize_system_table_pointer();
+ if (ret != EFI_SUCCESS)
+ goto out;
+ }
+
if (IS_ENABLED(CONFIG_EFI_ECPT)) {
ret = efi_ecpt_register();
if (ret != EFI_SUCCESS)
--
2.39.5
