efi: add EFI_SYSTEM_TABLE_POINTER for debug

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.

Cc: Peter Robinson <pbrobinson@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de> # change memset(systab_pointer, 0 ...) -> systab_pointer->crc32 = 0;
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

diff --git a/include/efi_api.h b/include/efi_api.h
index eb61eafa0289a4fd4dbf023337a5237f6b2a5899..6c4c1a0cc7b037dc8cf27017d45b39d854e6bee0 100644 (file)
--- 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 8fd09aad2d0fe766b17a2b15c60a12906bbc59c1..ada29a5bad334a6664e1958771ef927e97128bbc 100644 (file)
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -643,6 +643,8 @@ 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 3dadbc54b58b115158f9542be00170a410b56a31..077466f01f002fa9e20600ce7d0722ca13c36122 100644 (file)
--- 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 cf050e5385dd3b4d594d03fb402f6cd4b99361af..51ccf1cd87e2c6be168d90c5997c3b7c92de3252 100644 (file)
--- 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 (file)
index 0000000..649d21e
--- /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.liu@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;
+       }
+
+       systab_pointer->crc32 = 0;
+
+       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 48f91da5df74fe2ca5f99e65be12ba635d435b2b..78c5059256ad744936cc9ee5a96a9a89fd178103 100644 (file)
--- 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)