diff mbox series

[v3,1/4] efi: add EFI_SYSTEM_TABLE_POINTER for debug

Message ID 20250522011749.3498970-2-paulliu@debian.org
State New
Headers show
Series Add EFI Debug Support Table feature | expand

Commit Message

Ying-Chun Liu (PaulLiu) May 22, 2025, 1:17 a.m. UTC 
From: "Ying-Chun Liu (PaulLiu)" <paul.liu@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.liu@linaro.org>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Peter Robinson <pbrobinson@gmail.com>
---
V2: add Kconfig options to turn on/off this feature.
V3: make efi_initialize_system_table_pointer() do the job as described.
---
 include/efi_api.h             | 16 ++++++++++++
 include/efi_loader.h          |  2 ++
 lib/efi_loader/Kconfig        |  7 ++++++
 lib/efi_loader/efi_boottime.c | 46 +++++++++++++++++++++++++++++++++++
 lib/efi_loader/efi_setup.c    |  8 ++++++
 5 files changed, 79 insertions(+)
diff mbox series

Patch

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..d878fc9021d 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -71,6 +71,13 @@  config EFI_SECURE_BOOT
 config EFI_SIGNATURE_SUPPORT
 	bool
 
+config EFI_DEBUG_SUPPORT_TABLE
+	bool "EFI Debug Support Table"
+	help
+	  Select this option if you want to setup the EFI Debug Support
+	  Table 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/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index dbebb37dc04..5a4349f8679 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -4001,6 +4001,8 @@  struct efi_system_table __efi_runtime_data systab = {
 	.tables = NULL,
 };
 
+struct efi_system_table_pointer __efi_runtime_data * systab_pointer = NULL;
+
 /**
  * efi_initialize_system_table() - Initialize system table
  *
@@ -4035,3 +4037,47 @@  efi_status_t efi_initialize_system_table(void)
 
 	return ret;
 }
+
+/**
+ * efi_initialize_system_table() - Initialize system table pointer
+ *
+ * Return:	status code
+ */
+efi_status_t efi_initialize_system_table_pointer(void)
+{
+	efi_status_t ret;
+	const int size_4MB = 0x00400000;
+	int pages = efi_size_in_pages(sizeof(struct efi_system_table_pointer));
+	int alignment_mask = size_4MB - 1;
+	int real_pages = pages + efi_size_in_pages(size_4MB);
+	u64 addr;
+	u64 aligned_addr;
+	u32 crc32_value;
+
+	/* Allocate configuration table array */
+	ret = efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES,
+				 EFI_RUNTIME_SERVICES_DATA,
+				 real_pages,
+				 &addr);
+
+	if (ret != EFI_SUCCESS) {
+		log_err("Installing EFI system table pointer failed\n");
+		return ret;
+	}
+
+	/* alignment to 4MB boundary */
+	aligned_addr = (addr + alignment_mask) & ~alignment_mask;
+
+	systab_pointer = (struct efi_system_table_pointer *)aligned_addr;
+	memset(systab_pointer, 0, sizeof(struct efi_system_table_pointer));
+
+	systab_pointer->signature = EFI_SYSTEM_TABLE_SIGNATURE;
+	systab_pointer->efi_system_table_base = (efi_physical_addr_t)&systab;
+	systab_pointer->crc32 = 0;
+	crc32_value = crc32(0,
+			    (const unsigned char *)systab_pointer,
+			    sizeof(struct efi_system_table_pointer));
+	systab_pointer->crc32 = crc32_value;
+
+	return ret;
+}
diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
index 48f91da5df7..a6b37d994f6 100644
--- a/lib/efi_loader/efi_setup.c
+++ b/lib/efi_loader/efi_setup.c
@@ -278,6 +278,14 @@  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_TABLE)) {
+		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)