[PATCH v10 3/7] x86/boot: Add efi_get_rsdp_addr() to dig out RSDP from EFI table

[Chao Fan]

Imitate ACPI code and EFI code to dig RSDP pointer from EFI tables.
Process: boot_param->systab->efi_config_table->RSDP.
Based on efi_init(), efi_config_init(), efi_config_parse_tables().

Used for later patch to dig out SRAT table and get the memory
information. So that we can figure out the immovable memory regions
to avoid KASLR extracts kernel on movable memory, so slove the
conflict between KASLR and movable_node feature.

Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/boot/compressed/acpitb.c | 96 +++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 arch/x86/boot/compressed/acpitb.c

diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
new file mode 100644
index 000000000000..56b54b0e0889
--- /dev/null
+++ b/arch/x86/boot/compressed/acpitb.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+#define BOOT_CTYPE_H
+#include "misc.h"
+#include "error.h"
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+#include <linux/numa.h>
+#include <linux/acpi.h>
+
+/* Search EFI table for RSDP table. */
+static void efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
+{
+#ifdef CONFIG_EFI
+	efi_system_table_t *systab;
+	bool efi_64 = false;
+	void *config_tables;
+	struct efi_info *e;
+	char *sig;
+	int size;
+	int i;
+
+	e = &boot_params->efi_info;
+	sig = (char *)&e->efi_loader_signature;
+
+	if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4))
+		efi_64 = true;
+	else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4))
+		efi_64 = false;
+	else {
+		debug_putstr("Wrong EFI loader signature.\n");
+		return;
+	}
+
+	/* Get systab from boot params. Based on efi_init(). */
+#ifdef CONFIG_X86_64
+	systab = (efi_system_table_t *)(
+			e->efi_systab | ((__u64)e->efi_systab_hi<<32));
+#else
+	if (e->efi_systab_hi || e->efi_memmap_hi) {
+		debug_putstr("Table located above 4GB. EFI should be disabled.\n");
+		return;
+	}
+	systab = (efi_system_table_t *)e->efi_systab;
+#endif
+
+	if (!systab)
+		return;
+
+	/*
+	 * Get EFI tables from systab. Based on efi_config_init() and
+	 * efi_config_parse_tables(). Only dig out the config_table.
+	 */
+	size = efi_64 ? sizeof(efi_config_table_64_t) :
+			sizeof(efi_config_table_32_t);
+
+	for (i = 0; i < systab->nr_tables; i++) {
+		efi_guid_t guid;
+		unsigned long table;
+
+		config_tables = (void *)(systab->tables + size * i);
+		if (efi_64) {
+			efi_config_table_64_t *tmp_table;
+
+			tmp_table = (efi_config_table_64_t *)config_tables;
+			guid = tmp_table->guid;
+			table = tmp_table->table;
+#ifndef CONFIG_64BIT
+			if (table >> 32) {
+				debug_putstr("Table located above 4G. EFI should be disabled.\n");
+				return;
+			}
+#endif
+		} else {
+			efi_config_table_32_t *tmp_table;
+
+			tmp_table = (efi_config_table_32_t *)config_tables;
+			guid = tmp_table->guid;
+			table = tmp_table->table;
+		}
+
+		/*
+		 * Get RSDP from EFI tables.
+		 * If ACPI20 table found, use it.
+		 * If ACPI20 table not found, but ACPI table found,
+		 * use the ACPI table.
+		 */
+		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID))) {
+			*rsdp_addr = (acpi_physical_address)table;
+		} else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID))) {
+			*rsdp_addr = (acpi_physical_address)table;
+			return;
+		}
+	}
+#endif
+}
-- 
2.17.2