In order to parse SRAT table and get memory information, RSDP pointer
should be found. In kernel, there are three methods to get RSDP:
EFI condition, BIOS condition and KEXEC condition. The first works
for EFI condition.
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().
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
+}
--
2.19.1
