[PATCH v15 3/6] x86/boot: Introduce efi_get_rsdp_addr() to find RSDP from EFI table

Chao Fan
2019-01-07T03:24:10Z

Memory information in SRAT is necessary to fix the conflict between
KASLR and memory-hotremove. So RSDP and SRAT should be parsed.

When booting form KEXEC/EFI/BIOS, the methods to compute RSDP
are different. When booting from EFI, EFI table points to RSDP.
So parse the EFI table and find the RSDP.

Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
---
arch/x86/boot/compressed/acpi.c | 83 +++++++++++++++++++++++++++++++++
1 file changed, 83 insertions(+)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 7ca5001d7639..f74c5d033d79 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -5,6 +5,8 @@
#include "../string.h"

#include <linux/acpi.h>
+#include <linux/efi.h>
+#include <asm/efi.h>

/*
* Max length of 64-bit hex address string is 19, prefix "0x" + 16 hex
@@ -28,3 +30,84 @@ static acpi_physical_address get_acpi_rsdp(void)
#endif
return 0;
}
+
+/* Search EFI table for RSDP. */
+static acpi_physical_address efi_get_rsdp_addr(void)
+{
+ acpi_physical_address rsdp_addr = 0;
+#ifdef CONFIG_EFI
+ efi_system_table_t *systab;
+ struct efi_info *ei;
+ bool efi_64;
+ char *sig;
+ int size;
+ int i;
+
+ ei = &boot_params->efi_info;
+ sig = (char *)&ei->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 0;
+ }
+
+ /* Get systab from boot params. Based on efi_init(). */
+#ifdef CONFIG_X86_64
+ systab = (efi_system_table_t *)(ei->efi_systab | ((__u64)ei->efi_systab_hi<<32));
+#else
+ if (ei->efi_systab_hi || ei->efi_memmap_hi) {
+ debug_putstr("Error getting RSDP address: EFI system table located above 4GB.\n");
+ return 0;
+ }
+ systab = (efi_system_table_t *)ei->efi_systab;
+#endif
+
+ if (!systab)
+ error("EFI system table is not found.");
+
+ /*
+ * Get EFI tables from systab. Based on efi_config_init() and
+ * efi_config_parse_tables().
+ */
+ size = efi_64 ? sizeof(efi_config_table_64_t) :
+ sizeof(efi_config_table_32_t);
+
+ for (i = 0; i < systab->nr_tables; i++) {
+ void *config_tables;
+ unsigned long table;
+ efi_guid_t guid;
+
+ config_tables = (void *)(systab->tables + size * i);
+ if (efi_64) {
+ efi_config_table_64_t *tmp_table;
+ u64 table64;
+
+ tmp_table = config_tables;
+ guid = tmp_table->guid;
+ table64 = tmp_table->table;
+ table = table64;
+
+ if (!IS_ENABLED(CONFIG_X86_64) && table64 >> 32) {
+ debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
+ return 0;
+ }
+ } else {
+ efi_config_table_32_t *tmp_table;
+
+ tmp_table = config_tables;
+ guid = tmp_table->guid;
+ table = tmp_table->table;
+ }
+
+ if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
+ rsdp_addr = table;
+ else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
+ return table;
+ }
+#endif
+ return rsdp_addr;
+}
--
2.20.1