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Subject[PATCH v12 2/5] x86/boot: Add efi_get_rsdp_addr() to find RSDP from EFI table
Date
To fix the conflict between KASLR and memory-hotremove, memory
information in SRAT table is necessary. So RSDP and SRAT table
should be parsed.

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

Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
---
arch/x86/boot/compressed/acpitb.c | 79 +++++++++++++++++++++++++++++++
1 file changed, 79 insertions(+)

diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
index 614c45655cff..c43546648638 100644
--- a/arch/x86/boot/compressed/acpitb.c
+++ b/arch/x86/boot/compressed/acpitb.c
@@ -31,3 +31,82 @@ static acpi_physical_address get_acpi_rsdp(void)
return 0;
#endif
}
+
+/* Search EFI table for RSDP. */
+static acpi_physical_address efi_get_rsdp_addr(void)
+{
+#ifdef CONFIG_EFI
+ acpi_physical_address rsdp_addr = 0;
+ efi_system_table_t *systab;
+ struct efi_info *e;
+ bool efi_64;
+ 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 0;
+ }
+
+ /* 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("Error getting RSDP address: EFI system table located above 4GB.\n");
+ return 0;
+ }
+ systab = (efi_system_table_t *)e->efi_systab;
+#endif
+
+ if (!systab)
+ return 0;
+
+ /*
+ * 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;
+
+ tmp_table = (efi_config_table_64_t *)config_tables;
+ guid = tmp_table->guid;
+ table = tmp_table->table;
+
+ if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
+ debug_putstr("Error getting RSDP address: EFI system table located above 4GB.\n");
+ return 0;
+ }
+ } 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;
+ }
+
+ if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
+ rsdp_addr = (acpi_physical_address)table;
+ else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
+ return (acpi_physical_address)table;
+ }
+ return rsdp_addr;
+#endif
+}
--
2.19.1


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