Abstract out support for locating an EFI config table

We want to grab a pointer to the TPM final events table, so abstract out
the existing code for finding an FDT table and make it generic.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/firmware/efi/libstub/efi-stub-helper.c

@@ -926,3 +926,18 @@ efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table_arg,
 fail:
 	return status;
 }
+
+void *get_efi_config_table(efi_system_table_t *sys_table, efi_guid_t guid)
+{
+	efi_config_table_t *tables = (efi_config_table_t *)sys_table->tables;
+	int i;
+
+	for (i = 0; i < sys_table->nr_tables; i++) {
+		if (efi_guidcmp(tables[i].guid, guid) != 0)
+			continue;
+
+		return (void *)tables[i].table;
+	}
+
+	return NULL;
+}

drivers/firmware/efi/libstub/efistub.h

@@ -65,6 +65,8 @@ efi_status_t check_platform_features(efi_system_table_t *sys_table_arg);
 
 efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg);
 
+void *get_efi_config_table(efi_system_table_t *sys_table, efi_guid_t guid);
+
 /* Helper macros for the usual case of using simple C variables: */
 #ifndef fdt_setprop_inplace_var
 #define fdt_setprop_inplace_var(fdt, node_offset, name, var) \

drivers/firmware/efi/libstub/fdt.c

@@ -363,26 +363,17 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 
 void *get_fdt(efi_system_table_t *sys_table, unsigned long *fdt_size)
 {
-	efi_guid_t fdt_guid = DEVICE_TREE_GUID;
-	efi_config_table_t *tables;
-	int i;
+	void *fdt;
 
-	tables = (efi_config_table_t *)sys_table->tables;
+	fdt = get_efi_config_table(sys_table, DEVICE_TREE_GUID);
 
-	for (i = 0; i < sys_table->nr_tables; i++) {
-		void *fdt;
+	if (!fdt)
+		return NULL;
 
-		if (efi_guidcmp(tables[i].guid, fdt_guid) != 0)
-			continue;
-
-		fdt = (void *)tables[i].table;
-		if (fdt_check_header(fdt) != 0) {
-			pr_efi_err(sys_table, "Invalid header detected on UEFI supplied FDT, ignoring ...\n");
-			return NULL;
-		}
-		*fdt_size = fdt_totalsize(fdt);
-		return fdt;
+	if (fdt_check_header(fdt) != 0) {
+		pr_efi_err(sys_table, "Invalid header detected on UEFI supplied FDT, ignoring ...\n");
+		return NULL;
 	}
-
-	return NULL;
+	*fdt_size = fdt_totalsize(fdt);
+	return fdt;
 }