efi/libstub: Distinguish between native/mixed not 32/64 bit

Currently, we support mixed mode by casting all boot time firmware
calls to 64-bit explicitly on native 64-bit systems, and to 32-bit
on 32-bit systems or 64-bit systems running with 32-bit firmware.

Due to this explicit awareness of the bitness in the code, we do a
lot of casting even on generic code that is shared with other
architectures, where mixed mode does not even exist. This casting
leads to loss of coverage of type checking by the compiler, which
we should try to avoid.

So instead of distinguishing between 32-bit vs 64-bit, distinguish
between native vs mixed, and limit all the nasty casting and
pointer mangling to the code that actually deals with mixed mode.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-10-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 15 insertions, 30 deletions

diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index e02579907f2e..1a814dc235ba 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -431,9 +431,7 @@ static efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg,
 	efi_file_handle_t *fh;
 	efi_guid_t fs_proto = EFI_FILE_SYSTEM_GUID;
 	efi_status_t status;
-	void *handle = (void *)(unsigned long)efi_table_attr(efi_loaded_image,
-							     device_handle,
-							     image);
+	void *handle = efi_table_attr(efi_loaded_image, device_handle, image);
 
 	status = efi_call_early(handle_protocol, handle,
 				&fs_proto, (void **)&io);
@@ -942,33 +940,20 @@ fail:
 	return status;
 }
 
-#define GET_EFI_CONFIG_TABLE(bits)					\
-static void *get_efi_config_table##bits(efi_system_table_t *_sys_table,	\
-					efi_guid_t guid)		\
-{									\
-	efi_system_table_##bits##_t *sys_table;				\
-	efi_config_table_##bits##_t *tables;				\
-	int i;								\
-									\
-	sys_table = (typeof(sys_table))_sys_table;			\
-	tables = (typeof(tables))(unsigned long)sys_table->tables;	\
-									\
-	for (i = 0; i < sys_table->nr_tables; i++) {			\
-		if (efi_guidcmp(tables[i].guid, guid) != 0)		\
-			continue;					\
-									\
-		return (void *)(unsigned long)tables[i].table;		\
-	}								\
-									\
-	return NULL;							\
-}
-GET_EFI_CONFIG_TABLE(32)
-GET_EFI_CONFIG_TABLE(64)
-
 void *get_efi_config_table(efi_system_table_t *sys_table, efi_guid_t guid)
 {
-	if (efi_is_64bit())
-		return get_efi_config_table64(sys_table, guid);
-	else
-		return get_efi_config_table32(sys_table, guid);
+	unsigned long tables = efi_table_attr(efi_system_table, tables, sys_table);
+	int nr_tables = efi_table_attr(efi_system_table, nr_tables, sys_table);
+	int i;
+
+	for (i = 0; i < nr_tables; i++) {
+		efi_config_table_t *t = (void *)tables;
+
+		if (efi_guidcmp(t->guid, guid) == 0)
+			return efi_table_attr(efi_config_table, table, t);
+
+		tables += efi_is_native() ? sizeof(efi_config_table_t)
+					  : sizeof(efi_config_table_32_t);
+	}
+	return NULL;
 }