efi/libstub/x86: Avoid thunking for native firmware calls

We use special wrapper routines to invoke firmware services in the
native case as well as the mixed mode case. For mixed mode, the need
is obvious, but for the native cases, we can simply rely on the
compiler to generate the indirect call, given that GCC now has
support for the MS calling convention (and has had it for quite some
time now). Note that on i386, the decompressor and the EFI stub are not
built with -mregparm=3 like the rest of the i386 kernel, so we can
safely allow the compiler to emit the indirect calls here as well.

So drop all the wrappers and indirection, and switch to either native
calls, or direct calls into the thunk routine for 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/20191224151025.32482-14-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 20 insertions, 14 deletions

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index c27323cb49e5..001905daa110 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -152,6 +152,7 @@ struct efi_setup_data {
 extern u64 efi_setup;
 
 #ifdef CONFIG_EFI
+extern efi_status_t efi64_thunk(u32, ...);
 
 static inline bool efi_is_mixed(void)
 {
@@ -205,7 +206,6 @@ struct efi_config {
 	u64 runtime_services;
 	u64 boot_services;
 	u64 text_output;
-	efi_status_t (*call)(unsigned long, ...);
 	bool is64;
 } __packed;
 
@@ -235,30 +235,36 @@ static inline bool efi_is_native(void)
 			(unsigned long)(attr), (attr))
 
 #define efi_table_attr(table, attr, instance) ({			\
-	__typeof__(((table##_t *)0)->attr) __ret;			\
+	__typeof__(instance->attr) __ret;				\
 	if (efi_is_native()) {						\
-		__ret = ((table##_t *)(unsigned long)instance)->attr;	\
+		__ret = instance->attr;					\
 	} else {							\
-		__ret = (__typeof__(__ret))efi_mixed_mode_cast(		\
-		((table##_t *)(unsigned long)instance)->mixed_mode.attr);\
+		__ret = (__typeof__(__ret))				\
+			efi_mixed_mode_cast(instance->mixed_mode.attr);	\
 	}								\
 	__ret;								\
 })
 
 #define efi_call_proto(protocol, f, instance, ...)			\
-	__efi_early()->call((unsigned long)				\
-				efi_table_attr(protocol, f, instance),	\
-		instance, ##__VA_ARGS__)
+	(efi_is_native()						\
+		? instance->f(instance, ##__VA_ARGS__)			\
+		: efi64_thunk(instance->mixed_mode.f, instance,	##__VA_ARGS__))
 
 #define efi_call_early(f, ...)						\
-	__efi_early()->call((unsigned long)				\
-				efi_table_attr(efi_boot_services, f,	\
-		__efi_early()->boot_services), __VA_ARGS__)
+	(efi_is_native()						\
+		? ((efi_boot_services_t *)(unsigned long)		\
+			__efi_early()->boot_services)->f(__VA_ARGS__)	\
+		: efi64_thunk(((efi_boot_services_t *)(unsigned long)	\
+			__efi_early()->boot_services)->mixed_mode.f,	\
+			__VA_ARGS__))
 
 #define efi_call_runtime(f, ...)					\
-	__efi_early()->call((unsigned long)				\
-				efi_table_attr(efi_runtime_services, f,	\
-		__efi_early()->runtime_services), __VA_ARGS__)
+	(efi_is_native()						\
+		? ((efi_runtime_services_t *)(unsigned long)		\
+			__efi_early()->runtime_services)->f(__VA_ARGS__)\
+		: efi64_thunk(((efi_runtime_services_t *)(unsigned long)\
+			__efi_early()->runtime_services)->mixed_mode.f,	\
+			__VA_ARGS__))
 
 extern bool efi_reboot_required(void);
 extern bool efi_is_table_address(unsigned long phys_addr);