[PATCH 2/4] efi: libstub: Permit mixed mode return types other than efi_status_t

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Rework the EFI stub macro wrappers around protocol method calls and
other indirect calls in order to allow return types other than
efi_status_t. This means the widening should be conditional on whether
or not the return type is efi_status_t, and should be omitted otherwise.

Note that this does not take into account that unsigned long types might
exist that are not efi_status_t, but that can be addressed when it
becomes an issue.

Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 arch/x86/boot/compressed/efi_thunk_64.S |  6 ----
 arch/x86/include/asm/efi.h              | 38 ++++++++------------
 drivers/firmware/efi/libstub/efistub.h  | 16 ++++++---
 3 files changed, 26 insertions(+), 34 deletions(-)

diff --git a/arch/x86/boot/compressed/efi_thunk_64.S b/arch/x86/boot/compressed/efi_thunk_64.S
index 67e7edcdfea8..0c988f2a1243 100644
--- a/arch/x86/boot/compressed/efi_thunk_64.S
+++ b/arch/x86/boot/compressed/efi_thunk_64.S
@@ -93,12 +93,6 @@ SYM_FUNC_START(__efi64_thunk)
 	movl	%ebx, %fs
 	movl	%ebx, %gs
 
-	/*
-	 * Convert 32-bit status code into 64-bit.
-	 */
-	roll	$1, %eax
-	rorq	$1, %rax
-
 	pop	%rbx
 	pop	%rbp
 	RET
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 233ae6986d6f..8edead8568ec 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -178,7 +178,7 @@ struct efi_setup_data {
 extern u64 efi_setup;
 
 #ifdef CONFIG_EFI
-extern efi_status_t __efi64_thunk(u32, ...);
+extern u64 __efi64_thunk(u32, ...);
 
 #define efi64_thunk(...) ({						\
 	u64 __pad[3]; /* must have space for 3 args on the stack */	\
@@ -344,31 +344,23 @@ static inline u32 efi64_convert_status(efi_status_t status)
 #define __efi_eat(...)
 #define __efi_eval(...) __VA_ARGS__
 
-/* The three macros below handle dispatching via the thunk if needed */
-
-#define efi_call_proto(inst, func, ...)					\
-	(efi_is_native()						\
-		? inst->func(inst, ##__VA_ARGS__)			\
-		: __efi64_thunk_map(inst, func, inst, ##__VA_ARGS__))
-
-#define efi_bs_call(func, ...)						\
-	(efi_is_native()						\
-		? efi_system_table->boottime->func(__VA_ARGS__)		\
-		: __efi64_thunk_map(efi_table_attr(efi_system_table,	\
-						   boottime),		\
-				    func, __VA_ARGS__))
+static inline efi_status_t __efi64_widen_efi_status(u64 status)
+{
+	return status ? status ^ 0x8000000080000000ULL : 0;
+}
 
-#define efi_rt_call(func, ...)						\
-	(efi_is_native()						\
-		? efi_system_table->runtime->func(__VA_ARGS__)		\
-		: __efi64_thunk_map(efi_table_attr(efi_system_table,	\
-						   runtime),		\
-				    func, __VA_ARGS__))
+/* The macro below handles dispatching via the thunk if needed */
 
-#define efi_dxe_call(func, ...)						\
+#define efi_fn_call(inst, func, ...)					\
 	(efi_is_native()						\
-		? efi_dxe_table->func(__VA_ARGS__)			\
-		: __efi64_thunk_map(efi_dxe_table, func, __VA_ARGS__))
+	? inst->func(__VA_ARGS__)					\
+	: __builtin_choose_expr(					\
+		__builtin_types_compatible_p(efi_status_t,		\
+			__typeof__(inst->func(__VA_ARGS__))),		\
+		__efi64_widen_efi_status(				\
+			__efi64_thunk_map(inst, func, ##__VA_ARGS__)),	\
+		(__typeof__(inst->func(__VA_ARGS__)))			\
+			__efi64_thunk_map(inst, func, ##__VA_ARGS__)))
 
 #else /* CONFIG_EFI_MIXED */
 
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index f403aebf0182..d26d3d7b99c0 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -44,15 +44,21 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 
 #ifndef ARCH_HAS_EFISTUB_WRAPPERS
 
-#define efi_is_native()		(true)
-#define efi_bs_call(func, ...)	efi_system_table->boottime->func(__VA_ARGS__)
-#define efi_rt_call(func, ...)	efi_system_table->runtime->func(__VA_ARGS__)
-#define efi_dxe_call(func, ...)	efi_dxe_table->func(__VA_ARGS__)
+#define efi_is_native()			(true)
 #define efi_table_attr(inst, attr)	(inst->attr)
-#define efi_call_proto(inst, func, ...) inst->func(inst, ##__VA_ARGS__)
+#define efi_fn_call(inst, func, ...)	inst->func(__VA_ARGS__)
 
 #endif
 
+#define efi_call_proto(inst, func, ...) \
+	efi_fn_call(inst, func, inst, ##__VA_ARGS__)
+#define efi_bs_call(func, ...) \
+	efi_fn_call(efi_table_attr(efi_system_table, boottime), func, ##__VA_ARGS__)
+#define efi_rt_call(func, ...) \
+	efi_fn_call(efi_table_attr(efi_system_table, runtime), func, ##__VA_ARGS__)
+#define efi_dxe_call(func, ...) \
+	efi_fn_call(efi_dxe_table, func, ##__VA_ARGS__)
+
 #define efi_info(fmt, ...) \
 	efi_printk(KERN_INFO fmt, ##__VA_ARGS__)
 #define efi_warn(fmt, ...) \
-- 
2.35.1




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