[PATCH 3/4] efi/runtime-wrappers: Remove duplicated macro for service returning void

Ard Biesheuvel
2023-08-04T16:04:32Z

__efi_call_virt() exists as an alternative for efi_call_virt() for the
sole reason that ResetSystem() returns void, and so we cannot use a call
to it in the RHS of an assignment.

Now that we support the use of _Generic, this is no longer needed, and
we can handle this by emitting a comma expression inside the default
branch of a _Generic() switch.

As a bonus, this ensures that the runtime service call is always
constructed and type checked by the compiler, as it is passed to
_Generic() to infer the return type. (both x86 and arm64 override
arch_efi_call_virt() to invoke a type unsafe variadic wrapper function
implemented in assembler)

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/efi/runtime-wrappers.c | 4 +---
include/linux/efi.h | 24 ++++----------------
2 files changed, 6 insertions(+), 22 deletions(-)

diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index 158685e26f430ac9..b3ef208299ae591e 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -41,8 +41,6 @@
*/
#define efi_call_virt(f, args...) \
efi_call_virt_pointer(efi.runtime, f, args)
-#define __efi_call_virt(f, args...) \
- __efi_call_virt_pointer(efi.runtime, f, args)

struct efi_runtime_work efi_rts_work;

@@ -422,7 +420,7 @@ static void virt_efi_reset_system(int reset_type,
return;
}
efi_rts_work.efi_rts_id = EFI_RESET_SYSTEM;
- __efi_call_virt(reset_system, reset_type, status, data_size, data);
+ efi_call_virt(reset_system, reset_type, status, data_size, data);
up(&efi_runtime_lock);
}

diff --git a/include/linux/efi.h b/include/linux/efi.h
index b34e11a5e969282c..c72715821016851b 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1171,8 +1171,7 @@ static inline void efi_check_for_embedded_firmwares(void) { }
#define arch_efi_call_virt(p, f, args...) ((p)->f(args))

/*
- * Arch code can implement the following three template macros, avoiding
- * reptition for the void/non-void return cases of {__,}efi_call_virt():
+ * Arch code must implement the following three template macros:
*
* * arch_efi_call_virt_setup()
*
@@ -1181,9 +1180,7 @@ static inline void efi_check_for_embedded_firmwares(void) { }
*
* * arch_efi_call_virt()
*
- * Performs the call. The last expression in the macro must be the call
- * itself, allowing the logic to be shared by the void and non-void
- * cases.
+ * Performs the call.
*
* * arch_efi_call_virt_teardown()
*
@@ -1198,7 +1195,9 @@ static inline void efi_check_for_embedded_firmwares(void) { }
arch_efi_call_virt_setup(); \
\
__flags = efi_call_virt_save_flags(); \
- __s = arch_efi_call_virt(p, f, args); \
+ __s = _Generic((p)->f(args), \
+ efi_status_t: arch_efi_call_virt((p), f, args), \
+ default: (arch_efi_call_virt((p), f, args), EFI_ABORTED));\
efi_call_virt_check_flags(__flags, __stringify(f)); \
\
arch_efi_call_virt_teardown(); \
@@ -1206,19 +1205,6 @@ static inline void efi_check_for_embedded_firmwares(void) { }
__s; \
})

-#define __efi_call_virt_pointer(p, f, args...) \
-({ \
- unsigned long __flags; \
- \
- arch_efi_call_virt_setup(); \
- \
- __flags = efi_call_virt_save_flags(); \
- arch_efi_call_virt(p, f, args); \
- efi_call_virt_check_flags(__flags, __stringify(f)); \
- \
- arch_efi_call_virt_teardown(); \
-})
-
#define EFI_RANDOM_SEED_SIZE 32U // BLAKE2S_HASH_SIZE

struct linux_efi_random_seed {
--
2.39.2