lwn.git/drivers/firmware/efi/runtime-wrappers.c, branch docs-mw

efi/runtime-wrappers: Keep track of the efi_runtime_lock owner

2025-11-11T18:59:22+00:00

The EFI runtime wrappers use a file local semaphore to serialize access to the EFI runtime services. This means that any calls to the arch wrappers around the runtime services will also be serialized, removing the need for redundant locking. For robustness, add a facility that allows those arch wrappers to assert that the semaphore was taken by the current task. Signed-off-by: Ard Biesheuvel Acked-by: Catalin Marinas Signed-off-by: Catalin Marinas

efi: Add missing __nocfi annotations to runtime wrappers

2024-06-05T08:18:58+00:00

The EFI runtime wrappers are a sandbox for calling into EFI runtime services, which are invoked using indirect calls. When running with kCFI enabled, the compiler will require the target of any indirect call to be type annotated. Given that the EFI runtime services prototypes and calling convention are governed by the EFI spec, not the Linux kernel, adding such type annotations for firmware routines is infeasible, and so the compiler must be informed that prototype validation should be omitted. Add the __nocfi annotation at the appropriate places in the EFI runtime wrapper code to achieve this. Note that this currently only affects 32-bit ARM, given that other architectures that support both kCFI and EFI use an asm wrapper to call EFI runtime services, and this hides the indirect call from the compiler. Fixes: 1a4fec49efe5 ("ARM: 9392/2: Support CLANG CFI") Reviewed-by: Linus Walleij Tested-by: Nathan Chancellor Signed-off-by: Ard Biesheuvel

efi/runtime-wrappers: Clean up white space and add __init annotation

2023-08-22T08:39:26+00:00

Some cosmetic changes as well as a missing __init annotation. Signed-off-by: Ard Biesheuvel

acpi/prmt: Use EFI runtime sandbox to invoke PRM handlers

2023-08-22T08:39:26+00:00

Instead of bypassing the kernel's adaptation layer for performing EFI runtime calls, wire up ACPI PRM handling into it. This means these calls can no longer occur concurrently with EFI runtime calls, and will be made from the EFI runtime workqueue. It also means any page faults occurring during PRM handling will be identified correctly as originating in firmware code. Acked-by: Rafael J. Wysocki Signed-off-by: Ard Biesheuvel

efi/runtime-wrappers: Don't duplicate setup/teardown code

2023-08-22T08:39:26+00:00

Avoid duplicating the EFI arch setup and teardown routine calls numerous times in efi_call_rts(). Instead, expand the efi_call_virt_pointer() macro into efi_call_rts(), taking the pre and post parts out of the switch. Signed-off-by: Ard Biesheuvel

efi/runtime-wrappers: Remove duplicated macro for service returning void

2023-08-22T08:39:26+00:00

__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. Given that there is only a single user, let's drop the macro, and expand it into the caller. That way, the remaining macro can be tightened somewhat in terms of type safety too. Note that the use of typeof() on the runtime service invocation does not result in an actual call being made, but it does require a few pointer types to be fixed up and converted into the proper function pointer prototypes. Signed-off-by: Ard Biesheuvel

efi/runtime-wrapper: Move workqueue manipulation out of line

2023-08-21T15:59:54+00:00

efi_queue_work() is a macro that implements the non-trivial manipulation of the EFI runtime workqueue and completion data structure, most of which is generic, and could be shared between all the users of the macro. So move it out of the macro and into a new helper function. Signed-off-by: Ard Biesheuvel

efi/runtime-wrappers: Use type safe encapsulation of call arguments

2023-08-21T15:59:54+00:00

The current code that marshalls the EFI runtime call arguments to hand them off to a async helper does so in a type unsafe and slightly messy manner - everything is cast to void* except for some integral types that are passed by reference and dereferenced on the receiver end. Let's clean this up a bit, and record the arguments of each runtime service invocation exactly as they are issued, in a manner that permits the compiler to check the types of the arguments at both ends. Signed-off-by: Ard Biesheuvel

Change DEFINE_SEMAPHORE() to take a number argument

2023-04-18T18:15:24+00:00

Fundamentally semaphores are a counted primitive, but DEFINE_SEMAPHORE() does not expose this and explicitly creates a binary semaphore. Change DEFINE_SEMAPHORE() to take a number argument and use that in the few places that open-coded it using __SEMAPHORE_INITIALIZER(). Signed-off-by: Peter Zijlstra (Intel) [mcgrof: add some tribal knowledge about why some folks prefer binary sempahores over mutexes] Reviewed-by: Sergey Senozhatsky Reviewed-by: Davidlohr Bueso Signed-off-by: Luis Chamberlain

efi: fix userspace infinite retry read efivars after EFI runtime services page fault

2023-01-03T09:52:16+00:00

After [1][2], if we catch exceptions due to EFI runtime service, we will clear EFI_RUNTIME_SERVICES bit to disable EFI runtime service, then the subsequent routine which invoke the EFI runtime service should fail. But the userspace cat efivars through /sys/firmware/efi/efivars/ will stuck and infinite loop calling read() due to efivarfs_file_read() return -EINTR. The -EINTR is converted from EFI_ABORTED by efi_status_to_err(), and is an improper return value in this situation, so let virt_efi_xxx() return EFI_DEVICE_ERROR and converted to -EIO to invoker. Cc: Fixes: 3425d934fc03 ("efi/x86: Handle page faults occurring while running EFI runtime services") Fixes: 23715a26c8d8 ("arm64: efi: Recover from synchronous exceptions occurring in firmware") Signed-off-by: Ding Hui Signed-off-by: Ard Biesheuvel