[PATCH v3 0/2] efi: Follow-up fixes for EFI runtime stack

Ard Biesheuvel
2023-01-06T17:47:46Z

Commit ff7a167961d1b ("arm64: efi: Execute runtime services from a
dedicated stack") introduced a dedicated stack for EFI runtime services,
in an attempt to make the execution of EFI runtime services more robust,
given that they execute at the same privilege level as the kernel.

However, this stack needs to be declared to the stacktrace machinery,
which is careful not to walk the stack when it leads into memory regions
that are not known to be allocated for stack use.

Also, given that the ACPI code may invoke the low-level EFI runtime call
wrapper without using the dedicated kernel thread and workqueue, we
should take this into account when trying to gracefully handle
synchronous exceptions.

Changes since v2:
- clear efi_rt_stack_top[-1] from asm code, and use READ_ONCE() to read
its value when not holding the spinlock, to ensure that all accesses
are safe under concurrency;
- add Mark's ack to patch #2

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Lee Jones <lee@kernel.org>

Ard Biesheuvel (2):
arm64: efi: Avoid workqueue to check whether EFI runtime is live
arm64: efi: Account for the EFI runtime stack in stack unwinder

arch/arm64/include/asm/efi.h | 9 +++++++++
arch/arm64/include/asm/stacktrace.h | 15 +++++++++++++++
arch/arm64/kernel/efi-rt-wrapper.S | 6 ++++++
arch/arm64/kernel/efi.c | 3 ++-
arch/arm64/kernel/stacktrace.c | 12 ++++++++++++
5 files changed, 44 insertions(+), 1 deletion(-)

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2.39.0