tree 625cf42ee7c74f560f20531ad1368ad74222076d
parent 9202040875f5da7618b0e1248170214ca697eb2b
author Ard Biesheuvel <ardb@kernel.org> 1670236285 +0100
committer Matthias Männich <maennich@google.com> 1677494649 +0000

UPSTREAM: arm64: efi: Execute runtime services from a dedicated stack

commit ff7a167961d1b97e0e205f245f806e564d3505e7 upstream.

With the introduction of PRMT in the ACPI subsystem, the EFI rts
workqueue is no longer the only caller of efi_call_virt_pointer() in the
kernel. This means the EFI runtime services lock is no longer sufficient
to manage concurrent calls into firmware, but also that firmware calls
may occur that are not marshalled via the workqueue mechanism, but
originate directly from the caller context.

For added robustness, and to ensure that the runtime services have 8 KiB
of stack space available as per the EFI spec, introduce a spinlock
protected EFI runtime stack of 8 KiB, where the spinlock also ensures
serialization between the EFI rts workqueue (which itself serializes EFI
runtime calls) and other callers of efi_call_virt_pointer().

While at it, use the stack pivot to avoid reloading the shadow call
stack pointer from the ordinary stack, as doing so could produce a
gadget to defeat it.

Bug: 260821414
Bug: 270683705
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Lee Jones <lee@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ie961576ae93cafc315cb37fb84cca0a6402eda59
(cherry picked from commit 592fa0235fac0ac3ed98a0e4cc9398ec8e5c5cb7)