On Thu, Jan 12, 2023 at 2:33 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
>
> The ACPI PRM address space handler calls efi_call_virt_pointer() to
> execute PRM firmware code, but doing so is only permitted when the EFI
> runtime environment is available. Otherwise, such calls are guaranteed
> to result in a crash, and must therefore be avoided.
>
> Given that the EFI runtime services may become unavailable after a crash
> occurring in the firmware, we need to check this each time the PRM
> address space handler is invoked. If the EFI runtime services were not
> available at registration time to being with, don't install the address
> space handler at all.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> Cc: Len Brown <lenb@xxxxxxxxxx>
> Cc: linux-acpi@xxxxxxxxxxxxxxx
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> v2: check both at registration and at invocation time
>
> drivers/acpi/prmt.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/acpi/prmt.c b/drivers/acpi/prmt.c
> index 998101cf16e47145..3d4c4620f9f95309 100644
> --- a/drivers/acpi/prmt.c
> +++ b/drivers/acpi/prmt.c
> @@ -236,6 +236,11 @@ static acpi_status acpi_platformrt_space_handler(u32 function,
> efi_status_t status;
> struct prm_context_buffer context;
>
> + if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> + pr_err_ratelimited("PRM: EFI runtime services no longer available\n");
> + return AE_NO_HANDLER;
This error code is only used in GPE handling ATM.
The one that actually causes ACPICA to log a "no handler" error (in
acpi_ex_access_region()) is AE_NOT_EXIST. Should it be used here?
> + }
> +
> /*
> * The returned acpi_status will always be AE_OK. Error values will be
> * saved in the first byte of the PRM message buffer to be used by ASL.
> @@ -325,6 +330,11 @@ void __init init_prmt(void)
>
> pr_info("PRM: found %u modules\n", mc);
>
> + if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> + pr_err("PRM: EFI runtime services unavailable\n");
> + return;
> + }
> +
> status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
> ACPI_ADR_SPACE_PLATFORM_RT,
> &acpi_platformrt_space_handler,
> --
> 2.39.0
>
