On Tue, Jan 17, 2023 at 4:51 PM Ard Biesheuvel ardb@kernel.org wrote:
On Tue, 17 Jan 2023 at 13:29, Rafael J. Wysocki rafael@kernel.org wrote:
On Thu, Jan 12, 2023 at 2:33 PM Ard Biesheuvel ardb@kernel.org 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@vger.kernel.org Cc: "Rafael J. Wysocki" rafael@kernel.org Cc: Len Brown lenb@kernel.org Cc: linux-acpi@vger.kernel.org Signed-off-by: Ard Biesheuvel ardb@kernel.org
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?
Not sure. Any error value is returned to the caller, the only difference is that AE_NOT_EXIST and AE_NOT_IMPLEMENTED trigger the non-ratelimited logging machinery.
Given that neither value seems appropriate (the region is implemented and it has a handler), and we already emit a rate limited error message, I think AE_NOT_EXIST is not the right choice.
OK, applied as-is as 6.2-rc material, thanks!