On Mon, 19 Oct 2020 at 12:00, Heinrich Schuchardt <xypron.glpk@xxxxxx> wrote: > > On 19.10.20 11:31, Ard Biesheuvel wrote: > > On Wed, 14 Oct 2020 at 20:41, Heinrich Schuchardt <xypron.glpk@xxxxxx> wrote: > >> > >> On 14.10.20 19:58, Ard Biesheuvel wrote: > >>> On Wed, 14 Oct 2020 at 19:45, Heinrich Schuchardt <xypron.glpk@xxxxxx> wrote: > >>>> > >>>> On 14.10.20 19:31, Heinrich Schuchardt wrote: > >>>>> Dear all, > >>>>> > >>>>> the fwts fails on U-Boot due to testing for a non-existent > >>>>> RuntimeServicesSupported variable. > >>>>> > >>>>> If you look at the UEFI specification 2.8 (Errata B) [1] you will > >>>>> discover in the change log: > >>>>> > >>>>> 2.8 A2049 > >>>>> RuntimeServicesSupported EFI variable should be a config table > >>>>> February 2020 > >>>>> > >>>>> Please, read the configuration table to determine if a runtime service > >>>>> is available on UEFI 2.8 systems. > >>>>> > >>>>> On lower UEFI firmware version neither the variable nor the table exists. > >>>>> > >>>>> Best regards > >>>>> > >>>>> Heinrich > >>>>> > >>>>> [1] UEFI Specification Version 2.8 (Errata B) (released June 2020), > >>>>> https://uefi.org/sites/default/files/resources/UEFI%20Spec%202.8B%20May%202020.pdf > >>>>> > >>>> > >>>> Hello Ard, > >>>> > >>>> what is your idea how the EFI_RT_PROPERTIES_TABLE shall be exposed to > >>>> the efi_test driver? > >>>> > >>>> Will the EFI runtime wrapper simply return EFI_UNSUPPORTED if the > >>>> function is not marked as supported in the table? Or will the > >>>> configuration table itself be make available? > >>>> > >>> > >>> The UEFI spec permits that runtime services return EFI_UNSUPPORTED at > >>> runtime, but requires that they are marked as such in the > >>> EFI_RT_PROPERTIES_TABLE. > >>> > >>> So assuming that the purpose of efi_test is compliance with the spec, > >>> it should only allow EFI_UNSUPPORTED as a return value for each of the > >>> tested runtime services if it is omitted from > >>> efi.runtime_supported_mask. > >>> > >>> Since the efi_test ioctl returns both an error code and the actual EFI > >>> status code, we should only fail the call on a EFI_UNSUPPORTED status > >>> code if the RTPROP mask does not allow that. > >>> > >>> E.g., > >>> > >>> --- a/drivers/firmware/efi/test/efi_test.c > >>> +++ b/drivers/firmware/efi/test/efi_test.c > >>> @@ -265,7 +265,12 @@ static long efi_runtime_set_variable(unsigned long arg) > >>> goto out; > >>> } > >>> > >>> - rv = status == EFI_SUCCESS ? 0 : -EINVAL; > >>> + if (status == EFI_SUCCESS || > >>> + (status == EFI_UNSUPPORTED && > >>> + !efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))) > >>> + rv = 0; > >>> + else > >>> + rv = -EINVAL; > >>> > >>> out: > >>> kfree(data); > >>> > >>> > >>> Do you think that could work? > >>> > >> > >> The current fwts implementation assumes that EFI_UNSUPPORTED leads to > >> ioctl() returning -1. This value should not be changed. It would be > >> preferable to use another error code than -EINVAL, e.g. -EDOM if there > >> is a mismatch with the EFI_RT_PROPERTIES_TABLE configuration table. Then > >> a future verision of fwts can evaluate errno to discover the problem. > >> > >> Do I read you correctly: the EFI runtime wrapper does not fend of calls > >> to runtime services marked as disallowed in EFI_RT_PROPERTIES_TABLE? > >> Directly returning an error code might help to avoid crashes on > >> non-compliant firmware. > >> > > > > It is not the kernel's job to work around non-compliant firmware. The > > EFI spec is crystal clear that every runtime service needs to be > > implemented, but is permitted to return EFI_UNSUPPORTED after > > ExitBootServices(). This means EFI_RT_PROPERTIES_TABLE does not tell > > you calling certain runtime services is disallowed, it tells you that > > there is no point in even trying. That is why users such as efi-pstore > > now take this information into account in their probe path (and > > efivarfs will only mount read/write if SetVariable() is not marked as > > unsupported). > > > > How about the return code? > As I attempted to explain, I think EFI_UNSUPPORTED should not be reported as an error if RT_PROP_TABLE permits it. The caller has access to the raw efi_status_t that was returned, so it can distinguish between the two cases.
