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).
