On 2/19/20 6:18 PM, Ard Biesheuvel wrote:
The UEFI spec version 2.8 errata A defines a configuration table called EFI_RT_PROPERTIES_TABLE that carries a mask describing which EFI runtime services are still functional at OS runtime.
This configuration table defined in UEFI spec 2.8A is replacing the RuntimeServicesSupported variable introduced in UEFI spec 2.8 (which is already implemented in U-Boot). Replacing APIs as an "erratum" is unfortunate. I am wondering whether in your implementation you will have to check for both the variable if the firmware implements UEFI 2.8 and for the table if the firmware implements UEFI 2.8A. Best regards Heinrich
Even though any runtime services that cease to be functional when exiting boot services are still required to return EFI_UNSUPPORTED when called by the OS, having this mask is helpful, since we can use it to prevent modules like efi-rtc or efivars from loading, instead of allowing them to probe and fail with an error. So let's wire this up: make some room in struct efi for the mask, read it from the EFI_RT_PROPERTIES_TABLE if available, and replace various instances of 'if (efi_enabled(EFI_RUNTIME_SERVICES))' with checks for the runtime service in question that the code relies upon. Cc: Leif Lindholm <leif@xxxxxxxxxxxx> Cc: Peter Jones <pjones@xxxxxxxxxx> Cc: Alexander Graf <agraf@xxxxxxxxx> Cc: Heinrich Schuchardt <xypron.glpk@xxxxxx> Cc: Jeff Brasen <jbrasen@xxxxxxxxxx> Cc: Atish Patra <Atish.Patra@xxxxxxx> Cc: x86@xxxxxxxxxx Ard Biesheuvel (9): efi: store mask of supported runtime services in struct efi efi: add support for EFI_RT_PROPERTIES table efi: use more granular check for availability for variable services efi: register EFI rtc platform device only when available infiniband: hfi1: use EFI GetVariable only when available scsi: iscsi: use EFI GetVariable only when available efi: use EFI ResetSystem only when available x86/ima: use EFI GetVariable only when available integrity: check properly whether EFI GetVariable() is available arch/x86/kernel/ima_arch.c | 2 +- drivers/firmware/efi/efi-pstore.c | 2 +- drivers/firmware/efi/efi.c | 70 +++++++++++-------- drivers/firmware/efi/efivars.c | 2 +- drivers/firmware/efi/reboot.c | 4 +- drivers/infiniband/hw/hfi1/efivar.c | 2 +- drivers/rtc/Makefile | 4 -- drivers/rtc/rtc-efi-platform.c | 35 ---------- drivers/scsi/isci/init.c | 2 +- fs/efivarfs/super.c | 2 +- include/linux/efi.h | 40 +++++++++++ security/integrity/platform_certs/load_uefi.c | 2 +- 12 files changed, 89 insertions(+), 78 deletions(-) delete mode 100644 drivers/rtc/rtc-efi-platform.c
