On Mon, Jun 25, 2018 at 08:34:05AM +0200, Ard Biesheuvel wrote: > There are various ways a platform can provide a device tree binary > to the kernel, with different levels of sophistication: > - ideally, the UEFI firmware, which is tightly coupled with the > platform, provides a device tree image directly as a UEFI > configuration table, and typically permits the contents to be > manipulated either via menu options or via UEFI environment > variables that specify a replacement image, > - GRUB for ARM has a 'devicetree' directive which allows a device > tree image to be loaded from any location accessible to GRUB, and > supersede the one provided by the firmware,
Just for comment - this too is considered an anomaly and will eventually be phased out. (Some part of the functionality may be retained in the form of overlay management.) > - the EFI stub implements a dtb= command line option that allows a > device tree image to be loaded from a file residing in the same > file system as the one the kernel image was loaded from. > > The dtb= command line option was never intended to be more than a > development feature, to allow the other options to be implemented > in parallel. So let's make it an opt-in feature that is disabled > by default, but can be re-enabled at will. > > Note that we already disable the dtb= command line option when we > detect that we are running with UEFI Secure Boot enabled. > > Signed-off-by: Ard Biesheuvel <[email protected]> Acked-by: Leif Lindholm <[email protected]> > --- > drivers/firmware/efi/Kconfig | 12 ++++++++++++ > drivers/firmware/efi/libstub/arm-stub.c | 7 ++++--- > 2 files changed, 16 insertions(+), 3 deletions(-) > > diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig > index 781a4a337557..fc1cb2961d5b 100644 > --- a/drivers/firmware/efi/Kconfig > +++ b/drivers/firmware/efi/Kconfig > @@ -87,6 +87,18 @@ config EFI_RUNTIME_WRAPPERS > config EFI_ARMSTUB > bool > > +config EFI_ARMSTUB_DTB_LOADER > + bool "Enable the DTB loader" > + depends on EFI_ARMSTUB > + help > + Select this config option to add support for the dtb= command > + line parameter, allowing a device tree blob to be loaded into > + memory from the EFI System Partition by the stub. > + > + The device tree is typically provided by the platform or by > + the bootloader, and so this option is mostly for development > + purposes only. > + > config EFI_BOOTLOADER_CONTROL > tristate "EFI Bootloader Control" > depends on EFI_VARS > diff --git a/drivers/firmware/efi/libstub/arm-stub.c > b/drivers/firmware/efi/libstub/arm-stub.c > index 01a9d78ee415..c98b1856fc3d 100644 > --- a/drivers/firmware/efi/libstub/arm-stub.c > +++ b/drivers/firmware/efi/libstub/arm-stub.c > @@ -202,9 +202,10 @@ unsigned long efi_entry(void *handle, efi_system_table_t > *sys_table, > * 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure > * boot is enabled if we can't determine its state. > */ > - if (secure_boot != efi_secureboot_mode_disabled && > - strstr(cmdline_ptr, "dtb=")) { > - pr_efi(sys_table, "Ignoring DTB from command line.\n"); > + if (!IS_ENABLED(CONFIG_EFI_ARMSTUB_DTB_LOADER) || > + secure_boot != efi_secureboot_mode_disabled) { > + if (strstr(cmdline_ptr, "dtb=")) > + pr_efi(sys_table, "Ignoring DTB from command line.\n"); > } else { > status = handle_cmdline_files(sys_table, image, cmdline_ptr, > "dtb=", > -- > 2.11.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
