[PATCH 9/9] ARM: add UEFI stub support

[Ard Biesheuvel]

On 2 October 2015 at 20:03, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
> On 2 October 2015 at 18:29, Ryan Harkin <ryan.harkin at linaro.org> wrote:
>> Hi Ard/Roy,
>>
>> On 1 October 2015 at 18:04, Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> wrote:
>>>
>>> From: Roy Franz <roy.franz at linaro.org>
>>>
>>> This patch adds EFI stub support for the ARM Linux kernel.
>>>
>>> The EFI stub operates similarly to the x86 and arm64 stubs: it is a
>>> shim between the EFI firmware and the normal zImage entry point, and
>>> sets up the environment that the zImage is expecting. This includes
>>> optionally loading the initrd and device tree from the system partition
>>> based on the kernel command line.
>>>
>>> Signed-off-by: Roy Franz <roy.franz at linaro.org>
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>>> ---
>>>  arch/arm/Kconfig                       |  19 +++
>>>  arch/arm/boot/compressed/Makefile      |   5 +-
>>>  arch/arm/boot/compressed/efi-header.S  | 130 ++++++++++++++++++++
>>>  arch/arm/boot/compressed/efi-stub.c    |  89 ++++++++++++++
>>>  arch/arm/boot/compressed/head.S        |  54 +++++++-
>>>  arch/arm/boot/compressed/vmlinux.lds.S |   7 ++
>>>  arch/arm/include/asm/efi.h             |  23 ++++
>>>  drivers/firmware/efi/libstub/Makefile  |  12 ++
>>>  8 files changed, 336 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>>> index e4b7d6cfd8eb..6d7fd83c2ee4 100644
>>> --- a/arch/arm/Kconfig
>>> +++ b/arch/arm/Kconfig
>>> @@ -2061,6 +2061,25 @@ config AUTO_ZRELADDR
>>>           0xf8000000. This assumes the zImage being placed in the first
>>> 128MB
>>>           from start of memory.
>>>
>>> +config EFI_STUB
>>> +       bool
>>> +
>>> +config EFI
>>> +       bool "UEFI runtime support"
>>> +       depends on OF && !CPU_BIG_ENDIAN && MMU && AUTO_ZRELADDR &&
>>> !XIP_KERNEL
>>> +       select UCS2_STRING
>>> +       select EFI_PARAMS_FROM_FDT
>>> +       select EFI_STUB
>>> +       select EFI_ARMSTUB
>>> +       select EFI_RUNTIME_WRAPPERS
>>
>>
>> Should we make this "default y" like ARM64?  I think so.
>>
>>
>
> It is not necessarily something that should be enabled by default,
> imo. The distro kernels will probably enabled it, which is good enough
> for me.
>
>>> +       ---help---
>>> +         This option provides support for runtime services provided
>>> +         by UEFI firmware (such as non-volatile variables, realtime
>>> +         clock, and platform reset). A UEFI stub is also provided to
>>> +         allow the kernel to be booted as an EFI application. This
>>> +         is only useful for kernels that may run on systems that have
>>> +         UEFI firmware.
>>> +
>>>  endmenu
>>>
>>>  menu "CPU Power Management"
>>> diff --git a/arch/arm/boot/compressed/Makefile
>>> b/arch/arm/boot/compressed/Makefile
>>> index 3f9a9ebc77c3..0e5624d6215d 100644
>>> --- a/arch/arm/boot/compressed/Makefile
>>> +++ b/arch/arm/boot/compressed/Makefile
>>> @@ -167,9 +167,12 @@ if [ $(words $(ZRELADDR)) -gt 1 -a
>>> "$(CONFIG_AUTO_ZRELADDR)" = "" ]; then \
>>>         false; \
>>>  fi
>>>
>>> +efi-obj-$(CONFIG_EFI_STUB) := $(obj)/efi-stub.o $(obj)/efi-banner.o \
>>
>>
>> When I try to compile the kernel from your branch, I get:
>>
>> make[2]: *** No rule to make target 'arch/arm/boot/compressed/efi-banner.o',
>> needed by 'arch/arm/boot/compressed/vmlinux'. Stop.
>>
>> Did I miss something or is this a problem?
>>
>
> It was I who missed something: I have been reshuffling some bits, and
> this fell through the cracks. I didn't spot it since I apparently did
> not try to rebuild it cleanly.
>
> I would like to get rid of the linux_banner reference in the stub
> completely, and I posted a patch here
>

Where? Here:
http://marc.info/?l=linux-arm-kernel&m=144313135923256

> In the mean time, could you try with this folded in?
>
> -------------------8<--------------------
> diff --git a/arch/arm/boot/compressed/Makefile
> b/arch/arm/boot/compressed/Makefile
> index 0e5624d6215d..a6aa7f9123a2 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -170,6 +170,10 @@ fi
>  efi-obj-$(CONFIG_EFI_STUB) := $(obj)/efi-stub.o $(obj)/efi-banner.o \
>                               $(objtree)/drivers/firmware/efi/libstub/lib.a
>
> +$(obj)/efi-banner.o: OBJCOPYFLAGS=-j .rodata
> +$(obj)/efi-banner.o: $(objtree)/init/version.o FORCE
> +       $(call if_changed,objcopy)
> +
>  $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.$(suffix_y).o \
>                 $(addprefix $(obj)/, $(OBJS)) $(lib1funcs) $(ashldi3) \
>                 $(bswapsdi2) $(efi-obj-y) FORCE
> diff --git a/drivers/firmware/efi/libstub/fdt.c
> b/drivers/firmware/efi/libstub/fdt.c
> index a7e87cd582f2..f45a6f715e73 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -16,6 +16,8 @@
>
>  #include "efistub.h"
>
> +extern __attribute__((__visibility__("hidden"))) const char linux_banner[];
> +
>  efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
>                         unsigned long orig_fdt_size,
>                         void *fdt, int new_fdt_size, char *cmdline_ptr,
> -------------------8<--------------------
>
> Thanks for testing!
>
> --
> Ard.