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

[Ard Biesheuvel]

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

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.