ARM: add UEFI stub support
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@linaro.org>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 06e983f..af11c2f 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -12,6 +12,8 @@
#include <asm/assembler.h>
#include <asm/v7m.h>
+#include "efi-header.S"
+
AR_CLASS( .arch armv7-a )
M_CLASS( .arch armv7-m )
@@ -126,7 +128,7 @@
start:
.type start,#function
.rept 7
- mov r0, r0
+ __nop
.endr
ARM( mov r0, r0 )
ARM( b 1f )
@@ -139,7 +141,8 @@
.word 0x04030201 @ endianness flag
THUMB( .thumb )
-1:
+1: __EFI_HEADER
+
ARM_BE8( setend be ) @ go BE8 if compiled for BE8
AR_CLASS( mrs r9, cpsr )
#ifdef CONFIG_ARM_VIRT_EXT
@@ -1353,6 +1356,53 @@
reloc_code_end:
+#ifdef CONFIG_EFI_STUB
+ .align 2
+_start: .long start - .
+
+ENTRY(efi_stub_entry)
+ @ allocate space on stack for passing current zImage address
+ @ and for the EFI stub to return of new entry point of
+ @ zImage, as EFI stub may copy the kernel. Pointer address
+ @ is passed in r2. r0 and r1 are passed through from the
+ @ EFI firmware to efi_entry
+ adr ip, _start
+ ldr r3, [ip]
+ add r3, r3, ip
+ stmfd sp!, {r3, lr}
+ mov r2, sp @ pass zImage address in r2
+ bl efi_entry
+
+ @ Check for error return from EFI stub. r0 has FDT address
+ @ or error code.
+ cmn r0, #1
+ beq efi_load_fail
+
+ @ Preserve return value of efi_entry() in r4
+ mov r4, r0
+ bl cache_clean_flush
+ bl cache_off
+
+ @ Set parameters for booting zImage according to boot protocol
+ @ put FDT address in r2, it was returned by efi_entry()
+ @ r1 is the machine type, and r0 needs to be 0
+ mov r0, #0
+ mov r1, #0xFFFFFFFF
+ mov r2, r4
+
+ @ Branch to (possibly) relocated zImage that is in [sp]
+ ldr lr, [sp]
+ ldr ip, =start_offset
+ add lr, lr, ip
+ mov pc, lr @ no mode switch
+
+efi_load_fail:
+ @ Return EFI_LOAD_ERROR to EFI firmware on error.
+ ldr r0, =0x80000001
+ ldmfd sp!, {ip, pc}
+ENDPROC(efi_stub_entry)
+#endif
+
.align
.section ".stack", "aw", %nobits
.L_user_stack: .space 4096