[kvm-unit-tests PATCH v3 22/27] arm64: Use code from the gnu-efi when booting with EFI

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arm/efi/crt0-efi-aarch64.S defines the header and the handover
sequence from EFI to a efi_main. This change includes the whole file
in arm/cstart64.S when we compile with EFI support.

In addition, we change the handover code in arm/efi/crt0-efi-aarch64.S
to align the stack pointer. This alignment is necessary because we
make assumptions about cpu0's stack alignment and most importantly we
place its thread_info at the bottom of this stack.

Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
---
 arm/cstart64.S             |  6 ++++++
 arm/efi/crt0-efi-aarch64.S | 21 +++++++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/arm/cstart64.S b/arm/cstart64.S
index 55b41ea..08cf02f 100644
--- a/arm/cstart64.S
+++ b/arm/cstart64.S
@@ -15,6 +15,10 @@
 #include <asm/thread_info.h>
 #include <asm/sysreg.h>
 
+#ifdef CONFIG_EFI
+#include "efi/crt0-efi-aarch64.S"
+#else
+
 .macro zero_range, tmp1, tmp2
 9998:	cmp	\tmp1, \tmp2
 	b.eq	9997f
@@ -107,6 +111,8 @@ start:
 	bl	exit
 	b	halt
 
+#endif
+
 .text
 
 /*
diff --git a/arm/efi/crt0-efi-aarch64.S b/arm/efi/crt0-efi-aarch64.S
index d50e78d..03d29b0 100644
--- a/arm/efi/crt0-efi-aarch64.S
+++ b/arm/efi/crt0-efi-aarch64.S
@@ -111,10 +111,19 @@ section_table:
 
 	.align		12
 _start:
-	stp		x29, x30, [sp, #-32]!
+	stp		x29, x30, [sp, #-16]!
+
+	/* Align sp; this is necessary due to way we store cpu0's thread_info */
 	mov		x29, sp
+	and		x29, x29, #THREAD_MASK
+	mov		x30, sp
+	mov		sp, x29
+	str		x30, [sp, #-16]!
+
+	mov             x29, sp
+
+	stp		x0, x1, [sp, #-16]!
 
-	stp		x0, x1, [sp, #16]
 	mov		x2, x0
 	mov		x3, x1
 	adr		x0, ImageBase
@@ -123,8 +132,12 @@ _start:
 	bl		_relocate
 	cbnz		x0, 0f
 
-	ldp		x0, x1, [sp, #16]
+	ldp		x0, x1, [sp], #16
 	bl		efi_main
 
-0:	ldp		x29, x30, [sp], #32
+	/* Restore sp */
+	ldr		x30, [sp], #16
+	mov             sp, x30
+
+0:	ldp		x29, x30, [sp], #16
 	ret
-- 
2.25.1




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