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1 files changed, 38 insertions, 0 deletions

diff --git a/src/baremetal/start_aarch64.S b/src/baremetal/start_aarch64.S
new file mode 100644
index 0000000..36b2752
--- /dev/null
+++ b/src/baremetal/start_aarch64.S
@@ -0,0 +1,38 @@
+/* AArch64 virt. Drop EL2 to EL1 if we came up there, enable SIMD
+   (the compiler copies the genome with q registers), then stack, bss, C. */
+.section .text.init
+.global _start
+_start:
+	mrs x0, CurrentEL
+	lsr x0, x0, #2
+	cmp x0, #2
+	b.ne 1f
+	mov x0, #(1 << 31)		/* EL1 is AArch64 */
+	msr HCR_EL2, x0
+	mrs x0, CPTR_EL2
+	bic x0, x0, #(1 << 10)		/* do not trap SIMD to EL2 */
+	msr CPTR_EL2, x0
+	mov x0, #0x3c5			/* EL1h, interrupts masked */
+	msr SPSR_EL2, x0
+	adr x0, 1f
+	msr ELR_EL2, x0
+	eret
+1:
+	mrs x0, CPACR_EL1
+	orr x0, x0, #(3 << 20)		/* FPEN: SIMD does not trap */
+	msr CPACR_EL1, x0
+	isb
+	ldr x0, =_stack_top
+	mov sp, x0
+	ldr x0, =_sbss
+	ldr x1, =_ebss
+2:
+	cmp x0, x1
+	b.hs 3f
+	str xzr, [x0], #8
+	b 2b
+3:
+	bl bare_main
+4:
+	wfe
+	b 4b