initial import of armv8-hello

AUTHORS

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+armv8-hello is written by:
+  Jim Huang <jserv.tw@gmail.com>
+
+Copyrighted by:
+  National Cheng Kung University, Taiwan

LICENSE

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+armv8-hello is freely redistributable under the two-clause BSD License:
+
+Copyright (C) 2016 National Cheng Kung University, Taiwan.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+1. Redistributions of source code must retain the above copyright notice,
+   this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+THE POSSIBILITY OF SUCH DAMAGE.

Makefile

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+IMAGE := kernel.elf
+
+CROSS_COMPILE = aarch64-linux-gnu-
+
+CC = $(CROSS_COMPILE)gcc
+LD = $(CROSS_COMPILE)ld
+OBJDUMP = $(CROSS_COMPILE)objdump
+
+CFLAGS = -Wall -fno-common -O0 -g \
+         -nostdlib -nostartfiles -ffreestanding \
+         -march=armv8-a
+
+OBJS = hello.o
+
+all: $(IMAGE)
+
+boot.o: boot.S
+	$(CC) boot.S -c -o boot.o
+
+$(IMAGE): kernel.ld boot.o $(OBJS)
+	$(LD) boot.o $(OBJS) -T kernel.ld -o $(IMAGE)
+	$(OBJDUMP) -d kernel.elf > kernel.list
+	$(OBJDUMP) -t kernel.elf | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
+
+qemu: $(IMAGE)
+	@qemu-system-aarch64 -M ? | grep virt >/dev/null || exit
+	@echo "Press Ctrl-A and then X to exit QEMU"
+	@echo
+	qemu-system-aarch64 -machine virt -cpu cortex-a57 \
+	                    -smp 4 -m 4096 \
+			    -nographic -serial mon:stdio \
+	                    -kernel $(IMAGE)
+
+clean:
+	rm -f $(IMAGE) *.o *.list *.sym
+
+.PHONY: all qemu clean

README.md

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+Hello World for bare metal ARM using QEMU
+
+Prerequisites
+-------------
+- Install [Linaro toolchain](http://www.linaro.org/downloads/) for Aarch64 little-endian
+```
+sudo apt-get install gcc-aarch64-linux-gnu
+```
+- Install recent QEMU with Aarch64 target
+```
+sudo apt-get install qemu-system-arm
+```
+
+Building and Verification
+-------------------------
+* Changes the current working directory to the specified one and then
+```
+make
+make qemu
+```
+
+Licensing
+---------
+`mini-arm-os` is freely redistributable under the two-clause BSD License.
+Use of this source code is governed by a BSD-style license that can be found
+in the `LICENSE` file.

boot.S

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+#include "reg.h"
+
+.text
+
+.globl	_start
+_start:
+	/* init UART (38400 8N1) */
+	ldr	x4, =UART_BASE		// UART base
+	mov	w5, #0x10		// IBRD
+	str	w5, [x4, #0x24]
+	mov	w5, #0xc300
+	orr	w5, w5, #0x0001		// CR
+	str	w5, [x4, #0x30]
+
+	/* check CPU ID */
+	mrs x0, mpidr_el1
+	tst x0, #15
+	b.ne    other_cpu
+	b.eq	boot_cpu
+
+boot_cpu:
+	/* configure stack */
+	adrp x0, stacktop
+	mov sp, x0
+
+	b main
+
+other_cpu:
+	b other_cpu

hello.c

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+#include "reg.h"
+
+int puts(const char *str)
+{
+	while (*str)
+		*((unsigned int *) UART_BASE) = *str++;
+	return 0;
+}
+
+void main(void)
+{
+	puts("Hello\n");
+	while (1);
+}

kernel.ld

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+OUTPUT_FORMAT("elf64-littleaarch64")
+OUTPUT_ARCH(aarch64)
+TARGET(binary)
+
+STACKTOP = 0x51000000;
+
+SECTIONS
+{
+	. = 0x40010000;
+	.text : { *(.text) }
+	.data : { *(.data) }
+	.bss : { *(.bss) }
+
+	. = STACKTOP;
+	stacktop = .;
+}

reg.h

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+#ifndef __REG_H__
+#define __REG_H__
+
+#define UART_BASE	0x09000000
+
+#endif