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11 changed files with 325 additions and 139 deletions

90
Makefile Normal file
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# environment
AARCH64_TOOLCHAIN ?= aarch64-linux-gnu
# Shortcuts
CC=clang --target=aarch64-none-elf -mcpu=cortex-a57
LD=ld.lld
OBJCOPY=$(AARCH64_TOOLCHAIN)-objcopy --target elf64-littleaarch64
CFLAGS += -O0
CFLAGS += -g
#CFLAGS += -nostdlib
#CFLAGS += -march=armv8-a
#CFLAGS += -std=c99
#CFLAGS += -pedantic
#CFLAGS += -Wall
#CFLAGS += -Wmissing-prototypes
#CFLAGS += -Wstrict-prototypes
#CFLAGS += -Wold-style-definition
BUILD_DIR=build
# Files
KERNEL_MEMMAP = aarch64/memmap
KERNEL_SOURCES = \
aarch64/boot.s \
sys/main.c \
sys/uart.c \
KERNEL_LIST := $(wildcard $(KERNEL_SOURCES))
KERNEL_OBJS := $(addsuffix .o, $(addprefix $(BUILD_DIR)/, ${KERNEL_LIST}))
all: kernel
# compilation
kernel: $(BUILD_DIR)/kernel.elf # $(BUILD_DIR)/kernel.sym
$(BUILD_DIR)/kernel.elf: $(KERNEL_OBJS)
$(info linking target: $@)
$(LD) -T$(KERNEL_MEMMAP) -nostdlib $^ -o $@
$(info done: $@)
$(BUILD_DIR)/kernel.bin: $(BUILD_DIR)/kernel.elf
$(OBJCOPY) -O binary $< $@
$(BUILD_DIR)/kernel.sym: $(BUILD_DIR)/kernel.elf
$(OBJCOPY) --only-keep-debug $< $@
$(OBJCOPY) --strip-debug $@
$(BUILD_DIR)/%.o: %
$(info compiling file: $<)
@mkdir -p $(dir ./$(BUILD_DIR)/$<)
$(CC) $(CFLAGS) -c $< -o $@
.PHONY: clean run
# helpers
QEMU_CMD = \
qemu-system-aarch64 \
-M virt \
-cpu cortex-a57 \
-nographic \
-smp 4 \
-m 4096 \
-kernel build/kernel.elf \
-serial stdio \
-monitor none \
clean:
rm -Rf ./$(BUILD_DIR)/*
run: kernel
$(QEMU_CMD)
debug: kernel
$(QEMU_CMD) -S -gdb tcp::1234 & \
gdb-multiarch -q \
-ex 'file build/kernel.elf' \
-ex 'target remote localhost:1234'
kill %1

18
aarch64/boot.s Normal file
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.globl _start
_start:
mrs x0, mpidr_el1 // Check CPU ID
mov x1, 0xC1000000
bic x0, x0, x1
cbz x0, set_stack
b idle
set_stack:
ldr x30, =stack_ptr // defined in sys/memmap
mov sp, x30
bl k_main
idle:
b idle

16
aarch64/memmap Normal file
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ENTRY(_start)
SECTIONS
{
/* For some reason qemu UART doesn't work with smaller address */
. = 0x40000000;
.boot . : { boot.o(.text) }
.text : { *(.text) }
.data : { *(.data) }
.bss : { *(.bss COMMON) }
. = ALIGN(8);
. = . + 0x1000;
stack_ptr = . ;
}

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ASM=clang
TARGET=aarch64-none-elf
CPU=cortex-a57
LD=ld.lld
OBJCOPY=objcopy --target elf64-littleaarch64
all: build/core.bin build/core.elf
# compilation -----------------------------------------------------------------
build/core.o: core/core.s
$(ASM) -c -triple --target=$(TARGET) -mcpu=$(CPU) -O0 -g $< -o $@
build/uart.o: core/uart.s
$(ASM) -c --target=$(TARGET) -mcpu=$(CPU) -O0 -g $< -o $@
# ELF -------------------------------------------------------------------------
build/core.elf: build/core.o build/uart.o
$(LD) -Tcore/core.ld $^ -o $@
# BIN -------------------------------------------------------------------------
build/core.bin: build/core.elf
$(OBJCOPY) -O binary $< $@
build/core.sym: build/core.elf
$(OBJCOPY) --only-keep-debug $< $@
$(OBJCOPY) --strip-debug build/core.elf
# Clean -----------------------------------------------------------------------
clean:
rm -f build/*

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ENTRY(_core_init)
SECTIONS
{
. = 0x40000000;
.text : { *(.text) }
.data : { *(.text) }
.bss : { *(.bss COMMON) }
. = ALIGN(10);
. = . + 0x1000;
stack_ptr = . ;
}

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# file : uart.s
# project : Löwe OS
# authors : Elias Löwe <elias@lowenware.com>
# address of UART for virt device in qemu
# -----------------------------------------------------------------------------
.global _uart_putc # print single character uart
.global _uart_putx # print integer in HEX format to uart
.global _uart_puts # print null-terminated string to uart
# -----------------------------------------------------------------------------
.text
# helper to avoid extra data moving
# @x1 character print
uart_putc:
STP x2, lr, [sp, -16]!
MOV x2, 0x09000000 # set UART address
STRB w1, [x2] # put character out
LDP x2, lr, [sp], 16
RET
# -----------------------------------------------------------------------------
# print character to uart
# @x0 character print
_uart_putc:
STR lr, [sp, -16]!
MOV x1, x0 # set arguments
BL uart_putc # put character out
LDR lr, [sp], 16
RET
# -----------------------------------------------------------------------------
# @x0 integer to print
_uart_putx:
STP lr, x3, [sp, -32]!
STP x0, x1, [sp, 16]
LDR x3, =60 # init bits counter 64-4
1:
LSR x1, x0, x3 # shift to digit
AND x1, x1, 0xF # keep only digit
CMP x1, 9 # compare it to 9
BLS 2f # less or equal
ADD x1, x1, 0x37 # turn into ASCII HEX char
B 3f # continue to output
2:
ADD x1, x1, 0x30 # turn into ASCII num char
3:
BL uart_putc # output carachter
CBZ x3, 0f # if counter == 0 return
SUB x3, x3, 4 # otherwise subtract counter by 4
B 1b # repeat
0:
LDP lr, x3, [sp], 16
LDP x0, x1, [sp], 16
RET
# -----------------------------------------------------------------------------
# @x0 pointer to string
_uart_puts:
STR lr, [sp, -16]!
STP x0, x1, [sp, -16]!
1:
LDRB w1, [x0], 1 # load byte of string from address in x0
CBZ w1, 0f # return if zero
BL uart_putc # put charcter out
B 1b # loop
0:
LDP x0, x1, [sp], 16
LDR lr, [sp], 16
RET
# -----------------------------------------------------------------------------

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sys/main.c Normal file
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/******************************************************************************
*
* Copyright (c) 2017-2019 by Löwenware Ltd
* Please, refer LICENSE file for legal information
*
******************************************************************************/
/**
* @file main.c
* @author Ilja Kartašov <ik@lowenware.com>
* @brief
*
* @see https://lowenware.com/
*/
#include "uart.h"
void
k_main(void);
void
k_main(void)
{
uart_init();
uart_puts((unsigned char *) "Lowe OS\n");
for (;;) {
__asm__("WFE");
}
}

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sys/uart.c Normal file
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/******************************************************************************
*
* Copyright (c) 2017-2019 by Löwenware Ltd
* Please, refer LICENSE file for legal information
*
******************************************************************************/
/**
* @file uart.c
* @author Ilja Kartašov <ik@lowenware.com>
* @brief
*
* @see https://lowenware.com/
*/
#include "uart.h"
volatile unsigned int *UART0 = (unsigned int *)UART_BASE;
void
uart_init(void)
{
}
void
uart_putc(unsigned char c)
{
*UART0 = (unsigned int) c;
}
void
uart_puts(const unsigned char *s)
{
while(*s) {
*UART0 = (unsigned int) *(s++);
}
}

33
sys/uart.h Normal file
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/******************************************************************************
*
* Copyright (c) 2017-2019 by Löwenware Ltd
* Please, refer LICENSE file for legal information
*
******************************************************************************/
/**
* @file uart.h
* @author Ilja Kartašov <ik@lowenware.com>
* @brief
*
* @see https://lowenware.com/
*/
#ifndef UART_H_8AFC47F9_2953_42C1_A5C1_1AE5A1F52CD0
#define UART_H_8AFC47F9_2953_42C1_A5C1_1AE5A1F52CD0
#define UART_BASE 0x09000000
void
uart_init(void);
void
uart_putc(unsigned char c);
void
uart_puts(const unsigned char *s);
#endif /* !UART_H */

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sys/uart.s Normal file
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// file : uart.s
// project : Löwe OS
// authors : Elias Löwe <elias@lowenware.com>
// address of UART for virt device in qemu
// -----------------------------------------------------------------------------
.global _uart_putc // print single character uart
.global _uart_putx // print integer in HEX format to uart
.global _uart_puts // print null-terminated string to uart
// -----------------------------------------------------------------------------
.text
// helper to avoid extra data moving
// @x1 character print
uart_putc:
STP x2, lr, [sp, -16]!
MOV x2, 0x09000000 // set UART address
STRB w1, [x2] // put character out
LDP x2, lr, [sp], 16
RET
// -----------------------------------------------------------------------------
// print character to uart
// @x0 character print
_uart_putc:
STR lr, [sp, -16]!
MOV x1, x0 // set arguments
BL uart_putc // put character out
LDR lr, [sp], 16
RET
// -----------------------------------------------------------------------------
// @x0 integer to print
_uart_putx:
STP lr, x3, [sp, -32]!
STP x0, x1, [sp, 16]
LDR x3, =60 // init bits counter 64-4
1:
LSR x1, x0, x3 // shift to digit
AND x1, x1, 0xF // keep only digit
CMP x1, 9 // compare it to 9
BLS 2f // less or equal
ADD x1, x1, 0x37 // turn into ASCII HEX char
B 3f // continue to output
2:
ADD x1, x1, 0x30 // turn into ASCII num char
3:
BL uart_putc // output carachter
CBZ x3, 0f // if counter == 0 return
SUB x3, x3, 4 // otherwise subtract counter by 4
B 1b // repeat
0:
LDP lr, x3, [sp], 16
LDP x0, x1, [sp], 16
RET
// -----------------------------------------------------------------------------
// @x0 pointer to string
_uart_puts:
STR lr, [sp, -16]!
STP x0, x1, [sp, -16]!
1:
LDRB w1, [x0], 1 // load byte of string from address in x0
CBZ w1, 0f // return if zero
BL uart_putc // put charcter out
B 1b // loop
0:
LDP x0, x1, [sp], 16
LDR lr, [sp], 16
RET
// -----------------------------------------------------------------------------