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lab7
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‎lab7/.gitignore‎

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.vscode
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build
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rootfs
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temp
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dump.*
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*.img
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*.dtb

‎lab7/Makefile‎

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ARMGNU ?= aarch64-linux-gnu
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CFLAGS = -Iinclude -nostdlib -nostartfiles -ffreestanding -mgeneral-regs-only -Wall -g
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ASMFLAGS = -Iinclude
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QEMUFLAGS = -M raspi3b -display none -serial null -serial stdio
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QEMUFLAGSDISP = -M raspi3b -serial null -serial stdio
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SRC_DIR = src
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BUILD_DIR = build
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all: clean kernel8.img
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clean:
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rm -rf $(BUILD_DIR) *.img
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build:
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mkdir -p $(BUILD_DIR)
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$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c | $(BUILD_DIR)
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$(ARMGNU)-gcc $(CFLAGS) -c $< -o $@
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$(BUILD_DIR)/_%.o: $(SRC_DIR)/%.S | $(BUILD_DIR)
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$(ARMGNU)-gcc $(ASMFLAGS) -c $< -o $@
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SRC_FILES = $(wildcard $(SRC_DIR)/*.c)
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ASM_FILES = $(wildcard $(SRC_DIR)/*.S)
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OBJ_FILES = $(SRC_FILES:$(SRC_DIR)/%.c=$(BUILD_DIR)/%.o)
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OBJ_FILES += $(ASM_FILES:$(SRC_DIR)/%.S=$(BUILD_DIR)/_%.o)
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kernel8.img: $(SRC_DIR)/linker.ld $(OBJ_FILES)
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$(ARMGNU)-ld -T $(SRC_DIR)/linker.ld -o $(BUILD_DIR)/kernel8.elf $(OBJ_FILES)
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$(ARMGNU)-objcopy -O binary $(BUILD_DIR)/kernel8.elf kernel8.img
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qemu: all initramfs.cpio bcm2710-rpi-3-b-plus.dtb
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clear & qemu-system-aarch64 $(QEMUFLAGS) -kernel kernel8.img -initrd initramfs.cpio -dtb bcm2710-rpi-3-b-plus.dtb
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dpqemu: all initramfs.cpio bcm2710-rpi-3-b-plus.dtb
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clear & qemu-system-aarch64 $(QEMUFLAGSDISP) -kernel kernel8.img -initrd initramfs.cpio -dtb bcm2710-rpi-3-b-plus.dtb
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debug: all initramfs.cpio bcm2710-rpi-3-b-plus.dtb
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qemu-system-aarch64 $(QEMUFLAGS) -kernel kernel8.img -initrd initramfs.cpio -dtb bcm2710-rpi-3-b-plus.dtb -S -s -d int

‎lab7/bootloader/Makefile‎

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ARMGNU ?= aarch64-linux-gnu
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CFLAGS = -nostdlib -nostartfiles -ffreestanding -mgeneral-regs-only -Wall -g
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QEMUFLAGS = -M raspi3b -display none -serial null -serial pty
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all: clean bootloader.img
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clean:
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rm -rf build *.img
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bootloader.img:
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mkdir -p build
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$(ARMGNU)-gcc $(CFLAGS) -c main.c -o build/main.o
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$(ARMGNU)-gcc $(CFLAGS) -c start.S -o build/start.o
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$(ARMGNU)-gcc $(CFLAGS) -c boot.c -o build/boot.o
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$(ARMGNU)-ld -T linker.ld -o build/bootloader.elf build/main.o build/start.o build/boot.o
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$(ARMGNU)-objcopy -O binary build/bootloader.elf bootloader.img
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qemu: clean bootloader.img
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qemu-system-aarch64 $(QEMUFLAGS) -kernel bootloader.img -initrd ../initramfs.cpio -dtb ../bcm2710-rpi-3-b-plus.dtb

‎lab7/bootloader/boot.c‎

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#include "boot.h"
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void init_uart() {
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// Configure GPIO pins
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register unsigned int r = *GPFSEL1;
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r &= ~((7 << 12) | (7 << 15));
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r |= (2 << 12) | (2 << 15);
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*GPFSEL1 = r;
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*GPPUD = 0;
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for (int i = 0; i < 150; i++) asm volatile("nop");
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*GPPUDCLK0 = (1 << 14) | (1 << 15);
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for (int i = 0; i < 150; i++) asm volatile("nop");
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*GPPUD = 0;
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*GPPUDCLK0 = 0;
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*AUX_ENABLE |= 1;
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*AUX_MU_CNTL = 0;
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*AUX_MU_IER = 0;
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*AUX_MU_LCR = 3;
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*AUX_MU_MCR = 0;
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*AUX_MU_BAUD = 270;
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*AUX_MU_IIR = 6;
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*AUX_MU_CNTL = 3;
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}
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char uart_recv() {
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while (!(*AUX_MU_LSR & 0x01)) asm volatile("nop");
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return (char)(*AUX_MU_IO);
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}
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void uart_putc(char c) {
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if (c == '\n') uart_putc('\r');
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while (!(*AUX_MU_LSR & 0x20)) asm volatile("nop");
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*AUX_MU_IO = c;
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}
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void uart_puts(const char *s) {
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while (*s) uart_putc(*s++);
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}
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int atoi(const char *s) {
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int result = 0;
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int sign = 1;
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int i = 0;
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while (s[i] == ' ') i++;
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if (s[i] == '-') {
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sign = -1;
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i++;
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} else if (s[i] == '+')
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i++;
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while (s[i] >= '0' && s[i] <= '9') {
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result = result * 10 + (s[i] - '0');
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i++;
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}
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return sign * result;
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}

‎lab7/bootloader/boot.h‎

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#ifndef BOOT_H
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#define BOOT_H
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/* ==================== GPIO ==================== */
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#define MMIO_BASE 0x3F000000
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#define GPFSEL0 ((volatile unsigned int *)(MMIO_BASE + 0x00200000))
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#define GPFSEL1 ((volatile unsigned int *)(MMIO_BASE + 0x00200004))
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#define GPFSEL2 ((volatile unsigned int *)(MMIO_BASE + 0x00200008))
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#define GPFSEL3 ((volatile unsigned int *)(MMIO_BASE + 0x0020000C))
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#define GPFSEL4 ((volatile unsigned int *)(MMIO_BASE + 0x00200010))
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#define GPFSEL5 ((volatile unsigned int *)(MMIO_BASE + 0x00200014))
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#define GPSET0 ((volatile unsigned int *)(MMIO_BASE + 0x0020001C))
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#define GPSET1 ((volatile unsigned int *)(MMIO_BASE + 0x00200020))
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#define GPCLR0 ((volatile unsigned int *)(MMIO_BASE + 0x00200028))
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#define GPCLR1 ((volatile unsigned int *)(MMIO_BASE + 0x0020002C))
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#define GPLEV0 ((volatile unsigned int *)(MMIO_BASE + 0x00200034))
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#define GPLEV1 ((volatile unsigned int *)(MMIO_BASE + 0x00200038))
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#define GPEDS0 ((volatile unsigned int *)(MMIO_BASE + 0x00200040))
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#define GPEDS1 ((volatile unsigned int *)(MMIO_BASE + 0x00200044))
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#define GPHEN0 ((volatile unsigned int *)(MMIO_BASE + 0x00200064))
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#define GPHEN1 ((volatile unsigned int *)(MMIO_BASE + 0x00200068))
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#define GPPUD ((volatile unsigned int *)(MMIO_BASE + 0x00200094))
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#define GPPUDCLK0 ((volatile unsigned int *)(MMIO_BASE + 0x00200098))
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#define GPPUDCLK1 ((volatile unsigned int *)(MMIO_BASE + 0x0020009C))
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/* ==================== UART ==================== */
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#define AUX_ENABLE ((volatile unsigned int *)(MMIO_BASE + 0x00215004))
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#define AUX_MU_IO ((volatile unsigned int *)(MMIO_BASE + 0x00215040))
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#define AUX_MU_IER ((volatile unsigned int *)(MMIO_BASE + 0x00215044))
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#define AUX_MU_IIR ((volatile unsigned int *)(MMIO_BASE + 0x00215048))
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#define AUX_MU_LCR ((volatile unsigned int *)(MMIO_BASE + 0x0021504C))
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#define AUX_MU_MCR ((volatile unsigned int *)(MMIO_BASE + 0x00215050))
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#define AUX_MU_LSR ((volatile unsigned int *)(MMIO_BASE + 0x00215054))
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#define AUX_MU_MSR ((volatile unsigned int *)(MMIO_BASE + 0x00215058))
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#define AUX_MU_SCRATCH ((volatile unsigned int *)(MMIO_BASE + 0x0021505C))
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#define AUX_MU_CNTL ((volatile unsigned int *)(MMIO_BASE + 0x00215060))
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#define AUX_MU_STAT ((volatile unsigned int *)(MMIO_BASE + 0x00215064))
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#define AUX_MU_BAUD ((volatile unsigned int *)(MMIO_BASE + 0x00215068))
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void init_uart();
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char uart_recv();
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void uart_putc(char c);
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void uart_puts(const char *s);
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/* ==================== UTILS ==================== */
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int atoi(const char *s);
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#endif // BOOT_H

‎lab7/bootloader/linker.ld‎

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SECTIONS
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{
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. = 0x60000;
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__loader_start = .;
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.text : { *(.text.boot) *(.text) }
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.rodata : { *(.rodata) }
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.data : { *(.data) }
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.bss : {
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__bss_start = .;
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*(.bss)
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__bss_end = .;
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}
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__loader_end = .;
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}
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__bss_size = SIZEOF(.bss);
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__loader_size = __loader_end - __loader_start;

‎lab7/bootloader/main.c‎

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#include "boot.h"
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int main() {
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init_uart();
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uart_puts("\033[2J\033[H");
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uart_puts(
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"UART Bootloader\n"
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"Waiting for kernel...\n");
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// Get kernel image size
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char buf[16] = {0};
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for (int i = 0; i < 16; i++) {
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buf[i] = uart_recv();
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if (buf[i] == '\n') {
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buf[i] = '\0';
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break;
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}
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}
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// Load kernel image
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uart_puts("Kernel size: ");
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uart_puts(buf);
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uart_puts(" bytes.\n");
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uart_puts("Loading the kernel image...\n");
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unsigned int size = atoi(buf);
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char *kernel = (char *)0x80000;
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while (size--) *kernel++ = uart_recv();
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// Restore registers x0 x1 x2 x3
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asm volatile(
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"mov x0, x10\n"
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"mov x1, x11\n"
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"mov x2, x12\n"
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"mov x3, x13\n"
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"mov x30, 0x80000\n"
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"ret\n" // Jump to the new kernel
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);
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return 0;
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}

‎lab7/bootloader/start.S‎

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.section ".text.boot"
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.global _start
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_start:
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/* save registers x0 x1 x2 x3 */
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mov x10, x0 /* dtb_base address */
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mov x11, x1
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mov x12, x2
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mov x12, x3
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/* relocate bootloader */
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ldr x1, =0x80000
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ldr x2, =__loader_start // 0x60000
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ldr w3, =__loader_size
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relocate:
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ldr x4, [x1], #8
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str x4, [x2], #8
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sub w3, w3, #1
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cbnz w3, relocate
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/* set stack pointer */
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ldr x1, =_start
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mov sp, x1
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/* clear bss section */
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ldr x1, =__bss_start
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ldr w2, =__bss_size
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bss_reset:
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cbz w2, run_main
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str xzr, [x1], #8
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sub w2, w2, #1
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cbnz w2, bss_reset
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run_main:
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/* branch to main function */
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bl main-0x20000
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b run_main

‎lab7/include/command.h‎

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#pragma once
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#define MAX_BUF_SIZE 1024
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#define END_OF_COMMAND_LIST "NULL"
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struct command {
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const char *name;
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const char *help;
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void (*func)(void);
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};
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extern struct command cmd_list[];
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extern unsigned int BOARD_REVISION;
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extern unsigned long BASE_MEMORY;
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extern unsigned int NUM_PAGES;
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// Commands
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void cmd_info();
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void cmd_hello();

‎lab7/include/devtree.h‎

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#pragma once
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#include <stdint.h>
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#include "hardware.h"
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struct fdt_header {
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uint32_t magic;
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uint32_t totalsize;
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uint32_t off_dt_struct;
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uint32_t off_dt_strings;
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uint32_t off_mem_rsvmap;
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uint32_t version;
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uint32_t last_comp_version;
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uint32_t boot_cpuid_phys;
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uint32_t size_dt_strings;
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uint32_t size_dt_struct;
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};
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/**
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* @brief Convert a 4-byte big-endian sequence to little-endian.
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*
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* @param s: big-endian sequence
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* @return little-endian sequence
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*/
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uint32_t be2le(const void *s);
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void fdt_traverse(void (*callback)(void *, char *));

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