Add Multiboot 2 i386 kernel example

examples/multiboot2-i386-kernel/.gitignore

@@ -0,0 +1,2 @@
+/image.iso
+/rootfs/boot/kernel

examples/multiboot2-i386-kernel/Makefile

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+CCPREFIX = i386-elftailix-
+
+AS = $(CCPREFIX)as
+CC = $(CCPREFIX)gcc
+
+IMAGE = image.iso
+LINKERSCR = linker.ld
+ROOTFS = rootfs
+
+GRUBCFG = $(ROOTFS)/boot/grub/grub.cfg
+KERNEL  = $(ROOTFS)/boot/kernel
+
+CFLAGS =               \
+	-std=c99             \
+	-pedantic            \
+	-Wall                \
+	-Wextra              \
+	-ffreestanding       \
+	-fno-builtin         \
+	-fno-stack-protector \
+	-I../../include
+
+OBJS = main.c.o start.S.o
+
+all: run
+
+run: $(IMAGE)
+	qemu-system-i386 -cdrom $< -serial stdio -display none
+
+clean:
+	rm -f $(IMAGE) $(KERNEL) $(OBJS)
+
+$(IMAGE): $(GRUBCFG) $(KERNEL)
+	grub-mkrescue $(ROOTFS) -o $@
+
+$(KERNEL): $(LINKERSCR) $(OBJS)
+	$(CC) -T $(LINKERSCR) -o $@ $(OBJS) -ffreestanding -nostdlib -lgcc -lkernaux -Wl,-L../..
+	grub-file --is-x86-multiboot2 $@
+
+%.c.o: %.c
+	$(CC) -c $< -o $@ $(CFLAGS)
+
+%.S.o: %.S
+	$(AS) $< -o $@

examples/multiboot2-i386-kernel/linker.ld

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+OUTPUT_ARCH("i386")
+ENTRY(_start)
+
+_kernel_offset = 0xC0000000; /* 3 GB */
+
+_kernel_phys_base = 4M;
+_kernel_virt_base = (_kernel_phys_base + _kernel_offset);
+
+_kernel_stack_size = _kernel_stack_end - _kernel_stack_start;
+
+SECTIONS
+{
+    . = _kernel_phys_base;
+
+    .text BLOCK(4K) : ALIGN(4K)
+    {
+        *(.multiboot)
+        *(.text)
+    }
+
+    .rodata BLOCK(4K) : ALIGN(4K)
+    {
+        *(.rodata)
+    }
+
+    .data BLOCK(4K) : ALIGN(4K)
+    {
+        *(.data)
+    }
+
+    .bss BLOCK(4K) : ALIGN(4K)
+    {
+        *(COMMON)
+        *(.bss)
+    }
+
+    _kernel_size = . - _kernel_phys_base;
+}

examples/multiboot2-i386-kernel/main.c

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+#include <stdint.h>
+
+#include <kernaux/asm/i386.h>
+#include <kernaux/drivers/console.h>
+#include <kernaux/multiboot2.h>
+
+void halt();
+
+static void panic(const char *str);
+
+void main(
+    const uint32_t multiboot2_magic,
+    const struct KernAux_Multiboot2 *const multiboot2_info
+) {
+    if (multiboot2_magic != KERNAUX_MULTIBOOT2_MAGIC) {
+        panic("Multiboot 2 magic number is invalid");
+    }
+
+    KernAux_Multiboot2_print(multiboot2_info, kernaux_console_printf);
+
+    if (!KernAux_Multiboot2_is_valid(multiboot2_info)) {
+        panic("Multiboot 2 info is invalid");
+    }
+}
+
+void halt()
+{
+    panic("Kernel main function returned");
+}
+
+void panic(const char *const str)
+{
+    kernaux_console_printf("panic: %s\n", str);
+    kernaux_asm_i386_hang();
+}

examples/multiboot2-i386-kernel/rootfs/boot/grub/grub.cfg

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+set timeout=0
+
+menuentry "Kernel" {
+    multiboot2 /boot/kernel hello kernel
+}

examples/multiboot2-i386-kernel/start.S

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+.set MULTIBOOT_MAGIC, 0xE85250D6
+.set MULTIBOOT_ARCH, 0
+.set MULTIBOOT_LENGTH, 16 + 8
+.set MULTIBOOT_CHECKSUM, -(MULTIBOOT_MAGIC + MULTIBOOT_ARCH + MULTIBOOT_LENGTH)
+
+
+
+.section .multiboot
+.align 4
+.long MULTIBOOT_MAGIC
+.long MULTIBOOT_ARCH
+.long MULTIBOOT_LENGTH
+.long MULTIBOOT_CHECKSUM
+.long 0
+.long 8
+
+
+
+.section .bss
+
+.global _kernel_stack_start
+.global _kernel_stack_end
+
+.align 16
+_kernel_stack_start:
+.skip 16384 # 16 KiB
+_kernel_stack_end:
+
+
+
+.section .text
+
+.global _start
+
+.type _start, @function
+.type main,   @function
+.type halt,   @function
+
+_start:
+    mov $_kernel_stack_end, %esp // Initialize stack
+
+    push %ebx // Multiboot information pointer
+    push %eax // Multiboot magic number
+    call main
+
+    call halt
+
+.size _start, . - _start