Hello world!

kernel/.gitignore

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+*.o
+mop2

kernel/Makefile

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+.PHONY: all clean
+
+CC := x86_64-elf-gcc
+LD := x86_64-elf-ld
+
+override CFLAGS = -Wall \
+					-Wextra \
+					-ffreestanding \
+					-fno-stack-protector \
+					-fno-stack-check \
+					-fno-lto \
+					-fno-PIC \
+					-ffunction-sections \
+					-fdata-sections \
+					-m64 \
+					-march=x86-64 \
+					-mabi=sysv \
+					-mno-80387 \
+					-mno-mmx \
+					-mno-sse \
+					-mno-sse2 \
+					-mno-red-zone \
+					-mcmodel=kernel \
+					-I. \
+					-I../limine
+
+override LDFLAGS = \
+	-m elf_x86_64 \
+	-nostdlib \
+	-static \
+	-z max-page-size=0x1000 \
+	--gc-sections \
+	-T link.ld
+
+override NASMFLAGS = \
+	-felf64 \
+	-Wall \
+	-F dwarf -g
+
+override SRCFILES := $(shell find -L . -type f 2>/dev/null | LC_ALL=C sort)
+override CFILES := $(filter %.c,$(SRCFILES))
+override ASFILES := $(filter %.asm,$(SRCFILES))
+override OBJ := $(patsubst %.c,%.o,$(CFILES)) $(patsubst %.asm,%.o,$(ASFILES))
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+%.o: %.asm
+	nasm $(NASMFLAGS) $< -o $@
+
+all: mop2
+
+mop2: $(OBJ)
+	$(LD) $^ $(LDFLAGS) -o $@
+
+clean:
+	rm *.o mop2
+

kernel/kmain.c

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+#include <limine.h>
+#include <types.h>
+
+__attribute__((used, section(".limine_requests")))
+static volatile LIMINE_BASE_REVISION(3);
+
+__attribute__((used, section(".limine_requests")))
+static volatile struct limine_framebuffer_request framebuffer_request = {
+    .id = LIMINE_FRAMEBUFFER_REQUEST,
+    .revision = 0
+};
+
+__attribute__((used, section(".limine_requests_start")))
+static volatile LIMINE_REQUESTS_START_MARKER;
+
+__attribute__((used, section(".limine_requests_end")))
+static volatile LIMINE_REQUESTS_END_MARKER;
+
+// Halt and catch fire function.
+static void hcf(void) {
+    for (;;) {
+        asm ("hlt");
+    }
+}
+
+void kmain(void) {
+    if (LIMINE_BASE_REVISION_SUPPORTED == false) {
+        hcf();
+    }
+
+    if (framebuffer_request.response == NULL
+     || framebuffer_request.response->framebuffer_count < 1) {
+        hcf();
+    }
+
+    struct limine_framebuffer *framebuffer = framebuffer_request.response->framebuffers[0];
+
+
+    hcf();
+}

kernel/link.ld

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+/* Tell the linker that we want an x86_64 ELF64 output file */
+OUTPUT_FORMAT(elf64-x86-64)
+
+/* We want the symbol kmain to be our entry point */
+ENTRY(kmain)
+
+/* Define the program headers we want so the bootloader gives us the right */
+/* MMU permissions; this also allows us to exert more control over the linking */
+/* process. */
+PHDRS
+{
+    limine_requests PT_LOAD;
+    text PT_LOAD;
+    rodata PT_LOAD;
+    data PT_LOAD;
+}
+
+SECTIONS
+{
+    /* We want to be placed in the topmost 2GiB of the address space, for optimisations */
+    /* and because that is what the Limine spec mandates. */
+    /* Any address in this region will do, but often 0xffffffff80000000 is chosen as */
+    /* that is the beginning of the region. */
+    . = 0xffffffff80000000;
+
+    /* Define a section to contain the Limine requests and assign it to its own PHDR */
+    .limine_requests : {
+        KEEP(*(.limine_requests_start))
+        KEEP(*(.limine_requests))
+        KEEP(*(.limine_requests_end))
+    } :limine_requests
+
+    /* Move to the next memory page for .text */
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
+
+    .text : {
+        *(.text .text.*)
+    } :text
+
+    /* Move to the next memory page for .rodata */
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
+
+    .rodata : {
+        *(.rodata .rodata.*)
+    } :rodata
+
+    /* Move to the next memory page for .data */
+    . = ALIGN(CONSTANT(MAXPAGESIZE));
+
+    .data : {
+        *(.data .data.*)
+    } :data
+
+    /* NOTE: .bss needs to be the last thing mapped to :data, otherwise lots of */
+    /* unnecessary zeros will be written to the binary. */
+    /* If you need, for example, .init_array and .fini_array, those should be placed */
+    /* above this. */
+    .bss : {
+        *(.bss .bss.*)
+        *(COMMON)
+    } :data
+
+    /* Discard .note.* and .eh_frame* since they may cause issues on some hosts. */
+    /DISCARD/ : {
+        *(.eh_frame*)
+        *(.note .note.*)
+    }
+}

kernel/types.h

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+#ifndef TYPES_H_
+#define TYPES_H_
+
+#define NULL ((void *)0)
+
+typedef char int8;
+typedef unsigned char uint8;
+typedef short int16;
+typedef unsigned short uint16;
+typedef int int32;
+typedef unsigned int uint32;
+typedef long long int64;
+typedef unsigned long long uint64;
+
+#endif // TYPES_H_