init

Makefile

@@ -0,0 +1,49 @@
+CC = i686-elf-gcc
+INCLUDE = -I./
+CFLAGS = -Wall -Wextra -Werror -ffreestanding $(INCLUDE)
+LDFLAGS = -T kernel.ld -ffreestanding -O3 -nostdlib -lgcc -mpreferred-stack-boundary=4
+
+BUILDDIR = build
+
+KERNELSRC := $(shell find . -name '*.c' -o -name '*.asm')
+KERNELOBJ := $(addprefix $(BUILDDIR)/, \
+			 $(notdir \
+			 $(patsubst %.c,%.o,\
+			 $(patsubst %.asm,%.o,$(KERNELSRC)))))
+
+LIBSRC 	  := $(shell find ./lib -name '*.c')
+LIBOBJ    := $(addprefix $(BUILDDIR)/, \
+			 $(notdir \
+			 $(patsubst %.c,%.o,$(LIBSRC))))
+
+KERNELIMG := $(BUILDDIR)/kernel.bin
+
+QEMUFLAGS = -d int -s \
+			-kernel $(KERNELIMG)
+
+.PHONY: all kernel qemu clean docs
+
+all: qemu
+
+qemu: kernel
+
+kernel: $(KERNELIMG)
+
+$(KERNELIMG): $(KERNELOBJ) $(LIBOBJ)
+	$(CC) $^ -o $@ $(LDFLAGS)
+$(BUILDDIR)/%.o: %.c
+	$(CC) $(CFLAGS) -c $^ -o $@ 
+$(BUILDDIR)/%.o: %.asm
+	nasm -felf32 $^ -o $@
+
+qemu: kernel
+	qemu-system-i386 $(QEMUFLAGS)
+
+iso: kernel
+	cp $(BUILDDIR)/kernel.bin iso/boot/kernel.bin
+	grub-mkrescue -o  $(BUILDDIR)/andewOS.iso iso/
+
+clean:
+	rm -rf build/*.o build/*.bin iso/boot/*.bin
+docs:
+	doxygen

acpi.c

@@ -0,0 +1,39 @@
+#include <acpi.h>
+
+struct rsdp *acpi_search_for_rsdp() {
+    char *ptr = (char *)BIOS_START;
+    char *str = RSDP_SIG;
+
+    while ((uint32_t)ptr <= (uint32_t)BIOS_END - RSDP_SIG_LEN) {
+        int i;
+        for (i = 0; i < RSDP_SIG_LEN; i++) {
+            if (ptr[i] != str[i])
+                break;
+        }
+        if (i == RSDP_SIG_LEN) {
+            return (struct rsdp *)ptr;
+        }
+        ptr++;
+    }
+
+    return 0;
+}
+
+int acpi_validate_rsdp_checksum(struct rsdp *s) {
+    uint8_t *bytes = (uint8_t *)s;
+    uint8_t sum = 0;
+    for (int i = 0; i < RSDP_SIZE; i++) {
+        sum += bytes[i];
+    }
+
+    return (sum & 0x0F) == 0;
+}
+
+int acpi_validate_sdt_checksum(struct ACPISDTHeader *s) {
+    uint8_t sum = 0;
+    for (uint32_t i = 0; i < s->Length; i++) {
+        sum += ((char *)s)[i];
+    }
+
+    return sum == 0;
+}

acpi.h

@@ -0,0 +1,45 @@
+#ifndef ACPI_H_
+#define ACPI_H_
+
+#include <stdint.h>
+
+#define BIOS_START   0x000E0000
+#define BIOS_END     0x000FFFFF
+#define RSDP_SIG     "RSD PTR "
+#define RSDP_SIG_LEN 8
+#define RSDP_SIZE    20
+
+#define ACPI_VER_1      0
+#define ACPI_VER_OTHER  2
+
+struct rsdp {
+    char Signature[RSDP_SIG_LEN];
+    uint8_t Checksum;
+    char OEMID[6];
+    uint8_t Revision;
+    uint32_t RsdtAddress;
+} __attribute__ ((packed));
+
+struct ACPISDTHeader {
+  char Signature[4];
+  uint32_t Length;
+  uint8_t Revision;
+  uint8_t Checksum;
+  char OEMID[6];
+  char OEMTableID[8];
+  uint32_t OEMRevision;
+  uint32_t CreatorID;
+  uint32_t CreatorRevision;
+};
+
+struct rsdt {
+  struct ACPISDTHeader h;
+  uint32_t other_sdt[];
+};
+
+struct rsdp *acpi_search_for_rsdp();
+int acpi_validate_rsdp_checksum(struct rsdp *s);
+int acpi_validate_sdt_checksum(struct ACPISDTHeader *s);
+struct ACPISDTHeader *acpi_find_table(struct rsdt *root, const char *signature);
+
+#endif

compile_commands.json

@@ -0,0 +1,7 @@
+[
+  {
+    "directory": "/home/rami/rk",
+    "file": "kmain.c",
+    "command": "i686-elf-gcc -Wall -Wextra -Werror -ffreestanding -I./ -c kmain.c -o build/kmain.o"
+  }
+]

io.c

@@ -0,0 +1,17 @@
+#include <io.h>
+
+uint8_t inportb(uint16_t port) {
+    uint8_t result;
+
+    asm volatile ("in %%dx, %%al"
+            : "=a" (result)
+            : "d"  (port));
+
+    return result;
+}
+
+void outportb(uint16_t port, uint8_t byte) {
+    asm volatile ("out %%al, %%dx"
+            : // no output
+            : "a" (byte), "d" (port));
+}

io.h

@@ -0,0 +1,9 @@
+#ifndef IO_H_
+#define IO_H_
+
+#include <stdint.h>
+
+uint8_t inportb(uint16_t port);
+void outportb(uint16_t port, uint8_t byte);
+
+#endif

kernel.ld

@@ -0,0 +1,28 @@
+ENTRY(_start)
+
+SECTIONS 
+{
+    . = 1M;
+
+    .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)
+    }
+}

kmain.c

@@ -0,0 +1,81 @@
+#include <multiboot.h>
+#include <acpi.h>
+
+struct kernel_context {
+    struct rsdp *rsdp;
+    struct xsdp *xsdp;
+
+    struct rsdt *rsdt;
+};
+
+struct kernel_context ctx = {0};
+
+int strncmp( const char * s1, const char * s2, int n )
+{
+    while ( n && *s1 && ( *s1 == *s2 ) )
+    {
+        ++s1;
+        ++s2;
+        --n;
+    }
+    if ( n == 0 )
+    {
+        return 0;
+    }
+    else
+    {
+        return ( *(unsigned char *)s1 - *(unsigned char *)s2 );
+    }
+}
+
+void *findFACP(void *RootSDT)
+{
+    struct rsdt *rsdt = (struct rsdt *) RootSDT;
+    int entries = (rsdt->h.Length - sizeof(rsdt->h)) / 4;
+ 
+    for (int i = 0; i < entries; i++)
+    {
+        struct ACPISDTHeader *h = (struct ACPISDTHeader *) rsdt->other_sdt[i];
+        if (!strncmp(h->Signature, "FACP", 4))
+            return (void *) h;
+    }
+ 
+    // No FACP found
+    return 0;
+}
+
+void kmain(struct multiboot_info *info) {
+    // Check if the bootloader gave us the upper and lower memory
+    if (!(info->flags & 0x1)) goto halt;
+
+    char *vmem = (char *)0xb8000;
+
+    struct rsdp *found_rsdp = acpi_search_for_rsdp();
+    if (!found_rsdp) goto halt;
+    if (found_rsdp->Revision == ACPI_VER_1) {
+        // ACPI v1.0 is being used
+        if (!acpi_validate_rsdp_checksum(found_rsdp)) goto halt;
+        ctx.rsdp = found_rsdp;
+        ctx.xsdp = 0;
+
+        if (!acpi_validate_sdt_checksum((struct ACPISDTHeader *)found_rsdp->RsdtAddress)) 
+            goto halt;
+
+        ctx.rsdt = (struct rsdt*)found_rsdp->RsdtAddress;
+
+    } else if (found_rsdp->Revision == ACPI_VER_OTHER) {
+        // ACPI v2.0+ is being used
+        // not supported yet....
+        goto halt;
+    } else goto halt;
+
+    void *fadt = findFACP(ctx.rsdt);
+    if (!fadt) goto halt;
+    char *next_sig = (char *)fadt;
+    vmem[0] = next_sig[0];
+    vmem[2] = next_sig[1];
+    vmem[4] = next_sig[2];
+    vmem[6] = next_sig[3];
+halt:
+    for (;;) {}
+}

multiboot.asm

@@ -0,0 +1,71 @@
+%define MAGIC 0x1BADB002
+%define FLAGS 0
+
+; Multiboot v1 Specification 
+; https://www.gnu.org/software/grub/manual/multiboot/multiboot.html
+section .multiboot
+align 4
+dd MAGIC 
+dd FLAGS
+dd -(MAGIC + FLAGS)
+
+section .text
+global _start
+_start:
+    cli
+
+    ; Check if EAX contains the multiboot magic number the bootloader is supposed to give us
+    cmp eax, 0x2BADB002
+    jne halt
+
+    lgdt [gdtp]
+    mov ax, 0x10 ; Offset to kernel data descriptor
+    mov es, ax
+    mov ds, ax
+    mov fs, ax
+    mov gs, ax
+    mov ss, ax
+    jmp 0x8:.use_code_seg ; Offset to kernel code descriptor
+.use_code_seg:
+    mov esp, stack_bottom
+    push ebx 
+    extern kmain
+    call kmain
+
+; If the kernel function somehow returns, disable interrupts and hang
+    cli
+halt:
+    hlt
+    jmp halt
+
+; GDT for a flat memory layout
+; We get access to all memory and can utilize paging
+gdt_start:
+gdt_null:
+    dq 0
+gdt_kern_code:
+    dw 0xffff
+    dw 0x0000
+    db 0x00
+    db 0b10011010
+    db 0b11001111
+    db 0x00
+gdt_kern_data:
+    dw 0xffff
+    dw 0x0000
+    db 0x00
+    db 0b10010010
+    db 0b11001111
+    db 0x00
+gdt_end:
+
+gdtp:
+    dw gdt_end - gdt_start - 1
+    dd gdt_start
+
+; Reserve 16KiB of kernel stack space
+section .bss
+align 4
+stack_top:
+    resb 16384 
+stack_bottom:

multiboot.h

@@ -0,0 +1,31 @@
+#ifndef MULTIBOOT_H_
+#define MULTIBOOT_H_
+
+#include <stdint.h>
+
+#define MULTIBOOT_MAGIC 0x2BADB002
+
+struct multiboot_info {
+    uint32_t flags;			//required
+    uint32_t memLower;		//if bit 0 in flags are set
+    uint32_t memUpper;		//if bit 0 in flags are set
+    uint32_t bootDevice;		//if bit 1 in flags are set
+    uint32_t commandLine;		//if bit 2 in flags are set
+    uint32_t moduleCount;		//if bit 3 in flags are set
+    uint32_t moduleAddress;		//if bit 3 in flags are set
+    uint32_t syms[4];		//if bits 4 or 5 in flags are set
+    uint32_t memMapLength;		//if bit 6 in flags is set
+    uint32_t memMapAddress;		//if bit 6 in flags is set
+    uint32_t drivesLength;		//if bit 7 in flags is set
+    uint32_t drivesAddress;		//if bit 7 in flags is set
+    uint32_t configTable;		//if bit 8 in flags is set
+    uint32_t apmTable;		//if bit 9 in flags is set
+    uint32_t vbeControlInfo;	//if bit 10 in flags is set
+    uint32_t vbeModeInfo;		//if bit 11 in flags is set
+    uint32_t vbeMode;		// all vbe_* set if bit 12 in flags are set
+    uint32_t vbeInterfaceSeg;
+    uint32_t vbeInterfaceOff;
+    uint32_t vbeInterfaceLength;
+}; 
+
+#endif