physical memory management and started usermode
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1
Makefile
1
Makefile
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@ -15,6 +15,7 @@ KERNELIMG := $(BUILDDIR)/kernel.bin
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QEMUFLAGS = -d int -s \
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-kernel $(KERNELIMG) \
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-m 512M \
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-device piix3-ide,id=ide -drive id=disk,file=image.img,format=raw,if=none -device ide-hd,drive=disk,bus=ide.0 \
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.PHONY: all kernel qemu clean docs
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12
idt.c
12
idt.c
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@ -1,4 +1,6 @@
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#include <idt.h>
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#include <vga.h>
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#include <printf.h>
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void encode_idt_entry(struct idt_entry idt[], int i, uint32_t offset, uint16_t segment_selector, uint8_t attributes) {
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idt[i].offset_lo = (uint16_t)(offset & 0xFFFF);
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@ -7,3 +9,13 @@ void encode_idt_entry(struct idt_entry idt[], int i, uint32_t offset, uint16_t s
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idt[i].attributes = attributes;
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idt[i].offset_hi = (uint16_t)(offset >> 16);
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}
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void exception_handler(struct registers regs) {
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clear_screen();
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printf("Exception 0x%X (0x%X) has occurred\nEAX: 0x%08X\nECX: 0x%08X\nEDX: 0x%08X\nEBX: 0x%08X\nESI: 0x%08X\nEDI: 0x%08X\nEBP: 0x%08X\nESP: 0x%08X\n",
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regs.int_no, regs.err_code, regs.eax, regs.ecx, regs.edx, regs.ebx, regs.esi, regs.edi, regs.ebp, regs.esp+24);
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printf("\nEIP: 0x%08X\nCS: 0x%08X\nEFLAGS: 0x%08X",
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regs.eip, regs.cs, regs.eflags);
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}
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34
include/fat12.h
Normal file
34
include/fat12.h
Normal file
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@ -0,0 +1,34 @@
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#ifndef RK_FAT12_H_
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#define RK_FAT12_H_
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#include <stdint.h>
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struct fat12_boot_sector {
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uint8_t jump_boot[3]; // Jump instruction to boot code
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uint8_t oem_name[8]; // OEM name and version
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uint16_t bytes_per_sector; // Bytes per sector
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uint8_t sectors_per_cluster; // Sectors per cluster
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uint16_t reserved_sectors; // Reserved sectors
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uint8_t num_fats; // Number of FATs
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uint16_t root_entry_count; // Number of root directory entries
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uint16_t total_sectors_16; // Total sectors (16-bit)
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uint8_t media; // Media descriptor
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uint16_t fat_size_16; // Sectors per FAT (16-bit)
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uint16_t sectors_per_track; // Sectors per track (for BIOS)
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uint16_t num_heads; // Number of heads (for BIOS)
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uint32_t hidden_sectors; // Hidden sectors
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uint32_t total_sectors_32; // Total sectors (32-bit)
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// Extended Boot Record (EBR) fields
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uint8_t drive_number; // Drive number
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uint8_t reserved1; // Reserved
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uint8_t boot_signature; // Extended boot signature
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uint32_t volume_id; // Volume ID (serial number)
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uint8_t volume_label[11]; // Volume label
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uint8_t file_system_type[8]; // File system type (e.g., "FAT12 ")
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uint8_t boot_code[448]; // Boot code
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uint16_t boot_sector_signature; // Boot sector signature (0xAA55)
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} __attribute__((packed));
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#endif
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@ -1,9 +1,50 @@
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#ifndef RK_GDT_H_
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#define RK_GDT_H_
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#include <stdint.h>
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#define GDT_NULL 0
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#define GDT_KERNEL_CODE 1
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#define GDT_KERNEL_DATA 2
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#define GDT_SEGMENT_SELECTOR(i, p) ((i << 3) | p)
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struct gdt_entry {
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uint16_t limit_low;
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uint16_t base_low;
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uint8_t base_middle;
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uint8_t access;
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uint8_t granularity;
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uint8_t base_high;
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} __attribute__((packed));
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struct tss_entry {
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uint32_t prev_tss; // The previous TSS - with hardware task switching this is used
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uint32_t esp0; // The stack pointer to load when we change to kernel mode
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uint32_t ss0; // The stack segment to load when we change to kernel mode
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uint32_t esp1; // Unused...
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uint32_t ss1;
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uint32_t esp2;
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uint32_t ss2;
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uint32_t cr3;
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uint32_t eip;
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uint32_t eflags;
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uint32_t eax;
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uint32_t ecx;
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uint32_t edx;
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uint32_t ebx;
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uint32_t esp;
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uint32_t ebp;
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uint32_t esi;
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uint32_t edi;
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uint32_t es; // The value to load into ES when we change to kernel mode
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uint32_t cs; // The value to load into CS when we change to kernel mode
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uint32_t ss; // The value to load into SS when we change to kernel mode
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uint32_t ds; // The value to load into DS when we change to kernel mode
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uint32_t fs; // The value to load into FS when we change to kernel mode
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uint32_t gs; // The value to load into GS when we change to kernel mode
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uint32_t ldt; // Unused...
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uint16_t trap;
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uint16_t iomap_base;
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} __attribute__((packed));
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#endif
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@ -36,7 +36,17 @@ enum IDT_ATTRIBUTES {
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INT_PRESENT = 0x80,
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};
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struct registers {
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uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax; /* Pushed by pusha. */
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uint32_t int_no, err_code; /* Interrupt number and error code (if applicable) */
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uint32_t eip;
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uint32_t cs;
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uint32_t eflags;
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};
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void encode_idt_entry(struct idt_entry idt[], int i, uint32_t offset, uint16_t segment_selector, uint8_t attributes);
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void flush_idt(uint32_t idt_pointer);
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void exception_handler(struct registers regs);
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#endif
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22
include/kernel.h
Normal file
22
include/kernel.h
Normal file
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@ -0,0 +1,22 @@
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#ifndef RK_KERNEL_H_
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#define RK_KERNEL_H_
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#include <multiboot.h>
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#include <acpi.h>
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struct kernel_context {
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struct rsdp *rsdp;
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struct xsdp *xsdp;
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struct rsdt *rsdt;
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struct mcfg *mcfg;
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uint32_t multi_mmap_size;
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struct multiboot_mmap_entry *multi_mmap;
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uint32_t available_bytes;
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uint32_t mmap_size;
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uint32_t *mmap;
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};
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#endif
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20
include/mem.h
Normal file
20
include/mem.h
Normal file
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@ -0,0 +1,20 @@
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#ifndef RK_MEM_H_
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#define RK_MEM_H_
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#include <kernel.h>
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#include <stdint.h>
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#define KERNEL_START 0x1000000 // 1 MiB
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#define KERNEL_SIZE 0xC800 // 50 KiB
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#define BLOCK_SIZE 4096
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#define BITS 32
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uint8_t mmap_init(struct kernel_context *ctx);
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void mmap_set_block(struct kernel_context *ctx, int block);
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void mmap_free_block(struct kernel_context *ctx, int block);
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void *mmap_find_first_free_block(struct kernel_context *ctx);
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void *mmap_block_to_physical(struct kernel_context *ctx, int block);
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void *memset(void *s, int c, uint32_t len);
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#endif
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@ -28,4 +28,19 @@ struct multiboot_info {
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uint32_t vbeInterfaceLength;
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};
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struct multiboot_mmap_entry
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{
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uint32_t size;
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uint32_t addr_low;
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uint32_t addr_high;
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uint32_t len_low;
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uint32_t len_high;
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#define MULTIBOOT_MEMORY_AVAILABLE 1
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#define MULTIBOOT_MEMORY_RESERVED 2
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#define MULTIBOOT_MEMORY_ACPI_RECLAIMABLE 3
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#define MULTIBOOT_MEMORY_NVS 4
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#define MULTIBOOT_MEMORY_BADRAM 5
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uint32_t type;
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} __attribute__((packed));
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#endif
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111
kmain.c
111
kmain.c
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@ -1,4 +1,4 @@
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#include "ide.h"
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#include <kernel.h>
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#include <multiboot.h>
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#include <acpi.h>
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#include <vga.h>
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@ -9,33 +9,112 @@
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#include <idt.h>
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#include <pic8259.h>
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#include <ps2.h>
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struct kernel_context {
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struct rsdp *rsdp;
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struct xsdp *xsdp;
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struct rsdt *rsdt;
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};
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#include <ide.h>
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#include <mem.h>
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#include <fat12.h>
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struct kernel_context ctx = {0};
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struct idt_entry g_idt[256] = {0};
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struct idtr g_idtr = {0};
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extern void exception_handler();
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extern uint32_t isr_stub_table[32];
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extern void ps2_isr();
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#define MAGIC_BREAKPOINT __asm__ volatile("xchgw %bx, %bx");
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#define USER_DS 0x23 // User data segment selector
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#define USER_CS 0x1B // User code segment selector
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extern struct gdt_entry gdt[6];
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struct tss_entry tss;
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void tss_flush(uint16_t tss_selector) {
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asm volatile (
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"ltr %0"
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: // no output
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: "r" (tss_selector)
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);
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}
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void test() {
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printf("\n\nHello from user mode!\n");
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for (;;) {}
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}
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void switch_to_user_mode(void *user_stack, void *user_entry) {
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asm volatile (
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"movl $0x23, %%eax \n" // User data segment selector
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"mov %%ax, %%ds \n"
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"mov %%ax, %%es \n"
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"mov %%ax, %%fs \n"
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"mov %%ax, %%gs \n"
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"pushl $0x23 \n" // User stack segment
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"pushl %0 \n" // User stack pointer
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"pushfl \n" // Push EFLAGS
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"popl %%eax \n"
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"orl $0x200, %%eax \n" // Enable interrupts (set IF)
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"pushl %%eax \n"
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"pushl $0x1B \n" // User code segment
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"pushl %1 \n" // User entry point
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"iret \n" // Interrupt return (switches to user mode)
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:
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: "r"(user_stack), "r"(user_entry)
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: "eax"
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);
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}
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void write_tss(int num, uint16_t ss0, uint32_t esp0) {
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uint32_t base = (uint32_t)&tss;
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uint32_t limit = base + sizeof(tss);
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gdt[num].base_low = base & 0xFFFF;
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gdt[num].base_middle = (base >> 16) & 0xFF;
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gdt[num].base_high = (base >> 24) & 0xFF;
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gdt[num].limit_low = limit & 0xFFFF;
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gdt[num].granularity = (limit >> 16) & 0x0F;
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gdt[num].granularity |= 0x40;
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gdt[num].access = 0x89;
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memset(&tss, 0, sizeof(tss));
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tss.ss0 = ss0;
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tss.esp0 = esp0;
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tss.cs = 0x0b;
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tss.ss = tss.ds = tss.es = tss.fs = tss.gs = 0x13;
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}
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void kmain(struct multiboot_info *info) {
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clear_screen();
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set_color(VGA_COLOR_CYAN);
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// Check if the bootloader gave us the upper and lower memory
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if (!(info->flags & 0x1)) goto halt;
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ctx.multi_mmap = (struct multiboot_mmap_entry *)info->memMapAddress;
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ctx.multi_mmap_size = info->memMapLength / sizeof(struct multiboot_mmap_entry);
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for (uint32_t i = 0; i < ctx.multi_mmap_size; i++) {
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struct multiboot_mmap_entry entry = ctx.multi_mmap[i];
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if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
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uint32_t len = (uint32_t)(entry.len_low | entry.len_high);
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uint32_t addr = (uint32_t)(entry.addr_low | entry.addr_high);
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printf("Region #%d: 0x%08X-0x%08X\n", i, addr, addr+len);
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}
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if (!mmap_init(&ctx)) {
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set_color(VGA_COLOR_RED);
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printf("Failed to create memory map\n");
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goto halt;
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}
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printf("Detected %d bytes of memory\n", ctx.available_bytes);
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// Create and load an IDT
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for (int i = 0; i < 32; i++) {
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encode_idt_entry(g_idt, i, (uint32_t)&exception_handler, GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, 0x00), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
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encode_idt_entry(g_idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, 0x00), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
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}
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g_idtr.size = (sizeof(struct idt_entry) * 256) - 1;
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@ -119,7 +198,17 @@ void kmain(struct multiboot_info *info) {
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}
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set_color(VGA_COLOR_WHITE);
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printf("\nYou are now being dropped into a kernel shell\n$ ");
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void *buf = mmap_find_first_free_block(&ctx);
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ata_read_sector(ATA_PRIMARY, ATA_MASTER, 0, (uint8_t *)buf);
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// struct fat12_boot_sector *boot_sect = (struct fat12_boot_sector *)buf;
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// int fat_size = boot_sect->total_sectors_16 * boot_sect->bytes_per_sector;
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write_tss(5, 0x10, 0x0);
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tss_flush(0x2B);
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void *stack_bottom = mmap_find_first_free_block(&ctx);
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void *stack_top = stack_bottom + 4096;
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switch_to_user_mode(stack_top, buf);
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halt:
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for (;;) {}
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}
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121
mem.c
Normal file
121
mem.c
Normal file
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@ -0,0 +1,121 @@
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#include <mem.h>
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#include <printf.h>
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// TODO: Fix this, it wastes memory when switching regions because the previous offset isnt being subtracted
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// Should work fine for now?
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void *mmap_block_to_physical(struct kernel_context *ctx, int block) {
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uint32_t offset = block * BLOCK_SIZE;
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for (uint32_t i = 0; i < ctx->multi_mmap_size; i++) {
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struct multiboot_mmap_entry entry = ctx->multi_mmap[i];
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if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
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uint32_t len = (uint32_t)(entry.len_low | entry.len_high);
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uint32_t addr = (uint32_t)(entry.addr_low | entry.addr_high);
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if (len > offset)
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return (void *)(addr + offset);
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}
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return 0;
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}
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void *memset(void *s, int c, uint32_t len) {
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unsigned char *dst = s;
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while (len > 0) {
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*dst = (unsigned char) c;
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dst++;
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len--;
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}
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return s;
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}
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uint8_t mmap_init(struct kernel_context *ctx) {
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// Calculate the number of bytes available to us
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for (uint32_t i = 0; i < ctx->multi_mmap_size; i++) {
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struct multiboot_mmap_entry entry = ctx->multi_mmap[i];
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if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
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uint32_t len = (uint32_t)(entry.len_low | entry.len_high);
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ctx->available_bytes += len;
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}
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ctx->mmap_size = ctx->available_bytes / BLOCK_SIZE / 8;
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printf("Memory map size: %d bytes\n", ctx->mmap_size);
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// Loop again to find the first region with enough space to hold the memory map
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int index = -1;
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for (uint32_t i = 0; i < ctx->multi_mmap_size; i++) {
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struct multiboot_mmap_entry entry = ctx->multi_mmap[i];
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if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
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uint32_t len = (uint32_t)(entry.len_low | entry.len_high);
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if (len > ctx->mmap_size) {
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index = i;
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break;
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}
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}
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if (index == -1) return 0; // Failed
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// Create map
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struct multiboot_mmap_entry entry = ctx->multi_mmap[index];
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uint32_t addr = (uint32_t)(entry.addr_low | entry.addr_high);
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ctx->mmap = (uint32_t *)addr;
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// Zero the map
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memset(ctx->mmap, 0, ctx->mmap_size);
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// Reserve the blocks that hold the memory map + 1
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uint32_t blocks_to_set = ctx->mmap_size / BLOCK_SIZE + 1;
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for (uint32_t i = 0; i < blocks_to_set; i++)
|
||||
mmap_set_block(ctx, i);
|
||||
// Reserve the kernel space
|
||||
int bits = ctx->mmap_size * 8;
|
||||
for (int i = 0; i < bits; i++) {
|
||||
uint32_t phys = (uint32_t)mmap_block_to_physical(ctx, i);
|
||||
if (phys > KERNEL_START && phys < KERNEL_START + KERNEL_SIZE)
|
||||
mmap_set_block(ctx, i);
|
||||
}
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
void mmap_set_block(struct kernel_context *ctx, int block) {
|
||||
int index = block / BITS;
|
||||
int bit = block;
|
||||
if (block >= BITS)
|
||||
bit -= BITS;
|
||||
|
||||
uint32_t mask = 1 << bit;
|
||||
if (!(ctx->mmap[index] & mask))
|
||||
ctx->mmap[index] |= mask;
|
||||
}
|
||||
|
||||
void mmap_free_block(struct kernel_context *ctx, int block) {
|
||||
int index = block / BITS;
|
||||
int bit = block;
|
||||
if (block >= BITS)
|
||||
bit -= BITS;
|
||||
|
||||
uint32_t mask = 1 << bit;
|
||||
if (ctx->mmap[index] & mask)
|
||||
ctx->mmap[index] ^= mask;
|
||||
}
|
||||
|
||||
void *mmap_find_first_free_block(struct kernel_context *ctx) {
|
||||
int bits = ctx->mmap_size * 8;
|
||||
for (int i = 0; i < bits; i++) {
|
||||
int index = i / BITS;
|
||||
int bit = i;
|
||||
if (i >= BITS)
|
||||
bit -= BITS;
|
||||
|
||||
uint32_t mask = 1 << bit;
|
||||
|
||||
uint32_t dword = ctx->mmap[index];
|
||||
if (!(dword & mask)) {
|
||||
return mmap_block_to_physical(ctx, i);
|
||||
}
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -1,5 +1,5 @@
|
|||
%define MAGIC 0x1BADB002
|
||||
%define FLAGS 0b100
|
||||
%define FLAGS 0b110
|
||||
|
||||
; Multiboot v1 Specification
|
||||
; https://www.gnu.org/software/grub/manual/multiboot/multiboot.html
|
||||
|
|
@ -49,13 +49,74 @@ _start:
|
|||
halt:
|
||||
hlt
|
||||
jmp halt
|
||||
global exception_handler
|
||||
exception_handler:
|
||||
add esp, 4
|
||||
mov byte [0xb8000], 'X'
|
||||
iret
|
||||
|
||||
extern exception_handler
|
||||
%macro isr_err_stub 1
|
||||
isr_stub_%+%1:
|
||||
cli
|
||||
push %1
|
||||
pusha
|
||||
call exception_handler
|
||||
popa
|
||||
add esp, 8
|
||||
iret
|
||||
%endmacro
|
||||
%macro isr_no_err_stub 1
|
||||
isr_stub_%+%1:
|
||||
cli
|
||||
push 0
|
||||
push %1
|
||||
pusha
|
||||
call exception_handler
|
||||
popa
|
||||
add esp, 12
|
||||
iret
|
||||
%endmacro
|
||||
|
||||
isr_no_err_stub 0
|
||||
isr_no_err_stub 1
|
||||
isr_no_err_stub 2
|
||||
isr_no_err_stub 3
|
||||
isr_no_err_stub 4
|
||||
isr_no_err_stub 5
|
||||
isr_no_err_stub 6
|
||||
isr_no_err_stub 7
|
||||
isr_err_stub 8
|
||||
isr_no_err_stub 9
|
||||
isr_err_stub 10
|
||||
isr_err_stub 11
|
||||
isr_err_stub 12
|
||||
isr_err_stub 13
|
||||
isr_err_stub 14
|
||||
isr_no_err_stub 15
|
||||
isr_no_err_stub 16
|
||||
isr_err_stub 17
|
||||
isr_no_err_stub 18
|
||||
isr_no_err_stub 19
|
||||
isr_no_err_stub 20
|
||||
isr_no_err_stub 21
|
||||
isr_no_err_stub 22
|
||||
isr_no_err_stub 23
|
||||
isr_no_err_stub 24
|
||||
isr_no_err_stub 25
|
||||
isr_no_err_stub 26
|
||||
isr_no_err_stub 27
|
||||
isr_no_err_stub 28
|
||||
isr_no_err_stub 29
|
||||
isr_err_stub 30
|
||||
isr_no_err_stub 31
|
||||
|
||||
global isr_stub_table
|
||||
isr_stub_table:
|
||||
%assign i 0
|
||||
%rep 32
|
||||
dd isr_stub_%+i
|
||||
%assign i i+1
|
||||
%endrep
|
||||
|
||||
global ps2_isr
|
||||
ps2_isr:
|
||||
cli
|
||||
extern ps2_handler
|
||||
pushad
|
||||
cld
|
||||
|
|
@ -66,7 +127,8 @@ ps2_isr:
|
|||
|
||||
; GDT for a flat memory layout
|
||||
; We get access to all memory and can utilize paging
|
||||
gdt_start:
|
||||
global gdt
|
||||
gdt:
|
||||
gdt_null:
|
||||
dq 0
|
||||
gdt_kern_code:
|
||||
|
|
@ -83,11 +145,27 @@ gdt_kern_data:
|
|||
db 0b10010010
|
||||
db 0b11001111
|
||||
db 0x00
|
||||
gdt_user_code:
|
||||
dw 0xffff
|
||||
dw 0x0000
|
||||
db 0x00
|
||||
db 0b11111010
|
||||
db 0b11001111
|
||||
db 0x00
|
||||
gdt_user_data:
|
||||
dw 0xffff
|
||||
dw 0x0000
|
||||
db 0x00
|
||||
db 0b11110010
|
||||
db 0b11001111
|
||||
db 0x00
|
||||
tss:
|
||||
dq 0
|
||||
gdt_end:
|
||||
|
||||
gdtp:
|
||||
dw gdt_end - gdt_start - 1
|
||||
dd gdt_start
|
||||
dw gdt_end - gdt - 1
|
||||
dd gdt
|
||||
|
||||
|
||||
; Reserve 16KiB of kernel stack space
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user