mirror of
https://github.com/gbowne1/ClassicOS.git
synced 2025-11-16 22:35:26 -08:00
multiple changes: BL1/BL2/kernel separation (build system, etc.) BL2 implementation. BL documentation
This commit is contained in:
vmttmv
82
Makefile
82
Makefile
@@ -1,64 +1,58 @@
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AS = nasm
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ASFLAGS = -f elf32 -g -F dwarf
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CC = gcc
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CFLAGS = -std=c11 -m32 -ffreestanding -c -fno-stack-protector -fno-pie
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LD = ld
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QEMU = qemu-system-i386
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IMG_SIZE = 1440k
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QEMU= qemu-system-i386
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BUILD_DIR = build
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BOOT_SRC = bootloader/boot.asm
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BOOT_OBJ = $(BUILD_DIR)/boot.o
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BOOT_ELF = $(BUILD_DIR)/boot.elf
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BOOT_IMG = $(BUILD_DIR)/boot.img
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DISK_IMG = $(BUILD_DIR)/disk.img
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STAGE2_SIZE = 2048
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KERNEL_C_SRC = $(wildcard kernel/*.c)
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KERNEL_ASM_SRC = $(wildcard kernel/*.asm)
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KERNEL_OBJ = $(patsubst kernel/%.c, $(BUILD_DIR)/%.o, $(KERNEL_C_SRC))
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KERNEL_OBJ += $(patsubst kernel/%.asm, $(BUILD_DIR)/asm_%.o, $(KERNEL_ASM_SRC))
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KERNEL_OBJ += $(BUILD_DIR)/boot1.o
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KERNEL_ELF = $(BUILD_DIR)/kernel.elf
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KERNEL_BIN = $(BUILD_DIR)/kernel.bin
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DISK_IMG = $(BUILD_DIR)/disk.img
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all: $(DISK_IMG)
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all: $(BOOT_IMG) $(KERNEL_BIN) $(DISK_IMG)
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.PHONY: stage1 stage2 kernel run gdb clean
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stage1: $(BUILD_DIR)
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$(AS) $(ASFLAGS) -o $(BUILD_DIR)/$@.o bootloader/$@.asm
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$(LD) -Ttext=0x7c00 -melf_i386 -o $(BUILD_DIR)/$@.elf $(BUILD_DIR)/$@.o
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objcopy -O binary $(BUILD_DIR)/$@.elf $(BUILD_DIR)/$@.bin
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# NOTE: Stage2 final size should be checked against `$(STAGE2_SIZE)` by the build system to avoid an overflow.
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# Alternatively, convey the final stage2 size through other means to stage1.
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stage2: $(BUILD_DIR)
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$(AS) $(ASFLAGS) -o $(BUILD_DIR)/stage2.o bootloader/stage2.asm
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$(CC) -std=c11 -ffreestanding -nostdlib -fno-stack-protector -m32 -g -c -o $(BUILD_DIR)/stage2_load.o bootloader/stage2_load.c
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$(LD) -Tbootloader/stage2.ld -melf_i386 -o $(BUILD_DIR)/$@.elf $(BUILD_DIR)/stage2.o $(BUILD_DIR)/stage2_load.o
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objcopy -O binary $(BUILD_DIR)/$@.elf $(BUILD_DIR)/$@.bin
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truncate -s $(STAGE2_SIZE) $(BUILD_DIR)/$@.bin
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$(BUILD_DIR)/asm_%.o: kernel/%.asm
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$(AS) $(ASFLAGS) -o $@ $<
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$(BUILD_DIR)/%.o: kernel/%.c
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$(CC) -std=c11 -ffreestanding -nostdlib -fno-stack-protector -m32 -g -c -o $@ $<
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kernel: $(KERNEL_OBJ) | $(BUILD_DIR)
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$(LD) -melf_i386 -Tbootloader/linker.ld -o $(BUILD_DIR)/kernel.elf $(KERNEL_OBJ)
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$(DISK_IMG): stage1 stage2 kernel
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dd if=$(BUILD_DIR)/stage1.bin of=$@
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dd if=$(BUILD_DIR)/stage2.bin of=$@ oflag=append conv=notrunc
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dd if=$(BUILD_DIR)/kernel.elf of=$@ oflag=append conv=notrunc
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truncate -s 1M $@
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$(BUILD_DIR):
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mkdir -p $@
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$(BOOT_OBJ): $(BOOT_SRC) | $(BUILD_DIR)
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$(AS) -f elf32 -g -F dwarf -o $@ $<
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run:
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qemu-system-i386 -s -S $(DISK_IMG)
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$(BOOT_ELF): $(BOOT_OBJ)
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$(LD) -Ttext=0x7c00 -melf_i386 -o $@ $<
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$(BOOT_IMG): $(BOOT_ELF)
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objcopy -O binary $< $@
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truncate -s $(IMG_SIZE) $@
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$(BUILD_DIR)/boot1.o: bootloader/boot1.asm
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$(AS) -f elf32 -o $@ $<
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$(BUILD_DIR)/asm_%.o: kernel/%.asm
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$(AS) -f elf32 -o $@ $<
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$(BUILD_DIR)/%.o: kernel/%.c
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$(CC) $(CFLAGS) $< -o $@
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$(KERNEL_BIN): $(KERNEL_OBJ) | $(BUILD_DIR)
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$(LD) -melf_i386 --oformat binary -T bootloader/linker.ld -o $@ $(KERNEL_OBJ)
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$(DISK_IMG): $(BOOT_IMG) $(KERNEL_BIN)
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dd if=$(BOOT_IMG) of=$@ bs=512 seek=4
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dd if=$(KERNEL_BIN) of=$@ bs=512 seek=200
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run: $(DISK_IMG)
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$(QEMU) -drive file=$<,format=raw,if=floppy
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.PHONY: stage1 clean
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stage1: $(BOOT_IMG)
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gdb:
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gdb -x gdb.txt
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clean:
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rm -rf $(BUILD_DIR)
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27
bootloader/README.md
Normal file
27
bootloader/README.md
Normal file
@@ -0,0 +1,27 @@
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# ClassicOS 2-stage bootloader
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Bootloader documentation for ClassicOS
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## Disk image organization:
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```
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[ 512 B ] [ 2048 B ] [ Unspecified ]
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Stage 1 Stage 2 Kernel
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```
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## Stage 1 (`stage1.asm`)
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Responsible for loading the second stage using BIOS routines, and switching to protected mode.
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- Queries CHS parameters from BIOS
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- Loads the second stage bootloader (2048 B) to `07c00h`
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- Sets up a GDT with descriptor entries for code and data both covering the whole 32-bit address space
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- Enables A20
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- Set CR0.PE (enable protected mode) and jump to stage 2
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## Stage 2 (`stage2.asm, stage2_load.c`)
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- Set up segment registers
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- Load the kernel ELF header
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- Parse the program headers, and load all `PT_LOAD` segments from disk
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- Jump to the kernel entry
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@@ -1,194 +0,0 @@
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; ==============================================================================
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; boot1.asm - Second Stage Bootloader (Fixed Real Mode Transition)
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; ==============================================================================
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[BITS 32]
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global _start
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extern kmain
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_start:
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; Set up segments
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mov ax, 0x10
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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; Stack (must be identity-mapped)
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mov esp, 0x90000
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; CPU Feature Detection: check CPUID support
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pushfd ; Save flags
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pop eax
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mov ecx, eax
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xor eax, 1 << 21 ; Flip ID bit
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push eax
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popfd
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pushfd
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pop eax
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xor eax, ecx
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jz .no_cpuid ; CPUID unsupported if no change
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; CPUID supported, verify features
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mov eax, 1
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cpuid
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; Check for paging support (bit 31 of edx)
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test edx, 1 << 31
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jz .no_paging_support
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; Additional CPU feature checks could be added here
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jmp .cpuid_check_done
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.no_cpuid:
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mov si, no_cpuid_msg
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call print_string_16
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jmp halt
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.no_paging_support:
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mov si, no_paging_msg
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call print_string_16
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jmp halt
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.cpuid_check_done:
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; Temporarily switch back to real mode
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cli
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mov eax, cr0
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and eax, 0x7FFFFFFE ; Clear PE & PG bits
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mov cr0, eax
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jmp 0x18:real_mode_entry
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; ----------------------------------------------------------------
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[BITS 16]
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real_mode_entry:
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; Real mode for BIOS access (E820, VESA)
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xor ax, ax
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mov es, ax
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; VESA call
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mov di, VbeControllerInfo
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mov ax, 0x4F00
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int 0x10
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jc vesa_error
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; E820 memory map
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xor ebx, ebx
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mov edx, 0x534D4150
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mov di, MemoryMapBuffer
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mov [MemoryMapEntries], dword 0
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.e820_loop:
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mov eax, 0xE820
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mov ecx, 24
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int 0x15
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jc e820_error
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add di, 24
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inc dword [MemoryMapEntries]
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test ebx, ebx
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jnz .e820_loop
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jmp e820_done
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e820_error:
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mov si, e820_error_msg
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call print_string_16
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jmp halt
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vesa_error:
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mov si, vesa_error_msg
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call print_string_16
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; Fallback: set VGA text mode 3 and continue
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mov ah, 0x00 ; BIOS Set Video Mode function
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mov al, 0x03 ; VGA 80x25 text mode
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int 0x10
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; Clear screen
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mov ah, 0x06 ; Scroll up function
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mov al, 0 ; Clear entire screen
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mov bh, 0x07 ; Text attribute (gray on black)
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mov cx, 0 ; Upper-left corner
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mov dx, 0x184F ; Lower-right corner
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int 0x10
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jmp e820_done ; Continue booting without VESA graphics
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e820_done:
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; Back to protected mode
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cli
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mov eax, cr0
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or eax, 1
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mov cr0, eax
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jmp 0x08:protected_entry
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; ----------------------------------------------------------------
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; removed duplicate print from here
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; suggested calling it from boot.asm
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e820_error_msg db "E820 Failed!", 0
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vesa_error_msg db "VESA Failed!", 0
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no_cpuid_msg db "No CPUID support detected!", 0
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no_paging_msg db "CPU lacks paging support!", 0
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; ----------------------------------------------------------------
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[BITS 32]
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protected_entry:
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; Paging setup
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xor eax, eax
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mov edi, page_directory
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mov ecx, 1024
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rep stosd
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mov edi, page_table
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rep stosd
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mov eax, page_table
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or eax, 0x3
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mov [page_directory], eax
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mov ecx, 1024
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mov edi, page_table
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mov eax, 0x00000003
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.fill_pages:
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mov [edi], eax
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add eax, 0x1000
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add edi, 4
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loop .fill_pages
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mov eax, page_directory
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mov cr3, eax
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mov eax, cr0
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or eax, 0x80000000
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mov cr0, eax
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jmp kmain
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halt:
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cli
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.hang:
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hlt
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jmp .hang
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; ----------------------------------------------------------------
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; Data buffers and variables must be appropriately defined in your data section
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MemoryMapBuffer times 128 db 0 ; 128*24 bytes reserved for E820 memory map (adjust size as needed)
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MemoryMapEntries dd 0
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VbeControllerInfo times 512 db 0 ; Buffer for VESA controller info (adjust size as needed)
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; Define page directory and page table aligned as needed (in your data section)
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align 4096
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page_directory times 1024 dd 0
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align 4096
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page_table times 1024 dd 0
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%assign pad_size 4096
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%ifdef __SIZE__
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%define size_current __SIZE__
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%else
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%define size_current ($ - $$)
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%endif
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%if size_current < pad_size
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times pad_size - size_current db 0
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%endif
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checksum_byte db 0
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@@ -2,10 +2,16 @@
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; boot.asm - First Stage Bootloader (CHS Based)
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; ==============================================================================
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[BITS 16]
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; [ORG 0x7C00]
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; Params for stage2
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%define s2_addr 1 ; stage2 disk offset, in sectors
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%define s2_laddr 0x7e00 ; stage2 load address
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%define s2_size 2048 ; stage2 size
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%define s2_nsect s2_size / 512 ; stage2 size in sectors
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start:
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[BITS 16]
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global _start
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_start:
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cli ; Disable interrupts
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mov [bootdev], dl ; Save boot device number (from BIOS in DL)
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@@ -20,29 +26,16 @@ start:
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mov ds, ax
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mov es, ax
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; Query bios for disk parameters
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call get_disk_params
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; Load second-stage bootloader (boot1.asm) to 0x7E00
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mov ax, 1 ; LBA of boot1.asm (starts at sector 1)
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call lba_to_chs
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mov al, 4 ; Number of sectors to read
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mov al, s2_nsect ; Number of sectors to read
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mov bx, 0x7E00 ; Destination address offset ES = 0 (0x0000:0x7E00)
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call read_chs
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; Load kernel to 0x100000 (1 MB)
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mov ax, 0xffff
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mov es, ax ; Set ES for destination address (0xffff << 4 == 0xffff0)
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mov ax, 5 ; LBA of kernel start (boot1 is 4 sectors: LBA 1–4 → kernel at LBA 5)
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call lba_to_chs
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mov al, 16 ; Number of sectors for kernel
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mov bx, 0x10 ; Destination address offset (0xffff:0x10 = 0xffff << 4 + 0x10 = 0x100000)
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call read_chs
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jc disk_error
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; Memory Validation: Verify checksum of second stage bootloader
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mov si, 0x7E00 ; Start of second stage
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mov cx, 512 * 4 ; Size in bytes (adjust if more sectors loaded)
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call verify_checksum
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jc disk_error ; Jump if checksum fails
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; Enable A20 line
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call enable_a20
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jc a20_error ; Jump if A20 enable fails
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@@ -95,17 +88,32 @@ verify_checksum:
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pop ax
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ret
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|
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get_disk_params:
|
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mov ah, 08h ; BIOS: Get Drive Parameters
|
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int 13h
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; TODO: error checking
|
||||
|
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; CL bits 0–5 contain sectors per track
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mov al, cl
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and al, 3Fh ; mask bits 0–5
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mov ah, 0
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mov [sectors_per_track], ax
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; DH = maximum head number (0-based)
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mov al, dh
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inc ax ; convert to count (heads = maxhead + 1)
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mov [heads_per_cylinder], ax
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ret
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|
||||
; ----------------------------------------------------------------
|
||||
; CHS Disk Read Routine
|
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; AL = number of sectors
|
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; CL = starting sector (1-based)
|
||||
; SI = destination offset (Segment:ES already set)
|
||||
; Inputs:
|
||||
; AL = sector count
|
||||
; CH = cylinder
|
||||
; DH = head
|
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; CL = sector (1–63, with top 2 bits as high cylinder bits)
|
||||
; SI = destination offset (segment ES must be set)
|
||||
|
||||
; ----------------------------------------------------------------
|
||||
; Convert LBA to CHS
|
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@@ -117,36 +125,29 @@ verify_checksum:
|
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; CL = sector (1-63, top 2 bits are upper cylinder bits)
|
||||
|
||||
lba_to_chs:
|
||||
pusha
|
||||
|
||||
; Sector
|
||||
xor dx, dx
|
||||
mov bx, [sectors_per_track]
|
||||
div bx ; AX = LBA / sectors_per_track, DX = remainder (sector number)
|
||||
mov si, ax ; SI = temp quotient (track index)
|
||||
mov cx, [heads_per_cylinder]
|
||||
xor dx, dx
|
||||
div cx ; AX = cylinder, DX = head
|
||||
mov ch, al ; CH = cylinder low byte
|
||||
mov dh, dl ; DH = head
|
||||
mov bx, ax
|
||||
div word [sectors_per_track] ; divide lba with max sectors
|
||||
add dl, 1 ; take the remainder, sectors start at 1
|
||||
mov cl, dl ; sector is in cl
|
||||
|
||||
; Now take sector number from earlier remainder
|
||||
mov cx, si ; Copy track index to CX to access CL
|
||||
and cl, 0x3F ; Mask to 6 bits (sector number)
|
||||
inc cl ; Sector numbers are 1-based
|
||||
; Head
|
||||
mov ax, bx
|
||||
mov dx, 0
|
||||
div word [sectors_per_track] ; divide lba with max sectors
|
||||
mov dx, 0
|
||||
div word [heads_per_cylinder] ; divide quotient with heads
|
||||
mov dh, dl ; take the remainder, head is in dh
|
||||
|
||||
; Insert upper 2 bits of cylinder into CL
|
||||
mov ah, al ; AH = cylinder again
|
||||
and ah, 0xC0 ; Get top 2 bits of cylinder
|
||||
or cl, ah ; OR them into sector byte
|
||||
|
||||
popa
|
||||
; Cylinder
|
||||
mov ch, al ; take the quotient, cylinder is in ch
|
||||
ret
|
||||
|
||||
read_chs:
|
||||
pusha
|
||||
push dx
|
||||
|
||||
mov cx, 5
|
||||
.retry:
|
||||
mov ah, 0x02 ; BIOS: Read sectors
|
||||
mov dl, [bootdev] ; Boot device
|
||||
@@ -262,7 +263,7 @@ switch_to_pm:
|
||||
mov eax, cr0
|
||||
or eax, 1
|
||||
mov cr0, eax
|
||||
jmp 0x08:0x7E00
|
||||
jmp 0x08:0x7E00 ; jump to S2
|
||||
|
||||
; ----------------------------------------------------------------
|
||||
print_string_16:
|
||||
@@ -284,8 +285,8 @@ halt:
|
||||
hlt
|
||||
|
||||
bootdev db 0
|
||||
sectors_per_track dw 63
|
||||
heads_per_cylinder dw 255
|
||||
sectors_per_track dw 0
|
||||
heads_per_cylinder dw 0
|
||||
|
||||
times 510 - ($ - $$) db 0
|
||||
dw 0xAA55
|
||||
98
bootloader/stage2.asm
Normal file
98
bootloader/stage2.asm
Normal file
@@ -0,0 +1,98 @@
|
||||
[BITS 32]
|
||||
global _start
|
||||
global ata_lba_read
|
||||
|
||||
extern load_kernel
|
||||
|
||||
_start:
|
||||
; Set up segments
|
||||
; Data segments
|
||||
mov ax, 0x10
|
||||
mov ds, ax
|
||||
mov es, ax
|
||||
mov fs, ax
|
||||
mov gs, ax
|
||||
mov ss, ax
|
||||
|
||||
; Code segment
|
||||
mov ax, 0x08
|
||||
mov cs, ax
|
||||
|
||||
; Stack (must be identity-mapped)
|
||||
mov esp, 0x90000
|
||||
|
||||
call load_kernel
|
||||
|
||||
jmp eax
|
||||
|
||||
; ----------------------------------------------------------------------------
|
||||
; ATA read sectors (LBA mode)
|
||||
;
|
||||
; sysv32 abi signature:
|
||||
; void ata_lba_read(uint32_t lba, uint8_t nsect, void *addr);
|
||||
; ----------------------------------------------------------------------------
|
||||
ata_lba_read:
|
||||
push ebp
|
||||
mov ebp, esp
|
||||
|
||||
push ebx
|
||||
push ecx
|
||||
push edx
|
||||
push edi
|
||||
|
||||
mov eax, [ebp+8] ; arg #1 = LBA
|
||||
mov cl, [ebp+12] ; arg #2 = # of sectors
|
||||
mov edi, [ebp+16] ; arg #3 = buffer address
|
||||
and eax, 0x0FFFFFFF
|
||||
|
||||
mov ebx, eax ; Save LBA in RBX
|
||||
|
||||
mov edx, 0x01F6 ; Port to send drive and bit 24 - 27 of LBA
|
||||
shr eax, 24 ; Get bit 24 - 27 in al
|
||||
or al, 11100000b ; Set bit 6 in al for LBA mode
|
||||
out dx, al
|
||||
|
||||
mov edx, 0x01F2 ; Port to send number of sectors
|
||||
mov al, cl ; Get number of sectors from CL
|
||||
out dx, al
|
||||
|
||||
mov edx, 0x1F3 ; Port to send bit 0 - 7 of LBA
|
||||
mov eax, ebx ; Get LBA from EBX
|
||||
out dx, al
|
||||
|
||||
mov edx, 0x1F4 ; Port to send bit 8 - 15 of LBA
|
||||
mov eax, ebx ; Get LBA from EBX
|
||||
shr eax, 8 ; Get bit 8 - 15 in AL
|
||||
out dx, al
|
||||
|
||||
mov edx, 0x1F5 ; Port to send bit 16 - 23 of LBA
|
||||
mov eax, ebx ; Get LBA from EBX
|
||||
shr eax, 16 ; Get bit 16 - 23 in AL
|
||||
out dx, al
|
||||
|
||||
mov edx, 0x1F7 ; Command port
|
||||
mov al, 0x20 ; Read with retry.
|
||||
out dx, al
|
||||
|
||||
mov bl, cl ; Save # of sectors in BL
|
||||
|
||||
.wait_drq:
|
||||
mov edx, 0x1F7
|
||||
.do_wait_drq:
|
||||
in al, dx
|
||||
test al, 8 ; the sector buffer requires servicing.
|
||||
jz .do_wait_drq ; keep polling until the sector buffer is ready.
|
||||
|
||||
mov edx, 0x1F0 ; Data port, in and out
|
||||
mov ecx, 256
|
||||
rep insw ; in to [RDI]
|
||||
|
||||
dec bl ; are we...
|
||||
jnz .wait_drq ; ...done?
|
||||
|
||||
pop edi
|
||||
pop edx
|
||||
pop ecx
|
||||
pop ebx
|
||||
pop ebp
|
||||
ret
|
||||
14
bootloader/stage2.ld
Normal file
14
bootloader/stage2.ld
Normal file
@@ -0,0 +1,14 @@
|
||||
SECTIONS {
|
||||
. = 0x7e00;
|
||||
|
||||
.text : { *(.text*) }
|
||||
.rodata : { *(.rodata*) }
|
||||
.data : { *(.data*) }
|
||||
|
||||
.bss : {
|
||||
*(.bss*)
|
||||
*(COMMON)
|
||||
}
|
||||
|
||||
read_buf = .;
|
||||
}
|
||||
118
bootloader/stage2_load.c
Normal file
118
bootloader/stage2_load.c
Normal file
@@ -0,0 +1,118 @@
|
||||
#include <stdint.h>
|
||||
|
||||
// ELF Ident indexes
|
||||
#define EI_NIDENT 16
|
||||
|
||||
// Program header types
|
||||
#define PT_NULL 0
|
||||
#define PT_LOAD 1
|
||||
|
||||
// ELF Header (32-bit)
|
||||
typedef struct {
|
||||
uint8_t e_ident[EI_NIDENT];
|
||||
uint16_t e_type;
|
||||
uint16_t e_machine;
|
||||
uint32_t e_version;
|
||||
uint32_t e_entry; // Entry point
|
||||
uint32_t e_phoff; // Program header table offset
|
||||
uint32_t e_shoff; // Section header table offset
|
||||
uint32_t e_flags;
|
||||
uint16_t e_ehsize;
|
||||
uint16_t e_phentsize;
|
||||
uint16_t e_phnum;
|
||||
uint16_t e_shentsize;
|
||||
uint16_t e_shnum;
|
||||
uint16_t e_shstrndx;
|
||||
} __attribute__((packed)) Elf32_Ehdr;
|
||||
|
||||
// Program Header (32-bit)
|
||||
typedef struct {
|
||||
uint32_t p_type;
|
||||
uint32_t p_offset;
|
||||
uint32_t p_vaddr;
|
||||
uint32_t p_paddr;
|
||||
uint32_t p_filesz;
|
||||
uint32_t p_memsz;
|
||||
uint32_t p_flags;
|
||||
uint32_t p_align;
|
||||
} __attribute__((packed)) Elf32_Phdr;
|
||||
|
||||
// Load an ELF executable into memory.
|
||||
static int elf_load(const void* data, void (*load_segment)(uint8_t *vaddr, uint32_t src, uint32_t size)) {
|
||||
const Elf32_Ehdr* header = (const Elf32_Ehdr*)data;
|
||||
const Elf32_Phdr* ph = (const Elf32_Phdr*)((uint8_t*)data + header->e_phoff);
|
||||
|
||||
for (int i = 0; i < header->e_phnum; i++) {
|
||||
if (ph[i].p_type != PT_LOAD)
|
||||
continue;
|
||||
|
||||
uint32_t offset = ph[i].p_offset;
|
||||
uint32_t vaddr = ph[i].p_vaddr;
|
||||
uint32_t filesz = ph[i].p_filesz;
|
||||
uint32_t memsz = ph[i].p_memsz;
|
||||
|
||||
// Copy data segment
|
||||
//load_segment((uint8_t *)vaddr, offset, filesz);
|
||||
load_segment((uint8_t *)vaddr, offset, filesz);
|
||||
|
||||
// Zero remaining BSS (if any)
|
||||
if (memsz > filesz) {
|
||||
uint8_t* bss_start = (uint8_t*)(vaddr + filesz);
|
||||
for (uint32_t j = 0; j < memsz - filesz; j++) {
|
||||
bss_start[j] = 0;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
return header->e_entry;
|
||||
}
|
||||
|
||||
#define KERN_START_SECT 5
|
||||
#define MAX(a, b) ((a)>(b) ? (a) : (b))
|
||||
|
||||
extern void ata_lba_read(uint32_t lba, uint8_t nsect, void *addr);
|
||||
extern uint8_t read_buf[];
|
||||
|
||||
static uint32_t
|
||||
total_header_size(const Elf32_Ehdr *header) {
|
||||
uint32_t phend = header->e_phoff + header->e_phentsize*header->e_phnum;
|
||||
|
||||
// Align to 512
|
||||
return (phend + 511) & ~511;
|
||||
}
|
||||
|
||||
static void read_sectors(uint8_t *vaddr, uint32_t offset, uint32_t size) {
|
||||
// # of sectors to read
|
||||
uint32_t rem_nsect = ((size + 511) & ~511) / 512;
|
||||
|
||||
// Current lba address, offset by the first sector already read
|
||||
uint32_t lba = KERN_START_SECT + offset / 512;
|
||||
|
||||
// Max 255 sectors at a time
|
||||
while (rem_nsect) {
|
||||
uint8_t nsect = rem_nsect > 255 ? 255 : rem_nsect;
|
||||
ata_lba_read(lba, nsect, vaddr);
|
||||
|
||||
vaddr += nsect * 512;
|
||||
rem_nsect -= nsect;
|
||||
lba += nsect;
|
||||
}
|
||||
}
|
||||
|
||||
void *load_kernel(void) {
|
||||
// Read the first sector
|
||||
ata_lba_read(KERN_START_SECT, 1, read_buf);
|
||||
|
||||
const Elf32_Ehdr* header = (const Elf32_Ehdr*)read_buf;
|
||||
|
||||
// Remaining data size, subtract the first 512B already read
|
||||
uint32_t rem = total_header_size(header) - 512;
|
||||
|
||||
// Read the rest if necessary
|
||||
if (rem)
|
||||
read_sectors(read_buf+512, 512, rem);
|
||||
|
||||
elf_load(read_buf, read_sectors);
|
||||
|
||||
return (void *)header->e_entry;
|
||||
}
|
||||
Reference in New Issue
Block a user