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46
Makefile
46
Makefile
@ -2,7 +2,7 @@ BUILD=./build
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# Default rule
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.PHONY: default
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default: all
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default: $(BUILD)/disk.img
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# Remove all build files
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.PHONY: clean
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@ -10,16 +10,12 @@ clean:
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rm -drf $(BUILD)
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cd tetros; cargo clean
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# Make everything
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# (but don't run qemu)
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.PHONY: all
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all: img
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#
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# MARK: boot
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# MARK: disk
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#
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# Compile tetros as library
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# Compile tetros as a library
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# (so that we can link it with a custom linker script)
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LIB_SRC = ./tetros/Cargo.toml ./tetros/Cargo.lock $(shell find ./tetros/src -type f)
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$(BUILD)/tetros.lib: $(LIB_SRC)
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@mkdir -p $(BUILD)
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@ -35,7 +31,7 @@ $(BUILD)/tetros.lib: $(LIB_SRC)
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-- \
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--emit link="$(CURDIR)/$@"
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# Link tetros
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# Link tetros using custom linker script
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BIOS_LD = ./tetros/linkers/x86-unknown-none.ld
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$(BUILD)/tetros.elf: $(BUILD)/tetros.lib $(BIOS_LD)
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ld \
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@ -49,13 +45,13 @@ $(BUILD)/tetros.elf: $(BUILD)/tetros.lib $(BIOS_LD)
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objcopy --only-keep-debug "$@" "$@.sym"
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objcopy --strip-debug "$@"
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# Wrap tetros in three-stage BIOS loader
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# Wrap tetros in BIOS loader
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# Parameters:
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# - BIOS_SRC: source directory of bios assembly
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# - STAGE2_SECTOR: the index of the first sector of the stage 2 binary on the disk
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BIOS_SRC = ./bios
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STAGE2_SECTOR = 1
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$(BUILD)/bios.bin: $(wildcard $(BIOS_SRC)/*.asm) $(BUILD)/tetros.elf
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$(BUILD)/disk.img: $(wildcard $(BIOS_SRC)/*.asm) $(BUILD)/tetros.elf
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@mkdir -p "$(BUILD)"
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nasm \
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-f bin \
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@ -66,30 +62,12 @@ $(BUILD)/bios.bin: $(wildcard $(BIOS_SRC)/*.asm) $(BUILD)/tetros.elf
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-i "$(BIOS_SRC)" \
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"$(BIOS_SRC)/main.asm"
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# Extract full mbr (first 512 bytes)
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$(BUILD)/mbr.bin: $(BUILD)/bios.bin
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@mkdir -p "$(BUILD)"
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@echo ""
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dd if="$<" bs=512 count=1 of="$@"
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# Extract stage 2 (rest of file)
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$(BUILD)/stage2.bin: $(BUILD)/bios.bin
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@mkdir -p "$(BUILD)"
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@echo ""
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dd if="$<" bs=512 skip=1 of="$@"
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#
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# MARK: bundle
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# MARK: qemu
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#
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# Do not use `-enable-kvm` or `-cpu host`,
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# this confuses gdb.
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#
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# Make full disk image
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.PHONY: img
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img: $(BUILD)/disk.img
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$(BUILD)/disk.img: $(BUILD)/mbr.bin $(BUILD)/stage2.bin
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@mkdir -p $(BUILD)
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@echo ""
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dd if="$(BUILD)/mbr.bin" of=$@ conv=notrunc bs=512
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dd if="$(BUILD)/stage2.bin" of=$@ conv=notrunc seek=$(STAGE2_SECTOR) bs=512
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.PHONY: qemu
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qemu: $(BUILD)/disk.img
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@ -129,5 +107,3 @@ qemu-gdb: $(BUILD)/disk.img
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-gdb tcp::26000 \
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-S
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# Do not use `-enable-kvm` or `-cpu host`,
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# this confuses gdb.
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@ -1,8 +1,5 @@
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# TetrOS: bare-metal tetris
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## TODO:
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- Fix stage 1 loader
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## Features
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- Compiles to a standalone disk image
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- Written from scratch using only Nasm and Rust
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@ -1,30 +1,25 @@
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sectalign off
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; This program expects two external macros:
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; The following code expects two external macros:
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; STAGE3, a path to the stage3 binary
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; STAGE2_SECTOR, the location of stage 2
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; on the disk, in 512-byte sectors.
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; On a gpt disk, this is probably 34.
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; Stage 1 is MBR code, and should fit in LBA 0
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; (512 bytes). Layout is as follows:
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; (Format is `offset, length: purpose`)
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; 0, 424: x86 boot code
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; 440, 4: Unique disk signature
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; 444, 2: unknown
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; 446, 16*4: Array of four legacy MBR records
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; 510, 2: signature 0x55 0xAA
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; 512 to end of logical block: reserved
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;
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; See https://uefi.org/specs/UEFI/2.10/05_GUID_Partition_Table_Format.html
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;
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; Both of these are set in the makefile.
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; BIOS loads stage 1 at 0x7C00
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ORG 0x7C00
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SECTION .text
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; stage 1 is sector 0, loaded into memory at 0x7C00
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; Stage 1 is MBR code, and should fit in LBA 0
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; (i.e, in the first 512 bytes).
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%include "stage1.asm"
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; Stage 1 is at most 440 bytes
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; This limit is set by the GPT spec.
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; See https://uefi.org/specs/UEFI/2.10/05_GUID_Partition_Table_Format.html
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;
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; This `times` will throw an error if the subtraction is negative.
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times 440-($-$$) db 0
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db 0xee
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@ -32,30 +27,38 @@ db 0xee
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times 510-($-$$) db 0
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; MBR signature.
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; This isn't loaded into memory, it's
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; only here for debugging.
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; This tells the BIOS that this disk is bootable.
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db 0x55
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db 0xaa
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; Include stage 2. This is loaded into memory by stage 1.
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; (stage 1 loads both stage 2 and stage 3)
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;
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; Stage 2 sets up protected mode, sets up the GDT,
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; and initializes a minimal environment for stage 3.
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;
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; On a "real" boot disk, this data will not immediately follow stage 1.
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; It would be stored in a special disk partition.
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;
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; We don't need this kind of complexity here, though, so we store
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; stage 2 right after stage 1. (This is why STAGE2_SECTOR is 1.)
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;
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; This is nice, because the layout of the code on our boot disk
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; matches the layout of the code in memory. THIS IS NOT USUALLY THE CASE.
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stage2:
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%include "stage2.asm"
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align 512, db 0
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stage2.end:
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; The maximum size of stage2 is 4 KiB,
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; This fill will throw an error if the subtraction is negative.
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times (4*1024)-($-stage2) db 0
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; Pad to 0x9000.
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; This needs to match the value configured in the stage3 linker script
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times (0x9000 - 0x7c00)-($-$$) db 0
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; Pad to 0x3000.
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; This makes sure that state3 is loaded at the address
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; the linker expects. Must match the value in `tetros/linkers/x86-unknown-none.ld`.
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times (0x8000 - 0x7c00)-($-$$) db 0
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; Include stage 3, the binary compiled from Rust sources.
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stage3:
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%defstr STAGE3_STR %[STAGE3]
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incbin STAGE3_STR
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align 512, db 0
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.end:
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; TODO: why? Of the disk, or of memory?
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; the maximum size of the boot loader portion is 384 KiB
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times (384*1024)-($-$$) db 0
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@ -1,22 +1,21 @@
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SECTION .text
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USE16
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; provide function for printing in x86 real mode
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; print a string and a newline
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; CLOBBER
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; ax
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; Print a string and a newline
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;
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; Clobbers ax
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print_line:
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mov al, 13
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call print_char
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mov al, 10
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jmp print_char
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; print a string
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; IN
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; Print a string
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;
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; Input:
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; si: points at zero-terminated String
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; CLOBBER
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; si, ax
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;
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; Clobbers si, ax
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print:
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pushf
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cld
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@ -30,8 +29,9 @@ print:
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popf
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ret
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; print a character
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; IN
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; Print a character
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;
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; Input:
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; al: character to print
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print_char:
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pusha
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@ -42,10 +42,11 @@ print_char:
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ret
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; print a number in hex
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; IN
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;
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; Input:
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; bx: the number
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; CLOBBER
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; al, cx
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;
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; Clobbers al, cx
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print_hex:
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mov cx, 4
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.lp:
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@ -1,46 +0,0 @@
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SECTION .text
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USE16
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protected_mode:
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.func: dd 0
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.entry:
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; disable interrupts
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cli
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; load protected mode GDT
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lgdt [gdtr]
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; set protected mode bit of cr0
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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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; far jump to load CS with 32 bit segment
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; (we are in 32-bit mode, but instruction pipeline
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; has 16-bit instructions.
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jmp gdt.pm32_code:.inner
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; gdt.pm32_code is a multiple of 8, so it always ends with three zero bits.
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; The GDT spec abuses this fact, and uses these last three bits to store other
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; data (table type and privilege). In this case, 000 is what we need anyway.
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;
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; Also note that CS isn't an address in protected mode---it's a GDT descriptor.
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USE32
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.inner:
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; load all the other segments with 32 bit data segments
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mov eax, gdt.pm32_data
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mov ds, eax
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mov es, eax
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mov fs, eax
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mov gs, eax
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mov ss, eax
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; jump to specified function
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mov eax, [.func]
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jmp eax
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121
bios/stage1.asm
121
bios/stage1.asm
@ -1,37 +1,39 @@
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USE16
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stage1: ; dl comes with disk
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; initialize segment registers
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xor ax, ax
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stage1:
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; Initialize segment registers
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xor ax, ax ; Set ax to 0
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mov ds, ax
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mov es, ax
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mov ss, ax
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; initialize stack
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; Initialize stack pointer
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; (stack grows up)
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mov sp, 0x7C00
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; initialize CS
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; far jump sets both CS and IP to a known-good state,
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; we don't know where the BIOS put us at startup.
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; (could be 0x00:0x7C00, could be 0x7C00:0x00.
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; Not everybody follows spec.)
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push ax
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; Initialize CS
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;
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; `retf` sets both CS and IP to a known-good state.
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; This is necessary because we don't know where the BIOS put us at startup.
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; (could be 0x00:0x7C00, could be 0x7C00:0x00. Not everybody follows spec.)
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push ax ; `ax` is still 0
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push word .set_cs
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retf
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.set_cs:
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; save disk number
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; Save disk number.
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; BIOS sets `dl` to the number of
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; the disk we're booting from.
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mov [disk], dl
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; Print "Stage 1"
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mov si, stage_msg
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call print
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mov al, '1'
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call print_char
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call print_line
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; read CHS gemotry
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; read CHS gemotry, save into [chs]
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; CL (bits 0-5) = maximum sector number
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; CL (bits 6-7) = high bits of max cylinder number
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; CH = low bits of maximum cylinder number
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@ -51,11 +53,10 @@ stage1: ; dl comes with disk
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and cl, 0x3f
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mov [chs.s], cl
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; disk address of stage 2
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; (start sector)
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; First sector of stage 2
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mov eax, STAGE2_SECTOR
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; where to load stage 2
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; Where to load stage 2
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mov bx, stage2
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; length of stage2 + stage3
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@ -63,36 +64,40 @@ stage1: ; dl comes with disk
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mov cx, (stage3.end - stage2) / 512
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mov dx, 0
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; Consume eax, bx, cx, dx
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; and load code from disk.
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call load
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jmp stage2.entry
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; load some sectors from disk to a buffer in memory
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; buffer has to be below 1MiB
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; IN
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; Load sectors from disk to memory.
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; Cannot load more than 1MiB.
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;
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; Input:
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; ax: start sector
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; bx: offset of buffer
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; cx: number of sectors (512 Bytes each)
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; dx: segment of buffer
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; CLOBBER
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; ax, bx, cx, dx, si
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; TODO rewrite to (eventually) move larger parts at once
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; if that is done increase buffer_size_sectors in startup-common to that (max 0x80000 - startup_end)
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;
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; Clobbers ax, bx, cx, dx, si
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load:
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; replaced 127 with 1.
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; see https://stackoverflow.com/questions/58564895/problem-with-bios-int-13h-read-sectors-from-drive
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; TODO: fix later
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||||
; Every "replace 1" comment means that the `1`
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; on that line could be bigger.
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;
|
||||
; See https://stackoverflow.com/questions/58564895/problem-with-bios-int-13h-read-sectors-from-drive
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; We have to load one sector at a time to avoid the 1K boundary error.
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; Would be nice to read more sectors at a time, though, that's faster.
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cmp cx, 1 ;127
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cmp cx, 1 ; replace 1
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jbe .good_size
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pusha
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mov cx, 1; 127
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mov cx, 1 ; replace 1
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call load
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popa
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add eax, 1; 127
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add dx, 1 * 512 / 16 ; 127
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sub cx, 1;127
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||||
add eax, 1 ; replace 1
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add dx, 1 * 512 / 16 ; replace 1
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||||
sub cx, 1 ; replace 1
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jmp load
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.good_size:
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@ -101,44 +106,37 @@ load:
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mov [DAPACK.count], cx
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mov [DAPACK.seg], dx
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||||
|
||||
; This should be a subroutine,
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||||
; but we don't call/ret to save a few bytes.
|
||||
; (we only use this once)
|
||||
;
|
||||
;call print_dapack
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;print_dapack:
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||||
mov bx, [DAPACK.addr + 2]
|
||||
; Print the data we're reading
|
||||
; Prints AAAAAAAA#BBBB CCCC:DDDD, where:
|
||||
; - A..A is the lba we're reading (printed in two parts)
|
||||
; - BBBB is the number of sectors we're reading
|
||||
; - CCCC is the index we're writing to
|
||||
; - DDDD is the buffer we're writing to
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||||
mov bx, [DAPACK.addr + 2] ; last two bytes
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||||
call print_hex
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||||
|
||||
mov bx, [DAPACK.addr]
|
||||
mov bx, [DAPACK.addr] ; first two bytes
|
||||
call print_hex
|
||||
|
||||
mov al, '#'
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||||
call print_char
|
||||
|
||||
mov bx, [DAPACK.count]
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||||
call print_hex
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||||
|
||||
mov al, ' '
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||||
call print_char
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||||
|
||||
mov bx, [DAPACK.seg]
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||||
call print_hex
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||||
|
||||
mov al, ':'
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||||
call print_char
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||||
|
||||
mov bx, [DAPACK.buf]
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||||
call print_hex
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||||
|
||||
call print_line
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||||
;ret
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||||
; End of print_dapack
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||||
|
||||
|
||||
; Read from disk.
|
||||
; int13h, ah=0x42 does not work on some disks.
|
||||
; use int13h, ah=0x02 in thes case.
|
||||
cmp byte [chs.s], 0
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||||
jne .chs
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||||
;INT 0x13 extended read does not work on CDROM!
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||||
|
||||
mov dl, [disk]
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mov si, DAPACK
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||||
mov ah, 0x42
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||||
@ -188,6 +186,10 @@ load:
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||||
jc error ; carry flag set on error
|
||||
ret
|
||||
|
||||
;
|
||||
; MARK: errors
|
||||
;
|
||||
|
||||
error_chs:
|
||||
mov ah, 0
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||||
|
||||
@ -200,13 +202,18 @@ error:
|
||||
|
||||
mov si, stage1_error_msg
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||||
call print
|
||||
call print_line
|
||||
call print_line
|
||||
|
||||
; halt after printing error details
|
||||
.halt:
|
||||
cli
|
||||
hlt
|
||||
jmp .halt
|
||||
|
||||
;
|
||||
; MARK: data
|
||||
;
|
||||
|
||||
%include "print.asm"
|
||||
|
||||
stage_msg: db "Stage ",0
|
||||
@ -215,9 +222,9 @@ stage1_error_msg: db " ERROR",0
|
||||
disk: db 0
|
||||
|
||||
chs:
|
||||
.c: dd 0
|
||||
.h: dd 0
|
||||
.s: dd 0
|
||||
.c: dd 0
|
||||
.h: dd 0
|
||||
.s: dd 0
|
||||
|
||||
DAPACK:
|
||||
db 0x10
|
||||
@ -225,6 +232,4 @@ DAPACK:
|
||||
.count: dw 0 ; int 13 resets this to # of blocks actually read/written
|
||||
.buf: dw 0 ; memory buffer destination address (0:7c00)
|
||||
.seg: dw 0 ; in memory page zero
|
||||
.addr: dq 0 ; put the lba to read in this spot
|
||||
|
||||
db 0xff
|
||||
.addr: dq 0 ; put the lba to read in this spot
|
||||
@ -1,6 +1,9 @@
|
||||
SECTION .text
|
||||
USE16
|
||||
|
||||
%include "gdt.asm"
|
||||
%include "thunk.asm"
|
||||
|
||||
stage2.entry:
|
||||
mov si, stage_msg
|
||||
call print
|
||||
@ -13,26 +16,57 @@ stage2.entry:
|
||||
or al, 2
|
||||
out 0x92, al
|
||||
|
||||
mov dword [protected_mode.func], stage3.entry
|
||||
jmp protected_mode.entry
|
||||
protected_mode:
|
||||
; disable interrupts
|
||||
cli
|
||||
|
||||
%include "gdt.asm"
|
||||
%include "protected_mode.asm"
|
||||
%include "thunk.asm"
|
||||
; load protected mode GDT
|
||||
lgdt [gdtr]
|
||||
|
||||
; set protected mode bit of cr0
|
||||
mov eax, cr0
|
||||
or eax, 1
|
||||
mov cr0, eax
|
||||
|
||||
; far jump to load CS with 32 bit segment
|
||||
; We need to do this because we are entering 32-bit mode,
|
||||
; but the instruction pipeline still has 16-bit instructions.
|
||||
;
|
||||
; gdt.pm32_code is a multiple of 8, so it always ends with three zero bits.
|
||||
; The GDT spec abuses this fact, and uses these last three bits to store other
|
||||
; data (table type and privilege). In this case, 000 is what we need anyway.
|
||||
;
|
||||
; Also note that CS isn't an address in protected mode---it's a GDT descriptor.
|
||||
jmp gdt.pm32_code:protected_mode_inner
|
||||
|
||||
; We can now use 32-bit instructions!
|
||||
USE32
|
||||
|
||||
stage3.entry:
|
||||
; stage3 stack at 448 KiB (512KiB minus 64KiB disk buffer)
|
||||
protected_mode_inner:
|
||||
; load all the other segments with 32 bit data segments
|
||||
mov eax, gdt.pm32_data
|
||||
mov ds, eax
|
||||
mov es, eax
|
||||
mov fs, eax
|
||||
mov gs, eax
|
||||
mov ss, eax
|
||||
|
||||
; Place stage 3 stack at 448 KiB
|
||||
; (512KiB minus 64KiB disk buffer)
|
||||
mov esp, 0x70000
|
||||
|
||||
; push arguments to `start()`
|
||||
mov eax, thunk.int10
|
||||
push eax
|
||||
|
||||
; Call `start()`.
|
||||
; 0x18 skips ELF headers.
|
||||
mov eax, [stage3 + 0x18]
|
||||
call eax
|
||||
|
||||
|
||||
.halt:
|
||||
; Halt if `start()` ever returns (it shouldn't, but just in case)
|
||||
; Without this, we'll try to execute whatever comes next in memory.
|
||||
cli
|
||||
hlt
|
||||
jmp .halt
|
||||
|
||||
@ -1,9 +1,10 @@
|
||||
/* This is the name of the Rust function we start in */
|
||||
ENTRY(start)
|
||||
OUTPUT_FORMAT(elf32-i386)
|
||||
|
||||
SECTIONS {
|
||||
/* The start address must match bootloader.asm */
|
||||
. = 0x9000;
|
||||
/* The start address must match main.asm */
|
||||
. = 0x8000;
|
||||
|
||||
. += SIZEOF_HEADERS;
|
||||
. = ALIGN(4096);
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user