Initial commit

Makefile

@@ -0,0 +1,41 @@
+NASM = nasm
+NASMFLAGS = -f win64
+STANDALONE_FLAGS = -Dfill_sector
+
+LINKER = clang
+LLD-FLAGS = --target=x86_64-unknown-windows -nostdlib -Wl,-entry:_start -Wl,-subsystem:efi_application -fuse-ld=lld
+
+SRC_DIR = .
+SRC = $(wildcard $(SRC_DIR)/*.asm)
+
+OBJ_DIR = .
+OBJ = $(SRC:.asm=.obj)
+
+EFI = uefi.efi
+BIOS = bios.bin
+BOOT_DRIVE = uefi.img
+
+.PHONY: clean qemu all standalone vhd
+
+all: $(OBJ)
+	$(LINKER) $(LLD-FLAGS) -o $(EFI) $<
+
+standalone: NASMFLAGS += $(STANDALONE_FLAGS)
+standalone: $(OBJ)
+
+clean:
+	rm -f $(OBJ) $(BOOT_DRIVE) $(EFI)
+
+qemu:
+	qemu-system-x86_64 -bios $(BIOS) -drive file=$(BOOT_DRIVE),format=raw
+
+# needs dosfstools and mtools
+vhd:
+	dd if=/dev/zero of=$(BOOT_DRIVE) bs=1M count=1
+	mkfs.vfat $(BOOT_DRIVE)
+	mmd -i $(BOOT_DRIVE) ::EFI
+	mmd -i $(BOOT_DRIVE) ::EFI/BOOT
+	mcopy -i $(BOOT_DRIVE) uefi.efi ::EFI/BOOT/BOOTX64.EFI
+
+%.obj: %.asm
+	$(NASM) $(NASMFLAGS) -o $@ $<

uefi.asm

@@ -0,0 +1,80 @@
+; generate 64-bit code
+bits 64
+
+; contains the code that will run
+section .text
+
+; allows the linker to see this symbol
+global _start
+
+; see http://www.uefi.org/sites/default/files/resources/UEFI Spec 2_7_A Sept 6.pdf#G8.1001729
+struc EFI_TABLE_HEADER
+    .Signature    RESQ 1
+    .Revision     RESD 1
+    .HeaderSize   RESD 1
+    .CRC32        RESD 1
+    .Reserved     RESD 1
+endstruc
+
+; see http://www.uefi.org/sites/default/files/resources/UEFI Spec 2_7_A Sept 6.pdf#G8.1001773
+struc EFI_SYSTEM_TABLE
+    .Hdr                  RESB EFI_TABLE_HEADER_size
+    .FirmwareVendor       RESQ 1
+    .FirmwareRevision     RESD 1
+    .ConsoleInHandle      RESQ 1
+    .ConIn                RESQ 1
+    .ConsoleOutHandle     RESQ 1
+    .ConOut               RESQ 1
+    .StandardErrorHandle  RESQ 1
+    .StdErr               RESQ 1
+    .RuntimeServices      RESQ 1
+    .BootServices         RESQ 1
+    .NumberOfTableEntries RESQ 1
+    .ConfigurationTable   RESQ 1
+endstruc
+
+; see http://www.uefi.org/sites/default/files/resources/UEFI Spec 2_7_A Sept 6.pdf#G16.1016807
+struc EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL
+    .Reset             RESQ 1
+    .OutputString      RESQ 1
+    .TestString	       RESQ 1
+    .QueryMode	       RESQ 1
+    .SetMode	       RESQ 1
+    .SetAttribute      RESQ 1
+    .ClearScreen       RESQ 1
+    .SetCursorPosition RESQ 1
+    .EnableCursor      RESQ 1
+    .Mode              RESQ 1
+endstruc
+
+
+_start:
+    ; reserve space for 4 arguments
+    sub rsp, 4 * 8
+
+    ; rdx points to the EFI_SYSTEM_TABLE structure
+    ; which is the 2nd argument passed to us by the UEFI firmware
+    ; adding 64 causes rcx to point to EFI_SYSTEM_TABLE.ConOut
+    mov rcx, [rdx + 64]
+
+    ; load the address of our string into rdx
+    lea rdx, [rel strHello]
+
+    ; EFI_SYSTEM_TABLE.ConOut points to EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL
+    ; call OutputString on the value in rdx
+    call [rcx + EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.OutputString]
+    
+    ; loop forever so we can see the string before the UEFI application exits
+    jmp $
+
+codesize equ $ - $$
+
+; contains nothing - but it is required by UEFI
+section .reloc
+
+; contains the data that will be displayed
+section .data
+    ; this must be a Unicode string
+    strHello db __utf16__ `Hello World !\0`
+
+datasize equ $ - $$