arm-none-eabi.json

{
    "arch": "arm",
    "cpu": "cortex-a8",
    "data-layout": "e-m:e-p:32:32-i1:8:32-i8:8:32-i16:16:32-i64:64-v128:64:128-a:0:32-n32-S64",
    "disable-redzone": true,
    "executables": true,
    "llvm-target": "arm-none-eabi",
    "morestack": false,
    "os": "none",
    "relocation-model": "static",
    "target-endian": "little",
    "target-word-size": "32",
    "target-pointer-width": "32",
    "no-compiler-rt" : true 
}

lib.rs

#![feature(no_std, lang_items)]
#![no_std]

#[no_mangle]
pub extern fn rust_main() {}

#[lang = "eh_personality"] extern fn eh_personality() {}
#[lang = "panic_fmt"] extern fn panic_fmt() -> ! {loop{}}

linker.ld

ENTRY(_reset)
SECTIONS
{
 . = 0x10000;
 .startup . : { build/startup.o(.text) }
 .text : { *(.text.rust_main) }
 . = ALIGN(0x1000);
 stack = .;
 . = . + 0x1000; /* 4kB of stack memory */
 stack_top = .;
}

makefile

CPU=arm926ej-s

TARGET=arm-none-eabi
AS=arm-none-eabi-as
CC=arm-none-eabi-gcc
RC=rustc
LD=arm-none-eabi-ld
OBJCOPY=arm-none-eabi-objcopy
OBJDUMP=arm-none-eabi-objdump

OBJS=$(patsubst %,%.o,$(basename $(wildcard *.[cs] *.rs)))

ASFLAGS = -mcpu=cortex-a8
CFLAGS = -Og

build/%.o: src/%.s
	@mkdir -p $(shell dirname $@)
	$(AS) $(ASFLAGS) -g $< -o $@

%.elf: %.ld $(OBJS)
	$(LD) -T $^ -o $@

%.bin: %.elf
	$(OBJCOPY) -O binary $< $@
	$(OBJDUMP) -dS $< > $*.code

kernel := build/kernel
rust_os := target/$(TARGET)/debug/libarm.a
linker_script := src/linker.ld

assembly_source_files := $(wildcard src/*.s)
assembly_object_files := $(patsubst src/%.s, build/%.o, $(assembly_source_files))

.PHONY: all clean run iso cargo

all: $(kernel)

clean:
	@cargo clean
	@rm -rf build

$(kernel).elf: cargo $(rust_os) $(assembly_object_files) $(linker_script)
	$(LD) -n --gc-sections -T $(linker_script) -o $@ $(assembly_object_files) $(rust_os)

$(kernel): $(kernel).elf
	$(OBJCOPY) -O binary $< $@
	$(OBJDUMP) -dS $< > $(kernel).code

cargo:
	@cargo rustc --target $(TARGET) -- -Z no-landing-pads

startup.s

.global _reset
.global rust_main
_reset:
 LDR sp, =stack_top
 BL rust_main
 B .