poggers

.gitignore

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+/target
+/build/*

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "grove"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "grove"
+version = "0.1.0"
+authors = ["Isabelle Lesko <me@izzabelle.dev>"]
+edition = "2018"
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+
+[dependencies]

asm/boot-1.s

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+// AArch32 mode
+.section ".text.boot"
+.globl _start
+	.org 0x8000
+_start:
+	mov 	sp,	 #0x8000
+	ldr 	r4, 	=__bss_start
+	ldr 	r9, 	=__bss_end
+	mov 	r5, 	#0
+	mov 	r6, 	#0
+	mov 	r7, 	#0
+	mov	r8, 	#0 
+	b	2f
+1:	stmia	r4!, 	{r4-r8}
+2:	cmp 	r4, 	r9
+	blo	1b
+	ldr	r4, 	=kernel_main
+	blx	r3
+halt:	wfe
+	b halt
+

asm/boot-2.s

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+// AArch64 mode
+.section ".text.boot"
+.globl _start 
+        .org 0x8000
+_start:
+	mrc p15, 0, r5, c0, c0, 5
+	and r5, r5, #3
+	cmp r5, #0
+	bne halt
+ 
+	ldr r5, =_start
+	mov sp, r5
+ 
+	ldr r4, =__bss_start
+	ldr r9, =__bss_end
+	mov r5, #0
+	mov r6, #0
+	mov r7, #0
+	mov r8, #0
+	b       2f
+ 
+1:	stmia r4!, {r5-r8}
+2:	cmp r4, r9
+	blo 1b
+ 
+	ldr r3, =kernel_main
+	blx r3
+ 
+halt:
+	wfe
+	b halt

justfile

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+build-os:
+	arm-none-eabi-gcc -mcpu=cortex-a7 -fpic -ffreestanding -c asm/boot-2.s -o build/boot.o
+	cargo xbuild --release --target armv7r-none-eabihf
+	arm-none-eabi-gcc -T linker.ld -o build/grove.img -ffreestanding -O2 -nostdlib build/boot.o target/target/release/libgrove.rlib
+
+run-os: build-os
+	qemu-system-arm -M raspi2 -kernel build/grove.img -serial stdio

linker.ld

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+ENTRY(_start)
+ 
+SECTIONS
+{
+    /* Starts at LOADER_ADDR. */
+    . = 0x8000;
+    /* For AArch64, use . = 0x80000; */
+    __start = .;
+    __text_start = .;
+    .text :
+    {
+        KEEP(*(.text.boot))
+        *(.text)
+    }
+    . = ALIGN(4096); 
+    __text_end = .;
+ 
+    __rodata_start = .;
+    .rodata :
+    {
+        *(.rodata)
+    }
+    . = ALIGN(4096); /* align to page size */
+    __rodata_end = .;
+ 
+    __data_start = .;
+    .data :
+    {
+        *(.data)
+    }
+    . = ALIGN(4096); /* align to page size */
+    __data_end = .;
+ 
+    __bss_start = .;
+    .bss :
+    {
+        bss = .;
+        *(.bss)
+    }
+    . = ALIGN(4096); /* align to page size */
+    __bss_end = .;
+    __bss_size = __bss_end - __bss_start;
+    __end = .;
+}

src/lib.rs

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+#![no_std]
+
+use core::panic::PanicInfo;
+use core::ptr::{read_volatile, write_volatile};
+
+const UART_DR: u32 = 0x3f20_1000;
+const UART_FR: u32 = 0x3f20_1018;
+
+fn mmio_write(reg: u32, val: u32) {
+    unsafe { write_volatile(reg as *mut u32, val) }
+}
+
+fn mmio_read(reg: u32) -> u32 {
+    unsafe { read_volatile(reg as *const u32) }
+}
+
+fn transmit_fifo_full() -> bool {
+    mmio_read(UART_FR) & (1 << 5) > 0
+}
+
+fn receive_fifo_empty() -> bool {
+    mmio_read(UART_FR) & (1 << 4) > 0
+}
+
+fn writec(c: u8) {
+    while transmit_fifo_full() {}
+    mmio_write(UART_DR, c as u32);
+}
+
+fn getc() -> u8 {
+    while receive_fifo_empty() {}
+    mmio_read(UART_DR) as u8
+}
+
+fn write(msg: &str) {
+    for c in msg.bytes() {
+        writec(c);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn kernel_main() {
+    write("hello rust raspberry pi kernel");
+    loop {
+        writec(getc())
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn __aeabi_unwind_cpp_pr0() {}
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {}
+}
+
+#[allow(non_snake_case)]
+#[no_mangle]
+pub extern "C" fn _Unwind_Resume() {
+    loop {}
+}