Raspi asm stub for loading kernel

Not quite working yet

ferrocyanide/raspi_os/Makefile

@@ -6,7 +6,18 @@ process:
 	arm-none-eabi-ld --no-undefined main.o -Map kernel.map -o output.elf -T kernel.ld
 	arm-none-eabi-objcopy output.elf -O binary kernel.img
 
+#arm-none-eabi-ld --no-undefined rust_kernel.o -Map kernel.map -o rust_kernel.elf -T kernel.ld
+rust_kernel: rust_kernel.rs
+	rustc --target arm-unknown-linux-gnueabihf --emit=obj rust_kernel.rs
+	arm-none-eabi-gcc -mfpu=vfp -mfloat-abi=hard -march=armv6zk -mtune=arm1176jzf-s -nostartfiles rust_kernel.o -o rust_kernel.elf
+	arm-none-eabi-objcopy rust_kernel.elf -O binary kernel.img
+
+rust_loader.o: rust_loader.s
+	arm-none-eabi-gcc -mcpu=arm1176jzf-s -fpic -ffreestanding -c rust_loader.s -o rust_loader.o
+
 clean:
-	rm -f main.o
-	rm -f output.elf
+	rm -f *.o
+	rm -f *.elf
+	rm -f *.a
 	rm -f kernel.img
+	rm -f kernel.map

ferrocyanide/raspi_os/kernel.map

@@ -1,32 +0,0 @@
-
-Discarded input sections
-
- .bss           0x0000000000000000        0x0 main.o
- .ARM.attributes
-                0x0000000000000000       0x14 main.o
-
-Memory Configuration
-
-Name             Origin             Length             Attributes
-*default*        0x0000000000000000 0xffffffffffffffff
-
-Linker script and memory map
-
-LOAD main.o
-
-.init           0x0000000000008000       0x50
- *(.init)
- .init          0x0000000000008000       0x50 main.o
-                0x0000000000008000                _start
-
-.text           0x0000000000008050        0x0
- *(.text)
- .text          0x0000000000008050        0x0 main.o
-
-.data           0x0000000000008050        0x0
- *(.data)
- .data          0x0000000000008050        0x0 main.o
-
-/DISCARD/
- *(*)
-OUTPUT(output.elf elf32-littlearm)

ferrocyanide/raspi_os/rust_kernel.rs

@@ -0,0 +1,54 @@
+#![feature(lang_items, asm)]
+#![crate_type = "staticlib"]
+#![no_std]
+
+const GPIO_BASE: u32 = 0x2020000;
+
+#[no_mangle]
+pub extern "C" fn kernel_main() {
+
+    let gpio = GPIO_BASE as *const u32;
+    let led_on = unsafe { gpio.offset(8) as *mut u32 };
+    let led_off = unsafe { gpio.offset(11) as *mut u32 };
+
+    loop {
+        unsafe { *(led_on) = 1 << 15 };
+        sleep(500_000);
+        unsafe { *(led_off) = 1 << 15 };
+        sleep(500_000);
+
+        unsafe { *(led_on) = 1 << 15 };
+        sleep(200_000);
+        unsafe { *(led_off) = 1 << 15 };
+        sleep(200_000);
+    }
+}
+
+fn sleep(value: u32) {
+    for _ in 1..value {
+        unsafe { asm!("") }
+    }
+}
+
+#[cfg(not(test))]
+#[lang = "eh_personality"]
+#[no_mangle]
+pub extern "C" fn eh_personality() {}
+
+#[cfg(not(test))]
+#[lang = "panic_fmt"]
+#[no_mangle]
+pub extern "C" fn panic_fmt() -> ! { loop {}}
+
+#[cfg(not(test))]
+#[lang = "eh_unwind_resume"]
+#[no_mangle]
+pub extern "C" fn eh_unwind_resume() { }
+
+/*
+#[allow(non_snake_case)]
+#[no_mangle]
+pub extern "C" fn _Unwind_Resume() -> ! {
+    loop {}
+}
+*/

ferrocyanide/raspi_os/rust_loader.s

@@ -0,0 +1,30 @@
+.section ".text.boot"
+
+.globl _start
+
+_start:
+/* r15 (SP) begins execution at 0x8000 */
+    mov sp, #0x8000
+
+/* zero out bss_start to bss_end */
+    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 // branch less than
+
+/* call kernel_main */
+    ldr r3, =kernel_main
+    blx r3 /* branch and change processor state from thumb -> arm */
+
+halt:
+    wfe /* wait for event */
+    b halt
+