Hacky debug output

Cargo.lock

@@ -9,6 +9,12 @@ dependencies = [
  "error",
 ]
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "cortex-a"
 version = "6.1.0"
@@ -26,6 +32,7 @@ version = "0.1.0"
 name = "kernel"
 version = "0.1.0"
 dependencies = [
+ "cfg-if",
  "cortex-a",
 ]
 

etc/aarch64-qemu.ld

@@ -1,6 +1,6 @@
 ENTRY(_entry);
 
-KERNEL_OFFSET = 0xFFFFFF8000000000;
+KERNEL_OFFSET = 0; /* 0xFFFFFF8000000000; */
 
 SECTIONS {
     . = 0x40080000 + KERNEL_OFFSET;
@@ -8,7 +8,7 @@ SECTIONS {
     PROVIDE(__kernel_start = .);
 
     .text : AT(. - KERNEL_OFFSET) {
-        *(.text.boot)
+        *(.text._entry)
         *(.text*)
     }
 
@@ -24,11 +24,11 @@ SECTIONS {
 
     . = ALIGN(4K);
     .bss : AT(. - KERNEL_OFFSET) {
-        PROVIDE(__bss_start_phys = . - KERNEL_OFFSET);
+        PROVIDE(__bss_start = .);
         *(COMMON)
         *(.bss*)
         . = ALIGN(4K);
-        PROVIDE(__bss_end_phys = . - KERNEL_OFFSET);
+        PROVIDE(__bss_end = .);
     }
 
     PROVIDE(__kernel_end = .);

kernel/Cargo.toml

@@ -5,8 +5,16 @@ edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
+[[bin]]
+name = "kernel"
+test = false
+
+[dependencies]
+cfg-if = "1.x.x"
+
 [target.'cfg(target_arch = "aarch64")'.dependencies]
 cortex-a = { version = "6.x.x" }
 
 [features]
 mach_qemu = []
+default = ["mach_qemu"]

kernel/src/arch/aarch64/boot/entry.S

@@ -0,0 +1,37 @@
+.macro ADR_REL reg, sym
+    adrp \reg, \sym
+    add \reg, \reg, #:lo12:\sym
+.endm
+
+.section .text._entry
+.global _entry
+_entry:
+    mrs x1, mpidr_el1
+    and x1, x1, #3
+    beq 2f
+1:
+    wfe
+    b 1b
+
+2:
+
+    // Zero .bss
+    ADR_REL x0, __bss_start
+    ADR_REL x1, __bss_end
+1:
+    cmp x0, x1
+    beq 2f
+    stp xzr, xzr, [x0], #16
+    b 1b
+2:
+
+    ADR_REL x0, bsp_stack_top
+    mov sp, x0
+
+    b __aa64_bsp_main
+
+.section .bss
+.p2align 4
+bsp_stack_bottom:
+    .skip 16384
+bsp_stack_top:

kernel/src/arch/aarch64/boot/mod.rs

@@ -0,0 +1,11 @@
+use cortex_a::asm;
+
+#[no_mangle]
+fn __aa64_bsp_main() {
+    debugln!("Test");
+    loop {
+        asm::wfe();
+    }
+}
+
+global_asm!(include_str!("entry.S"));

kernel/src/arch/aarch64/mod.rs

@@ -0,0 +1 @@
+pub mod boot;

kernel/src/arch/mod.rs

@@ -0,0 +1,7 @@
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        pub mod aarch64;
+
+        pub use aarch64 as platform;
+    }
+}

kernel/src/debug.rs

@@ -0,0 +1,30 @@
+use core::fmt;
+
+struct Output;
+
+impl fmt::Write for Output {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        for &byte in s.as_bytes() {
+            // XXX
+            unsafe {
+                core::ptr::write_volatile(0x09000000 as *mut u32, byte as u32);
+            }
+        }
+        Ok(())
+    }
+}
+
+#[macro_export]
+macro_rules! debug {
+    ($($it:tt)+) => ($crate::debug::_debug(format_args!($($it)+)))
+}
+
+#[macro_export]
+macro_rules! debugln {
+    ($($it:tt)+) => (debug!("{}\n", format_args!($($it)+)))
+}
+
+pub fn _debug(args: fmt::Arguments) {
+    use fmt::Write;
+    drop(Output {}.write_fmt(args));
+}

kernel/src/main.rs

@@ -3,24 +3,15 @@
 #![no_std]
 #![no_main]
 
-use core::panic::PanicInfo;
+#[macro_use]
+extern crate cfg_if;
+
+#[macro_use]
+pub mod debug;
+pub mod arch;
+pub mod mem;
 
 #[panic_handler]
-fn panic_handler(_pi: &PanicInfo) -> ! {
+fn panic_handler(_pi: &core::panic::PanicInfo) -> ! {
     loop {}
 }
-
-global_asm!(r#"
-.section .text._entry
-.global _entry
-_entry:
-    mrs x1, mpidr_el1
-    and x1, x1, #3
-    beq 2f
-1:
-    wfe
-    b 1b
-
-2:
-    b .
-"#);

kernel/src/mem/mod.rs

@@ -0,0 +1,8 @@
+#[no_mangle]
+pub unsafe extern "C" fn memcpy(dst: *mut u8, src: *mut u8, mut len: usize) -> *mut u8 {
+    while len != 0 {
+        len -= 1;
+        *dst.add(len) = *src.add(len);
+    }
+    dst
+}