feat: enable FP instructions in EL0/1

kernel/src/arch/aarch64/asm.rs

@@ -0,0 +1,48 @@
+//! Assembly intrinsics for AArch64 platform
+#![allow(missing_docs)]
+
+use tock_registers::{
+    interfaces::{Readable, Writeable},
+    register_bitfields
+};
+
+register_bitfields! {
+    u64,
+    pub CPACR_EL1 [
+        FPEN OFFSET(20) NUMBITS(2) [
+            TrapAll = 0,
+            TrapEl0 = 1,
+            TrapNone = 3
+        ]
+    ]
+}
+
+pub struct Reg;
+
+impl Readable for Reg {
+    type T = u64;
+    type R = CPACR_EL1::Register;
+
+    #[inline(always)]
+    fn get(&self) -> Self::T {
+        let mut tmp;
+        unsafe {
+            asm!("mrs {}, cpacr_el1", out(reg) tmp);
+        }
+        tmp
+    }
+}
+
+impl Writeable for Reg {
+    type T = u64;
+    type R = CPACR_EL1::Register;
+
+    #[inline(always)]
+    fn set(&self, value: Self::T) {
+        unsafe {
+            asm!("msr cpacr_el1, {}", in(reg) value);
+        }
+    }
+}
+
+pub const CPACR_EL1: Reg = Reg;

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

@@ -1,8 +1,12 @@
 //! aarch64 common boot logic
+use crate::arch::aarch64::asm::CPACR_EL1;
+use tock_registers::interfaces::Writeable;
 
 #[no_mangle]
 fn __aa64_bsp_main() {
-    debugln!("Test");
+    // Disable FP instruction trapping
+    CPACR_EL1.write(CPACR_EL1::FPEN::TrapNone);
+
     use crate::arch::machine;
     use crate::dev::{serial::SerialDevice, timer::TimestampSource, Device};
 

kernel/src/arch/aarch64/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod boot;
 pub mod timer;
+pub mod asm;
 
 cfg_if! {
     if #[cfg(feature = "mach_qemu")] {

kernel/src/main.rs

@@ -1,5 +1,6 @@
 //! osdve5 crate (lol)
 #![feature(
+    asm,
     global_asm,
     const_for,
     const_mut_refs,

kernel/src/mem/mod.rs

@@ -34,3 +34,18 @@ pub unsafe extern "C" fn memcmp(a: *mut u8, b: *mut u8, mut len: usize) -> isize
     }
     0
 }
+
+/// See memset(3p)
+///
+/// # Safety
+///
+/// Unsafe: writes to arbitrary memory locations, performs no pointer
+/// validation.
+#[no_mangle]
+pub unsafe extern "C" fn memset(buf: *mut u8, val: u8, mut len: usize) -> *mut u8 {
+    while len != 0 {
+        len -= 1;
+        *buf.add(len) = val;
+    }
+    buf
+}