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75 lines
2.0 KiB
Rust
75 lines
2.0 KiB
Rust
// SPDX-License-Identifier: MIT OR Apache-2.0
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//
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// Copyright (c) 2018-2020 Andre Richter <andre.o.richter@gmail.com>
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//! Architectural processor code.
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use crate::{bsp, cpu};
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use cortex_a::{asm, regs::*};
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//--------------------------------------------------------------------------------------------------
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// Boot Code
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//--------------------------------------------------------------------------------------------------
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/// The entry of the `kernel` binary.
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///
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/// The function must be named `_start`, because the linker is looking for this exact name.
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///
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/// # Safety
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///
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/// - Linker script must ensure to place this function where it is expected by the target machine.
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/// - We have to hope that the compiler omits any stack pointer usage before the stack pointer is
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/// actually set (`SP.set()`).
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#[no_mangle]
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pub unsafe fn _start() -> ! {
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use crate::relocate;
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// Expect the boot core to start in EL2.
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if bsp::cpu::BOOT_CORE_ID == cpu::smp::core_id() {
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SP.set(bsp::memory::boot_core_stack_end() as u64);
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relocate::relocate_self()
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} else {
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// If not core0, infinitely wait for events.
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wait_forever()
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}
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}
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//--------------------------------------------------------------------------------------------------
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// Public Code
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//--------------------------------------------------------------------------------------------------
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pub use asm::nop;
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/// Spin for `n` cycles.
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#[cfg(feature = "bsp_rpi3")]
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#[inline(always)]
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pub fn spin_for_cycles(n: usize) {
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for _ in 0..n {
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asm::nop();
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}
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}
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/// Pause execution on the core.
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#[inline(always)]
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pub fn wait_forever() -> ! {
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loop {
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asm::wfe()
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}
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}
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/// Branch to a raw integer value.
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///
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/// # Safety
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///
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/// - This is highly unsafe. Use with care.
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#[inline(always)]
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pub unsafe fn branch_to_raw_addr(addr: usize) -> ! {
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asm!(
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"blr {destination:x}",
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destination = in(reg) addr,
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options(nomem, nostack)
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);
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core::intrinsics::unreachable()
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}
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