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84 lines
2.3 KiB
Rust
84 lines
2.3 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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//! Rust runtime initialization code.
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use crate::memory;
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use core::ops::Range;
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//--------------------------------------------------------------------------------------------------
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// Private Code
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//--------------------------------------------------------------------------------------------------
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/// Return the range spanning the .bss section.
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///
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/// # Safety
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///
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/// - The symbol-provided addresses must be valid.
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/// - The symbol-provided addresses must be usize aligned.
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unsafe fn bss_range() -> Range<*mut usize> {
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extern "C" {
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// Boundaries of the .bss section, provided by linker script symbols.
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static mut __bss_start: usize;
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static mut __bss_end: usize;
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}
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Range {
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start: &mut __bss_start,
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end: &mut __bss_end,
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}
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}
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/// Zero out the .bss section.
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///
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/// # Safety
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///
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/// - Must only be called pre `kernel_init()`.
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#[inline(always)]
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unsafe fn zero_bss() {
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memory::zero_volatile(bss_range());
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}
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//--------------------------------------------------------------------------------------------------
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// Public Code
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//--------------------------------------------------------------------------------------------------
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/// Equivalent to `crt0` or `c0` code in C/C++ world. Clears the `bss` section, then jumps to kernel
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/// init code.
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///
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/// # Safety
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///
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/// - Only a single core must be active and running this function.
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pub unsafe fn runtime_init() -> ! {
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extern "Rust" {
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fn kernel_init() -> !;
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}
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zero_bss();
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kernel_init()
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}
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//--------------------------------------------------------------------------------------------------
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// Testing
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//--------------------------------------------------------------------------------------------------
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#[cfg(test)]
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mod tests {
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use super::*;
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use test_macros::kernel_test;
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/// Check `bss` section layout.
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#[kernel_test]
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fn bss_section_is_sane() {
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use core::mem;
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let start = unsafe { bss_range().start } as *const _ as usize;
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let end = unsafe { bss_range().end } as *const _ as usize;
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assert_eq!(start % mem::size_of::<usize>(), 0);
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assert_eq!(end % mem::size_of::<usize>(), 0);
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assert!(end >= start);
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}
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}
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