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55 lines
1.6 KiB
ArmAsm
55 lines
1.6 KiB
ArmAsm
// SPDX-License-Identifier: MIT OR Apache-2.0
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//
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// Copyright (c) 2021 Andre Richter <andre.o.richter@gmail.com>
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//--------------------------------------------------------------------------------------------------
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// Definitions
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//--------------------------------------------------------------------------------------------------
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// Load the address of a symbol into a register, PC-relative.
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//
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// The symbol must lie within +/- 4 GiB of the Program Counter.
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//
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// # Resources
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//
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// - https://sourceware.org/binutils/docs-2.36/as/AArch64_002dRelocations.html
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.macro ADR_REL register, symbol
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adrp \register, \symbol
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add \register, \register, #:lo12:\symbol
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.endm
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.equ _core_id_mask, 0b11
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//--------------------------------------------------------------------------------------------------
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// Public Code
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//--------------------------------------------------------------------------------------------------
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.section .text._start
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//------------------------------------------------------------------------------
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// fn _start()
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//------------------------------------------------------------------------------
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_start:
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// Only proceed on the boot core. Park it otherwise.
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mrs x1, MPIDR_EL1
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and x1, x1, _core_id_mask
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ldr x2, BOOT_CORE_ID // provided by bsp/__board_name__/cpu.rs
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cmp x1, x2
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b.ne 1f
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// If execution reaches here, it is the boot core. Now, prepare the jump to Rust code.
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// Set the stack pointer.
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ADR_REL x0, __boot_core_stack_end_exclusive
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mov sp, x0
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// Jump to Rust code.
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b _start_rust
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// Infinitely wait for events (aka "park the core").
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1: wfe
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b 1b
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.size _start, . - _start
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.type _start, function
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.global _start
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