Robin Randhawa
52 lines
1.8 KiB
ArmAsm
52 lines
1.8 KiB
ArmAsm
// Early initialisation for AArch64 systems.
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//
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// This code is responsible for taking over control of the boot CPU from
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// the bootloader and setting up enough of the CPU so Rust code can take
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// over (in kstart).
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//
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// Readers are recommended to refer to the Arm Architecture Reference Manual
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// when studying this code. The latest version of the Arm Arm can be found at:
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//
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// https://developer.arm.com/products/architecture/cpu-architecture/a-profile/docs
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//
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// The code is structured such that different phases/functionality are
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// in separate files included by this central one.
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//
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// This is hopefully easier to grok and study than one gigantic file.
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//
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// The emphasis is on clarity and not optimisation. Clarity is hard without
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// a decent understanding of the Arm architecture.
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//
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// Optimisation is not too much of a concern given that this is boot code.
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// That said, future revisions will aim to optimise.
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#include "helpers/consts.h"
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#include "helpers/pre_mmu_enabled.S"
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#include "helpers/build_page_tables.S"
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#include "helpers/post_mmu_enabled.S"
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#include "helpers/vectors.S"
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// Entry point for the boot CPU. We assume that x0 contains the physical address of a DTB image
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// passed in by the bootloader.
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//
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// Note that the kernel linker script arranges for this code to lie at the start of the kernel
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// image.
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.text
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.align 2
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.pushsection ".early_init.text", "ax"
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.globl early_init
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early_init:
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bl early_setup
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bl disable_mmu
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bl create_page_tables
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bl enable_mmu
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b mmu_on_trampoline // With the mmu now on, this returns below to
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// mmu_on using Virtual Addressing
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mmu_on:
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bl setup_kstart_context // Setup environment for kstart
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b kstart // Let the show begin! :)
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.popsection
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