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https://github.com/RGBCube/serenity
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697c5ca5e5
The handling of page tables is very architecture specific, so belongs
in the Arch directory. Some parts were already architecture-specific,
however this commit moves the rest of the PageDirectory class into the
Arch directory.
While we're here the aarch64/PageDirectory.{h,cpp} files are updated to
be aarch64 specific, by renaming some members and removing x86_64
specific code.
64 lines
2.1 KiB
C++
64 lines
2.1 KiB
C++
/*
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* Copyright (c) 2023, Timon Kruiper <timonkruiper@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/StringView.h>
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#include <AK/Types.h>
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#include <Kernel/Arch/aarch64/CPU.h>
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#include <Kernel/Sections.h>
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// We arrive here from boot.S with the MMU disabled and in an unknown exception level (EL).
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// The kernel is linked at the virtual address, so we have to be really carefull when accessing
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// global variables, as the MMU is not yet enabled.
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// FIXME: This should probably be shared with the Prekernel.
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namespace Kernel {
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extern "C" [[noreturn]] void init();
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extern "C" [[noreturn]] void pre_init();
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extern "C" [[noreturn]] void pre_init()
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{
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// We want to drop to EL1 as soon as possible, because that is the
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// exception level the kernel should run at.
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initialize_exceptions();
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// Next step is to set up page tables and enable the MMU.
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Memory::init_page_tables();
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// At this point the MMU is enabled, physical memory is identity mapped,
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// and the kernel is also mapped into higher virtual memory. However we are still executing
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// from the physical memory address, so we have to jump to the kernel in high memory. We also need to
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// switch the stack pointer to high memory, such that we can unmap the identity mapping.
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// Continue execution at high virtual address, by using an absolute jump.
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asm volatile(
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"ldr x0, =1f \n"
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"br x0 \n"
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"1: \n" ::
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: "x0");
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// Add kernel_mapping_base to the stack pointer, such that it is also using the mapping
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// in high virtual memory.
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asm volatile(
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"mov x0, %[base] \n"
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"add sp, sp, x0 \n" ::[base] "r"(kernel_mapping_base)
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: "x0");
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// We can now unmap the identity map as everything is running in high virtual memory at this point.
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Memory::unmap_identity_map();
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// Clear the frame pointer (x29) and link register (x30) to make sure the kernel cannot backtrace
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// into this code, and jump to actual init function in the kernel.
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asm volatile(
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"mov x29, xzr \n"
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"mov x30, xzr \n"
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"b init \n");
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VERIFY_NOT_REACHED();
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}
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}
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