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https://github.com/SerenityOS/serenity.git
synced 2026-11-07 04:29:30 -10:00
Sönke Holz
e6ae1993ea
Now that all declarations have hidden visibility, we don't need to use inline asm to avoid GOT references here anymore.
81 lines
3.1 KiB
C++
81 lines
3.1 KiB
C++
/*
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* Copyright (c) 2023, Timon Kruiper <[email protected]>
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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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#include <LibELF/Relocation.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" u8 start_of_kernel_image[];
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extern "C" u8 _DYNAMIC[];
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extern "C" [[noreturn]] void init();
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extern "C" [[noreturn]] void pre_init(PhysicalPtr flattened_devicetree_paddr);
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extern "C" [[noreturn]] void pre_init(PhysicalPtr flattened_devicetree_paddr)
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{
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// Apply relative relocations as if we were running at KERNEL_MAPPING_BASE.
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// This means that we shouldn't access anything during pre_init that relies on relocations (e.g. vtables).
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// Otherwise, we would have to relocate twice: once while running identity mapped, and again when we enable the MMU.
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auto physical_load_base = bit_cast<PhysicalPtr>(+start_of_kernel_image);
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auto dynamic_section_addr = bit_cast<PhysicalPtr>(+_DYNAMIC);
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if (!ELF::perform_relative_relocations(physical_load_base, KERNEL_MAPPING_BASE, dynamic_section_addr))
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panic_without_mmu("Failed to perform relative relocations"sv);
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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(flattened_devicetree_paddr);
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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.
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asm volatile(
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"adrp x0, 1f \n"
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"add x0, x0, :lo12:1f \n"
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"add x0, x0, %[base] \n"
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"br x0 \n"
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"1: \n" ::[base] "r"(g_boot_info.physical_to_virtual_offset)
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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"(g_boot_info.physical_to_virtual_offset)
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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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register FlatPtr const x0 asm("x0") = bit_cast<FlatPtr>(&g_boot_info);
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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" ::"r"(x0));
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VERIFY_NOT_REACHED();
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}
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}
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