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Justin C. Miller
f7f8bb3f45
In order to reduce the amount of tracked state, now use the vm_area_buffers instead of a VMA with buffer_cache on top.
75 lines
2.3 KiB
C++
75 lines
2.3 KiB
C++
#pragma once
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/// \file kernel_memory.h
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/// Constants related to the kernel's memory layout
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#include <stddef.h>
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#include <stdint.h>
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namespace memory {
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/// Size of a single page frame.
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constexpr size_t frame_size = 0x1000;
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/// Start of kernel memory.
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constexpr uintptr_t kernel_offset = 0xffff800000000000ull;
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/// Offset from physical where page tables are mapped.
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constexpr uintptr_t page_offset = 0xffffc00000000000ull;
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/// Max number of pages for a kernel stack
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constexpr unsigned kernel_stack_pages = 4;
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/// Max number of pages for a kernel buffer
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constexpr unsigned kernel_buffer_pages = 16;
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/// Max size of the kernel heap
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constexpr size_t kernel_max_heap = 0x8000000000ull; // 512GiB
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/// Start of the kernel heap
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constexpr uintptr_t heap_start = page_offset - kernel_max_heap;
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/// Max size of the kernel stacks area
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constexpr size_t kernel_max_stacks = 0x8000000000ull; // 512GiB
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/// Start of the kernel stacks
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constexpr uintptr_t stacks_start = heap_start - kernel_max_stacks;
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/// Max size of kernel buffers area
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constexpr size_t kernel_max_buffers = 0x10000000000ull; // 1TiB
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/// Start of kernel buffers
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constexpr uintptr_t buffers_start = stacks_start - kernel_max_buffers;
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/// First kernel space PML4 entry
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constexpr unsigned pml4e_kernel = 256;
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/// First offset-mapped space PML4 entry
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constexpr unsigned pml4e_offset = 384;
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/// Number of page_table entries
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constexpr unsigned table_entries = 512;
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/// Helper to determine if a physical address can be accessed
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/// through the page_offset area.
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inline bool page_mappable(uintptr_t a) { return (a & page_offset) == 0; }
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/// Convert a physical address to a virtual one (in the offset-mapped area)
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template <typename T> T * to_virtual(uintptr_t a) {
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return reinterpret_cast<T*>(a|page_offset);
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}
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/// Get the number of pages needed for a given number of bytes.
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/// \arg bytes The number of bytes desired
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/// \returns The number of pages needed to contain the desired bytes
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inline size_t page_count(size_t bytes) {
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return ((bytes - 1) >> 12) + 1;
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}
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/// Get the given address, aligned to the next lowest page
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inline uintptr_t page_align_down(uintptr_t a) { return a & ~(frame_size-1); }
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/// Get the given address, aligned to the next page
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inline uintptr_t page_align_up(uintptr_t a) { return page_align_down(a-1) + frame_size; }
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} // namespace memory
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