79 lines
2.1 KiB
C++
79 lines
2.1 KiB
C++
#include "memory/KernelHeap.h"
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#include "assert.h"
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static uint8_t page_bitmap[2048];
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#define ALLOC_BASE 0xfffffffff8000000
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#define ALLOC_END 0xfffffffffc000000
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static uint64_t start_index = 0;
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static bool bitmap_read(uint64_t index)
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{
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return (page_bitmap[index / 8] & (0b10000000 >> (index % 8))) > 0;
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}
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static void bitmap_set(uint64_t index, bool value)
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{
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uint64_t byteIndex = index / 8;
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uint8_t bitIndexer = 0b10000000 >> (index % 8);
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page_bitmap[byteIndex] &= ~bitIndexer;
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if (value) { page_bitmap[byteIndex] |= bitIndexer; }
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}
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uint64_t KernelHeap::request_virtual_page()
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{
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for (uint64_t index = start_index; index < sizeof(page_bitmap) * 8; index++)
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{
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if (bitmap_read(index)) continue;
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bitmap_set(index, true);
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start_index = index + 1;
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return ALLOC_BASE + (index * 4096);
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}
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return 0;
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}
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uint64_t KernelHeap::request_virtual_pages(uint64_t count)
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{
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uint64_t contiguous = 0;
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uint64_t contiguous_start = 0;
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for (uint64_t index = start_index; index < sizeof(page_bitmap) * 8; index++)
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{
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if (bitmap_read(index))
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{
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contiguous = 0;
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continue;
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}
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if (contiguous == 0)
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{
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contiguous_start = index;
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contiguous++;
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}
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else
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contiguous++;
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if (contiguous == count)
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{
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for (uint64_t i = 0; i < count; i++) bitmap_set(contiguous_start + i, true);
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return ALLOC_BASE + (contiguous_start * 4096);
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}
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}
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return 0;
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}
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void KernelHeap::free_virtual_page(uint64_t address)
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{
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ASSERT(address >= ALLOC_BASE && address < ALLOC_END);
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uint64_t index = (address - ALLOC_BASE) / 4096;
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bitmap_set(index, false);
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if (start_index > index) start_index = index;
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}
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void KernelHeap::free_virtual_pages(uint64_t address, uint64_t count)
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{
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ASSERT(address >= ALLOC_BASE && address < ALLOC_END);
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uint64_t index = (address - ALLOC_BASE) / 4096;
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for (uint64_t i = 0; i < count; i++) { bitmap_set(index + i, false); }
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if (start_index > index) start_index = index;
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} |