karina
82 lines
2.7 KiB
C
82 lines
2.7 KiB
C
#include <VM/PMM.h>
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#include <Lib/String.h>
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extern char _kernelStart[];
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extern char _kernelEnd[];
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static Address sPMMRamBase = 0;
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static MemoryPointer sPMMBitmap;
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static Size sPMMBitmapSize;
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static Size sPMMTotalPages;
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static inline Size BitmapGetByteIndex(Address address) {
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return ((address - sPMMRamBase) / kVMPageSize) / kVMBlocksPerByte;
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}
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static inline UInt8 BitmapGetBitOffset(Address address) {
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return (UInt8)(((address - sPMMRamBase) / kVMPageSize) % kVMBlocksPerByte);
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}
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static inline void BitmapSet(MemoryPointer bitmap, Address address) {
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bitmap[BitmapGetByteIndex(address)] |= (1U << BitmapGetBitOffset(address));
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}
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static inline void BitmapUnset(MemoryPointer bitmap, Address address) {
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bitmap[BitmapGetByteIndex(address)] &= ~(1U << BitmapGetBitOffset(address));
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}
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void PMMInitialize(VMBootMemoryMap* bootMap) {
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sPMMRamBase = bootMap->totalRAM.base;
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sPMMTotalPages = bootMap->totalRAM.size / kVMPageSize;
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sPMMBitmapSize = sPMMTotalPages / kVMBlocksPerByte;
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sPMMBitmap = (MemoryPointer)_kernelEnd;
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MemorySet(sPMMBitmap, 0, sPMMBitmapSize);
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UInt32 safeIndex = bootMap->reservedCount;
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bootMap->reserved[safeIndex].base = sPMMRamBase;
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bootMap->reserved[safeIndex].size = 16 * 1024 * 1024; // 16 Mb
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bootMap->reservedCount++;
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UInt32 kIndex = bootMap->reservedCount;
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bootMap->reserved[kIndex].base = (Address)_kernelStart;
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bootMap->reserved[kIndex].size = (Address)_kernelEnd - (Address)_kernelStart;
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bootMap->reservedCount++;
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UInt32 bIndex = bootMap->reservedCount;
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bootMap->reserved[bIndex].base = (Address)sPMMBitmap;
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bootMap->reserved[bIndex].size = sPMMBitmapSize;
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bootMap->reservedCount++;
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for (Size i = 0; i < bootMap->reservedCount; i++) {
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Address regionBase = bootMap->reserved[i].base;
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Size regionSize = bootMap->reserved[i].size;
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Size pagesToReserve = (regionSize + kVMPageSize - 1) / kVMPageSize;
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for (Size p = 0; p < pagesToReserve; p++) {
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Address pageAddress = regionBase + (p * kVMPageSize);
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if (pageAddress >= sPMMRamBase && pageAddress < (sPMMRamBase + bootMap->totalRAM.size)) {
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BitmapSet(sPMMBitmap, pageAddress);
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}
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}
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}
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}
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Pointer PMMAllocatePage() {
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for (Size i = 0; i < sPMMBitmapSize; i++) {
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if (sPMMBitmap[i] == 0xFF) continue;
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for (Size bit = 0; bit < kVMBlocksPerByte; bit++) {
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if ((sPMMBitmap[i] & (1 << bit)) == 0) {
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Address address = sPMMRamBase + (i * kVMBlocksPerByte + bit) * kVMPageSize;
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BitmapSet(sPMMBitmap, address);
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return (Pointer)address;
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}
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}
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}
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return nullptr;
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}
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void PMMFreePage(Address address) {
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BitmapUnset(sPMMBitmap, address);
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} |