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[讨论]有关句柄分配算法
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发表于:
2009-2-28 17:14
7376
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一直在想windows下的句柄是怎么进行分配和管理的
而这个句柄分配的算法又是windows不与公布的
在网上找了下 发现这方面的资料很少啊 于是自己对着WRK和reactOS看了一下午
虽然明白了一点点 但是还是有好多地方很迷糊 希望大牛们指导一下
从ExCreateHandle开始
到ExpAllocateHandleEntry
再到ExpAllocateHandleTableEntrySlow
定位句柄分配算法大概就位于此处
if ( TableLevel == 0 ) {
NewMidLevel = ExpAllocateMidLevelTable( HandleTable, DoInit, &NewLowLevel );
if (NewMidLevel == NULL) {
return FALSE;
}
NewMidLevel[1] = NewMidLevel[0];
NewMidLevel[0] = (PHANDLE_TABLE_ENTRY)CapturedTable;
CapturedTable = ((ULONG_PTR)NewMidLevel) | 1;
OldValue = InterlockedExchangePointer( (PVOID *)&HandleTable->TableCode, (PVOID)CapturedTable );
} else if (TableLevel == 1) {
PHANDLE_TABLE_ENTRY *TableLevel2 = (PHANDLE_TABLE_ENTRY *)CapturedTable;
i = HandleTable->NextHandleNeedingPool / (LOWLEVEL_COUNT * HANDLE_VALUE_INC);
if (i < MIDLEVEL_COUNT) {
NewLowLevel = ExpAllocateLowLevelTable( HandleTable, DoInit );
if (NewLowLevel == NULL) {
return FALSE;
}
OldValue = InterlockedExchangePointer( (PVOID *) (&TableLevel2[i]), NewLowLevel );
EXASSERT (OldValue == NULL);
} else {
NewHighLevel = ExpAllocateTablePagedPool( HandleTable->QuotaProcess,
HIGHLEVEL_SIZE
);
if (NewHighLevel == NULL) {
return FALSE;
}
NewMidLevel = ExpAllocateMidLevelTable( HandleTable, DoInit, &NewLowLevel );
if (NewMidLevel == NULL) {
ExpFreeTablePagedPool( HandleTable->QuotaProcess,
NewHighLevel,
HIGHLEVEL_SIZE
);
return FALSE;
}
NewHighLevel[0] = (PHANDLE_TABLE_ENTRY*)CapturedTable;
NewHighLevel[1] = NewMidLevel;
CapturedTable = ((ULONG_PTR)NewHighLevel) | 2;
OldValue = InterlockedExchangePointer( (PVOID *)&HandleTable->TableCode, (PVOID)CapturedTable );
}
} else if (TableLevel == 2) {
ULONG RemainingIndex;
PHANDLE_TABLE_ENTRY **TableLevel3 = (PHANDLE_TABLE_ENTRY **)CapturedTable;
i = HandleTable->NextHandleNeedingPool / (MIDLEVEL_THRESHOLD * HANDLE_VALUE_INC);
if (i >= HIGHLEVEL_COUNT) {
return FALSE;
}
if (TableLevel3[i] == NULL) {
NewMidLevel = ExpAllocateMidLevelTable( HandleTable, DoInit, &NewLowLevel );
if (NewMidLevel == NULL) {
return FALSE;
}
OldValue = InterlockedExchangePointer( (PVOID *) &(TableLevel3[i]), NewMidLevel );
EXASSERT (OldValue == NULL);
} else {
RemainingIndex = (HandleTable->NextHandleNeedingPool / HANDLE_VALUE_INC) -
i * MIDLEVEL_THRESHOLD;
j = RemainingIndex / LOWLEVEL_COUNT;
NewLowLevel = ExpAllocateLowLevelTable( HandleTable, DoInit );
if (NewLowLevel == NULL) {
return FALSE;
}
OldValue = InterlockedExchangePointer( (PVOID *)(&TableLevel3[i][j]) , NewLowLevel );
EXASSERT (OldValue == NULL);
}
}
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