public unsafe static IntPtr AllocateThunk(IntPtr commonStubAddress)
{
lock (s_Lock)
{
LowLevelList <ThunksTemplateMap> mappings;
if (!s_ThunkMaps.TryGetValue(commonStubAddress, out mappings))
{
s_ThunkMaps[commonStubAddress] = mappings = new LowLevelList <ThunksTemplateMap>();
}
IntPtr thunkStub = GetThunkFromAllocatedPool(mappings, commonStubAddress);
if (thunkStub == IntPtr.Zero)
{
// No available thunks, so we need a new mapping of the thunks template page
IntPtr thunkBase = AsmCode.GetThunksBase();
Debug.Assert(thunkBase != IntPtr.Zero);
IntPtr moduleHandle = RuntimeAugments.GetModuleFromTypeHandle(typeof(ThunkPool).TypeHandle);
Debug.Assert(moduleHandle != IntPtr.Zero);
int templateRva = (int)((long)thunkBase - (long)moduleHandle);
Debug.Assert(templateRva % ALLOCATION_GRANULARITY == 0);
IntPtr thunkMap = IntPtr.Zero;
if (s_ThunksTemplate == IntPtr.Zero)
{
// First, we use the thunks directly from the thunks template sections in the module until all
// thunks in that template are used up.
thunkMap = moduleHandle + templateRva;
s_ThunksTemplate = thunkMap;
}
else
{
// We've already used the thunks tempate in the module for some previous thunks, and we
// cannot reuse it here. Now we need to create a new mapping of the thunks section in order to have
// more thunks
thunkMap = RuntimeImports.RhAllocateThunksFromTemplate(moduleHandle, templateRva, NUM_THUNK_BLOCKS * PAGE_SIZE * 2);
if (thunkMap == IntPtr.Zero)
{
// We either ran out of memory and can't do anymore mappings of the thunks templates sections,
// or we are using the managed runtime services fallback, which doesn't provide the
// file mapping feature (ex: older version of mrt100.dll, or no mrt100.dll at all).
// The only option is for the caller to attempt and recycle unused thunks to be able to
// find some free entries.
return(IntPtr.Zero);
}
}
Debug.Assert(thunkMap != IntPtr.Zero && (long)thunkMap % ALLOCATION_GRANULARITY == 0);
// Each mapping consists of multiple blocks of thunk stubs/data pairs. Keep track of those
// so that we do not create a new mapping until all blocks in the sections we just mapped are consumed
for (int i = 0; i < NUM_THUNK_BLOCKS; i++)
{
s_RecentlyMappedThunksBlock[i] = thunkMap + (PAGE_SIZE * i * 2);
}
s_RecentlyMappedThunksBlockIndex = 1;
thunkStub = AllocateThunksTemplateMapFromMapping(thunkMap, commonStubAddress, mappings);
}
return(SetThumbBit(thunkStub));
}
}