internal static unsafe StackHead *GetStackSegmentRaw(UIntPtr size,
ref ThreadContext context,
bool kernelAllocation,
bool initialStack)
{
// Allocate a new chunk, making room for StackHead at the top.
// If you change these constants to add more data, see the
// comment about InitialStackSize at the top of this file!
#if DO_TRACE_STACKS
Kernel.Waypoint(667);
#endif
if (size == UIntPtr.Zero)
{
size = InitialStackSize;
}
size = MemoryManager.PagePad(size + sizeof(StackHead) + SafetyBufferSize);
UIntPtr chunk;
Process owner = Process.GetProcessByID(context.processId);
//
//// NOTE: here's where we should be clever about
//// whether to allocate a stack chunk in the user range
//// or the kernel range. Except, if we switch contexts
//// during an ABI call while using a user-range stack
//// segment on a paging machine, we die. Gloss over
//// this hackily by always getting stack segments
//// from the kernel range.
//if (kernelAllocation || (owner == Process.kernelProcess)) {
// chunk = MemoryManager.KernelAllocate(
// MemoryManager.PagesFromBytes(size), owner, 0, PageType.Stack);
//}
//else {
// chunk = MemoryManager.UserAllocate(
// MemoryManager.PagesFromBytes(size), owner, 0, PageType.Stack);
//}
//
UIntPtr pageCount = MemoryManager.PagesFromBytes(size);
#if DEBUG_STACK_VERBOSE
fixed(ThreadContext *ptr = &context)
{
Tracing.Log(Tracing.Debug,
"GetStackSegmentRaw(ctx={0:x8},size={1:d}) pages={2} [{3:x8}..{4:x8}]",
(UIntPtr)ptr, size, pageCount,
context.stackLimit, context.stackBegin);
}
#endif
chunk = MemoryManager.StackAllocate(pageCount, owner, 0, kernelAllocation, initialStack);
if (chunk != UIntPtr.Zero)
{
// NB: We do _not_ zero out stack memory!
// We assume that Bartok prevents access to prev contents.
StackHead *head = (StackHead *)(chunk + size - sizeof(StackHead));
context.stackBegin = chunk + size;
context.stackLimit = chunk + SafetyBufferSize;
#if DEBUG_STACK_VERBOSE
Tracing.Log(Tracing.Debug,
"GetStackSegmentRaw(size={0:d}) -> [{1:x8}..{2:x8}]",
size, context.stackLimit, context.stackBegin);
#endif
return(head);
}
else
{
// Stack allocation failed. In the future, we should
// trigger a kernel exception; for now, we break to the
// debugger.
#if DEBUG_STACK_VERBOSE
Tracing.Log(Tracing.Debug,
"GetStackSegmentRaw: KernelAllocate failed!(siz={0:d})",
size);
#endif
//DebugStub.Break();
return(null);
}
}
