+2015-07-01 Corinna Vinschen <corinna@vinschen.de>
+
+ * fork.cc (frok::parent): Set stacktop value based on requested stack
+ pointer value in child. Explain why.
+
2015-06-30 Corinna Vinschen <corinna@vinschen.de>
* signal.cc (sigaltstack): Add comment.
ch.forker_finished = forker_finished;
PTEB teb = NtCurrentTeb ();
- ch.stackbottom = _tlsbase;
- ch.stacktop = (void *) _tlstop;
ch.stackaddr = teb->DeallocationStack;
+ ch.stackbottom = _tlsbase;
+ /* If DeallocationStack is NULL, we're running on an application-provided
+ stack. If so, the entire stack is committed anyway and StackLimit points
+ to the allocation address of the stack. Otherwise we're running on a
+ system-allocated stack and using StackLimit is dangerous, in case the
+ application encountered a stack overflow and recovered from it via
+ a signal handler running on an alternate stack. Since stack_here is
+ the address of the stack pointer we start the child with anyway, we
+ can set ch.stacktop to this value rounded down to page size. The
+ child will not need the rest of the stack anyway. */
+ if (!ch.stackaddr)
+ ch.stacktop = _tlstop;
+ else
+ ch.stacktop = (void *) ((uintptr_t) stack_here & ~wincap.page_size ());
ch.guardsize = 0;
if (&_my_tls != _main_tls)
{