1 files changed, 70 insertions, 0 deletions
diff --git a/newlib/libc/sys/go32/setstack.S b/newlib/libc/sys/go32/setstack.S
new file mode 100644
index 00000000000..dcd3ac0b246
--- /dev/null
+++ b/newlib/libc/sys/go32/setstack.S
@@ -0,0 +1,70 @@
+/*  This routine potentially increases the stack size at runtime based on
+    the _stklen variable.  Only used by DPMI code.
+    Copyright (c) 1993  C. Sandmann
+    Environment:  called by crt0.s (and gcrt0.s)
+                  EAX, EBX, EBP, EDI, ESI disposable (cleared on return) */
+
+	.text
+	.globl	__setstack
+__setstack:
+	movl	%esp,%eax
+	andl	$0xc0000000,%eax	/* clear all except upper bits */
+	jne	ok_stack		/* obviously not DPMI! */
+	movw	%ss,%ax
+	lsll	%eax,%ebx		/* stack segment limit */
+	movl	%esp,%eax		/* current location */
+	subl	%ebx,%eax		/* Free stack */
+	cmpl	%eax,__stklen
+	jb	ok_stack
+
+/* Not enough stack.  Call sbrk() to get a new area.  Copy current ESP + 20
+   to end of new area (3 args + our stack).  Change ESP to new area.  Set new
+   limit to start of new area using DPMI services.  */
+
+	pushl	__stklen
+	call	_sbrk			/* eax = got memory base */
+	popl	%ebx			/* remove _stklen */
+	cmpl	$0xffffffff,%eax	/* if eax = -1 failure */
+	je	badstack
+	addl	%eax,%ebx		/* ebx now is end of new stack area */
+	andl	$0xfffffff0,%ebx	/* 16 byte alignment */
+	addl	$0xfff,%eax		/* make stack base page aligned */
+	andl	$0xfffff000,%eax	/* 4096 byte alignment */
+
+/* Now copy old stack to new stack.  We only need our part + 4 words, 3 for
+   the parameters to pass to main, one for our return EIP (4 extra safety) */
+	movl	%esp, %esi		/* Source is current stack */
+	subl	$0x20, %ebx		/* 8 longwords */
+	movl	%ebx, %edi		/* Destination is new stack */
+	movl	$8,%ecx
+	rep
+	movsl
+
+/* New stack in place.  Change ESP to point to it.  Assumes new stack is
+   higher in memory so we don't get caught by limit.  Change limit using 
+   DPMI services. */
+
+	movl	%ebx,%esp		/* Switch to new stack */
+	subl	$1,%eax			/* Low 12 bits all 1s */
+	pushl	%eax			/* Easiest way to move long to words */
+	popw	%dx
+	popw	%cx
+	movl	$8,%eax			/* DPMI function Set Segment Limit */
+	movw	%ss,%bx			/* Selector */
+	int	$0x31			/* Do service */
+
+	xor	%ecx,%ecx		/* Clean up */
+	xor	%edx,%edx		/* Clean up */
+
+ok_stack:
+	ret				/* What we have is already bigger */
+
+badstack:
+	movl	$0x4c01,%eax
+	int	$0x21
+	jmp	badstack
+
+	.data
+	.globl	__stklen
+	.comm	__stklen,4
+