From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Wed, 17 Jan 2001 20:04:48 +0000 Subject: Re: [Linux-ia64] Incorrect unwind data in entry.S Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Wed, 17 Jan 2001 10:54:26 -0800, Cary Coutant said: Cary> Perhaps there's something in the first set of "assorted Cary> .spillsp directives," but I don't see where the outer 416-byte Cary> stack frame is being allocated or deallocated. That happens in a very different place of the kernel (the IVT). Basically, what's happening is that a code fragment A sets up a stack frame and then calls a handler B, while arranging that B will return to a code fragment C. Logically, A and C form a single procedure, but there really are several different As (and only one C). Cary> The code then allocates an additional 576 bytes, but prologue Cary> 2 describes the *total* frame size as 576. It then pops Cary> prologue 2, but doesn't deallocate the 576 bytes until the Cary> beginning of body region 3, leaving a narrow window where the Cary> unwinder will think the frame size is 416 bytes. Oops, you are right: the size/offsets should have been adjusted by the size of the first frame. However, I think we can just drop prologue 1 and 3. I believe the reason we used to need those was because the return pointer didn't point to the right place (because the handler B knew that it's going to "return" to C and simply hardcoded a branch to C), but with the current setup, "rp" (or the location at which it was saved) will point to the right place so there is no need to manually craft unwind info for the frame set up by A. --david