From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6516 invoked by alias); 5 Mar 2010 00:41:22 -0000 Received: (qmail 6479 invoked by uid 48); 5 Mar 2010 00:41:04 -0000 Date: Fri, 05 Mar 2010 00:41:00 -0000 Message-ID: <20100305004104.6478.qmail@sourceware.org> From: "jkenisto at us dot ibm dot com" To: systemtap@sources.redhat.com In-Reply-To: <20100204125941.11249.mjw@redhat.com> References: <20100204125941.11249.mjw@redhat.com> Reply-To: sourceware-bugzilla@sourceware.org Subject: [Bug runtime/11249] Tracking executable plus library fails on i386 X-Bugzilla-Reason: AssignedTo Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2010-q1/txt/msg00597.txt.bz2 ------- Additional Comments From jkenisto at us dot ibm dot com 2010-03-05 00:41 ------- The general protection fault on the call suggests that the destination address of the call is bad. (I think the IP is left at the faulting instruction.) The destination is computed by adding the displacement in the call instruction to the address of the next instruction. If you're in a big vma (e.g., libc-x.x.so), that displacement can be big. If you move the call instruction to the (1-page) SSOL area, that big displacement can take you out of the SSOL vma, to a potentially unmapped address. Does that warrant a GP fault? Uprobes adjusts the IP after the call, so it's back in the probed vma, but by then it may be too late. I haven't explicitly tested uprobes on relative calls and jumps, so maybe they've never worked. Perhaps all the calls and [conditional] jumps listed in Comment #4 of PR #5509 are suspect. (If that turns out to be the case, I have an idea of how to support these instructions correctly.) This hypothesis doesn't explain why Srikar doesn't see the problem in utrace-gdbstub-uprobes. -- http://sourceware.org/bugzilla/show_bug.cgi?id=11249 ------- You are receiving this mail because: ------- You are the assignee for the bug, or are watching the assignee.