Bug 671004

Summary: user-space probes wrongly reject repnz;ret instructions
Product: Red Hat Enterprise Linux 6 Reporter: Frank Ch. Eigler <fche>
Component: systemtapAssignee: Frank Ch. Eigler <fche>
Status: CLOSED ERRATA QA Contact: qe-baseos-tools-bugs
Severity: medium Docs Contact:
Priority: low    
Version: 6.1CC: mjw, pmuller
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Unspecified   
Whiteboard:
Fixed In Version: systemtap-1.4-2.el6 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2011-05-19 13:54:50 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Frank Ch. Eigler 2011-01-19 21:44:30 UTC
GCC sometimes emits the code sequence "repnz;ret" to end a function.
systemtap's uprobes module rejects that as an unknown instruction
sequence, but this is unnecessary.  We have a patch in hand to let
such instructions be treated just like "rep;ret" = "ret".  This
should let stap run even with such optimized gcc code, without
risk.

commit 9ee518c4d6c36770aa5da534ae85754962bfe305
Author: Roland McGrath <roland>
Date:   Wed Jan 19 11:23:43 2011 -0800

    PR12419: fix x86 uprobes decoding of "repnz ret"

Comment 3 errata-xmlrpc 2011-05-19 13:54:50 UTC
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2011-0651.html