[Bug 1659185] [NEW] User probes on ppc64le are not returning the correct values of the probed function's arguments.

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== Comment: #0 - David J. Wilder <wilder at us.ibm.com> - 2015-07-15 19:51:49 ==
---Problem Description---
User probes on ppc64le are not returning the correct values of the probed function's arguments.
 
Contact Information = wilder at us.ibm.com 
 
---uname output---
Linux Daves-sandbox 3.19.0-21-generic #21-Ubuntu SMP Sun Jun 14 19:33:37 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux
 
Machine Type = 8284-22A  (power8, running on a VM on top of powerKVM) 
 
---Debugger---
A debugger is not configured
 
---Steps to Reproduce---

$ cat doit.c
#include <stdio.h>

doit( int i )
{
	printf("%s: i=%d\n",__func__,i);
	pause();
}

main()
{
	doit(42);
}

$ cat doit.stp
probe process("doit").function("doit") {
	printf("function doit called with i=%ld\n",$i);
}

$ gcc -g -o doit doit.c

$ sudo stap doit.stp -c ./doit

doit: i=42
function doit called with i=16383  <<<< I expect 42
---------

If I run the same example on a x86-64 system I get the expected results.
So I think this is a problem with ppc64 only.

$ uname -a
Linux ubuntu-15 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
$ sudo stap doit.stp -c ./doit

doit: i=42
function doit called with i=42

Other information (from ppc64le system):

I build systemtap from upstream git.  The version Canonical is shipping
is broken.

$ stap --version
Systemtap translator/driver (version 2.9/0.160, commit release-2.8-19-ga7396f637e7c)
Copyright (C) 2005-2015 Red Hat, Inc. and others
This is free software; see the source for copying conditions.
enabled features: TR1_UNORDERED_MAP NLS

$ grep CONFIG_UPROBES /boot/config-`uname -r` 
CONFIG_UPROBES=y

 ----------------------------------------------------
Userspace tool common name: stap 
 
The userspace tool has the following bit modes: 64-bit 

Userspace rpm: systemtap

Userspace tool obtained from project website:  na 
 
*Additional Instructions for wilder at us.ibm.com: 
-Post a private note with access information to the machine that the bug is occuring on.
-Attach ltrace and strace of userspace application.

Please cherry pick the fix.

https://www.sourceware.org/git/?p=systemtap.git;a=commit;h=b0cfcdb4886be5654e94cd7893a01531345e961d

https://www.sourceware.org/git/?p=systemtap.git;a=commit;h=c3d8c09c03abd4b212a24b94601a7d5a2d9b74a1

** Affects: systemtap (Ubuntu)
     Importance: Undecided
     Assignee: Taco Screen team (taco-screen-team)
         Status: New


** Tags: architecture-ppc64le bugnameltc-127718 severity-medium targetmilestone-inin1704
-- 
User probes on ppc64le are not returning the correct values of the probed function's arguments.
https://bugs.launchpad.net/bugs/1659185
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