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[Bug runtime/15775] New: relay host/guest functionality is broken on RHEL6
- From: "dsmith at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sourceware dot org
- Date: Tue, 23 Jul 2013 19:02:35 +0000
- Subject: [Bug runtime/15775] New: relay host/guest functionality is broken on RHEL6
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=15775
Bug ID: 15775
Summary: relay host/guest functionality is broken on RHEL6
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: runtime
Assignee: systemtap at sourceware dot org
Reporter: dsmith at redhat dot com
On RHEL6, the systemtap.printf/sharedbuf.exp test fails:
====
Running
/es/scratch/dsmith/systemtap/src/testsuite/systemtap.printf/sharedbuf.exp ...
spawn stap
/es/scratch/dsmith/systemtap/src/testsuite/systemtap.printf/sharedbuf.stp
-DRELAY_HOST=test1
Host: begin
PASS: shared buffer hosting
WARNING: "stp_print_flush_test1"
[/tmp/stap3qLPPW/stap_3afb871f7052c2f8b13ef4bc30d1f01a_1033.ko] undefined!
ERROR: Couldn't insert module
'/tmp/stap3qLPPW/stap_3afb871f7052c2f8b13ef4bc30d1f01a_1033.ko': Unknown symbol
in module
WARNING: /usr/local/bin/staprun exited with status: 1
Pass 5: run failed. [man error::pass5]
PASS: shared buffer guest
FAIL: buffer sharing (1, 0)
testcase
/es/scratch/dsmith/systemtap/src/testsuite/systemtap.printf/sharedbuf.exp
completed in 127 seconds
====
In /var/log/messages, you'll see this:
====
Jul 23 13:03:09 kvm-el6-64-1 kernel:
stap_2a284551e36db9394c1f2b499dfa812_12005: no symbol version for
stp_print_flush_test1
Jul 23 13:03:09 kvm-el6-64-1 kernel:
stap_2a284551e36db9394c1f2b499dfa812_12005: Unknown symbol
stp_print_flush_test1
====
I believe this is happening because of kernel symbol versioning. When the 2nd
module gets built, is doesn't have access to the Module.symvers from the 1st
module.
Here's what the kernel's Documentation/kbuild/modules.txt file says about
symbol versioning:
====
--- 6.3 Symbols From Another External Module
Sometimes, an external module uses exported symbols from
another external module. kbuild needs to have full knowledge of
all symbols to avoid spliitting out warnings about undefined
symbols. Three solutions exist for this situation.
NOTE: The method with a top-level kbuild file is recommended
but may be impractical in certain situations.
Use a top-level kbuild file
If you have two modules, foo.ko and bar.ko, where
foo.ko needs symbols from bar.ko, you can use a
common top-level kbuild file so both modules are
compiled in the same build. Consider the following
directory layout:
./foo/ <= contains foo.ko
./bar/ <= contains bar.ko
The top-level kbuild file would then look like:
#./Kbuild (or ./Makefile):
obj-y := foo/ bar/
And executing
$ make -C $KDIR M=$PWD
will then do the expected and compile both modules with
full knowledge of symbols from either module.
Use an extra Module.symvers file
When an external module is built, a Module.symvers file
is generated containing all exported symbols which are
not defined in the kernel. To get access to symbols
from bar.ko, copy the Module.symvers file from the
compilation of bar.ko to the directory where foo.ko is
built. During the module build, kbuild will read the
Module.symvers file in the directory of the external
module, and when the build is finished, a new
Module.symvers file is created containing the sum of
all symbols defined and not part of the kernel.
Use "make" variable KBUILD_EXTRA_SYMBOLS
If it is impractical to copy Module.symvers from
another module, you can assign a space separated list
of files to KBUILD_EXTRA_SYMBOLS in your build file.
These files will be loaded by modpost during the
initialization of its symbol tables.
====
Based on that, I tried using the 3rd solution.
In one terminal for the server:
====
# stap -p4 -k testsuite/systemtap.printf/sharedbuf.stp -DRELAY_HOST=test1
stap_14594.ko
Keeping temporary directory "/tmp/stapie3sXR"
# staprun /tmp/stapie3sXR/stap_14594.ko
Host: begin
HelloWorld
====
In another terminal for the client. Notice I try first without setting
'KBUILD_EXTRA_SYMBOLS'.
====
# stap testsuite/systemtap.printf/hello.stp -DRELAY_GUEST=test1
ERROR: Couldn't insert module
'/tmp/stapYX78X6/stap_2a284551e36db9394c1f2b499dfa812b_1006.ko': Unknown symbol
in module
WARNING: /usr/local/bin/staprun exited with status: 1
Pass 5: run failed. [man error::pass5]
# KBUILD_EXTRA_SYMBOLS=/tmp/stapie3sXR/Module.symvers stap --disable-cache -v
testsuite/systemtap.printf/hello.stp -DRELAY_GUEST=test1
Pass 1: parsed user script and 95 library script(s) using
200112virt/26232res/2936shr/23760data kb, in 180usr/20sys/196real ms.
Pass 2: analyzed script: 1 probe(s), 1 function(s), 0 embed(s), 0 global(s)
using 200640virt/27016res/3208shr/24288data kb, in 0usr/0sys/5real ms.
Pass 3: translated to C into "/tmp/stap7CL6zk/stap_14836_src.c" using
200764virt/27252res/3428shr/24412data kb, in 0usr/0sys/1real ms.
Pass 4: compiled C into "stap_14836.ko" in 6950usr/1220sys/8715real ms.
Pass 5: starting run.
Pass 5: run completed in 20usr/30sys/318real ms.
====
Strangely enough sharedbuf.exp passes on rawhide
(3.11.0-0.rc0.git7.1.fc20.x86_64).
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