mod_perl segmentation fault - apache

HI,
I'm running an apache 2.2.3 on an Oracle64-bit (Red Hat clone) and I'm hitting a brick wall with an issue. I have a program which utilizes MIME::Lite to send mail through sendmail (I apologize, not sure what versions of sendmail or mod_perl I'm running, although I do believe the sendmail portion is irrelevant as you'll see in a moment)
On occasion, apache will segfault (11), and digging deep into the MIME::Lite module, I see it is on the following line:
open SENDMAIL, "|$sendmailcmd" or Carp::croak "open |$sendmailcmd: $!\n"; (this is in MIME::Lite)
Now, one would automatically suspect sendmail, but if I did the same line to use /bin/cat (as shown):
open SENDMAIL, "|/bin/cat"
apache still segfaults.
I attached an strace to the apache processes and see the following:
(when it does NOT crash)
12907 write(2, "SENDMAIL send_by_sendmail 1\n", 28) = 28
12907 write(2, "SENDMAIL /usr/lib/sendmail -t -o"..., 40) = 40
12907 pipe([24, 26]) = 0
12907 pipe([28, 29]) = 0
12907 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x2b4bcbbd75d0) = 13186
Note the "SENDMAIL sent_by_sendmail" are my comments. You can clearly see pipes opening. When it DOES crash, you'll see the following:
10805 write(2, "SENDMAIL send_by_sendmail (for y"..., 40) = 40
10805 --- SIGSEGV (Segmentation fault) # 0 (0) ---
Now notice it never pipes. I've tried GDB and it hasn't really shown me anything.
Finally, I wrote a simple program to run through mod_perl and regular cgi:
print header();
print "test";
open SENDMAIL, "|/bin/cat" or Carp::croak "open |sendmailcmd: $!\n";
print SENDMAIL "foodaddy";
close SENDMAIL;
print "test done <br/>";
Under mod_perl it has successfully crashed.
My analysis is telling me it has to do with it trying to open a file handle, the piping function returns either false or a corrupt file handle.
I also increased the file descriptor limit to 2048, no dice.
Does anyone have any thoughts as to where I should look? Any thoughts?
I appreciate the help

I just spent a long time tracking down a problem that started with identical symptoms. I eventually discovered that Test::More does not play well with mod_perl . Removing this module from my code appears to have solved the problem (so far!). I didn't follow this any deeper, but I suspect that the problem actually lies in Test::Builder.

I managed to treat perhaps only the symptoms, not the cause. I happened to have this issue when used global/package scope variables on the package level, used inside a perl object instance, as soon as I passed them as object properties instead, not as automatic default perl variables scoping, I stopped to experience perl segmentation fault suddenly.

Related

Valgrind(memcheck) not showing all contexts

My last context/error I see in my valgrind output file is...
==3030== 1075 errors in context 61 of 540:
==3030== Syscall param ioctl(SIOCETHTOOL,ir) points to uninitialised byte(s)
==3030== at 0x7525248: ioctl (syscall-template.S:84)
==3030== by 0x686A2A7: ??? (in /lib/libpal.so)
==3030== Address 0x96cf958 is on thread 16's stack
==3030== Uninitialised value was created by a stack allocation
==3030== at 0x686A20C: ??? (in /lib/libpal.so)
...but I don't see error contexts 62 - 540. My first thought was maybe in closing the program, valgrind crashed, but after this context it printed the ERROR SUMMARY
ERROR SUMMARY: 9733 errors from 540 contexts (suppressed: 0 from 0)
I don't think it's because we came across a frame without debug info because I can see this exact same issue get hit the first time at the very beginning of my output file. Or maybe the printing of error contexts specifically, is halted when a stacktrace has missing debug info?
Any ideas? Need an additional command line argument for valgrind? I know in helgrind it'll quit after seeing 1000000 errors(something like that) but it explicitly tells you what it's doing.
So for my version of valgrind I also executed helgrind and saw all contexts(647) as expected. I think the problem above is simply a result of valgrind coming across a frame with no debug symbols and saying, "If there's no debug info, I'm moving on"
All of my logs I'm producing end with this same libpal frame at various context numbers 100-something, 200-something, etc.

How to interact with a subprocess through its stdin, stdout, stderr in Smalltalk?

This Python code shows how to call some process in Windows 10 and to send to it string commands, to read its string responses through stdin, stdout pipes of the process:
Python 3.8.0 (tags/v3.8.0:fa919fd, Oct 14 2019, 19:37:50) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from subprocess import *
>>> p = Popen("c:/python38/python.exe", stdin=PIPE, stdout=PIPE)
>>> p.stdin.write(b"print(1+9)\n")
11
>>> p.communicate()
(b'10\r\n', None)
>>>
As you can see the python.exe process returned 10 as an answer to print(1+9). Now I want to do the same in Pharo (or Squeak): in Windows 10 OS - I suppose something similar, i.e. short, simple, understandable, really working.
I installed OSProcess, ProcessWrapper (they were missing in Pharo, also its strange that I got warning that they are not marked for Pharo 8.0 and were not checked to work in Pharo 8.0, but OK), and I tried ProcessWrapper, PipeableOSProcess (copy-pasted different snippets from the Web), etc - with zero success! The results were:
nothing happens, python.exe was not started
VM errors console was opened (white console in the bottom of the Pharo, which is controlled with F2 menu)
different exceptions
etc
Would somebody show me simple working example how to start a process and to to send it commands, read answers, then send again, and so on in some loop - I plan to have such communication in a detached thread and to use it as some service, because Pharo, Smalltalk in general is missing most bindings, so then I will use subprocess communication like in "good" old days...
I know how to call a command and to get its output:
out := LibC resultOfCommand: 'dir ', aDir.
but I am talking about another scenario: a communication with a running process interactively (for example, with SSH or similar like in the example above - python.exe).
PS. Maybe it's possible to do it with LibC #pipe:mode even?
Let me start with that the PipeableOsProcess is probably broken on Windows. I have tried it and it just opened a command line and nothing else (it does not freeze my Pharo 8). The whole OSProcess does not work correctly in my eyes.
So I took a shot at LibC which is supposed to not work with Windows.
I’m a module defining access to standard LibC. I’m available under Linux and OSX, but not under Windows for obvious reasons :)
Next is to say that Python's Windows support is probably much better than Pharo's.
The solution, which is more like a workaround using files, is to use LibC and #runCommand: (I tried to come up with a similar example as you had shown above):
| count command result outputFile errorFile |
count := 9+1. "The counting"
command := 'echo ', count asString. "command run at the command line"
outputFile := 'output'. "a file into which the output is redirected"
errorFile := 'error'. "a file where the error output is redirected "
result := LibC runCommand: command, "run the command "
' >', outputFile, "redirect the output to output file"
' 2>', errorFile.
"reading back the value from output file"
outputFile asFileReference contents lines.
"reading back the value from the error file - which is empty in this case"
errorFile asFileReference contents lines.

Is it possible to enable exit on error behavior in an interactive Tcl shell?

I need to automate a huge interactive Tcl program using Tcl expect.
As I realized, this territory is really dangerous, as I need to extend the already existing mass of code, but I can't rely on errors actually causing the program to fail with a positive exit code as I could in a regular script.
This means I have to think about every possible thing that could go wrong and "expect" it.
What I currently do is use a "die" procedure instead of raising an error in my own code, that automatically exits. But this kind of error condition can not be catched, and makes it hard to detect errors especially in code not written by me, since ultimately, most library routines will be error-based.
Since I have access to the program's Tcl shell, is it possible to enable fail-on-error?
EDIT:
I am using Tcl 8.3, which is a severe limitation in terms of available tools.
Examples of errors I'd like to automatically exit on:
% puts $a(2)
can't read "a(2)": no such element in array
while evaluating {puts $a(2)}
%
% blublabla
invalid command name "blublabla"
while evaluating blublabla
%
As well as any other error that makes a normal script terminate.
These can bubble up from 10 levels deep within procedure calls.
I also tried redefining the global error command, but not all errors that can occur in Tcl use it. For instance, the above "command not found" error did not go through my custom error procedure.
Since I have access to the program's Tcl shell, is it possible to
enable fail-on-error?
Let me try to summarize in my words: You want to exit from an interactive Tcl shell upon error, rather than having the prompt offered again?
Update
I am using Tcl 8.3, which is a severe limitation in terms of available
tools [...] only source patches to the C code.
As you seem to be deep down in that rabbit hole, why not add another source patch?
--- tclMain.c 2002-03-26 03:26:58.000000000 +0100
+++ tclMain.c.mrcalvin 2019-10-23 22:49:14.000000000 +0200
## -328,6 +328,7 ##
Tcl_WriteObj(errChannel, Tcl_GetObjResult(interp));
Tcl_WriteChars(errChannel, "\n", 1);
}
+ Tcl_Exit(1);
} else if (tsdPtr->tty) {
resultPtr = Tcl_GetObjResult(interp);
Tcl_GetStringFromObj(resultPtr, &length);
This is untested, the Tcl 8.3.5 sources don't compile for me. But this section of Tcl's internal are comparable to current sources, tested using my Tcl 8.6 source installation.
For the records
With a stock shell (tclsh), this is a little fiddly, I am afraid. The following might work for you (though, I can imagine cases where this might fail you). The idea is
to intercept writes to stderr (this is to where an interactive shell redirects error messages, before returning to the prompt).
to discriminate between arbitrary writes to stderr and error cases, one can use the global variable ::errorInfo as a sentinel.
Step 1: Define a channel interceptor
oo::class create Bouncer {
method initialize {handle mode} {
if {$mode ne "write"} {error "can't handle reading"}
return {finalize initialize write}
}
method finalize {handle} {
# NOOP
}
method write {handle bytes} {
if {[info exists ::errorInfo]} {
# This is an actual error;
# 1) Print the message (as usual), but to stdout
fconfigure stdout -translation binary
puts stdout $bytes
# 2) Call on [exit] to quit the Tcl process
exit 1
} else {
# Non-error write to stderr, proceed as usual
return $bytes
}
}
}
Step 2: Register the interceptor for stderr in interactive shells
if {[info exists ::tcl_interactive]} {
chan push stderr [Bouncer new]
}
Once registered, this will make your interactive shell behave like so:
% puts stderr "Goes, as usual!"
Goes, as usual!
% error "Bye, bye"
Bye, bye
Some remarks
You need to be careful about the Bouncer's write method, the error message has already been massaged for the character encoding (therefore, the fconfigure call).
You might want to put this into a Tcl package or Tcl module, to load the bouncer using package req.
I could imagine that your program writes to stderr and the errorInfo variable happens to be set (as a left-over), this will trigger an unintended exit.

opensplice dds Hello Word Example

I am posting here after asking the question at the openslice dds forum, and not receiving any reply.I am trying to use opensplice dds on a ubuntu machine. I am not sure if it serves as a proof of proper installation, but I have pasted my release.com file below. Now, I was able to run the ping pong example just fine. But when I ran the executable sac_helloworld_pub ( HelloWorld example in the C programming language), I got the following error
vishal#expmach:~/HDE/x86.linux2.6/examples/dcps/HelloWorld/c/standalone$ ./sac_helloworld_pub
Error in DDS_DomainParticipantFactory_create_participant: Creation failed: invalid handle
I did some searching, and it looks like I need to be running the ospl start command from the terminal. But when I do so, I get a No command ospl found message. Below is the release.comfile's contents
echo "<<< OpenSplice HDE Release V6.3.130716OSS For x86.linux2.6, Date 2013-07-30 >>>"
if [ "${SPLICE_ORB:=}" = "" ]
then
SPLICE_ORB=DDS_OpenFusion_1_6_1
export SPLICE_ORB
fi
if [ "${SPLICE_JDK:=}" = "" ]
then
SPLICE_JDK=jdk
export SPLICE_JDK
fi
OSPL_HOME="/home/vishal/HDE/x86.linux2.6"
OSPL_TARGET=x86.linux2.6
PATH=$OSPL_HOME/bin:$PATH
LD_LIBRARY_PATH=$OSPL_HOME/lib${LD_LIBRARY_PATH:+:}$LD_LIBRARY_PATH
CPATH=$OSPL_HOME/include:$OSPL_HOME/include/sys:${CPATH:=}
OSPL_URI=file://$OSPL_HOME/etc/config/ospl.xml
OSPL_TMPL_PATH=$OSPL_HOME/etc/idlpp
. $OSPL_HOME/etc/java/defs.$SPLICE_JDK
export OSPL_HOME OSPL_TARGET PATH LD_LIBRARY_PATH CPATH OSPL_TMPL_PATH OSPL_URI
$#
release.com (END)
Sorry for the holidays-driven lack of 'reactivity' on the OpenSplice forum .. I've answered your question there though ..
Here's that same answer for completeness:
*For the 6.3 community-edition, the deployment-model changed from shared-memory (v5.x) to the so-called single-process standalone deployment mode where the middleware is simply linked (as libraries) with the application so you don't need to start any daemons first (as was the case for the federated 'shared-memory' mode that was the default in V5).
So its OK that you get the error when trying to call 'ospl' as thats not used anymore so isn't in the distribution.
Now to your issue, your release.com looks OK to me, but perhaps you didn't actually 'source' it in your environment i.e. calling it with a '.' in front of it:
promtp> . release.com
you can verify that by doing an 'echo $OSPL_HOME' in your shell and see if it actually shows the value of the env. variable as set by the release.com.
Hope that helps,
-Hans*

Bad spawn_id while executing expect command

I am writing a script that will copy Valgrind onto whatever shelf that we enter on the command line. The syntax is as follows:
vgrindCopy [shelf number]
For some reason, the files will copy over without any issue, but after the copy completes the follow error is observed:
bad spawn_id (process died earlier?)
while executing
"expect "#""
Here is a copy of the relevant code:
function login_shelf {
expect -c "
set timeout 15
spawn $1
expect \"password:\"
send \"$PW\r\"
expect \"#\"
sleep 1
exit
"
}
# login and make the valgrind directory at /sfs/software/shelf/current
set -- /opt/swe/tools/ext/gnu/valgrind-3.7.0/i686-linux2.6/lib/valgrind/*
login_shelf "/opt/corp/projects/shelftools/bin/app rsync -Lau $* $shelf:/shelf/valgrind"
After playing around with the code, I found that if I remove the line "expect \"#\"", then the program doesn't copy any of the files over anymore. What odd as well is that I'm seeing the issue when I run the script, but a co-worker is not.
Has anyone had a similar issue and determined the cause? Any help would be greatly appreciated as always!
Your code is spawning the rsync and at the expect \"#\" is waiting for rsync to output a #, which it never does, so it exits and expect reports the error.
When you remove the expect \"#\" the expect script exits, terminating the rsync.
Instead of expect \"#\" you should wait for rsync to exit:
expect eof
wait