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From Steve Waltner <swalt...@lsil.com>
Subject Re: Need Help Debugging Shared Library (libaprutil-0.so)
Date Thu, 06 May 2004 15:54:13 GMT
On May 5, 2004, at 6:50 PM, Stas Bekman wrote:
> Steve Waltner wrote:
>> http://nagoya.apache.org/bugzilla/show_bug.cgi?id=21719
>> Since my submitted bug hasn't been resolved in the 9 months since I 
>> first reported it, I figure it's about time I try and resolve this 
>> problem myself since I do have the source code. I've done a partial 
>> debug on the failure but can't get everything figured out since I 
>> can't get DDD/gdb to debug some of the code (coming from 
>> apr_ldap_url.c).
>> I'm currently using the 2.0.49 source tree for my testing. The 
>> problem starts in mod_auth_ldap.c. When I load the source in ddd, I 
>> get an error stating:
>> Line 1 of "mod_auth_ldap.c" is at address 0x2ebd4 
>> <derive_codepage_from_lang> but contains no code.
>
> You need two things:
>
> 1) compile with debug symbols retained which you get when building 
> apache with --enable-maintainer-mode
>
> 2) make sure to load the library from gdb (or DDD's gdb console):
>
> gdb> sharedlib apr
>
> or whichever lib it is.
>
> You may find some useful notes here:
> http://perl.apache.org/docs/2.0/devel/debug/c.html
> There are for debugging mod_perl 2.0, but most of it applies to any 
> other shared C library.

Thanks for the information but it still doesn't seem to be working 
correctly. If this is a topic that I should take over to a gdb mailing 
list, let me know. I started with a clean unpack of the Apache 2.0.49 
source tarball and configure it with the following command:

./configure --enable-maintainer-mode --with-ldap --enable-ldap 
--enable-auth-ldap --prefix=/tmp/apache-test
make
make install
cp /tmp/httpd.conf /tmp/apache-test/conf/httpd.conf

I made the following changes to the httpd.conf file. This go into the 
cgi-bin Directory block since I'm trying to protect the cgi-bin 
directory:

=================
dumbo:/tmp/apache-test> diff -c /tmp/apache-test/conf/httpd-std.conf 
/tmp/httpd.conf
*** /tmp/apache-test/conf/httpd-std.conf        Thu May  6 10:10:55 2004
--- /tmp/httpd.conf     Wed May  5 09:15:22 2004
***************
*** 609,614 ****
--- 609,621 ----
       Options None
       Order allow,deny
       Allow from all
+
+     AuthName "Admin Page"
+     AuthType Basic
+     AuthLDAPEnabled on
+     AuthLDAPAuthoritative on
+     AuthLDAPURL ldap://ldap.lsil.com/ou=lsil.com,o=LSI%20Logic?uid
+     require valid-user
   </Directory>

   #
dumbo:/tmp/apache-test>
=================

Trying this with straight gdb instead of ddd/gdb, I get the following:

=====================
dumbo:/tmp/apache-test> gdb bin/httpd
GNU gdb 6.1
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and 
you are
welcome to change it and/or distribute copies of it under certain 
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for 
details.
This GDB was configured as "sparc-sun-solaris2.9"...
(gdb) info shared
No shared libraries loaded at this time.
(gdb) b mod_auth_ldap.c:702
Breakpoint 1 at 0x2fec8: file mod_auth_ldap.c, line 702.
(gdb) run -k start
Starting program: /tmp/apache-test/bin/httpd -k start

Breakpoint 1, mod_auth_ldap_parse_url (cmd=0xffbffb78, config=0xea998,
     url=0xeaa80 "ldap://ldap.lsil.com/ou=lsil.com,o=LSI%20Logic?uid")
     at mod_auth_ldap.c:702
702         result = apr_ldap_url_parse(url, &(urld));
(gdb) info shared
 From        To          Syms Read   Shared Object Library
0xff3847f4  0xff3929d0  Yes         
/tmp/apache-test/lib/libaprutil-0.so.0
0xff20d5a0  0xff2cb564  Yes         /usr/lib/libldap.so.5
0xff342638  0xff35aa48  Yes         /tmp/apache-test/lib/libexpat.so.0
0xff1c8064  0xff1dd4e4  Yes         /tmp/apache-test/lib/libapr-0.so.0
0xff3104bc  0xff310634  Yes         /usr/lib/libsendfile.so.1
0xff1a2494  0xff1a51b8  Yes         /usr/lib/librt.so.1
0xff171a40  0xff180f24  Yes         /usr/lib/libm.so.1
0xff1535e0  0xff1595a4  Yes         /usr/lib/libsocket.so.1
0xff0940f8  0xff10098c  Yes         /usr/lib/libnsl.so.1
0xff028ab8  0xff057134  Yes         /usr/lib/libresolv.so.2
0xff0039f4  0xff003ffc  Yes         /usr/lib/libpthread.so.1
0xff3b0704  0xff3b075c  Yes         /usr/lib/libdl.so.1
0xfef1ca08  0xfef9f038  Yes         /usr/lib/libc.so.1
0xfefd04f4  0xfefd1510  Yes         /usr/lib/libmd5.so.1
0xfeee1a8c  0xfeee7dd4  Yes         /usr/lib/libaio.so.1
0xfeec09a0  0xfeec2950  Yes         /usr/lib/libmp.so.2
0xfeeb0420  0xfeeb34e8  Yes         
/usr/platform/SUNW,Ultra-Enterprise/lib/libc_psr.so.1
0xfee873b0  0xfee96100  Yes         /usr/lib/libthread.so.1
(gdb) b apr_ldap_url.c:255
No line 255 in file "apr_ldap_url.c".
(gdb) b ldap_url_parse_ext
Function "ldap_url_parse_ext" not defined.
Make breakpoint pending on future shared library load? (y or [n])
(gdb) quit
The program is running.  Exit anyway? (y or n) y
dumbo:/tmp/apache-test>
=====================

I haven't turned off the autoload shared libraries, so gdb does try to 
load debug symbols from the libaprutil file, but it still appears as 
though it's not working properly since I can't set a breakpoint in 
apr_ldap_url.c or step into the function.

Looking at the output of make, it appears as though the build process 
does the needed debugging flags...

=====================
make[4]: Entering directory `/tmp/httpd-2.0.49/srclib/apr-util/ldap'
/bin/bash /tmp/httpd-2.0.49/srclib/apr/libtool --silent --mode=compile 
gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes 
-Wmissing-declarations -pthreads   -DHAVE_CONFIG_H -DSOLARIS2=9 
-D_POSIX_PTHREAD_SEMANTICS -D_REENTRANT   
-I/tmp/httpd-2.0.49/srclib/apr-util/include 
-I/tmp/httpd-2.0.49/srclib/apr-util/include/private  
-I/tmp/httpd-2.0.49/srclib/apr/include  
-I/tmp/httpd-2.0.49/srclib/apr-util/xml/expat/lib  -c apr_ldap_compat.c 
&& touch apr_ldap_compat.lo
/bin/bash /tmp/httpd-2.0.49/srclib/apr/libtool --silent --mode=compile 
gcc -g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes 
-Wmissing-declarations -pthreads   -DHAVE_CONFIG_H -DSOLARIS2=9 
-D_POSIX_PTHREAD_SEMANTICS -D_REENTRANT   
-I/tmp/httpd-2.0.49/srclib/apr-util/include 
-I/tmp/httpd-2.0.49/srclib/apr-util/include/private  
-I/tmp/httpd-2.0.49/srclib/apr/include  
-I/tmp/httpd-2.0.49/srclib/apr-util/xml/expat/lib  -c apr_ldap_url.c && 
touch apr_ldap_url.lo
make[4]: Leaving directory `/tmp/httpd-2.0.49/srclib/apr-util/ldap'

[snip]

make[3]: Entering directory `/tmp/httpd-2.0.49/srclib/apr-util'
/bin/bash /tmp/httpd-2.0.49/srclib/apr/libtool --silent --mode=link gcc 
-g -O2 -Wall -Wmissing-prototypes -Wstrict-prototypes 
-Wmissing-declarations -pthreads -DHAVE_CONFIG_H -DSOLARIS2=9 
-D_POSIX_PTHREAD_SEMANTICS -D_REENTRANT 
-I/tmp/httpd-2.0.49/srclib/apr-util/include 
-I/tmp/httpd-2.0.49/srclib/apr-util/include/private 
-I/tmp/httpd-2.0.49/srclib/apr/include 
-I/tmp/httpd-2.0.49/srclib/apr-util/xml/expat/lib -version-info 9:5:9 
-o libaprutil-0.la -rpath /tmp/apache-test/lib 
buckets/apr_buckets_refcount.lo buckets/apr_buckets_pool.lo 
buckets/apr_buckets_simple.lo buckets/apr_buckets.lo 
buckets/apr_buckets_flush.lo buckets/apr_buckets_heap.lo 
buckets/apr_buckets_file.lo buckets/apr_buckets_eos.lo 
buckets/apr_buckets_mmap.lo buckets/apr_buckets_socket.lo 
buckets/apr_buckets_pipe.lo buckets/apr_buckets_alloc.lo 
buckets/apr_brigade.lo crypto/uuid.lo crypto/getuuid.lo 
crypto/apr_md4.lo crypto/apr_md5.lo crypto/apr_sha1.lo 
dbm/sdbm/sdbm_hash.lo dbm/sdbm/sdbm_lock.lo dbm/sdbm/sdbm_pair.lo 
dbm/sdbm/sdbm.lo dbm/apr_dbm_berkeleydb.lo dbm/apr_dbm_gdbm.lo 
dbm/apr_dbm_ndbm.lo dbm/apr_dbm_sdbm.lo dbm/apr_dbm.lo 
encoding/apr_base64.lo hooks/apr_hooks.lo ldap/apr_ldap_compat.lo 
ldap/apr_ldap_url.lo uri/apr_uri.lo xml/apr_xml.lo misc/apu_version.lo 
misc/apr_reslist.lo misc/apr_queue.lo misc/apr_rmm.lo misc/apr_date.lo 
strmatch/apr_strmatch.lo xlate/xlate.lo
=====================

I posted a screen capture out the DDD output after apr_ldap_url_parse 
returns at http://homepage.mac.com/swaltner/corrupted.gif. You can see 
that the structure that is returned is corrupted with many values 
placed in the wrong location as well as a char* in the lud_attrs 
pointing off into space which is causing my segmentation fault a couple 
lines of code later on.

Is it possible to easily statically link httpd and libaprutil.so? This 
might be a way to workaround the problem I'm having debugging the 
apr_ldap_url.c file.

Steve


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