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Posted to dev@httpd.apache.org by Steve Waltner <sw...@lsil.com> on 2004/05/06 00:57:48 UTC
Need Help Debugging Shared Library (libaprutil-0.so)
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.
This doesn't seem to be a fatal error since I can go in and set
breakpoints in the file. I set a breakpoint at line 702 and start the
program. At this point, url looks good since it contains the
AuthLDAPURL entry from my config file. I continue on to line 703 and
urld contains bogus data. The host and filter parameters are swapped,
the lud_attrs points off into oblivion (causing the segfault in the
apr_pstrdup call on line 755, which is the final death for the
process).
The problem comes in the fact that I can't seem to trace anything
inside apr_ldap_url.c, which is where the real problems seem to lie.
When I load this source file, gdb spits out the error:
Line number 1 is out of range for "apr_ldap_url.c".
The function ldap_url_parse_ext() is not processing URLs properly on
Solaris-SPARC, but does work fine on Linux-x86 (endian-ness error?).
When I try to set a breakpoint in apr_ldap_url.c, I get:
No line 255 in file "apr_ldap_url.c".
I believe this is due to the fact that this is coming in from a shared
library instead of statically linked libraries and have tried to get
around this by linking httpd statically, but that seems to be a royal
pain to accomplish. Even when I add the --enable-static-htpasswd
argument to configure, it comes up with a dynamically linked
executable. Is there any way to get httpd to be statically linked so I
can do source level debugging on ldap_url_parse_ext(). I could just
read through the ~300 lines of code, but it would be much easier to
find the problem by looking at all the variables as the function is
running to see where the problems are.
Steve
Re: Need Help Debugging Shared Library (libaprutil-0.so)
Posted by Stas Bekman <st...@stason.org>.
Steve Waltner wrote:
>> 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
[...]
> (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...
right
> 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
[...]
> encoding/apr_base64.lo hooks/apr_hooks.lo ldap/apr_ldap_compat.lo
> ldap/apr_ldap_url.lo
.lo gets linked alright, but it doesn't have any symbols:
httpd-2.0/srclib> nm apr-util/ldap/apr_ldap*o
The explanation comes from:
#if APR_HAS_LDAP
#if !APR_HAS_LDAP_URL_PARSE
in apr_ldap_url.c and the header file apr_ldap_url.h:
#if APR_HAS_LDAP
#if APR_HAS_LDAP_URL_PARSE
#define apr_ldap_url_desc_t LDAPURLDesc
#define apr_ldap_is_ldap_url(url) ldap_is_ldap_url(url)
#define apr_ldap_is_ldaps_url(url) ldap_is_ldaps_url(url)
#define apr_ldap_is_ldapi_url(url) ldap_is_ldapi_url(url)
#define apr_ldap_url_parse(url, ludpp) ldap_url_parse(url, ludpp)
#define apr_ldap_free_urldesc(ludp) ldap_free_urldesc(ludp)
#else /* ! APR_HAS_LDAP_URL_PARSE */
So you have the implementation elsewhere. ldap_url_parse_ext doesn't exist at
all. You need to break at: ldap_url_parse or similar, I can't see
ldap_url_parse_ext there.
Though I'm not sure who links against libldap (neither libaprutil nor httpd
are linked against it on my machine), I will leave it here for you to discover
that. ldd and nm, should help you to discover that.
--
__________________________________________________________________
Stas Bekman JAm_pH ------> Just Another mod_perl Hacker
http://stason.org/ mod_perl Guide ---> http://perl.apache.org
mailto:stas@stason.org http://use.perl.org http://apacheweek.com
http://modperlbook.org http://apache.org http://ticketmaster.com
Re: Need Help Debugging Shared Library (libaprutil-0.so)
Posted by Steve Waltner <sw...@lsil.com>.
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
Re: Need Help Debugging Shared Library (libaprutil-0.so)
Posted by Stas Bekman <st...@stason.org>.
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.
__________________________________________________________________
Stas Bekman JAm_pH ------> Just Another mod_perl Hacker
http://stason.org/ mod_perl Guide ---> http://perl.apache.org
mailto:stas@stason.org http://use.perl.org http://apacheweek.com
http://modperlbook.org http://apache.org http://ticketmaster.com