Executing perl via cgid on solaris fails in 64 bit, but works in 32 bit – Apache

I have a custom build of apache’s httpd version 2.2 together with perl version 5.22 on solaris 10. The httpd runs in a chroot environment, and the perl script is executed via httpd’s mod_cgid. So far all was in 32 bit things worked. Now I have compiled everything in 64 bit (because another httpd module is only provided as a 64 bit binary), and now I cannot get the perl script to be executed via cgid.

The http error log contains the line

Premature end of script headers.

So I tried to execute my test script without cgid, just using perl inside the chroot, and besides some warnings it just worked fine. Here is my script, if its of any interest:

#!/local/perl5/bin/perl
print "Content-type: text/plainnn";
opendir(DIRHANDLE, "/");
@filenames = readdir(DIRHANDLE);
foreach $file (@filenames) { print "$filen"; }
closedir(DIRHANDLE);

(I know its not a great one :))

The warnings were about the locale not being set, so I fixed that by adding /usr/lib/locale to the chroot. This fixed the warnings, but did not fix the original problem. So I assume this was not the root cause. Even more so, when I compared to the 32 bit build, I got the same warnings, however the script would execute fine via cgid.

Next thing I did was to trace the systemcalls via truss -f -o mylogfile.txt. The full output can be found on pastebin (32 bit truss). Here is an excerpt for the 32 bit build (line 4296 on pastebin) – note that paths are not exactly the same as on pastebin, but the observed result is the same:

28420:  sigaction(SIGCLD, 0xFFBFF6A8, 0xFFBFF748)       = 0
28420:  chdir("/path/to/my/chroot/cgi-bin/") = 0
28420:  execve("/path/to/my/chroot/cgi-bin/test.pl", 0x00183DB8, 0x00183570)  argc = 3
28420:      *** SUID: ruid/euid/suid = 50001 / 50001 / 50001  ***
28420:      *** SGID: rgid/egid/sgid = 50001 / 50001 / 50001  ***
28420:  sysinfo(SI_MACHINE, "sun4u", 257)               = 6

And here is the truss output for the 64 bit build. The following is an excerpt (line 4489), note I left out some lines, denoted by [...]:

28906/21:       open("/dev/urandom", O_RDONLY)                  = 12
[...]
28911:  sigaction(SIGCLD, 0xFFFFFFFF7FFFF150, 0xFFFFFFFF7FFFF250) = 0
28911:  chdir("/path/to/my/chroot/cgi-bin/") = 0
28906/21:       pollsys(0xFFFFFFFF747F7080, 1, 0xFFFFFFFF747F6FA0, 0x00000000) = 1
28906/21:       read(12, 0x10034BB38, 8000)                     = 0
28906/21:       close(12)                                       = 0
[...]
28906/21:       read(10, " pEF", 4)                         = 4
28906/21:       kill(28911, SIGTERM)                            Err#3 ESRCH
28904:  close(4)                                        = 0

As Andrew Haenle noticed, I did not execute the same scripts in 32 bit vs 64 bit – at least in the truss output shown above. So here is the truss output for the failing 64 bit, where I execute the same script as in 32 bit: https://pastebin.com/Nz1jBjne

Here is some more truss output from the 64 bit build, with the additional flags -a -e -d: https://pastebin.com/4NMGD2aR

The way I interpret this is that after changing to the cgi-bin directory, cgid gets killed in 64 bit, vs. executing the script in 32 bit.
Permissions are the same, so I do not see what is the problem here. At least it explains the message from the error log – since the script is not executed, no headers are ever printed.

Anyway, I am a bit lost where to go from here. Any hints how to debug this further would be highly appreciated.