Debugging glibc / startup stuff via a subhurd

[Thomas Schwinge]

Hello!

So, I got glibc 2.5 natively built with a number of patches and other
ugly workarounds.  It built completely, i.e. it didn't even break at the
time where the new `ld.so' and libraries are being used for the first
time when running `rpcgen' during the build.

It even manages to run ``./testrun.sh /usr/bin/emacs -q''.  Wooho!  (Even
though I had to symlink various libraries residing in `/usr/lib/' into
`/lib/'.)

Next idea was to test it by means of using it in a subhurd.  With
Roland's ``Running a Subhurd'',
<http://gnu.org/software/hurd/howto/subhurd.html>, I tried to do exactly
that -- after having verified that the subhurd per se works with glibc
2.3 -- but it fails with glibc 2.5.  Well, it works in a way, but I was
not yet able to extract something usable from it.

(``#v+ Wx'' translates to terminal window `x'.)

#v+ W1
$ sudo boot -I -d -s -D one.full/ one.full/boot/script.boot one.full.ext2
Pausing. . .
#v-

#v+ W2
$ ps -Af
[...]
    root   851   385  p4  0:00.01 boot -I -d -s -D one.full/ 
one.full/boot/script.boot one.full.ext2
       -   853     1   ?  0:00.00 ?
       -   854     1   ?  0:00.00 ?
[...]
$ sudo gdb /var/tmp/one.full/hurd/ext2fs.static
[...]
(gdb) attach 853
Attaching to program `/var/tmp/one.full/hurd/ext2fs.static', pid 853
warning: Can't modify tracing state for pid 853: No signal thread
Can't fetch registers from thread 1: No such thread
#v-

#v+ W3
$ sudo gdb /var/tmp/one.full/hurd/exec
[...]
(gdb) set solib-absolute-prefix /var/tmp/one.full
(gdb) attach 854
Attaching to program `/var/tmp/one.full/hurd/exec', pid 854
warning: Can't modify tracing state for pid 854: No signal thread
Can't fetch registers from thread 1: No such thread
#v-

#v+ W1
[<Enter>.]
/hurd/ext2fs.static --bootflags=-dsf --host-priv-port=38 
--device-master-port=43 --exec-server-task=47 -Tdevice pseudo-root
/lib/ld.so.1 /hurd/exec
#v-

#v+ W2
(gdb) continue
Continuing.
warning: Can't wait for pid 853: No child processes
#v-

#v+ W1
Hurd server bootstrap: ext2fs.static[pseudo-root] exec
#v-

#v+ W3
(gdb) continue
Continuing.
warning: Can't wait for pid 854: No child processes

Program received signal EXC_BAD_ACCESS, Could not access memory.
0x000168f2 in ?? ()
(gdb) bt
#0  0x000168f2 in ?? ()
Cannot access memory at address 0xbeffffe4
(gdb) info threads
* 1 thread 1005.1  0x000168f2 in ?? ()
(gdb) disassemble 
No function contains program counter for selected frame.
#v-


Regards,
 Thomas

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