uclibc segfault in ldso

[Nigel Kukard]

Hi,

> > Ok, here is a vanilla uClibc from SVN....  its x86 architecture.
> > i386/pentium-mmx .
> > 
> > 
> > $ rpm
> > argc=1 argv=0xbfbe8094 envp=0xbfbe809c
> 
> [SNIP]
> > _dl_malloc:926: mmapping more memory
> > _dl_get_ready_to_run:748: Beginning relocation fixups
> > _dl_get_ready_to_run:831: calling INIT: /lib/libc.so.0, tpnt->loadaddr =
> > 0xb7bfa000, tpnt->dynamic_info[DT_INIT] = 0x54c7f, dl_elf_func =
> > 0xb7c4ec7f
> > 
> > Segmentation fault
> 
> This trace looks like it is missing LD_DEBUG=1 rpm or LD_DEBUG=all rpm,
> such a trace can get very big so you need to trim it down before
> posting. You also need SUPPORT_LD_DEBUG=y in .config

Stupid busybox, it didn't export the env variable .... I'm rebuilding a
static sh now.

Uploaded RPM debug to ... http://www.linuxrulz.org/nkukard/rpm.log

Uploaded my test PIE app to ... http://www.linuxrulz.org/nkukard/rpm.log

> Are you sure that it is the call to 
> DL_CALL_FUNC_AT_ADDR (dl_elf_func, tpnt->loadaddr, (void(*)(void)));
> that SEGVs? A printout before and after will confirm that.

Just confirmed it, thats definitely where its choking.

> Also, you said earlier that dl_elf_func was the same for a successful
> and a failed run? You need to do the printout I asked for in both cases
> to confirm that.

RPM always fails. Other executables which aren't PIE work no problem at
all. And the test C app I wrote works fine, simple hello world'er with
-fPIE -pie .

> Anyhow, assuming it is the libc's INIT that SEGs, try setting a BP in
> libc/misc/internals/__uClibc_main.c, __uClibc_init() and single step to
> see what SEGs.

I wrote a simple 5 liner C app to test PIE ... it works, the RPM
executable doesn't so it must be something unique to this case.

Let me see what I can do. Just having trouble getting the symbol names
in gdb, I've enabled all debugging info with -g3 and rebuilt uclibc,
then copied the .so's over ... but still getting ??'s in my gdb
backtrace ... hrmmm.


-N
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