busybox segfault in __uClibc_main

[Joakim Tjernlund]

> 
> Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:
> >> Christopher, thanx for the hints. Rob, I think I found the problem.
> >> I made the following changes and it works (for me!):
> >>
> >>
> >> --- uClibc-0.9.28.orig/libc/sysdeps/linux/powerpc/crt1.S	
> >> 2005-12-05 21:19:20.000000000 -0500
> >> +++ uClibc-0.9.28/libc/sysdeps/linux/powerpc/crt1.S	
> >> 2005-12-05 21:19:09.000000000 -0500
> >> @@ -61,6 +61,10 @@ _start:
> >> 	/* find argv one word offset from the stack pointer */
> >> 	addi	r5,r9,4
> >> 	mr	r8,r7 /* Pass _dl_fini from ldso or NULL if 
> >> statically linked */
> >> +        mr.     r4,r4 /* abi said top of stack must be NULL */
> >> +        beq     from_ldso
> >> +        li      r8,0
> >> +from_ldso:      
> >> 	/* Ok, now run uClibc's main() -- shouldn't return */
> >> #ifdef __PIC__
> >> 	lwz	r6,_init at got(r31)
> >
> > uh, this looks strange, I checked in 2.4 that linux cleared all
> > relevant registers(r7 in this case) before calling user space. Why
> > is this not true anymore in 2.6? hmm, I can run 2.6.15-rc1 here so I
> > think you kernel is broken.
> 
> I run vanilla 2.6.14 and I dont think it's broken.
> 
> >
> > Anyhow this patch is wrong and won't work for the non static case,
> > r8 will always be cleared and thus no destructors will be executed
> > during exit().
> 
> Did you test it? it works for me both static and dynamic (i.e
> rtld_fini got called in a dynamic linked prog)

Nope, didn't test it.

> 
> I think you mis-read the patch.

Maybe(need to check my assembler skills I guess), I read it as:
if(r4)
   r8 = 0;

r4 holds argc and I don't get how it can be anything but non zero so
this should always clear r8 and you don't want that for dynamic apps.

 Jocke