Re: CFA expression failure

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Jun 24, 2008 at 08:40:18PM -0700, H.J. Lu wrote:
> On Wed, Jun 25, 2008 at 10:02:40AM +0800, Joey Ye wrote:
> > Daniel,
> > 
> > We generate following DWARF2 instructions for stack alignment prologue.
> > Basically we use expression to calculate CFA. But it run into some
> > segfault in libmudflap and libjava. Do you have any hints what's wrong?
> > 
> >   DW_CFA_def_cfa: r4 (esp) ofs 4
> >   DW_CFA_offset: r8 (eip) at cfa-4
> >   DW_CFA_nop
> >   DW_CFA_nop
> > 
> > 0000001c 0000002c 00000020 FDE cie=00000000 pc=00000000..00000083
> >   DW_CFA_advance_loc: 1 to 00000001
> >   DW_CFA_def_cfa_offset: 8
> >   DW_CFA_offset: r7 (edi) at cfa-8
> >   DW_CFA_advance_loc: 4 to 00000005
> >   DW_CFA_def_cfa: r7 (edi) ofs 0
> >   DW_CFA_advance_loc: 7 to 0000000c
> >   DW_CFA_expression: r5 (ebp) (DW_OP_breg5: 0)
> >   DW_CFA_advance_loc: 37 to 00000031
> >   DW_CFA_def_cfa_expression (DW_OP_breg5: -4; DW_OP_deref)
> >   DW_CFA_expression: r6 (esi) (DW_OP_breg5: -8)
> >   DW_CFA_expression: r3 (ebx) (DW_OP_breg5: -12)
> > 
> > 00000000 <_Z3bariii>:
> >    0:   57                      push   %edi
> >    1:   8d 7c 24 08             lea    0x8(%esp),%edi
> >    5:   83 e4 e0                and    $0xffffffe0,%esp
> >    8:   ff 77 fc                pushl  -0x4(%edi)
> >    b:   55                      push   %ebp
> >    c:   89 e5                   mov    %esp,%ebp
> >    e:   81 ec 88 00 00 00       sub    $0x88,%esp
> >   14:   89 45 c4                mov    %eax,-0x3c(%ebp)
> >   17:   89 c8                   mov    %ecx,%eax
> >   19:   83 c0 1e                add    $0x1e,%eax
> >   1c:   83 e0 f0                and    $0xfffffff0,%eax
> >   1f:   89 5c 24 7c             mov    %ebx,0x7c(%esp)
> >   23:   89 b4 24 80 00 00 00    mov    %esi,0x80(%esp)
> >   2a:   89 bc 24 84 00 00 00    mov    %edi,0x84(%esp)
> >   31:   29 c4                   sub    %eax,%esp
> > 
> 
> I think the problem is in uw_update_context_1.  REG_SAVED_EXP
> and REG_SAVED_VAL_EXP may use other registers as shown above:
> 
>    DW_CFA_expression: r6 (esi) (DW_OP_breg5: -8)
> 
> They should be handle last.  I am testing this patch. Does it
> make senses?
> 
> Joey, Xuepeng, please check out our stack branch.
> 
> Thanks.
> 
> 
> H.J.
> ---
> 2008-06-24  H.J. Lu  <hongjiu.lu@intel.com>
> 
> 	* unwind-dw2.c (uw_update_context_1): Handle REG_SAVED_EXP and
> 	REG_SAVED_VAL_EXP after other registers.
> 
> +
> +      /* Compute the addresses of registers saved with REG_SAVED_EXP
> +	 and REG_SAVED_VAL_EXP.  They may use other registers.  */
> +      orig_context = *context;

It doesn't work with C++ exceptions.


H.J.