Re: objdump, 64-bit objects and Solaris kernel modules

[Gabriel Marin <mgabi at rice dot edu>]

Hi Nick, Steve

> First step - download the latest binutils release (2.13.2) or the
> latest CVS sources.  It is possible that the problem has already been
> fixed.
This problem exists for at least one year, when I noticed it first time. 
It is not solved by the latest version.


> I'm willing to help debug this problem, but I'll need some pointers
> on where to start.
>  
>
> Have a look at binutils/objdump.c:show_line().  This is the function
> that should display the source lines.  The problem, however is most
> likely to be with the function: bfd_find_nearest_line().  This is
> vectored function whoes actual code depends upon the target you are
> using, and the file formats and debug formats that it uses.  I do not
> know which debug format the Forte Developer package uses, but it is
> probably generating ELF format binaries using either the DWARF or
> STABS debug formats.  So have a look at
> bfd/elf.c:_bfd_elf_find_nearest_line() and follow the code from there.
You are right. The problem is in bfd_find_nearest_line. Hence, addr2line 
cannot find the correct file and line number either.
The problem is not limited at 64-bit binaries. I had this problem with 
32-bit binaries.
I just tried to solve it about 10 days ago and the problem is indeed in 
_bfd_stab_section_find_nearest_line() in syms.c. Stabs is the debug 
format used by the Sun Forte compiler.
The stab section contains a mix of debug info: N_SO (for files), N_FUN 
(for routines), N_SLINE (for line info in text segment).
The code in _bfd_stab_section_find_nearest_line() expects to find the 
absolute start address of the routine in the value field for N_FUN 
entries. But the Sun compiler does not generate this value so it is 
always zero. What I did was to search for the routine symbols in the 
symbol table and compute their absolute start address from there.
More comments are in the patch that I attached. It is generated against 
the cvs repository on 02/07/2003.

Gabriel

>  
Index: bfd/syms.c
===================================================================
RCS file: /cvs/src/src/bfd/syms.c,v
retrieving revision 1.27
diff -c -3 -p -r1.27 syms.c
*** bfd/syms.c	30 Nov 2002 08:39:40 -0000	1.27
--- bfd/syms.c	7 Feb 2003 22:05:13 -0000
*************** _bfd_stab_section_find_nearest_line (abf
*** 1223,1230 ****
        ++i;
  
        info->indextablesize = i;
!       qsort (info->indextable, (size_t) i, sizeof (struct indexentry),
! 	     cmpindexentry);
  
        *pinfo = (PTR) info;
      }
--- 1223,1272 ----
        ++i;
  
        info->indextablesize = i;
! 
!       /* For binaries produced by the Sun compiler the field 'value'
!        * in stabs is zero for all N_FUN type of entries. In this case the 
!        * find_nearest_line always returns the last N_SLINE entry in the stabs
!        * because the binary search will always stop just at the end of the 
!        * table, before the last entry which has a special value (0xFFFFFFFF)
!        * and after all the other entries with a value zero.
!        * Try to find the value for each entry by searching in the symbols 
!        * array. This search is done only once so we can live with a linear,
!        * unoptimized search. It is also possible to organize the symbols in
!        * another data structure using the name as a key (hashtable or sorted
!        * list). 
!        * In stabs, the function name in the case of a Sun compiler binary has
!        * this format: symbolName:F... or symbolName:P... where ... means a 
!        * sequence of other characters. We are interested only in the entries
!        * with the first format, I do not know what the second format means 
!        * and we can leave those at zero. - mgabi 28-01-2003
!        */
!        for (i=0 ; i<info->indextablesize ; i++)
!          {
!            char* pos;
!            int k;
!            asymbol *sym;
!            if (info->indextable[i].val==0 && info->indextable[i].function_name
!               && ((pos=strchr(info->indextable[i].function_name, ':'))==NULL
!                  || *(pos+1)=='F') )
!              {
!                if (pos) *pos = '\0';
!                /* search for the symbol with this name */
!                for (k=0 ; symbols[k] != NULL ; k++)
!                  {
!                    sym = symbols[k];
!                    if (!strcmp(info->indextable[i].function_name, sym->name))
!                      {
!                        info->indextable[i].val = 
!                                   sym->value + sym->section->vma;
!                        break;
!                      }
!                  }
!                if (pos) *pos = ':';
!              }
!          }
!       qsort (info->indextable, (size_t) info->indextablesize, 
!               sizeof (struct indexentry), cmpindexentry);
  
        *pinfo = (PTR) info;
      }