Re: [PATCH RFA] solib-svr4.c patch for dynamic executables

[Kevin Buettner <kevinb at cygnus dot com>]

On Nov 7,  6:34pm, Kevin Buettner wrote:

> I withdraw my former patch in favor of the one below.
> 
> 	Changes based on a patch from Ulrich Drepper:
> 	* solib-svr4.c (svr4_relocate_main_executable): New function.
> 	(svr4_solib_create_inferior_hook):  Call
> 	svr4_relocate_main_executable.

Committed.

I added the additional test that Jim Blandy asked for which makes
sure that the executable is dynamic.  Here are what the comments
and the code for the test look like:

  /* Decide if the objfile needs to be relocated.  As indicated above,
     we will only be here when execution is stopped at the beginning
     of the program.  Relocation is necessary if the address at which
     we are presently stopped differs from the start address stored in
     the executable AND there's no interpreter section.  The condition
     regarding the interpreter section is very important because if
     there *is* an interpreter section, execution will begin there
     instead.  When there is an interpreter section, the start address
     is (presumably) used by the interpreter at some point to start
     execution of the program.

     If there is an interpreter, it is normal for it to be set to an
     arbitrary address at the outset.  The job of finding it is
     handled in enable_break().

     So, to summarize, relocations are necessary when there is no
     interpreter section and the start address obtained from the
     executable is different from the address at which GDB is
     currently stopped.
     
     [ The astute reader will note that we also test to make sure that
       the executable in question has the DYNAMIC flag set.  It is my
       opinion that this test is unnecessary (undesirable even).  It
       was added to avoid inadvertent relocation of an executable
       whose e_type member in the ELF header is not ET_DYN.  There may
       be a time in the future when it is desirable to do relocations
       on other types of files as well in which case this condition
       should either be removed or modified to accomodate the new file
       type.  (E.g, an ET_EXEC executable which has been built to be
       position-independent could safely be relocated by the OS if
       desired.  It is true that this violates the ABI, but the ABI
       has been known to be bent from time to time.)  - Kevin, Nov 2000. ]
     */

  interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
  if (interp_sect == NULL 
      && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
      && bfd_get_start_address (exec_bfd) != pc)