relocation of shared libs not based at 0

["Kris Warkentin" <kewarken@qnx.com>]

I recently came across a problem debugging a core file with some of our
older shared libs.  Info shared showed the relocations of the shared libs to
be mangled (offset to 0x60... range rather than 0xb0... range).  We had
recently changed our tools to always set the vaddr of shared libs to be zero
because of this but I was speaking to one of our architects and he says that
this shouldn't be.

One of the future optimizations we're looking at is pre-relocating shared
libs so that they can be executed in place (on flash for instance) and the
fact that the SysV stuff seems to assume that everything is based at zero is
not particularily compatable with that.  I've attached an ugly patch that
shows a fix.  This is for illustration only since solib.c is the wrong place
to put this but it makes it clear what the issue is.

Can anyone with more knowledge than I enlighten me as to a) whether it is
proper to allow shared objects to be non zero-based and b) a better way to
do this.  I looked at putting it in solib-svr4.c but I don't have access to
the bfd in there, at least in svr4_relocate_section_addresses().

cheers,

Kris

Index: solib.c
===================================================================
RCS file: /product/tools/gdb/gdb/solib.c,v
retrieving revision 1.4
diff -c -r1.4 solib.c
*** solib.c 14 Nov 2002 20:57:23 -0000 1.4
--- solib.c 17 Dec 2002 20:10:14 -0000
***************
*** 26,31 ****
--- 26,34 ----
  #include <fcntl.h>
  #include "gdb_string.h"
  #include "symtab.h"
+ #ifdef __QNXTARGET__
+ #include "elf-bfd.h"
+ #endif
  #include "bfd.h"
  #include "symfile.h"
  #include "objfiles.h"
***************
*** 206,211 ****
--- 209,229 ----
     expansion stuff?).
   */

+ #ifdef __QNXTARGET__
+ Elf_Internal_Phdr *find_load_phdr( bfd *abfd )
+ {
+ Elf32_Internal_Phdr *phdr;
+ unsigned int i;
+
+     phdr = elf_tdata (abfd)->phdr;
+     for (i = 0; i < elf_elfheader (abfd)->e_phnum; i++, phdr++) {
+  if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
+      return phdr;
+     }
+     return NULL;
+ }
+ #endif
+
  static int
  solib_map_sections (PTR arg)
  {
***************
*** 263,268 ****
--- 281,296 ----
           object's file by the base address to which the object was
actually
           mapped. */
        TARGET_SO_RELOCATE_SECTION_ADDRESSES (so, p);
+ #ifdef __QNXTARGET__
+       /* hack for solibs not based at 0 */
+       {
+        Elf32_Internal_Phdr *phdr = find_load_phdr(abfd);
+        if(phdr){
+          p->addr -= phdr->p_vaddr;
+          p->endaddr -= phdr->p_vaddr;
+        }
+       }
+ #endif
        if (STREQ (p->the_bfd_section->name, ".text"))
   {
     so->textsection = p;