[Bug shlibs/15507] New: .dynamic section is not at the expected address

["bccheng at android dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=15507

             Bug #: 15507
           Summary: .dynamic section is not at the expected address
           Product: gdb
           Version: 7.6
            Status: NEW
          Severity: normal
          Priority: P2
         Component: shlibs
        AssignedTo: unassigned@sourceware.org
        ReportedBy: bccheng@android.com
    Classification: Unclassified


Currently Android is using gdbserver from 7.1 and gdb from 7.3. I tried to
upgrade Android gdb to 7.6 but I found it complained with the following
message: 

(gdb) b main
Breakpoint 1 at 0xb6fc2448: file <test_program>/main.c, line 10.
(gdb) c
Continuing.
warning: .dynamic section for "<test_program>" is not at the expected address
(wrong library or version mismatch?)
Error in re-setting breakpoint 1: Cannot access memory at address 0xffffe570
Error in re-setting breakpoint 1: Cannot access memory at address 0xffffe570
Error in re-setting breakpoint 1: Cannot access memory at address 0xffffe570
Error in re-setting breakpoint 1: Cannot access memory at address 0xffffe570

After digging into the problem a bit more, I think the problem is in
solib-svr4.c/svr4_current_sos() where if gdbserver responds to the
svr4_current_sos_via_xfer_libraries call, it is not skipping the first entry in
the link map:


  if (svr4_current_sos_via_xfer_libraries (&library_list))
    {
      if (library_list.main_lm)
        {
          info = get_svr4_info ();
          info->main_lm_addr = library_list.main_lm;
        }

      return library_list.head ? library_list.head : svr4_default_sos ();
    }

And here is the xml string:

<library-list-svr4 version="1.0"><library name="<test_program>" lm="0xb6fed108"
l_addr="0x0" l_ld="0x0"/><library name="/system/bin/linker" lm="0xb6ffe75c"
l_addr="0xb6fee000" l_ld="0xb6ffded8"/></library-list-svr4>

In the same function it has the following code to deal with older gdbserver
where it can ignore the first entry in the link map:


  /* Assume that everything is a library if the dynamic loader was loaded
     late by a static executable.  */
  if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
    ignore_first = 0;
  else
    ignore_first = 1;

  back_to = make_cleanup (svr4_free_library_list, &head);

  /* Walk the inferior's link map list, and build our list of
     `struct so_list' nodes.  */
  lm = solib_svr4_r_map (info);
  if (lm)
    svr4_read_so_list (lm, &link_ptr, ignore_first);

I tried a simple hack and gdb 7.6 starts to work for Android with gdbserver
7.6:

-      return library_list.head ? library_list.head : svr4_default_sos ();
+      if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
+       return library_list.head ? library_list.head : svr4_default_sos ();
+      else
+       return library_list.head ? library_list.head : svr4_default_sos ();

Not sure if there is a better patch fix the problem.

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