http://sourceware.org/ml/gdb-patches/2010-03/msg00868.html
Subject: [patch] PIE: Fix back re-run  [Re: [patch] svr4_exec_displacement  success indicator]

Hi,

currently:

$ echo 'main(){}'|gcc -o 1 -fPIE -pie -x c -; ./gdb -nx -ex 'set disable-randomization off' -ex 'b main' -ex r -ex c -ex r ./1
Breakpoint 1 at 0x6b0
Starting program: /home/jkratoch/redhat/gdb-clean/gdb/testsuite/1 
Breakpoint 1, 0x00007fbf73e8c6b0 in main ()
Continuing.
Program exited with code 0140.
Starting program: /home/jkratoch/redhat/gdb-clean/gdb/testsuite/1 
Error in re-setting breakpoint 1: Cannot access memory at address 0x7fbf73e8c6ac

It is since:
	[patch] svr4_exec_displacement success indicator [Re: PIE question]
	http://sourceware.org/ml/gdb-patches/2010-03/msg00336.html


On Mon, 08 Mar 2010 22:53:58 +0100, Jan Kratochvil wrote:
> Attached these changes:
> 
> * svr4_exec_displacement calling convention should have success indicator.
> 
> * Preserving now section_offsets if they are already set, inspired by
>   init_objfile_sect_indices.
> 
> I believe either of parts would be sufficient for this problem.

The first part has caused the regression for PIE on native x86* GNU/Linux host.

As I believe for Daniel J.'s seen regression of `qOffsets' the second already
checked-in part is sufficient - I would like to remove the first part.

OK to check it in?

No regressions on {x86_64,x86_64-m32,i686}-fedora12-linux-gnu.

(I do not think one needs to think about 7.1-branch as it is not a regression
against any FSF GDB release.)


Thanks,
Jan


gdb/
2010-03-25  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix re-run of PIE executable.
	* solib-svr4.c (svr4_relocate_main_executable) <symfile_objfile>: Remove
	the part of pre-set SYMFILE_OBJFILE->SECTION_OFFSETS.

gdb/testsuite/
2010-03-25  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix re-run of PIE executable.
	* gdb.base/break-interp.exp (test_ld): Turn off "disable-randomization".
	Remove $displacement_main to match the solib-svr4.c change.  New "kill"
	and re-"run" of the inferior.

--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -1791,17 +1791,10 @@ svr4_relocate_main_executable (void)
 {
   CORE_ADDR displacement;
 
-  if (symfile_objfile)
-    {
-      int i;
-
-      /* Remote target may have already set specific offsets by `qOffsets'
-	 which should be preferred.  */
-
-      for (i = 0; i < symfile_objfile->num_sections; i++)
-	if (ANOFFSET (symfile_objfile->section_offsets, i) != 0)
-	  return;
-    }
+  /* SYMFILE_OBJFILE->SECTION_OFFSETS may now contain displacement from the
+     previous run of the inferior.  Re-set it according to the current value,
+     if we can find it out.  But otherwise keep it as for remote target it may
+     have been pre-set by the `qOffsets' packet.  */
 
   if (! svr4_exec_displacement (&displacement))
     return;
--- a/gdb/testsuite/gdb.base/break-interp.exp
+++ b/gdb/testsuite/gdb.base/break-interp.exp
@@ -416,25 +416,28 @@ proc test_ld {file ifmain trynosym displacement} {
     # Print the "PIE (Position Independent Executable) displacement" message.
     gdb_test "set verbose on"
 
+    # A bit better test coverage.
+    gdb_test "set disable-randomization off"
+
     reach "dl_main" "run segv" $displacement
 
     gdb_test "bt" "#0 +\[^\r\n\]*\\mdl_main\\M.*" "dl bt"
 
     if $ifmain {
 	# Displacement message will be printed the second time on initializing
-	# the linker from svr4_special_symbol_handling.  If any ANOFFSET has
-	# been already set as non-zero the detection will no longer be run.
-	if {$displacement == "NONZERO"} {
-	    set displacement_main "NONE"
-	} else {
-	    set displacement_main $displacement
-	}
-	reach "main" continue $displacement_main
+	# the linker from svr4_special_symbol_handling.
+	reach "main" continue $displacement
 
 	reach "libfunc" continue "NONE"
 
 	gdb_test "bt" "#0 +\[^\r\n\]*\\mlibfunc\\M\[^\r\n\]*\r\n#1 +\[^\r\n\]*\\mmain\\M.*" "main bt"
+    }
 
+    # Try re-run if the new PIE displacement takes effect.
+    gdb_test "kill" "" "kill" {Kill the program being debugged\? \(y or n\) } "y"
+    reach "dl_main" "run  segv" $displacement
+
+    if $ifmain {
 	test_core $file $displacement
 
 	test_attach $file $displacement