gdb/

Fix re-run of PIE executable, PR shlibs/11776.
	* solib-svr4.c (svr4_relocate_main_executable) <symfile_objfile>: Remove
	the part of pre-set SYMFILE_OBJFILE->SECTION_OFFSETS.

gdb/testsuite/
	Fix re-run of PIE executable, PR shlibs/11776.
	* 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.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
+	    Joel Brobecker  <brobecker@adacore.com>
+
+	Fix re-run of PIE executable, PR shlibs/11776.
+	* solib-svr4.c (svr4_relocate_main_executable) <symfile_objfile>: Remove
+	the part of pre-set SYMFILE_OBJFILE->SECTION_OFFSETS.
+
 2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
 	    Joel Brobecker  <brobecker@adacore.com>
 

gdb/solib-svr4.c

@@ -1989,17 +1989,32 @@ svr4_relocate_main_executable (void)
 {
   CORE_ADDR displacement;
 
-  if (symfile_objfile)
+  /* If we are re-running this executable, SYMFILE_OBJFILE->SECTION_OFFSETS
-    {
+     probably contains the offsets computed using the PIE displacement
-      int i;
+     from the previous run, which of course are irrelevant for this run.
+     So we need to determine the new PIE displacement and recompute the
+     section offsets accordingly, even if SYMFILE_OBJFILE->SECTION_OFFSETS
+     already contains pre-computed offsets.
 
-      /* Remote target may have already set specific offsets by `qOffsets'
+     If we cannot compute the PIE displacement, either:
-	 which should be preferred.  */
 
-      for (i = 0; i < symfile_objfile->num_sections; i++)
+       - The executable is not PIE.
-	if (ANOFFSET (symfile_objfile->section_offsets, i) != 0)
+
-	  return;
+       - SYMFILE_OBJFILE does not match the executable started in the target.
-    }
+	 This can happen for main executable symbols loaded at the host while
+	 `ld.so --ld-args main-executable' is loaded in the target.
+
+     Then we leave the section offsets untouched and use them as is for
+     this run.  Either:
+
+       - These section offsets were properly reset earlier, and thus
+	 already contain the correct values.  This can happen for instance
+	 when reconnecting via the remote protocol to a target that supports
+	 the `qOffsets' packet.
+
+       - The section offsets were not reset earlier, and the best we can
+	 hope is that the old offsets are still applicable to the new run.
+   */
 
   if (! svr4_exec_displacement (&displacement))
     return;

gdb/testsuite/ChangeLog

@@ -1,3 +1,11 @@
+2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
+	    Joel Brobecker  <brobecker@adacore.com>
+
+	Fix re-run of PIE executable, PR shlibs/11776.
+	* 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.
+
 2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
 	    Joel Brobecker  <brobecker@adacore.com>
 

gdb/testsuite/gdb.base/break-interp.exp

@@ -337,6 +337,11 @@ proc test_ld {file ifmain trynosym displacement} {
     # Print the "PIE (Position Independent Executable) displacement" message.
     gdb_test_no_output "set verbose on"
 
+    # We want to test the re-run of a PIE in the case where the executable
+    # is loaded with a different displacement, but disable-randomization
+    # prevents that from happening.  So turn it off.
+    gdb_test "set disable-randomization off"
+
     reach "dl_main" "run segv" $displacement
 
     gdb_test "bt" "#0 +\[^\r\n\]*\\mdl_main\\M.*" "dl bt"
@@ -347,7 +352,13 @@ proc test_ld {file ifmain trynosym 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