Re: ping: [patch 2/6] PIE: Attach binary even after ld.so re-prelinked underneath

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi Joel,

checked-in.


Thanks,
Jan


http://sourceware.org/ml/gdb-cvs/2010-07/msg00025.html

--- src/gdb/ChangeLog	2010/07/05 17:57:49	1.11964
+++ src/gdb/ChangeLog	2010/07/05 17:58:55	1.11965
@@ -1,6 +1,11 @@
 2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
 	    Joel Brobecker  <brobecker@adacore.com>
 
+	* auxv.c (ld_so_xfer_auxv): Do not error on failed read of data_address.
+
+2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
+	    Joel Brobecker  <brobecker@adacore.com>
+
 	Fix attaching to PIEs prelinked on the disk after the process was
 	started.
 	* solib-svr4.c (svr4_exec_displacement): New variable arch_size.
--- src/gdb/auxv.c	2010/05/18 19:23:37	1.27
+++ src/gdb/auxv.c	2010/07/05 17:58:55	1.28
@@ -96,7 +96,27 @@
 
   pointer_address = SYMBOL_VALUE_ADDRESS (msym);
 
-  data_address = read_memory_typed_address (pointer_address, ptr_type);
+  /* The location of the _dl_auxv symbol may no longer be correct if
+     ld.so runs at a different address than the one present in the file.
+     This is very common case - for unprelinked ld.so or with a PIE executable.
+     PIE executable forces random address even for libraries already being
+     prelinked to some address.  PIE executables themselves are never prelinked
+     even on prelinked systems.  Prelinking of a PIE executable would block
+     their purpose of randomizing load of everything including the executable.
+
+     If the memory read fails, return -1 to fallback on another mechanism for
+     retrieving the AUXV.
+
+     In most cases of a PIE running under valgrind there is no way to find
+     out the base addresses of any of ld.so, executable or AUXV as everything
+     is randomized and /proc information is not relevant for the virtual
+     executable running under valgrind.  We think that we might need a valgrind
+     extension to make it work.  This is PR 11440.  */
+
+  if (target_read_memory (pointer_address, ptr_buf, ptr_size) != 0)
+    return -1;
+
+  data_address = extract_typed_address (ptr_buf, ptr_type);
 
   /* Possibly still not initialized such as during an inferior startup.  */
   if (data_address == 0)
--- src/gdb/testsuite/ChangeLog	2010/07/05 17:57:50	1.2371
+++ src/gdb/testsuite/ChangeLog	2010/07/05 17:58:56	1.2372
@@ -1,6 +1,12 @@
 2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
 	    Joel Brobecker  <brobecker@adacore.com>
 
+	* gdb.base/break-interp.exp (test_attach): Keep $interp changed.  Move
+	its restore after the <$relink_args != ""> loop.  new comment.
+
+2010-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
+	    Joel Brobecker  <brobecker@adacore.com>
+
 	* gdb.base/break-interp.exp: Run $binpie with new value "ATTACH", new
 	code for it.  New variable relink_args.
 	(prelinkYES): Call prelinkNO.
--- src/gdb/testsuite/gdb.base/break-interp.exp	2010/07/05 17:57:50	1.14
+++ src/gdb/testsuite/gdb.base/break-interp.exp	2010/07/05 17:58:56	1.15
@@ -425,12 +425,24 @@
 	global exec interp_saved interp
 
 	foreach relink {YES NO} {
-	    if {[prelink$relink $relink_args [file tail $exec]]
-	        && [copy $interp_saved $interp]} {
+	    # Formerly this test was testing only prelinking of $EXEC.  As the
+	    # prelink command automatically prelinks all of $EXEC's libraries,
+	    # even $INTERP got prelinked.  Therefore, we formerly had to
+	    # `[copy $interp_saved $interp]' to make $INTERP not affected by
+	    # this prelinking of $EXEC.
+	    #
+	    # But now we need to test even prelinking of $INTERP.  We could
+	    # create a separate test to test just the $INTERP prelinking.  For
+	    # test simplicity, we merged this test and the test above by not
+	    # restoring $INTERP after $EXEC prelink.  $INTERP gets restored
+	    # later below.
+
+	    if [prelink$relink $relink_args [file tail $exec]] {
 		# /proc/PID/exe cannot be loaded as it is "EXECNAME (deleted)".
 		test_attach_gdb $exec $pid $displacement "attach-relink$relink"
 	    }
 	}
+	copy $interp_saved $interp
     }
 
     remote_exec host "kill -9 $pid"