[PATCH] Fix Gold/strip discrepancies for PR 11786

[Doug Evans <dje@google.com>]

Hi.

This patch addresses the discrepancy in the flags and align fields
of PT_GNU_RELRO between Gold and strip.

Ref: https://sourceware.org/bugzilla/show_bug.cgi?id=11786

Ok to check in?

2013-10-25  Doug Evans  <dje@google.com>

	PR 11786
	*  solib-svr4.c (svr4_exec_displacement): Ignore flags and align fields
	for PT_GNU_RELRO segments.

	testsuite/
	* gdb.base/gcore-relro-pie.c: New file.
	* gdb.base/gcore-relro-pie.exp: New file.

diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index ddbbd94..d3b55e5 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -2608,6 +2608,22 @@ svr4_exec_displacement (CORE_ADDR *displacementp)
 		  if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
 		    continue;
 
+		  /* Gold and strip differ on the flags and alignment of
+		     PT_GNU_RELRO.  See PR 11786.  */
+		  if (phdr2[i].p_type == PT_GNU_RELRO)
+		  {
+		    Elf32_External_Phdr tmp_phdr = *phdrp;
+		    Elf32_External_Phdr tmp_phdr2 = *phdr2p;
+
+		    memset (tmp_phdr.p_flags, 0, 4);
+		    memset (tmp_phdr.p_align, 0, 4);
+		    memset (tmp_phdr2.p_flags, 0, 4);
+		    memset (tmp_phdr2.p_align, 0, 4);
+
+		    if (memcmp (&tmp_phdr, &tmp_phdr2, sizeof (tmp_phdr)) == 0)
+		      continue;
+		  }
+
 		  /* prelink can convert .plt SHT_NOBITS to SHT_PROGBITS.  */
 		  plt2_asect = bfd_get_section_by_name (exec_bfd, ".plt");
 		  if (plt2_asect)
@@ -2717,6 +2733,22 @@ svr4_exec_displacement (CORE_ADDR *displacementp)
 		  if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
 		    continue;
 
+		  /* Gold and strip differ on the flags and alignment of
+		     PT_GNU_RELRO.  See PR 11786.  */
+		  if (phdr2[i].p_type == PT_GNU_RELRO)
+		  {
+		    Elf64_External_Phdr tmp_phdr = *phdrp;
+		    Elf64_External_Phdr tmp_phdr2 = *phdr2p;
+
+		    memset (tmp_phdr.p_flags, 0, 4);
+		    memset (tmp_phdr.p_align, 0, 8);
+		    memset (tmp_phdr2.p_flags, 0, 4);
+		    memset (tmp_phdr2.p_align, 0, 8);
+
+		    if (memcmp (&tmp_phdr, &tmp_phdr2, sizeof (tmp_phdr)) == 0)
+		      continue;
+		  }
+
 		  /* prelink can convert .plt SHT_NOBITS to SHT_PROGBITS.  */
 		  plt2_asect = bfd_get_section_by_name (exec_bfd, ".plt");
 		  if (plt2_asect)
diff --git a/gdb/testsuite/gdb.base/gcore-relro-pie.c b/gdb/testsuite/gdb.base/gcore-relro-pie.c
new file mode 100644
index 0000000..1594385
--- /dev/null
+++ b/gdb/testsuite/gdb.base/gcore-relro-pie.c
@@ -0,0 +1,41 @@
+/* Copyright 2013 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+void
+break_here ()
+{
+  *(int *) 0 = 0;
+}
+
+void
+foo ()
+{
+  break_here ();
+}
+
+void
+bar ()
+{
+  foo ();
+}
+
+int
+main (void)
+{
+  bar ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/gcore-relro-pie.exp b/gdb/testsuite/gdb.base/gcore-relro-pie.exp
new file mode 100644
index 0000000..1fcfd8c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/gcore-relro-pie.exp
@@ -0,0 +1,70 @@
+# Copyright 2013 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# PR 11786 (Gold and strip differ on flags,align fields of PT_GNU_RELRO).
+# Generate a core file from the stripped version of the program,
+# and then try to debug the core with the unstripped version.
+
+standard_testfile
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile {debug additional_flags=-fpie additional_flags=-pie additional_flags=-Wl,-z,relro}]} {
+    return -1
+}
+
+set stripped_binfile ${binfile}.stripped
+set gcorefile ${binfile}.gcore
+
+set strip_program [transform strip]
+remote_file host delete ${stripped_binfile}
+if [run_on_host "strip" "$strip_program" "-g -o ${stripped_binfile} $binfile"] {
+    return -1
+}
+
+clean_restart ${stripped_binfile}
+
+# Does this gdb support gcore?
+set test "help gcore"
+gdb_test_multiple $test $test {
+    -re "Undefined command: .gcore.*\r\n$gdb_prompt $" {
+	# gcore command not supported -- nothing to test here.
+	unsupported "gdb does not support gcore on this target"
+	return -1
+    }
+    -re "Save a core file .*\r\n$gdb_prompt $" {
+	pass $test
+    }
+}
+
+# The binary is stripped of debug info, but not minsyms.
+if ![runto break_here] {
+    fail "Can't run to break_here"
+    return -1
+}
+
+if {![gdb_gcore_cmd $gcorefile "save a corefile"]} {
+    return -1
+}
+
+# Now restart gdb with the unstripped binary and load the corefile.
+
+clean_restart ${binfile}
+
+gdb_test "core ${gcorefile}" \
+    "Core was generated by .*" "re-load generated corefile"
+
+# Put $pc in gdb.log for debug purposes for comparison with stripped case.
+gdb_test "x/i \$pc" "break_here.*"
+
+gdb_test "frame" "#0 \[^\r\n\]* break_here .*" "unstripped + core ok"