[PATCH] Fix Gold/strip discrepancies for PR 11786

Doug Evans
2013-10-25T23:26:28Z

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"