Non-SFI NaCl: Fix browser_tests based on libc_free.c

chrome/test/data/nacl/nacl_test_data.gyp

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'includes': [
     '../../../../ppapi/ppapi_nacl_test_common.gypi',
   ],
   'targets': [
     {
@@ skipping 1134 matching lines @@
             # such thing might be adding them in, and those options wind up
             # coming after the -fno-stack-protector we added above.
             '-fstack-protector',
             '-fstack-protector-all',
             '-fprofile-generate',
             '-finstrument-functions',
           ],
           'ldflags': [
             '-nostdlib',
             '-shared',
+            # This binary cannot relocate itself, so we should have no
+            # undefined references left.
+            '-Wl,--no-undefined',
+            # Clang emits .data.rel.ro.local for local struct values
+            # with initializers, and let the linker emit a few
+            # relocation info. We work around this issue by not using
+            # GNU_RELRO.
+            '-Wl,-z,norelro',

[Mark Seaborn, 2014/07/10 17:17:45]

I don't think adding "norelro" works.

For example:

struct S {
  int *x[6];
};

struct S global1;
struct S global2;

static int val1;
static int val2;

void foo1() {
  struct S local = {
    &val1, &val1, &val1, &val1, &val1, &val1
  };
  global1 = local;
}

void foo2() {
  int i = 0;
  global2.x[i++] = &val2;
  global2.x[i++] = &val2;
  global2.x[i++] = &val2;
  global2.x[i++] = &val2;
  global2.x[i++] = &val2;
  global2.x[i++] = &val2;
}

If you run:

clang libc_free_reloc.c -shared -fPIC -Wl,-z,norelro && objdump -R a.out

then you'll see there are still R_X86_64_RELATIVE relocs on 'local' that refer
to val1.  The linker can't make those go away when producing a
position-independent binary.

[hamaji, 2014/07/11 05:16:48]

True. I might have been testing this in a wrong way. Removed.

           ],
           'ldflags!': [
             # Explicitly remove the -pthread flag to avoid a link time warning.
             '-pthread',
           ],
           'defines': [
             # The code depends on NaCl's headers. This is a macro for them.
             'NACL_LINUX=1',
           ],
           # For native_client/src/include/...
@@ skipping 43 matching lines @@
               'files': [
                 '>@(test_files)',
               ],
             },
           ],
         },
       ],
     }],
   ],
 }