Bug 664366 - Automatically disable elfhack when the linker creates PT_GNU_RELRO segments. r=khuey

configure.in

@@ -7624,6 +7624,36 @@ if test "$USE_ELF_HACK" = 1; then
     esac
 fi
 
+if test "$USE_ELF_HACK" = 1; then
+    dnl PT_GNU_RELRO segment makes the dynamic linker set a read-only flag on
+    dnl memory addresses it maps to. The result is that by the time elfhack
+    dnl kicks in, it is not possible to apply relocations because of that,
+    dnl thus elfhack effectively skips relocations inside the PT_GNU_RELRO
+    dnl segment. It makes elfhack mostly useless, so considering the problems
+    dnl we have we PT_GNU_RELRO (e.g. bug 664366), and until elfhack can deal
+    dnl with PT_GNU_RELRO segments, it's just simpler to disable elfhack when
+    dnl the linker creates PT_GNU_RELRO segments.
+    AC_CACHE_CHECK([whether linker creates PT_GNU_RELRO segments],
+        LINK_WITH_PT_GNU_RELRO,
+        [echo "int main() {return 0;}" > conftest.${ac_ext}
+         if AC_TRY_COMMAND(${CC-cc} -o conftest${ac_exeext} $LDFLAGS conftest.${ac_ext} $LIBS 1>&2) &&
+            test -s conftest${ac_exeext}; then
+            if readelf -l conftest${ac_exeext} | grep GNU_RELRO > /dev/null; then
+                LINK_WITH_PT_GNU_RELRO=yes
+            else
+                LINK_WITH_PT_GNU_RELRO=no
+            fi
+         else
+             dnl We really don't expect to get here, but just in case
+             AC_ERROR([couldn't compile a simple C file])
+         fi
+         rm -rf conftest*])
+    if test "$LINK_WITH_PT_GNU_RELRO" = yes; then
+        AC_MSG_WARN([Disabling elfhack])
+        USE_ELF_HACK=
+    fi
+fi
+
 dnl ========================================================
 dnl = libstdc++ compatibility hacks
 dnl ========================================================