xtensa: Move EXCEPTION_TABLE to RO_DATA segment

Since the EXCEPTION_TABLE is read-only, collapse it into RO_DATA.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Will Deacon <will@kernel.org>
Cc: x86-ml <x86@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: https://lkml.kernel.org/r/20191029211351.13243-26-keescook@chromium.org

arch/xtensa/kernel/vmlinux.lds.S

@@ -14,6 +14,8 @@
  * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
  */
 
+#define RO_EXCEPTION_TABLE_ALIGN	16
+
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/page.h>
 #include <asm/thread_info.h>
@@ -130,7 +132,6 @@ SECTIONS
 
   .fixup   : { *(.fixup) }
 
-  EXCEPTION_TABLE(16)
   /* Data section */
 
   _sdata = .;