arm64: Move EXCEPTION_TABLE to RO_DATA segment

Since the EXCEPTION_TABLE is read-only, collapse it into RO_DATA. Also
removes the redundant ALIGN, which is already present at the end of the
RO_DATA macro.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
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: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Cc: x86-ml <x86@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: https://lkml.kernel.org/r/20191029211351.13243-19-keescook@chromium.org

arch/arm64/kernel/vmlinux.lds.S

@@ -5,6 +5,8 @@
  * Written by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
  */
 
+#define RO_EXCEPTION_TABLE_ALIGN	8
+
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/cache.h>
 #include <asm/kernel-pgtable.h>
@@ -135,10 +137,9 @@ SECTIONS
 	. = ALIGN(SEGMENT_ALIGN);
 	_etext = .;			/* End of text section */
 
-	RO_DATA(PAGE_SIZE)		/* everything from this point to     */
-	EXCEPTION_TABLE(8)		/* __init_begin will be marked RO NX */
+	/* everything from this point to __init_begin will be marked RO NX */
+	RO_DATA(PAGE_SIZE)
 
-	. = ALIGN(PAGE_SIZE);
 	idmap_pg_dir = .;
 	. += IDMAP_DIR_SIZE;