audit: define AUDIT_ARCH_OPENRISC

When using audit on OpenRISC, an audit arch is needed. This defines
it and fixes a compile-time bug uncovered in linux-next, likely from a
cut/paste from an arch with 64/32-bit modes that defined arch_arch():
arch/openrisc/kernel/ptrace.c:190:2: error: implicit declaration of function 'audit_arch'

This replaces it with the newly defined AUDIT_ARCH_OPENRISC, since it
is only 32-bit, and currently only operates in big-endian mode.
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonas Bonn <jonas@southpole.se>

arch/openrisc/kernel/ptrace.c

@@ -187,7 +187,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 		 */
 		ret = -1L;
 
-	audit_syscall_entry(audit_arch(), regs->gpr[11],
+	audit_syscall_entry(AUDIT_ARCH_OPENRISC, regs->gpr[11],
 			    regs->gpr[3], regs->gpr[4],
 			    regs->gpr[5], regs->gpr[6]);
 

include/linux/audit.h

@@ -337,6 +337,7 @@ enum {
 #define AUDIT_ARCH_MIPSEL	(EM_MIPS|__AUDIT_ARCH_LE)
 #define AUDIT_ARCH_MIPS64	(EM_MIPS|__AUDIT_ARCH_64BIT)
 #define AUDIT_ARCH_MIPSEL64	(EM_MIPS|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
+#define AUDIT_ARCH_OPENRISC	(EM_OPENRISC)
 #define AUDIT_ARCH_PARISC	(EM_PARISC)
 #define AUDIT_ARCH_PARISC64	(EM_PARISC|__AUDIT_ARCH_64BIT)
 #define AUDIT_ARCH_PPC		(EM_PPC)