selftests/seccomp: mips: Define SYSCALL_NUM_SET macro

Remove the mips special-case in change_syscall().
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/lkml/20200912110820.597135-4-keescook@chromium.orgAcked-by: Christian Brauner <christian.brauner@ubuntu.com>

tools/testing/selftests/seccomp/seccomp_bpf.c

@@ -1742,6 +1742,13 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 # define ARCH_REGS		struct pt_regs
 # define SYSCALL_NUM(_regs)	(_regs).regs[2]
 # define SYSCALL_SYSCALL_NUM	regs[4]
+# define SYSCALL_NUM_SET(_regs, _nr)			\
+	do {						\
+		if ((_regs).regs[2] == __NR_O32_Linux)	\
+			(_regs).regs[4] = _nr;		\
+		else					\
+			(_regs).regs[2] = _nr;		\
+	} while (0)
 # define SYSCALL_RET(_regs)	(_regs).regs[2]
 # define SYSCALL_NUM_RET_SHARE_REG
 #elif defined(__xtensa__)
@@ -1839,17 +1846,11 @@ void change_syscall(struct __test_metadata *_metadata,
 
 #if defined(__x86_64__) || defined(__i386__) || defined(__powerpc__) || \
 	defined(__s390__) || defined(__hppa__) || defined(__riscv) || \
-	defined(__xtensa__) || defined(__csky__) || defined(__sh__)
+	defined(__xtensa__) || defined(__csky__) || defined(__sh__) || \
+	defined(__mips__)
 	{
 		SYSCALL_NUM_SET(regs, syscall);
 	}
-#elif defined(__mips__)
-	{
-		if (SYSCALL_NUM(regs) == __NR_O32_Linux)
-			regs.SYSCALL_SYSCALL_NUM = syscall;
-		else
-			SYSCALL_NUM_SET(regs, syscall);
-	}
 
 #elif defined(__arm__)
 # ifndef PTRACE_SET_SYSCALL