selftests/seccomp: Provide generic syscall setting macro

In order to avoid "#ifdef"s in the main function bodies, create a new
macro, SYSCALL_NUM_SET(), where arch-specific logic can live.

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/lkml/20200912110820.597135-3-keescook@chromium.org
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index a261643..c44abe7 100644 (file)
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -1760,6 +1760,17 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 # error "Do not know how to find your architecture's registers and syscalls"
 #endif
 
+/*
+ * Most architectures can change the syscall by just updating the
+ * associated register. This is the default if not defined above.
+ */
+#ifndef SYSCALL_NUM_SET
+# define SYSCALL_NUM_SET(_regs, _nr)           \
+       do {                                    \
+               SYSCALL_NUM(_regs) = (_nr);     \
+       } while (0)
+#endif
+
 /* When the syscall return can't be changed, stub out the tests for it. */
 #ifdef SYSCALL_NUM_RET_SHARE_REG
 # define EXPECT_SYSCALL_RETURN(val, action)    EXPECT_EQ(-1, action)
@@ -1830,14 +1841,14 @@ void change_syscall(struct __test_metadata *_metadata,
        defined(__s390__) || defined(__hppa__) || defined(__riscv) || \
        defined(__xtensa__) || defined(__csky__) || defined(__sh__)
        {
-               SYSCALL_NUM(regs) = syscall;
+               SYSCALL_NUM_SET(regs, syscall);
        }
 #elif defined(__mips__)
        {
                if (SYSCALL_NUM(regs) == __NR_O32_Linux)
                        regs.SYSCALL_SYSCALL_NUM = syscall;
                else
-                       SYSCALL_NUM(regs) = syscall;
+                       SYSCALL_NUM_SET(regs, syscall);
        }
 
 #elif defined(__arm__)