selftests/seccomp: Refactor arch register macros to avoid xtensa special case

To avoid an xtensa special-case, refactor all arch register macros to
take the register variable instead of depending on the macro expanding
as a struct member name.
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/lkml/20200912110820.597135-2-keescook@chromium.orgAcked-by: Christian Brauner <christian.brauner@ubuntu.com>

tools/testing/selftests/seccomp/seccomp_bpf.c

@@ -1698,64 +1698,64 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 }
 
 #if defined(__x86_64__)
-# define ARCH_REGS	struct user_regs_struct
-# define SYSCALL_NUM	orig_rax
-# define SYSCALL_RET	rax
+# define ARCH_REGS		struct user_regs_struct
+# define SYSCALL_NUM(_regs)	(_regs).orig_rax
+# define SYSCALL_RET(_regs)	(_regs).rax
 #elif defined(__i386__)
-# define ARCH_REGS	struct user_regs_struct
-# define SYSCALL_NUM	orig_eax
-# define SYSCALL_RET	eax
+# define ARCH_REGS		struct user_regs_struct
+# define SYSCALL_NUM(_regs)	(_regs).orig_eax
+# define SYSCALL_RET(_regs)	(_regs).eax
 #elif defined(__arm__)
-# define ARCH_REGS	struct pt_regs
-# define SYSCALL_NUM	ARM_r7
-# define SYSCALL_RET	ARM_r0
+# define ARCH_REGS		struct pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).ARM_r7
+# define SYSCALL_RET(_regs)	(_regs).ARM_r0
 #elif defined(__aarch64__)
-# define ARCH_REGS	struct user_pt_regs
-# define SYSCALL_NUM	regs[8]
-# define SYSCALL_RET	regs[0]
+# define ARCH_REGS		struct user_pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).regs[8]
+# define SYSCALL_RET(_regs)	(_regs).regs[0]
 #elif defined(__riscv) && __riscv_xlen == 64
-# define ARCH_REGS	struct user_regs_struct
-# define SYSCALL_NUM	a7
-# define SYSCALL_RET	a0
+# define ARCH_REGS		struct user_regs_struct
+# define SYSCALL_NUM(_regs)	(_regs).a7
+# define SYSCALL_RET(_regs)	(_regs).a0
 #elif defined(__csky__)
-# define ARCH_REGS	struct pt_regs
-#if defined(__CSKYABIV2__)
-# define SYSCALL_NUM	regs[3]
-#else
-# define SYSCALL_NUM	regs[9]
-#endif
-# define SYSCALL_RET	a0
+# define ARCH_REGS		struct pt_regs
+#  if defined(__CSKYABIV2__)
+#   define SYSCALL_NUM(_regs)	(_regs).regs[3]
+#  else
+#   define SYSCALL_NUM(_regs)	(_regs).regs[9]
+#  endif
+# define SYSCALL_RET(_regs)	(_regs).a0
 #elif defined(__hppa__)
-# define ARCH_REGS	struct user_regs_struct
-# define SYSCALL_NUM	gr[20]
-# define SYSCALL_RET	gr[28]
+# define ARCH_REGS		struct user_regs_struct
+# define SYSCALL_NUM(_regs)	(_regs).gr[20]
+# define SYSCALL_RET(_regs)	(_regs).gr[28]
 #elif defined(__powerpc__)
-# define ARCH_REGS	struct pt_regs
-# define SYSCALL_NUM	gpr[0]
-# define SYSCALL_RET	gpr[3]
+# define ARCH_REGS		struct pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).gpr[0]
+# define SYSCALL_RET(_regs)	(_regs).gpr[3]
 #elif defined(__s390__)
-# define ARCH_REGS     s390_regs
-# define SYSCALL_NUM   gprs[2]
-# define SYSCALL_RET   gprs[2]
+# define ARCH_REGS		s390_regs
+# define SYSCALL_NUM(_regs)	(_regs).gprs[2]
+# define SYSCALL_RET(_regs)	(_regs).gprs[2]
 # define SYSCALL_NUM_RET_SHARE_REG
 #elif defined(__mips__)
-# define ARCH_REGS	struct pt_regs
-# define SYSCALL_NUM	regs[2]
-# define SYSCALL_SYSCALL_NUM regs[4]
-# define SYSCALL_RET	regs[2]
+# define ARCH_REGS		struct pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).regs[2]
+# define SYSCALL_SYSCALL_NUM	regs[4]
+# define SYSCALL_RET(_regs)	(_regs).regs[2]
 # define SYSCALL_NUM_RET_SHARE_REG
 #elif defined(__xtensa__)
-# define ARCH_REGS	struct user_pt_regs
-# define SYSCALL_NUM	syscall
+# define ARCH_REGS		struct user_pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).syscall
 /*
  * On xtensa syscall return value is in the register
  * a2 of the current window which is not fixed.
  */
-#define SYSCALL_RET(reg) a[(reg).windowbase * 4 + 2]
+#define SYSCALL_RET(_regs)	(_regs).a[(_regs).windowbase * 4 + 2]
 #elif defined(__sh__)
-# define ARCH_REGS	struct pt_regs
-# define SYSCALL_NUM	gpr[3]
-# define SYSCALL_RET	gpr[0]
+# define ARCH_REGS		struct pt_regs
+# define SYSCALL_NUM(_regs)	(_regs).gpr[3]
+# define SYSCALL_RET(_regs)	(_regs).gpr[0]
 #else
 # error "Do not know how to find your architecture's registers and syscalls"
 #endif
@@ -1804,10 +1804,10 @@ int get_syscall(struct __test_metadata *_metadata, pid_t tracee)
 #endif
 
 #if defined(__mips__)
-	if (regs.SYSCALL_NUM == __NR_O32_Linux)
+	if (SYSCALL_NUM(regs) == __NR_O32_Linux)
 		return regs.SYSCALL_SYSCALL_NUM;
 #endif
-	return regs.SYSCALL_NUM;
+	return SYSCALL_NUM(regs);
 }
 
 /* Architecture-specific syscall changing routine. */
@@ -1830,14 +1830,14 @@ void change_syscall(struct __test_metadata *_metadata,
 	defined(__s390__) || defined(__hppa__) || defined(__riscv) || \
 	defined(__xtensa__) || defined(__csky__) || defined(__sh__)
 	{
-		regs.SYSCALL_NUM = syscall;
+		SYSCALL_NUM(regs) = syscall;
 	}
 #elif defined(__mips__)
 	{
-		if (regs.SYSCALL_NUM == __NR_O32_Linux)
+		if (SYSCALL_NUM(regs) == __NR_O32_Linux)
 			regs.SYSCALL_SYSCALL_NUM = syscall;
 		else
-			regs.SYSCALL_NUM = syscall;
+			SYSCALL_NUM(regs) = syscall;
 	}
 
 #elif defined(__arm__)
@@ -1871,11 +1871,8 @@ void change_syscall(struct __test_metadata *_metadata,
 	if (syscall == -1)
 #ifdef SYSCALL_NUM_RET_SHARE_REG
 		TH_LOG("Can't modify syscall return on this architecture");
-
-#elif defined(__xtensa__)
-		regs.SYSCALL_RET(regs) = result;
 #else
-		regs.SYSCALL_RET = result;
+		SYSCALL_RET(regs) = result;
 #endif
 
 #ifdef HAVE_GETREGS