selftests/mm: Enable pkey_sighandler_tests on arm64

pkey_sighandler_tests.c makes raw syscalls using its own helper,
syscall_raw(). One of those syscalls is clone, which is problematic
as every architecture has a different opinion on the order of its
arguments.

To complete arm64 support, we therefore add an appropriate
implementation in syscall_raw(), and introduce a clone_raw() helper
that shuffles arguments as needed for each arch.

Having done this, we enable building pkey_sighandler_tests for arm64
in the Makefile.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Link: https://lore.kernel.org/r/20241029144539.111155-6-kevin.brodsky@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: kevin-brodsky-arm

tools/testing/selftests/mm/Makefile

@@ -105,12 +105,12 @@ endif
 ifeq ($(CAN_BUILD_X86_64),1)
 TEST_GEN_FILES += $(BINARIES_64)
 endif
-else
 
-ifneq (,$(filter $(ARCH),arm64 powerpc))
+else ifeq ($(ARCH),arm64)
+TEST_GEN_FILES += protection_keys
+TEST_GEN_FILES += pkey_sighandler_tests
+else ifeq ($(ARCH),powerpc)
 TEST_GEN_FILES += protection_keys
-endif
-
 endif
 
 ifneq (,$(filter $(ARCH),arm64 mips64 parisc64 powerpc riscv64 s390x sparc64 x86_64 s390))

tools/testing/selftests/mm/pkey_sighandler_tests.c

@@ -60,12 +60,44 @@ long syscall_raw(long n, long a1, long a2, long a3, long a4, long a5, long a6)
 		      : "=a"(ret)
 		      : "a"(n), "b"(a1), "c"(a2), "d"(a3), "S"(a4), "D"(a5)
 		      : "memory");
+#elif defined __aarch64__
+	register long x0 asm("x0") = a1;
+	register long x1 asm("x1") = a2;
+	register long x2 asm("x2") = a3;
+	register long x3 asm("x3") = a4;
+	register long x4 asm("x4") = a5;
+	register long x5 asm("x5") = a6;
+	register long x8 asm("x8") = n;
+	asm volatile ("svc #0"
+		      : "=r"(x0)
+		      : "r"(x0), "r"(x1), "r"(x2), "r"(x3), "r"(x4), "r"(x5), "r"(x8)
+		      : "memory");
+	ret = x0;
 #else
 # error syscall_raw() not implemented
 #endif
 	return ret;
 }
 
+static inline long clone_raw(unsigned long flags, void *stack,
+			     int *parent_tid, int *child_tid)
+{
+	long a1 = flags;
+	long a2 = (long)stack;
+	long a3 = (long)parent_tid;
+#if defined(__x86_64__) || defined(__i386)
+	long a4 = (long)child_tid;
+	long a5 = 0;
+#elif defined(__aarch64__)
+	long a4 = 0;
+	long a5 = (long)child_tid;
+#else
+# error clone_raw() not implemented
+#endif
+
+	return syscall_raw(SYS_clone, a1, a2, a3, a4, a5, 0);
+}
+
 /*
  * Returns the most restrictive pkey register value that can be used by the
  * tests.
@@ -294,14 +326,13 @@ static void test_sigsegv_handler_with_different_pkey_for_stack(void)
 	memset(&siginfo, 0, sizeof(siginfo));
 
 	/* Use clone to avoid newer glibcs using rseq on new threads */
-	long ret = syscall_raw(SYS_clone,
-			       CLONE_VM | CLONE_FS | CLONE_FILES |
-			       CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
-			       CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID |
-			       CLONE_DETACHED,
-			       (long) ((char *)(stack) + STACK_SIZE),
-			       (long) &parent_pid,
-			       (long) &child_pid, 0, 0);
+	long ret = clone_raw(CLONE_VM | CLONE_FS | CLONE_FILES |
+			     CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
+			     CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID |
+			     CLONE_DETACHED,
+			     stack + STACK_SIZE,
+			     &parent_pid,
+			     &child_pid);
 
 	if (ret < 0) {
 		errno = -ret;
@@ -466,14 +497,13 @@ static void test_pkru_sigreturn(void)
 	sigstack.ss_size = STACK_SIZE;
 
 	/* Use clone to avoid newer glibcs using rseq on new threads */
-	long ret = syscall_raw(SYS_clone,
-			       CLONE_VM | CLONE_FS | CLONE_FILES |
-			       CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
-			       CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID |
-			       CLONE_DETACHED,
-			       (long) ((char *)(stack) + STACK_SIZE),
-			       (long) &parent_pid,
-			       (long) &child_pid, 0, 0);
+	long ret = clone_raw(CLONE_VM | CLONE_FS | CLONE_FILES |
+			     CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM |
+			     CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID |
+			     CLONE_DETACHED,
+			     stack + STACK_SIZE,
+			     &parent_pid,
+			     &child_pid);
 
 	if (ret < 0) {
 		errno = -ret;