arm64: Implement cpu_ptrace().

Add a minimal implementation of cpu_ptrace() for arm64. It is only used to
get/set VFP registers for 32bits binaries, as it is apparently what we use
there, instead of the MI PT_GETFPREGS/PT_SETFPREGS.

PR:	267361
MFC After: 1 week

sys/arm64/arm64/ptrace_machdep.c

@@ -49,6 +49,36 @@ __FBSDID("$FreeBSD$");
 
 #include <machine/armreg.h>
 
+/* Only used to get/set 32bits VFP regs */
+int
+cpu_ptrace(struct thread *td, int req, void *arg, int data)
+{
+#if defined(VFP) && defined(COMPAT_FREEBSD32)
+	mcontext32_vfp_t vfp;
+	int error;
+
+	if (!SV_CURPROC_FLAG(SV_ILP32))
+		return (EINVAL);
+	switch (req) {
+		case PT_GETVFPREGS32:
+			get_fpcontext32(td, &vfp);
+			error = copyout(&vfp, arg, sizeof(vfp));
+			break;
+		case PT_SETVFPREGS32:
+			error = copyin(arg, &vfp, sizeof(vfp));
+			if (error == 0)
+				set_fpcontext32(td, &vfp);
+			break;
+		default:
+			error = EINVAL;
+	}
+
+	return (error);
+#else
+	return (EINVAL);
+#endif
+}
+
 #if defined(VFP) && defined(COMPAT_FREEBSD32)
 static bool
 get_arm_vfp(struct regset *rs, struct thread *td, void *buf, size_t *sizep)

sys/arm64/include/ptrace.h

@@ -1 +1,11 @@
 /* $FreeBSD$ */
+
+#ifndef _MACHINE_PTRACE_H_
+#define _MACHINE_PTRACE_H_
+
+#define __HAVE_PTRACE_MACHDEP
+
+#define PT_GETVFPREGS32	(PT_FIRSTMACH + 0)
+#define PT_SETVFPREGS32	(PT_FIRSTMACH + 1)
+
+#endif /* _MACHINE_PTRACE_H_ */