--- zzzz-none-000/linux-3.10.107/arch/um/kernel/skas/syscall.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/um/kernel/skas/syscall.c	2021-02-04 17:41:59.000000000 +0000
@@ -8,9 +8,7 @@
 #include <kern_util.h>
 #include <sysdep/ptrace.h>
 #include <sysdep/syscalls.h>
-
-extern int syscall_table_size;
-#define NR_SYSCALLS (syscall_table_size / sizeof(void *))
+#include <os.h>
 
 void handle_syscall(struct uml_pt_regs *r)
 {
@@ -18,22 +16,19 @@
 	long result;
 	int syscall;
 
-	syscall_trace_enter(regs);
+	if (syscall_trace_enter(regs)) {
+		result = -ENOSYS;
+		goto out;
+	}
+
+	syscall = get_syscall(r);
 
-	/*
-	 * This should go in the declaration of syscall, but when I do that,
-	 * strace -f -c bash -c 'ls ; ls' breaks, sometimes not tracing
-	 * children at all, sometimes hanging when bash doesn't see the first
-	 * ls exit.
-	 * The assembly looks functionally the same to me.  This is
-	 *     gcc version 4.0.1 20050727 (Red Hat 4.0.1-5)
-	 * in case it's a compiler bug.
-	 */
-	syscall = UPT_SYSCALL_NR(r);
-	if ((syscall >= NR_SYSCALLS) || (syscall < 0))
+	if ((syscall > __NR_syscall_max) || syscall < 0)
 		result = -ENOSYS;
-	else result = EXECUTE_SYSCALL(syscall, regs);
+	else
+		result = EXECUTE_SYSCALL(syscall, regs);
 
+out:
 	PT_REGS_SET_SYSCALL_RETURN(regs, result);
 
 	syscall_trace_leave(regs);