Index: tests/sys/kern/ptrace_test.c
===================================================================
--- tests/sys/kern/ptrace_test.c
+++ tests/sys/kern/ptrace_test.c
@@ -3904,6 +3904,86 @@
 	ATF_REQUIRE(errno == ECHILD);
 }
 
+/*
+ * A simple test of PT_GET_SC_ARGS.
+ */
+ATF_TC_WITHOUT_HEAD(ptrace__syscall_args);
+ATF_TC_BODY(ptrace__syscall_args, tc)
+{
+	struct ptrace_lwpinfo pl;
+	pid_t fpid, wpid;
+	register_t args[2];
+	int events, status;
+
+	ATF_REQUIRE((fpid = fork()) != -1);
+	if (fpid == 0) {
+		trace_me();
+		kill(getpid(), 0);
+		exit(1);
+	}
+
+	/* The first wait() should report the stop from SIGSTOP. */
+	wpid = waitpid(fpid, &status, 0);
+	ATF_REQUIRE(wpid == fpid);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP);
+
+	/*
+	 * Continue the process ignoring the signal, but enabling
+	 * syscall entry traps.
+	 */
+	ATF_REQUIRE(ptrace(PT_TO_SCE, fpid, (caddr_t)1, 0) == 0);
+
+	/*
+	 * The next stop should be the syscall entry from getpid().
+	 */
+	wpid = waitpid(fpid, &status, 0);
+	ATF_REQUIRE(wpid == fpid);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+	ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+	ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCE);
+	ATF_REQUIRE(pl.pl_syscall_code == SYS_getpid);
+
+	ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+	/*
+	 * The next stop should be the syscall entry from kill().
+	 */
+	wpid = waitpid(fpid, &status, 0);
+	ATF_REQUIRE(wpid == fpid);
+	ATF_REQUIRE(WIFSTOPPED(status));
+	ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP);
+
+	ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1);
+	ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCE);
+	ATF_REQUIRE(pl.pl_syscall_code == SYS_kill);
+	ATF_REQUIRE(pl.pl_syscall_narg == 2);
+
+	ATF_REQUIRE(ptrace(PT_GET_SC_ARGS, wpid, (caddr_t)args,
+	    sizeof(args)) != -1);
+	ATF_REQUIRE(args[0] == wpid);
+	ATF_REQUIRE(args[1] == 0);
+
+	/* Disable syscall tracing and continue the child to let it exit. */
+	ATF_REQUIRE(ptrace(PT_GET_EVENT_MASK, fpid, (caddr_t)&events,
+	    sizeof(events)) == 0);
+	events &= ~PTRACE_SYSCALL;
+	ATF_REQUIRE(ptrace(PT_SET_EVENT_MASK, fpid, (caddr_t)&events,
+	    sizeof(events)) == 0);
+	ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0);
+
+	/* The last event should be for the child process's exit. */
+	wpid = waitpid(fpid, &status, 0);
+	ATF_REQUIRE(WIFEXITED(status));
+	ATF_REQUIRE(WEXITSTATUS(status) == 1);
+
+	wpid = wait(&status);
+	ATF_REQUIRE(wpid == -1);
+	ATF_REQUIRE(errno == ECHILD);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 
@@ -3965,6 +4045,7 @@
 	ATF_TP_ADD_TC(tp, ptrace__PT_CONTINUE_different_thread);
 #endif
 	ATF_TP_ADD_TC(tp, ptrace__PT_LWPINFO_stale_siginfo);
+	ATF_TP_ADD_TC(tp, ptrace__syscall_args);
 
 	return (atf_no_error());
 }