arm64: Remove unimplemented syscall log message

From: Michael Weiser <[email protected]>

commit 1962682d2b2fbe6cfa995a85c53c069fadda473e upstream.

Stop printing a (ratelimited) kernel message for each instance of an unimplemented syscall being called. Userland making an unimplemented syscall is not necessarily misbehaviour and to be expected with a current userland running on an older kernel. Also, the current message looks scary to users but does not actually indicate a real problem nor help them narrow down the cause. Just rely on sys_ni_syscall() to return -ENOSYS.

---
This was backported to v4.14 and later, but is missing in v4.4 and before, apparently because of a trivial merge conflict. This is a manual backport I did after I saw a report about the issue by Martin Vajnar on the musl mailing list.

---
 arch/arm64/kernel/traps.c | 8 --------
 1 file changed, 8 deletions(-)

index 9322be69ca09..db4163808c76 100644
@@ -363,14 +363,6 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs)
 	}
 #endif
 
-	if (show_unhandled_signals && printk_ratelimit()) {
-		pr_info("%s[%d]: syscall %d\n", current->comm,
-			task_pid_nr(current), (int)regs->syscallno);
-		dump_instr("", regs);
-		if (user_mode(regs))
-			__show_regs(regs);
-	}
-
 	return sys_ni_syscall();
 }
 

2.29.2

Nevermind, I forgot the 4.1.y line had ended. The 4.4 version is still needed though, and also applies to 4.9.

Arnd