linux-kernel - [PATCH 3.16 269/410] arm64: Remove unimplemented syscall log message

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Message-ID: <lsq.1528380321.88828682@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Will Deacon" <will.deacon@....com>,
        "Michael Weiser" <michael.weiser@....de>
Subject: [PATCH 3.16 269/410] arm64: Remove unimplemented syscall log message

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Weiser <michael.weiser@....de>

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.

Acked-by: Will Deacon <will.deacon@....com>
Signed-off-by: Michael Weiser <michael.weiser@....de>
Signed-off-by: Will Deacon <will.deacon@....com>
[bwh: Backported to 3.16: Deleted code was slightly different]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm64/kernel/traps.c | 8 --------
 1 file changed, 8 deletions(-)

--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -251,14 +251,6 @@ asmlinkage long do_ni_syscall(struct pt_
 	}
 #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();
 }