[PATCH] arm64: ni_syscall should be similar to other archs

[Catalin Marinas]

(I forgot about this email, some two months ago)

On Wed, Feb 24, 2016 at 03:54:59PM +0100, per.hallsmark at windriver.com wrote:
> From: Per Hallsmark <per.hallsmark at windriver.com>
> 
> Today arm64 have it's own variant when a userspace app is doing a
> non-implemented syscall in that it dumps on console process name,
> registers and such. This makes a different behaviour on arm64 than
> on all other archs.

Are you hitting a real issue with this? Test apps doing random syscalls?

> This patch propose to get inline with other archs.

Well, it's not fully in line, for example on arch/arm we generate a
SIGILL (and I think we should fix the compat path in the arm64
do_ni_syscall() to do the same).

> If we want to have a note on console, syslog or so when doing a
> nonimplemented syscall, it would be better to add a variable
> show_nonimplemented_syscalls and sense on it in the generic
> kernel/sys_ni.c::sys_ni_syscall() which could dump info (and then
> it would be generic for all archs). But that is another discussion
> alltogether, lets first synchronize the archs to behave similar.

Or we could have finer grained show_unhandled_signals variable. The user
visible /proc/sys/debug/exception-trace doesn't say anything about
signals.

> Signed-off-by: Per Hallsmark <per.hallsmark at windriver.com>
> ---
>  arch/arm64/kernel/traps.c | 8 --------
>  1 file changed, 8 deletions(-)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index cbedd72..980ff63 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -403,14 +403,6 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs)
>  	}
>  #endif
>  
> -	if (show_unhandled_signals_ratelimited()) {
> -		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();
>  }

-- 
Catalin