Re: [PATCH] arm64: ptrace: don't warn on missing siginfo in a group-stop

[Oleg Nesterov <oleg@redhat.com>]

On 10/16, Zhao Gongyi wrote:
>
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -573,9 +573,11 @@ static void update_syscall_orig_x0_after_ptrace(struct task_struct *target)
>  	if (regs->syscallno == NO_SYSCALL)
>  		return;
>  
> -	/* We should only be called when target is in a ptrace stop */
> -	if (WARN_ON_ONCE(!info))
> +	/* Only non-seized group-stops lack siginfo (see do_jobctl_trap()). */
> +	if (!info) {
> +		WARN_ON_ONCE(target->ptrace & PT_SEIZED);
>  		return;
> +	}

Perhaps we can simply remove this WARN_ON_ONCE? 

Oleg.

--- x/arch/arm64/kernel/ptrace.c
+++ x/arch/arm64/kernel/ptrace.c
@@ -573,10 +573,6 @@ static void update_syscall_orig_x0_after
 	if (regs->syscallno == NO_SYSCALL)
 		return;
 
-	/* We should only be called when target is in a ptrace stop */
-	if (WARN_ON_ONCE(!info))
-		return;
-
 	/*
 	 * For compat tasks, orig_r0 is provided directly through GPR index
 	 * 17.
@@ -588,7 +584,7 @@ static void update_syscall_orig_x0_after
 	 * Don't update orig_x0 for a syscall-exit-stop, as x0 now contains the
 	 * return value of the system call.
 	 */
-	if ((info->si_code & ~0x80) == SIGTRAP &&
+	if (info && info->si_code == (SIGTRAP | 0x80) &&
 	    target->ptrace_message == PTRACE_EVENTMSG_SYSCALL_EXIT) {
 		return;
 	}