Re: [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO

[Dmitry V. Levin]

On Tue, Nov 27, 2018 at 04:07:32AM +0100, Elvira Khabirova wrote:
> On Mon, 26 Nov 2018 15:35:24 +0100, Oleg Nesterov wrote:
> > On 11/25, Elvira Khabirova wrote:
> > >
> > > Extend PTRACE_GET_SYSCALL_INFO to support PTRACE_EVENT_SECCOMP stops.
> > > The information returned is the same as for syscall-enter-stops.  
> > 
> > Oh, this is not nice ;) there must be a better option, I hope... Plus
> > 
> > Can't ptrace_get_syscall() check
> > 
> > 	child->exit_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP;
> > 
> > to detect the PTRACE_EVENT_SECCOMP case?
> 
> Nope; looks like exit_code is zeroed after wait().

It's explicitly reset to zero in wait_task_stopped() unless WNOWAIT wait
option is set.  When strace requests PTRACE_GET_SYSCALL_INFO after
wait4(), child->exit_code is already set to zero.


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