Re: [PATCH v4 1/2] ptrace: save the type of syscall-stop in ptrace_message

[Oleg Nesterov]

On 11/30, Dmitry V. Levin wrote:
>
> On Thu, Nov 29, 2018 at 03:47:43PM +0100, Oleg Nesterov wrote:
>
> > > so that PTRACE_GETEVENTMSG users can easily tell
> > > whether this new semantics is supported by the kernel or not.
> >
> > Yes. And how much this can help? Again, an application can trivially detect
> > if this feature implemented or not, and it should do this anyway if it wants
> > to (try to) use PTRACE_EVENTMSG_SYSCALL_ENTRY/EXIT ?
>
> How an application can easily detect whether this feature is implemented?

As I already said, it can just do ptrace(PTRACE_GET_SYSCALL_INFO, NULL) ?
If it returns -EIO then this feature is not implemented. Any other error
code (actually EINVAL or EFAULT) means it is implemented.

Oleg.