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Date: Tue, 06 Mar 2012 08:35:00 -0000
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From: Mark Kettenis <mark.kettenis@xs4all.nl>
To: jan.kratochvil@redhat.com
CC: gdb-patches@sourceware.org
In-reply-to: <20120306061739.GC24004@host2.jankratochvil.net> (message from	Jan Kratochvil on Tue, 6 Mar 2012 07:17:39 +0100)
Subject: Re: [patch 3/3] attach-fail-reasons: SELinux deny_ptrace
References:  <20120306061739.GC24004@host2.jankratochvil.net>
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> Date: Tue, 6 Mar 2012 07:17:39 +0100
> From: Jan Kratochvil <jan.kratochvil@redhat.com>
> 
> Hi,
> 
> and here is the last bit for new SELinux 'deny_ptrace':
> 	https://bugzilla.redhat.com/show_bug.cgi?id=786878
> 
> As even PTRACE_TRACEME fails in such case it needs to install hook for even
> that event.

A few comments inline below...

> --- a/gdb/gdbserver/linux-low.c
> +++ b/gdb/gdbserver/linux-low.c
> @@ -550,6 +550,25 @@ add_lwp (ptid_t ptid)
>    return lwp;
>  }
>  
> +/* Execute PTRACE_TRACEME with error checking.  */
> +
> +static void
> +linux_traceme (const char *program)
> +{
> +  int save_errno;
> +
> +  errno = 0;
> +  if (ptrace (PTRACE_TRACEME, 0, NULL, NULL) == 0)
> +    return;

Setting errno to zero here is pointless isn't it?

> +  save_errno = errno;
> +  linux_ptrace_create_warnings ();
> +  fprintf (stderr, _("Cannot trace created process %s: %s.\n"), program,
> +	   strerror (save_errno));
> +  fflush (stderr);
> +  _exit (0177);
> +}

> --- a/gdb/inf-ptrace.c
> +++ b/gdb/inf-ptrace.c
> @@ -105,7 +105,15 @@ static void
>  inf_ptrace_me (void)
>  {
>    /* "Trace me, Dr. Memory!"  */
> +  errno = 0;
>    ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3)0, 0);
> +  if (errno != 0)
> +    {
> +      fprintf_unfiltered (gdb_stderr, _("Cannot create process: %s\n"),

"Cannot trace process: %s"?

> +			  safe_strerror (errno));
> +      gdb_flush (gdb_stderr);
> +      _exit (0177);
> +    }
>  }