Re: [LTP] [PATCH] mprotect04: fix powerpc crash when copying exec_func

[Jan S. <jst...@re...>]

----- Original Message -----
> From: "Cyril Hrubis" <ch...@su...>
> To: "Jan Stancek" <jst...@re...>
> Cc: ltp...@li...
> Sent: Wednesday, 9 September, 2015 2:37:37 PM
> Subject: Re: [LTP] [PATCH] mprotect04: fix powerpc crash when copying exec_func
> 
> Hi!
> > Testcase tried to copy page size area starting at &exec_func.
> > This results in crash on powerpc, because &exec_func is too close
> > to end of page and subsequent page is not mapped:
> 
> I was wondering about this problem when I was fixing the test, but could
> not actually hit it.
> 
> > -static void *get_func(void *mem)
> > +static int page_present(void *p)
> >  {
> > -	memcpy(mem, exec_func, getpagesize());
> > +	int fd;
> > +
> > +	fd = SAFE_OPEN(cleanup, "page_present", O_WRONLY|O_CREAT, 0644);
> 
> Why don't we use "/dev/null"?

It doesn't seem reliable:

open("/dev/null", O_WRONLY|O_CREAT, 0644) = 3
write(3, NULL, 1)                       = 1
close(3)                                = 0

I'm seeing this on RHEL6.7 kernel, I haven't tried latest upstream yet.

Regards,
Jan

> 
> 
> The rest looks good to me.
> 
> --
> Cyril Hrubis
> ch...@su...
>