linux-kernel - Re: [PATCH 1/5] perf tests: Add tip/pid mmap automated tests

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Date:	Mon, 17 Mar 2014 11:39:05 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Don Zickus <dzickus@...hat.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH 1/5] perf tests: Add tip/pid mmap automated tests

On Mon, Mar 17, 2014 at 01:50:12PM +0900, Namhyung Kim wrote:
> Hi Jiri,
> 
> On Fri, 14 Mar 2014 15:00:02 +0100, Jiri Olsa wrote:
> > +static int thread_init(struct thread_data *td)
> > +{
> > +	void *map;
> > +
> > +	map = mmap(NULL, page_size, PROT_READ|PROT_WRITE,
> > +		   MAP_SHARED|MAP_ANONYMOUS, -1, 0);
> 
> Shouldn't it be an executable mapping to be found by MAP__FUNCTION?

yea.. looks like my arch implies PROT_EXEC via PROT_READ, man mmap:

  On some hardware architectures (e.g., i386), PROT_WRITE implies PROT_READ.   It  is  architecture  dependent  whether  PROT_READ
  implies PROT_EXEC or not.  Portable programs should always set PROT_EXEC if they intend to execute code in the new mapping.


mm/mmap.c:

        /*
         * Does the application expect PROT_READ to imply PROT_EXEC?
         *
         * (the exception is when the underlying filesystem is noexec
         *  mounted, in which case we dont add PROT_EXEC.)
         */
        if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
                if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
                        prot |= PROT_EXEC;


I'll set the PROT_EXEC as the man page says.


thanks,
jirka
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