From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH XEN v6 20/32] tools/libs/foreignmemory:
 Support err == NULL to map.
Date: Wed, 9 Dec 2015 12:56:38 +0000
Message-ID: <20151209125638.GN23818@citrix.com>
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To: Ian Campbell <ian.campbell@citrix.com>
Cc: ian.jackson@eu.citrix.com, Wei Liu <wei.liu2@citrix.com>, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

On Wed, Dec 09, 2015 at 12:41:49PM +0000, Ian Campbell wrote:
> On Wed, 2015-12-09 at 12:22 +0000, Wei Liu wrote:
> > > diff --git a/tools/libs/foreignmemory/core.c
> > > b/tools/libs/foreignmemory/core.c
> > > index 21dc7ee..91bea55 100644
> > > --- a/tools/libs/foreignmemory/core.c
> > > +++ b/tools/libs/foreignmemory/core.c
> > > @@ -14,6 +14,8 @@
> > > =A0 */
> > > =A0
> > > =A0#include <stdlib.h>
> > > +#include <assert.h>
> > > +#include <errno.h>
> > > =A0
> > > =A0#include "private.h"
> > > =A0
> > > @@ -64,7 +66,33 @@ void *xenforeignmemory_map(xenforeignmemory_handle
> > > *fmem,
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0uint32_t dom, int prot,
> > > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0const xen_pfn_t *arr, int *err, size_t num)
> > > =A0{
> > > -=A0=A0=A0=A0return osdep_xenforeignmemory_map(fmem, dom, prot, arr, =
err, num);
> > > +=A0=A0=A0=A0void *ret;
> > > +=A0=A0=A0=A0int *err_to_free =3D NULL;
> > > +
> > > +=A0=A0=A0=A0if ( err =3D=3D NULL )
> > > +=A0=A0=A0=A0=A0=A0=A0=A0err =3D err_to_free =3D malloc(num * sizeof(=
int));
> > > +
> > =

> > malloc can fail, which means when user passes in err=3D=3DNULL there is=
 two
> > possible behaviours of this function?
> =

> Partially/Full success and "fail entirely reporting an error" you mean?
> There are always those two possibilities, yes, regardless of err=3D=3DNUL=
L. I
> think that's inline with the doc comment too.
> =

> If that's not what you were asking then I'm afraid I don't see what you a=
re
> getting at.
> =


What I meant was we should check err !=3D NULL after malloc because
osdep_xenforeignmeory_map dereferences it unconditionally.

Wei.

> Ian.