Re: [PATCH v2 1/3] checks: add phandle with arg property checks

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Thu, Aug 24, 2017 at 02:19:27PM -0500, Rob Herring wrote:
> On Thu, Aug 24, 2017 at 12:23 PM, Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> > On Wed, Aug 23, 2017 at 9:03 PM, David Gibson
> > <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org> wrote:
> >> On Tue, Aug 22, 2017 at 06:02:06PM -0500, Rob Herring wrote:
> >>> Many common bindings follow the same pattern of client properties
> >>> containing a phandle and N arg cells where N is defined in the provider
> >>> with a '#<specifier>-cells' property such as:
> 
> [...]
> 
> >>> +             if (prop->val.len < ((cell + cellsize + 1) * sizeof(cell_t))) {
> >>> +                     FAIL(c, dti, "%s property size (%d) too small for cell size %d in %s",
> >>> +                          prop->name, prop->val.len, cellsize, node->fullpath);
> >>> +             }
> >>
> >> How will this cope if the property is really badly formed - e.g. a 3
> >> byte property, so you can't even grab a whole first phandle?  I think
> >> it will trip the assert() in propval_cell_n() which isn't great.
> >
> > At least for your example, we'd exit the loop (cell < 3/4). But I need
> > to a check for that because it would be silent currently. I'll add a
> > check that the size is a multiple of 4 and greater than 0.
> >
> > However, the check here is not perfect because we could have
> > "<&phandle1 1 2>" when really it should be "<&phandle1 &phandle2
> > &phandle3>". We don't fail until we're checking the 2nd phandle.
> > That's why I added the "or bad phandle" and the cell # in the message
> > above. In the opposite case, we'd be silent. One thing that could be
> > done is double check things against the markers if they are present.
> 
> Here's what that looks like:
> 
> /* If we have markers, verify the current cell is a phandle */
> if (prop->val.markers) {
>   struct marker *m = prop->val.markers;
>   for_each_marker_of_type(m, REF_PHANDLE) {
>     if (m->offset == (cell * sizeof(cell_t)))
>       break;
>   }
>   if (!m)
>   FAIL(c, dti, "Property '%s', cell %d is not a valid phandle in %s",
>     prop->name, cell, node->fullpath);

The logic seems sound, but I don't like the message.  An integer
literal is no less a phandle than a reference, just usually not the
best way of entering one.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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