Re: [PATCH v2 13/19] remoteproc: core: Append resource only if spare resource present

[loic pallardy]

On 09/08/2016 11:33 AM, Lee Jones wrote:
> On Wed, 31 Aug 2016, Loic Pallardy wrote:
>
> > This patch renames rproc_add_resource_table_entry in __add_rsc_tbl_entry
> > to have shorter function name and adds spare resource support.
> > To guarantee remoteproc won't overwrite firmware data when copying
> > back modified resource table, __add_rsc_tbl_entry verifies first that
> > resource table owns a spare resource and uses spare bytes to create
> > a new resource entry. Spare resource is updated according to changes.
> >
> > Signed-off-by: Loic Pallardy <loic.pallardy@xxxxxx>
> > ---
> >  drivers/remoteproc/remoteproc_core.c | 54 ++++++++++++++++++++----------------
> >  1 file changed, 30 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > index aff1a00..25a429b 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -1107,39 +1107,34 @@ static int __update_rsc_tbl_entry(struct rproc *rproc,
> >  	return !updated;
> >  }
> >
> > -static struct resource_table*
> > -rproc_add_resource_table_entry(struct rproc *rproc,
> > +static int __add_rsc_tbl_entry(struct rproc *rproc,
>
> Once again, I prefer plain English over cryptic abbreviations.  Makes
> things much more difficult for developers who are new to, or are just
> dipping into RemoteProc code.

OK
> >  			       struct rproc_request_resource *request,
> > -			       struct resource_table *old_table, int *tablesz)
> > +			       struct resource_table *table, int tablesz)
> >  {
> > -	struct resource_table *table;
> >  	struct fw_rsc_hdr h;
> > +	struct fw_rsc_spare spare;
> >  	void *new_rsc_loc;
> >  	void *fw_header_loc;
> >  	void *start_of_rscs;
> >  	int new_rsc_offset;
> > -	int size = *tablesz;
> > -	int i;
> > +	int new_spare_offset;
> > +	int i, spare_index = 0;
> >
> >  	h.type = request->type;
> >
> > -	new_rsc_offset = size;
> > +	/* check available spare size */
>
> In keeping with the existing comments, please use correct grammar.
>
> Capital letters to start and for names etc.
>
> Much more professional IMO.

I'll correct
> > +	spare.len = __get_rsc_tbl_spare_size(rproc, table, tablesz, &spare_index);
> > +	if (spare.len < (sizeof(h) + request->size + 4)) /* new offset entry */
>
> Not sure that comment makes the code any clearer?
>
> All you're doing here is checking if we have enough space, right?
>
> I think the 4 is a 'magic' number.  I'd either provide a comment (like
> I did below), or define it.
I'll add a comment as you did to explain the "4".

> > +		return -EPERM;
>
> What does this have to do with permissions?
Yes sure, I'll replaced by -EINVAL as resource too large compare to 
spare area capability.

> > -	/*
> > -	 * Allocate another contiguous chunk of memory, large enough to
> > -	 * contain the new, expanded resource table.
> > -	 *
> > -	 * The +4 is for the extra offset[] element in the top level header
> > -	 */
> > -	size += sizeof(struct fw_rsc_hdr) + request->size + 4;
> > -	table = devm_kmemdup(&rproc->dev, old_table, size, GFP_KERNEL);
> > -	if (!table)
> > -		return ERR_PTR(-ENOMEM);
> > +	new_rsc_offset = table->offset[spare_index];
> >
> >  	/* Shunt table by 4 Bytes to account for the extra offset[] element */
> >  	start_of_rscs = (void *)table + table->offset[0];
> >  	memmove(start_of_rscs + 4,
> >  		start_of_rscs, new_rsc_offset - table->offset[0]);
> > +
> > +	spare.len -= 4;
>
> This probably deserves a comment too.
I'll add a comment too
> /*
>  * The spare area is finite.  Since we are increasing the size of the
>  * header and shunting the tables, we need to reduce the size of the
>  * available 'spare' area by the shunt size.
>  */
>
> >  	new_rsc_offset += 4;
> >
> >  	/* Update existing resource entry's offsets */
> > @@ -1153,13 +1148,27 @@ rproc_add_resource_table_entry(struct rproc *rproc,
> >  	/* Copy new firmware header into table */
> >  	fw_header_loc = (void *)table + new_rsc_offset;
> >  	memcpy(fw_header_loc, &h, sizeof(h));
> > +	spare.len -= sizeof(h);
> >
> >  	/* Copy new resource entry into table */
> >  	new_rsc_loc = (void *)fw_header_loc + sizeof(h);
> >  	memcpy(new_rsc_loc, request->resource, request->size);
> > +	spare.len -= request->size;
> >
> > -	*tablesz = size;
> > -	return table;
> > +	/* create new rsc spare resource at the end of remaining spare */
>
> Same comment about using nice grammar in comments.
Ok
Thanks,
Loic
> > +	new_spare_offset = new_rsc_offset + sizeof(h) + request->size;
> > +	h.type = RSC_SPARE;
> > +
> > +	fw_header_loc = (void *)table + new_spare_offset;
> > +	memcpy(fw_header_loc, &h, sizeof(h));
> > +
> > +	new_rsc_loc = (void *)fw_header_loc + sizeof(h);
> > +	memcpy(new_rsc_loc, &spare, sizeof(spare));
> > +
> > +	/* update spare offset */
> > +	table->offset[spare_index] = new_spare_offset;
> > +
> > +	return 0;
> >  }
> >
> >  static struct resource_table*
> > @@ -1203,12 +1212,9 @@ rproc_apply_resource_overrides(struct rproc *rproc,
> >  			continue;
> >
> >  		/* Didn't find matching resource entry -- creating a new one. */
> > -		table = rproc_add_resource_table_entry(rproc, resource,
> > -						       table, &size);
> > -		if (IS_ERR(table))
> > +		updated = __add_rsc_tbl_entry(rproc, resource, table, size);
> > +		if (updated)
> >  			goto out;
> > -
> > -		*orig_table = table;
> >  	}
> >
> >  	rproc_dump_resource_table(rproc, table, size);