linux-kernel - Re: [PATCH] cxl/mem: Force array size of mem_commands[] to CXL_MEM_COMMAND_ID

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Message-ID: <YFxF6/LerP9OD8n9@rric.localdomain>
Date:   Thu, 25 Mar 2021 09:12:27 +0100
From:   Robert Richter <rrichter@....com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ben Widawsky <ben.widawsky@...el.com>,
        linux-cxl@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl/mem: Force array size of mem_commands[] to
 CXL_MEM_COMMAND_ID_MAX

On 24.03.21 12:08:20, Dan Williams wrote:
> On Wed, Mar 24, 2021 at 11:43 AM Ira Weiny <ira.weiny@...el.com> wrote:

> > Can't we use ARRAY_SIZE?
> 
> An ARRAY_SIZE() check in cxl_validate_cmd_from_user() would work too,
> but it wouldn't give the compiler protection that Robert mentions for
> going the other way where mem_commands tries to add an entry that is
> out of bounds relative to CXL_CMDS.

I was considering that too. Another reason apart from above was to
treat 'holes' in the array caused by #ifdefs the same regardless its
position in the array. Thus, all should show up as being zeroed
instead of cutting those at the end from the array.

Thanks for applying,

-Robert