linux-kernel - Re: [PATCH 27/36] tty: synclinkmp: Mark never checked 'readval' as __always

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20201105112728.GJ4488@dell>
Date:   Thu, 5 Nov 2020 11:27:28 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Jiri Slaby' <jirislaby@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "paulkf@...rogate.com" <paulkf@...rogate.com>
Subject: Re: [PATCH 27/36] tty: synclinkmp: Mark never checked 'readval' as
 __always_unused

On Thu, 05 Nov 2020, David Laight wrote:

> > >> And the loop can be turned into ndelay:
> > >>
> > >>          /*
> > >>           * Force at least 170ns delay before clearing
> > >>           * reset bit. Each read from LCR takes at least
> > >>           * 30ns so 10 times for 300ns to be safe.
> > >>           */
> > >>          for(i=0;i<10;i++)
> > >>                  readval = *MiscCtrl;
> > >
> > > Again, since I can't test this, I do not want this patch to contain
> > > any functional changes.  AFAIC, the 10 register reads must still
> > > happen after this patch is applied.
> 
> You can't use ndelay(); the writes can get posted so can appear
> much closer together by the time they get to the actual hardware.
> Multiple volatile reads don't need a target variable.
> (Shouldn't they also real readl()?)
> 
> Deleting the driver works...

Will post the removal patches when my tests finish.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog