netdev - Re: [PATCH] net: dsa: remove deprecated strncpy

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Date: Tue, 18 Jul 2023 12:41:56 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Kees Cook <kees@...nel.org>, justinstitt@...gle.com, Florian Fainelli
 <f.fainelli@...il.com>, Vladimir Oltean <olteanv@...il.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>, Nick
 Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] net: dsa: remove deprecated strncpy

On Tue, 18 Jul 2023 21:31:04 +0200 Andrew Lunn wrote:
> On Tue, Jul 18, 2023 at 12:11:16PM -0700, Jakub Kicinski wrote:
> > On Tue, 18 Jul 2023 11:05:23 -0700 Kees Cook wrote:  
> > > Honestly I find the entire get_strings API to be very fragile given
> > > the lack of passing the length of the buffer, instead depending on
> > > the string set length lookups in each callback, but refactoring that
> > > looks like a ton of work for an uncertain benefit.  
> > 
> > We have been adding better APIs for long term, and a print helper short
> > term - ethtool_sprintf(). Should we use ethtool_sprintf() here?  
> 
> I was wondering about that as well. There is no variable expansion in
> most cases, so the vsnprintf() is a waste of time.
> 
> Maybe we should actually add another helper:
> 
> ethtool_name_cpy(u8 **data, unsigned int index, const char *name);

I wasn't sure if vsnprintf() is costly enough to bother, but SG.

Probably without the "unsigned int index", since the ethtool_sprintf()
API updates the first argument for the caller.

> Then over the next decade, slowly convert all drivers to it. And then
> eventually replace the u8 with a struct including the length.
> 
> The netlink API is a bit better. It is one kAPI call which does
> everything, and it holds RTNL. So it is less likely the number of
> statistics will change between the calls into the driver.