linux-kernel - Re: [RFC][PATCH 1/2] lib: printf: append support of '%*p[Mm][FR]'

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Date:	Sat, 30 Jun 2012 07:48:53 -0700
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	proski@....org, Andrei Emeltchenko <andrei.emeltchenko@...el.com>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 1/2] lib: printf: append support of '%*p[Mm][FR]'

On Fri, 2012-06-29 at 16:26 -0700, Andrew Morton wrote:
> On Fri, 29 Jun 2012 09:08:06 -0700
> Joe Perches <joe@...ches.com> wrote:
> 
> > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> > []
> > > @@ -655,11 +655,12 @@ char *resource_string(char *buf, char *end, struct resource *res,
> > >  }
> > >  
> > >  static noinline_for_stack
> > > -char *mac_address_string(char *buf, char *end, u8 *addr,
> > > -			 struct printf_spec spec, const char *fmt)
> > > +char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
> > > +		 const char *fmt)
> > >  {
> > > -	char mac_addr[sizeof("xx:xx:xx:xx:xx:xx")];
> > > -	char *p = mac_addr;
> > > +	char hex_str[64*3];	/* support up to 64 bytes to print */
> > 
> > Might be too much stack though.
> 
> Yes, it's a bit marginal, as this new capability might be used in debug
> or crash situations where we're deep into the stack.  The average case
> could be improved by using alloca()-style allocation.

Or maybe support larger sizes with a smaller
stack buffer and a while loop.

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