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

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Message-Id: <20120629162649.f277177f.akpm@linux-foundation.org>
Date:	Fri, 29 Jun 2012 16:26:49 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joe Perches <joe@...ches.com>
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, 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.

Documentation/printk-formats.txt would need to be updated please.  Also
the big comment over vsnprintf().
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