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

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 29 Jun 2012 09:08:06 -0700
Joe Perches <joe@perches.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().