linux-kernel - Re: [RFC/PATCH] lib/vsprintf: Add support to store cpumask

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Date:	Tue, 28 Jun 2016 18:06:47 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [RFC/PATCH] lib/vsprintf: Add support to store cpumask

On Tue, 28 Jun 2016 21:27:29 +0200
Rasmus Villemoes <linux@...musvillemoes.dk> wrote:

> > I probably should make a trace_printk() that doesn't default to the
> > binary print, to handle things like this.
> >
> >   trace_printk_ptr()?
> >
> > Or even just see if I can find a way that detects this in the fmt
> > string. Hmm, that probably can't be done at compile time :-/  
> 
> Well, not with gcc itself, but it wouldn't be too hard to make smatch
> complain loudly if trace_printk is used on a format string with any %p
> extension (directing people to use trace_printk_ptr()) - the format
> parsing (and type checking) is already there.

Well, actually gcc can (see below). Although, the more I think about
this, the more I'm thinking that the bin_printk() should be default
just copy the pointer content. As the whole point of bin_printk() is to
print the content at another time. And since pointers should not be
dereferenced later, it should be saved at the moment the bprintk() is
called and not dereferenced later.

-- Steve

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 94aa10ffe156..62693900cc4b 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -631,7 +631,24 @@ do {									\
 									\
 	__trace_printk_check_format(fmt, ##args);			\
 									\
-	if (__builtin_constant_p(fmt))					\
+	if (__builtin_constant_p(fmt) &&				\
+	    !__builtin_strstr(fmt, "%pF") &&				\
+	    !__builtin_strstr(fmt, "%pf") &&				\
+	    !__builtin_strstr(fmt, "%pR") &&				\
+	    !__builtin_strstr(fmt, "%pr") &&				\
+	    !__builtin_strstr(fmt, "%pb") &&				\
+	    !__builtin_strstr(fmt, "%pM") &&				\
+	    !__builtin_strstr(fmt, "%pI") &&				\
+	    !__builtin_strstr(fmt, "%pE") &&				\
+	    !__builtin_strstr(fmt, "%pU") &&				\
+	    !__builtin_strstr(fmt, "%pV") &&				\
+	    !__builtin_strstr(fmt, "%pN") &&				\
+	    !__builtin_strstr(fmt, "%pa") &&				\
+	    !__builtin_strstr(fmt, "%pd") &&				\
+	    !__builtin_strstr(fmt, "%pC") &&				\
+	    !__builtin_strstr(fmt, "%pD") &&				\
+	    !__builtin_strstr(fmt, "%pg") &&				\
+	    !__builtin_strstr(fmt, "%pG"))				\
 		__trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args);	\
 	else								\
 		__trace_printk(_THIS_IP_, fmt, ##args);			\