RE: [PATCH] checkpatch: add warning on %pk instead of %pK usage

[Roberts, William C]

> -----Original Message-----
> From: Joe Perches [mailto:joe@xxxxxxxxxxx]
> Sent: Friday, February 10, 2017 2:50 PM
> To: Roberts, William C <william.c.roberts@xxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx; apw@xxxxxxxxxxxxx; Andew Morton <akpm@linux-
> foundation.org>
> Cc: keescook@xxxxxxxxxxxx; kernel-hardening@xxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH] checkpatch: add warning on %pk instead of %pK usage
> 
> On Fri, 2017-02-10 at 22:26 +0000, Roberts, William C wrote:
> > <snip>
> >
> > > >
> > > > On Fri, 2017-02-10 at 11:37 -0800, william.c.roberts@xxxxxxxxx wrote:
> > > > > From: William Roberts <william.c.roberts@xxxxxxxxx>
> > > > >
> > > > > Sample output:
> > > > > WARNING: %pk is close to %pK, did you mean %pK?.
> > > > > \#20: FILE: drivers/char/applicom.c:230:
> > > > > +			printk(KERN_INFO "Could not allocate IRQ %d for
> PCI
> > > >
> > > > Applicom
> > > > > +device. %pk\n", dev->irq, pci_get_class);
> > > >
> > > > There isn't a single instance of this in the kernel tree.
> > > >
> > > > Maybe if this is really useful, then all the %p<foo> extensions
> > > > should be enumerated and all unknown uses should have warnings.
> > >
> > > I was thinking of doing that, but I figured I would start with the
> > > bare minimum patch.
> > >
> > > >
> > > > Something like:
> > > >
> > > > ---
> > > >  scripts/checkpatch.pl | 9 +++++++++
> > > >  1 file changed, 9 insertions(+)
> > > >
> > > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index
> > > > ad5ea5c545b2..8a90b457e8b5 100755
> > > > --- a/scripts/checkpatch.pl
> > > > +++ b/scripts/checkpatch.pl
> > > > @@ -5305,6 +5305,15 @@ sub process {
> > > >  			}
> > > >  		}
> > > >
> > > > +# check for vsprintf extension %p<foo> misuses
> > > > +		if ($line =~ /\b$logFunctions\s*\(.*$String/) {
> >
> > I don't see the normal string formatting routines in that list... I think this is too
> restrictive.
> 
> I don't.  There are no "normal" string formatting routines.

By "normal" I'm referring to things that call into pointer(), just casually looking
I see bstr_printf vsnprintf kvasprintf, which would be easy enough to add

> What do you think is missing?  sn?printf ? That's easy to add.

The problem starts to get hairy when we think of how often folks roll their own logging macros (see some small sampling at the end).

I think we would want to add DEBUG DBG and sn?printf and maybe consider dropping the \b on the regex so it's a bit more matchy but still shouldn't
end up matching on any ASM as you pointed out in the V2 nack.

Ill break this down into:
1. the patch as I know you'll take it, as you wrote it :-P
2. Adding to the logging macros
3. exploring making it less matchy

Data:
arch/alpha/kernel/pci_iommu.c:25:# define DBGA(args...)		printk(KERN_DEBUG args)
arch/alpha/kernel/pci_iommu.c:30:# define DBGA2(args...)		printk(KERN_DEBUG args)
arch/alpha/kernel/core_tsunami.c:50:# define DBG_CFG(args)	printk args
arch/alpha/kernel/core_titan.c:50:# define DBG_CFG(args)	printk args
arch/alpha/kernel/ptrace.c:34:#define DBG(fac,args)	{if ((fac) & DEBUG) printk args;}
arch/alpha/kernel/core_apecs.c:42:# define DBGC(args)	printk args
arch/alpha/kernel/core_irongate.c:38:# define DBG_CFG(args)	printk args
arch/alpha/kernel/core_wildfire.c:30:# define DBG_CFG(args)	printk args
arch/alpha/kernel/smc37c93x.c:18:# define DBG_DEVS(args)         printk args
arch/alpha/boot/misc.c:27:#define puts		srm_printk
arch/alpha/mm/numa.c:27:#define DBGDCONT(args...) printk(args)
arch/powerpc/sysdev/tsi108_pci.c:43:#define DBG(x...) printk(x)
arch/powerpc/sysdev/ge/ge_pic.c:31:#define DBG(fmt...) do { printk(KERN_DEBUG "gef_pic: " fmt); } while (0)
arch/powerpc/sysdev/tsi108_dev.c:34:#define DBG(fmt...) do { printk(fmt); } while(0)
arch/powerpc/sysdev/mpic.c:45:#define DBG(fmt...) printk(fmt)
arch/powerpc/kernel/process.c:69:#define TM_DEBUG(x...) printk(KERN_INFO x)
arch/powerpc/kernel/vdso.c:42:#define DBG(fmt...) printk(fmt)
arch/powerpc/kernel/legacy_serial.c:21:#define DBG(fmt...) do { printk(fmt); } while(0)
arch/powerpc/kernel/traps.c:89:#define TM_DEBUG(x...) printk(KERN_INFO x)
arch/powerpc/kernel/prom.c:65:#define DBG(fmt...) printk(KERN_ERR fmt)
arch/powerpc/kvm/book3s_paired_singles.c:33:#define dprintk printk