linux-kernel - Re: drivers/pci/probe.c compile warnings on -tip

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Message-ID: <18659.21853.41967.715062@harpo.it.uu.se>
Date:	Wed, 1 Oct 2008 12:47:57 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	"Steven Noonan" <steven@...inklabs.net>
Cc:	"Ingo Molnar" <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Hugh Dickins" <hugh@...itas.com>,
	"Jesse Barnes" <jbarnes@...tuousgeek.org>
Subject: Re: drivers/pci/probe.c compile warnings on -tip

Steven Noonan writes:
 > I was hunting down some warnings I got when compiling -tip, and with
 > one of them, I'm not sure what would be a proper way to handle it.
 > 
 > If CONFIG_PHYS_ADDR_T_64BIT is not enabled, these warnings show up:
 > 
 > drivers/pci/probe.c: In function '__pci_read_base':
 > drivers/pci/probe.c:308: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 4 has type 'resource_size_t'
 > drivers/pci/probe.c:308: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 5 has type 'resource_size_t'
 > drivers/pci/probe.c:320: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 5 has type 'resource_size_t'
 > drivers/pci/probe.c:320: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 6 has type 'resource_size_t'
 > drivers/pci/probe.c: In function 'pci_read_bridge_bases':
 > drivers/pci/probe.c:392: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 3 has type 'resource_size_t'
 > drivers/pci/probe.c:392: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 4 has type 'resource_size_t'
 > drivers/pci/probe.c:405: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 3 has type 'resource_size_t'
 > drivers/pci/probe.c:405: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 4 has type 'resource_size_t'
 > drivers/pci/probe.c:443: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 4 has type 'resource_size_t'
 > drivers/pci/probe.c:443: warning: format '%llx' expects type 'long
 > long unsigned int', but argument 5 has type 'resource_size_t'
 > 
 > 
 > Each of the lines is something like this:
 > 
 > printk(KERN_DEBUG "PCI: %s reg %x 64bit mmio: [%llx, %llx]\n",
 > pci_name(dev), pos, res->start, res->end);
 > 
 > res->start and res->end are resource_size_t (which is phys_addr_t),
 > and are sized either 32-bit or 64-bit, based on whether
 > CONFIG_PHYS_ADDR_T_64BIT is set.

Oh not those again. Similar warnings in 27-rc's drivers/pci
were fixed recently, but apparently someone out there likes
to create new ones.

The fix is to cast the resource_size_t arguments to unsigned long long.
With "%llx" that's the /only/ valid argument type.

Also note that these warnings aren't harmless. On 32-bit machines
with parameters passed on the stack the mismatch in size between
32-bit resource_size_t and the 64-bit %llx causes undefined
behaviour as printk mis-enumerates its parameters.

/Mikael
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