linux-kernel - Re: [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only property

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Message-ID: <20150814145755.GE26431@google.com>
Date:	Fri, 14 Aug 2015 09:57:55 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Will Deacon <will.deacon@....com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Alexander Graf <agraf@...e.de>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only
 property

Hi Marc,

On Fri, Aug 14, 2015 at 03:41:07PM +0100, Marc Zyngier wrote:
> When find_and_init_phbs() looks for the probe-only property, it seems
> to trust the firmware to be correctly written, and assumes that there
> is a parameter to the property.
> 
> It is conceivable that the firmware could not be that perfect, and it
> could expose this property naked (at least one arm64 platform seems to
> exhibit this exact behaviour). The setup code the ends up making
> a decision based on whatever the property pointer points to, which
> is likely to be junk.
> 
> Instead, let's check for the validity of the property, and ignore
> it if the firmware couldn't make up its mind.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  arch/powerpc/platforms/pseries/setup.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
> index df6a704..6bdc1f9 100644
> --- a/arch/powerpc/platforms/pseries/setup.c
> +++ b/arch/powerpc/platforms/pseries/setup.c
> @@ -490,14 +490,19 @@ static void __init find_and_init_phbs(void)
>  	 */
>  	if (of_chosen) {
>  		const int *prop;
> +		int len;
>  
>  		prop = of_get_property(of_chosen,
> -				"linux,pci-probe-only", NULL);
> +				"linux,pci-probe-only", &len);
>  		if (prop) {
> -			if (*prop)
> -				pci_add_flags(PCI_PROBE_ONLY);
> -			else
> -				pci_clear_flags(PCI_PROBE_ONLY);
> +			if (len) {
> +				if (be32_to_cpup(prop))
> +					pci_add_flags(PCI_PROBE_ONLY);
> +				else
> +					pci_clear_flags(PCI_PROBE_ONLY);
> +			} else {
> +				pr_warn("linux,pci-probe-only set without value, ignoring\n");
> +			}

This seems essentially identical to the pci-host-generic version.
Is there a way we can factor it out so there's only one copy?

>  		}
>  	}
>  }
> -- 
> 2.1.4
> 
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