linux-kernel - Re: [PATCH v13 01/16] PCI: Let pci_mmap_page

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Message-ID: <CAE9FiQXKVLWZaiD0CgSGEMN6c4g6GeCNGS=NE=gC-CEAymo1eQ@mail.gmail.com>
Date:	Tue, 21 Jun 2016 21:32:49 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <helgaas@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	David Miller <davem@...emloft.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	Khalid Aziz <khalid.aziz@...cle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	"sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
	linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH v13 01/16] PCI: Let pci_mmap_page_range() take resource address

On Sat, Jun 18, 2016 at 5:17 AM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> On Fri, Jun 17, 2016 at 07:24:46PM -0700, Yinghai Lu wrote:
>> In 8c05cd08a7 ("PCI: fix offset check for sysfs mmapped files"), try
>> to check exposed value with resource start/end in proc mmap path.
>>
>> |        start = vma->vm_pgoff;
>> |        size = ((pci_resource_len(pdev, resno) - 1) >> PAGE_SHIFT) + 1;
>> |        pci_start = (mmap_api == PCI_MMAP_PROCFS) ?
>> |                        pci_resource_start(pdev, resno) >> PAGE_SHIFT : 0;
>> |        if (start >= pci_start && start < pci_start + size &&
>> |                        start + nr <= pci_start + size)
>>
>> That breaks sparc that exposed value is BAR value, and need to be offseted
>> to resource address.
>
> I asked this same question of the v12 patch, but I don't think you
> answered it:
>
> I'm not quite sure what you're saying here.  Are you saying that sparc
> is currently broken, and this patch fixes it?  If so, what exactly is
> broken?  Can you give a small example of an mmap that is currently
> broken?

Yes, for sparc that path (proc mmap) is broken, but only according to
code checking.

The reason for the problem is not discovered is that seem all users
(other than x86) are not
use proc_mmap ?

vma->vm_pgoff is that code segment is User/BAR value >> PAGE_SHIFT.
pci_start is resource->start >> PAGE_SHIFT.

For sparc, resource start is different from BAR start aka pci bus address.
pci bus address add offset to be the resource start.

Thanks

Yinghai