On Fri, Nov 21, 2014 at 05:51:14PM +0000, Bjorn Helgaas wrote: > On Thu, Nov 13, 2014 at 11:19:15AM +0000, Lorenzo Pieralisi wrote: > > The introduction of pci_mmap_fits() in commit: > > > > b5ff7df3df9efab511244d5a299fce706c71af48 > > "Check mapped ranges on sysfs resource files" > > > > allowed to check for valid range mappings of PCI resources to user space > > when mapping PCI resources through the sysfs filesystem. > > > > The mapping of resources through the sysfs expects the offset passed > > by the user through the mmap syscall to be 0, and the pgoff is adjusted > > by the kernel to memory map the resource to the CPU physical address > > corresponding to the PCI resource in question. > > > > The usage of procfs mapping of PCI resources (/proc/bus/pci files) > > is more controversial in that userspace programs mapping PCI resources > > are expected to pass in the mmap offset field either a CPU physical address > > or a PCI bar value, depending on the architecture. > > > > By the time pci_mmap_fits() was used to check PCI resource ranges for > > procfs PCI resources mapping in commit: > > > > 9eff02e2042f96fb2aedd02e032eca1c5333d7 > > "PCI: check mmap range of /proc/bus/pci files too" > > > > the procfs interface for mmapping resources to user space broke, since > > pci_mmap_fits() expected the offset passed from user space in the mmap > > call to be 0, not the CPU physical address or PCI BAR value of the > > resource in question. > > > > Subsequent attempts at fixing the pci_mmap_fits() implementation failed > > to fix the issue (or fixed the issue in some architectures but not for > > all of them, ARM and SPARC procfs interface PCI resources mapping stayed > > broken throughout) in particular commits: > > > > 8c05cd08a7504b855c265263e84af61aabafa329 > > "PCI: fix offset check for sysfs mmapped files" > > > > and > > > > 3b519e4ea618b6943a82931630872907f9ac2c2b > > "PCI: fix size checks for mmap() on /proc/bus/pci files" > > > > fixed procfs PCI resources mapping checks in pci_mmap_fits for some > > architectures, but not for architectures like SPARC that expects > > the offset value passed from user space through the mmap syscall > > (when mapping through procfs) to represent the PCI BAR value of the > > resource to be mapped. > > > > The reason behind the breakage is the following. The addresses stored > > in PCI device resources for memory spaces correspond to CPU physical > > addresses, which do not necessarily map 1:1 to PCI bus addresses as > > programmed in PCI devices configuration spaces. > > > > This implies that the sanity checks carried out in pci_mmap_fits() to > > ensure that the user executes an mmap of a "real" pci resource are > > erroneous when executed through procfs. Some platforms (ie SPARC) > > expect the offset value to be passed in (procfs mapping) to be the > > PCI BAR configuration value as read from the PCI device configuration > > space, not the fixed-up CPU physical address that is present in PCI > > device resources. > > > > The required pgoff (offset in mmap syscall) value passed from userspace > > is supposed to represent the resource value exported through > > /proc/bus/pci/devices when the resource is mmapped though procfs (and 0 > > when the mapping is carried out through sysfs resource files), which > > corresponds to the PCI resource filtered through the pci_resource_to_user() > > API. > > > > This patch converts the PCI resource to the expected "user visible" > > value through pci_resource_to_user() before carrying out sanity checks > > in pci_mmap_fits() so that the check is carried out on the resource > > values as expected from the userspace mmap API. > > > > Cc: Arnd Bergmann <arnd@xxxxxxxx> > > Cc: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> > > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > > Cc: Russell King <linux@xxxxxxxxxxxxxxxx> > > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > > Cc: Michal Simek <monstr@xxxxxxxxx> > > Cc: Martin Wilck <martin.wilck@xxxxxxxxxxxxxx> > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > > Hi Lorenzo, > > I think this patch is the right thing to do. I'm going to try to write > patches for microblaze, mips, powerpc, and sparc that implement their > pci_resource_to_user() in terms of pcibios_resource_to_bus() (the patches > are easy; it's the arguments for correctness that take time). Then I'll > try to convince myself that those arches are currently broken and will be > fixed by your patch below. I think that in doing that you might end up breaking at least powerpc and microblaze proc and sys interfaces, but I agree with the process. > But I'll be on vacation all next week, so this will take me some time and > it may not make the next merge window. I understand that, it holds back patch 2, but it is fine since it can get in as a fix even if it misses the merge window, as long as you agree with the overall approach. Thank you, Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
