Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e8de1481 authored Oct 22, 2008 by Arjan van de Ven Committed by Jesse Barnes Jan 07, 2009

resource: allow MMIO exclusivity for device drivers

Device drivers that use pci_request_regions() (and similar APIs) have a
reasonable expectation that they are the only ones accessing their device.
As part of the e1000e hunt, we were afraid that some userland (X or some
bootsplash stuff) was mapping the MMIO region that the driver thought it
had exclusively via /dev/mem or via various sysfs resource mappings.

This patch adds the option for device drivers to cause their reserved
regions to the "banned from /dev/mem use" list, so now both kernel memory
and device-exclusive MMIO regions are banned.
NOTE: This is only active when CONFIG_STRICT_DEVMEM is set.

In addition to the config option, a kernel parameter iomem=relaxed is
provided for the cases where developers want to diagnose, in the field,
drivers issues from userspace.

Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

parent 23616941

Documentation/kernel-parameters.txt

+4 −0

Original line number	Diff line number	Diff line
		@@ -918,6 +918,10 @@ and is between 256 and 4096 characters. It is defined in the file

		inttest= [IA64]

		iomem= Disable strict checking of access to MMIO memory
		strict regions from userspace.
		relaxed

		iommu= [x86]
		off
		force

arch/x86/mm/init_32.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -328,6 +328,8 @@ int devmem_is_allowed(unsigned long pagenr)
		{
		if (pagenr <= 256)
		return 1;
		if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
		return 0;
		if (!page_is_ram(pagenr))
		return 1;
		return 0;

arch/x86/mm/init_64.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -888,6 +888,8 @@ int devmem_is_allowed(unsigned long pagenr)
		{
		if (pagenr <= 256)
		return 1;
		if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
		return 0;
		if (!page_is_ram(pagenr))
		return 1;
		return 0;

drivers/net/e1000e/netdev.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -4807,7 +4807,7 @@ static int __devinit e1000_probe(struct pci_dev *pdev,
		}
		}

		err = pci_request_selected_regions(pdev,
		err = pci_request_selected_regions_exclusive(pdev,
		pci_select_bars(pdev, IORESOURCE_MEM),
		e1000e_driver_name);
		if (err)

drivers/pci/pci-sysfs.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -620,6 +620,9 @@ pci_mmap_resource(struct kobject kobj, struct bin_attribute attr,
		vma->vm_pgoff += start >> PAGE_SHIFT;
		mmap_type = res->flags & IORESOURCE_MEM ? pci_mmap_mem : pci_mmap_io;

		if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(start))
		return -EINVAL;

		return pci_mmap_page_range(pdev, vma, mmap_type, write_combine);
		}