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>

2 files changed, 98 insertions, 12 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 388440e0d22..d5cdccf27a6 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -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);
 }
 
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 2cfa41e367a..47663dc0daf 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1395,7 +1395,8 @@ void pci_release_region(struct pci_dev *pdev, int bar)
  *	Returns 0 on success, or %EBUSY on error.  A warning
  *	message is also printed on failure.
  */
-int pci_request_region(struct pci_dev *pdev, int bar, const char *res_name)
+static int __pci_request_region(struct pci_dev *pdev, int bar, const char *res_name,
+									int exclusive)
 {
 	struct pci_devres *dr;
 
@@ -1408,8 +1409,9 @@ int pci_request_region(struct pci_dev *pdev, int bar, const char *res_name)
 			goto err_out;
 	}
 	else if (pci_resource_flags(pdev, bar) & IORESOURCE_MEM) {
-		if (!request_mem_region(pci_resource_start(pdev, bar),
-				        pci_resource_len(pdev, bar), res_name))
+		if (!__request_mem_region(pci_resource_start(pdev, bar),
+					pci_resource_len(pdev, bar), res_name,
+					exclusive))
 			goto err_out;
 	}
 
@@ -1428,6 +1430,47 @@ err_out:
 }
 
 /**
+ *	pci_request_region - Reserved PCI I/O and memory resource
+ *	@pdev: PCI device whose resources are to be reserved
+ *	@bar: BAR to be reserved
+ *	@res_name: Name to be associated with resource.
+ *
+ *	Mark the PCI region associated with PCI device @pdev BR @bar as
+ *	being reserved by owner @res_name.  Do not access any
+ *	address inside the PCI regions unless this call returns
+ *	successfully.
+ *
+ *	Returns 0 on success, or %EBUSY on error.  A warning
+ *	message is also printed on failure.
+ */
+int pci_request_region(struct pci_dev *pdev, int bar, const char *res_name)
+{
+	return __pci_request_region(pdev, bar, res_name, 0);
+}
+
+/**
+ *	pci_request_region_exclusive - Reserved PCI I/O and memory resource
+ *	@pdev: PCI device whose resources are to be reserved
+ *	@bar: BAR to be reserved
+ *	@res_name: Name to be associated with resource.
+ *
+ *	Mark the PCI region associated with PCI device @pdev BR @bar as
+ *	being reserved by owner @res_name.  Do not access any
+ *	address inside the PCI regions unless this call returns
+ *	successfully.
+ *
+ *	Returns 0 on success, or %EBUSY on error.  A warning
+ *	message is also printed on failure.
+ *
+ *	The key difference that _exclusive makes it that userspace is
+ *	explicitly not allowed to map the resource via /dev/mem or
+ * 	sysfs.
+ */
+int pci_request_region_exclusive(struct pci_dev *pdev, int bar, const char *res_name)
+{
+	return __pci_request_region(pdev, bar, res_name, IORESOURCE_EXCLUSIVE);
+}
+/**
  * pci_release_selected_regions - Release selected PCI I/O and memory resources
  * @pdev: PCI device whose resources were previously reserved
  * @bars: Bitmask of BARs to be released
@@ -1444,20 +1487,14 @@ void pci_release_selected_regions(struct pci_dev *pdev, int bars)
 			pci_release_region(pdev, i);
 }
 
-/**
- * pci_request_selected_regions - Reserve selected PCI I/O and memory resources
- * @pdev: PCI device whose resources are to be reserved
- * @bars: Bitmask of BARs to be requested
- * @res_name: Name to be associated with resource
- */
-int pci_request_selected_regions(struct pci_dev *pdev, int bars,
-				 const char *res_name)
+int __pci_request_selected_regions(struct pci_dev *pdev, int bars,
+				 const char *res_name, int excl)
 {
 	int i;
 
 	for (i = 0; i < 6; i++)
 		if (bars & (1 << i))
-			if(pci_request_region(pdev, i, res_name))
+			if (__pci_request_region(pdev, i, res_name, excl))
 				goto err_out;
 	return 0;
 
@@ -1469,6 +1506,26 @@ err_out:
 	return -EBUSY;
 }
 
+
+/**
+ * pci_request_selected_regions - Reserve selected PCI I/O and memory resources
+ * @pdev: PCI device whose resources are to be reserved
+ * @bars: Bitmask of BARs to be requested
+ * @res_name: Name to be associated with resource
+ */
+int pci_request_selected_regions(struct pci_dev *pdev, int bars,
+				 const char *res_name)
+{
+	return __pci_request_selected_regions(pdev, bars, res_name, 0);
+}
+
+int pci_request_selected_regions_exclusive(struct pci_dev *pdev,
+				 int bars, const char *res_name)
+{
+	return __pci_request_selected_regions(pdev, bars, res_name,
+			IORESOURCE_EXCLUSIVE);
+}
+
 /**
  *	pci_release_regions - Release reserved PCI I/O and memory resources
  *	@pdev: PCI device whose resources were previously reserved by pci_request_regions
@@ -1502,6 +1559,29 @@ int pci_request_regions(struct pci_dev *pdev, const char *res_name)
 }
 
 /**
+ *	pci_request_regions_exclusive - Reserved PCI I/O and memory resources
+ *	@pdev: PCI device whose resources are to be reserved
+ *	@res_name: Name to be associated with resource.
+ *
+ *	Mark all PCI regions associated with PCI device @pdev as
+ *	being reserved by owner @res_name.  Do not access any
+ *	address inside the PCI regions unless this call returns
+ *	successfully.
+ *
+ *	pci_request_regions_exclusive() will mark the region so that
+ * 	/dev/mem and the sysfs MMIO access will not be allowed.
+ *
+ *	Returns 0 on success, or %EBUSY on error.  A warning
+ *	message is also printed on failure.
+ */
+int pci_request_regions_exclusive(struct pci_dev *pdev, const char *res_name)
+{
+	return pci_request_selected_regions_exclusive(pdev,
+					((1 << 6) - 1), res_name);
+}
+
+
+/**
  * pci_set_master - enables bus-mastering for device dev
  * @dev: the PCI device to enable
  *
@@ -2149,10 +2229,13 @@ EXPORT_SYMBOL(pci_find_capability);
 EXPORT_SYMBOL(pci_bus_find_capability);
 EXPORT_SYMBOL(pci_release_regions);
 EXPORT_SYMBOL(pci_request_regions);
+EXPORT_SYMBOL(pci_request_regions_exclusive);
 EXPORT_SYMBOL(pci_release_region);
 EXPORT_SYMBOL(pci_request_region);
+EXPORT_SYMBOL(pci_request_region_exclusive);
 EXPORT_SYMBOL(pci_release_selected_regions);
 EXPORT_SYMBOL(pci_request_selected_regions);
+EXPORT_SYMBOL(pci_request_selected_regions_exclusive);
 EXPORT_SYMBOL(pci_set_master);
 EXPORT_SYMBOL(pci_set_mwi);
 EXPORT_SYMBOL(pci_try_set_mwi);