PCI: Unify ECAM constants in native PCI Express drivers

Add ECAM-related constants to provide a set of standard constants
defining memory address shift values to the byte-level address that can
be used to access the PCI Express Configuration Space, and then move
native PCI Express controller drivers to use the newly introduced
definitions retiring driver-specific ones.

Refactor pci_ecam_map_bus() function to use newly added constants so
that limits to the bus, device function and offset (now limited to 4K as
per the specification) are in place to prevent the defective or
malicious caller from supplying incorrect configuration offset and thus
targeting the wrong device when accessing extended configuration space.

This refactor also allows for the ".bus_shift" initialisers to be
dropped when the user is not using a custom value as a default value
will be used as per the PCI Express Specification.

Thanks to Qian Cai <qcai@redhat.com>, Michael Walle <michael@walle.cc>,
and Vladimir Oltean <olteanv@gmail.com> for reporting a pci_ecam_create()
issue with .bus_shift and to Vladimir for proposing the fix.

[bhelgaas: incorporate Vladimir's fix, update commit log]
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20201129230743.3006978-2-kw@linux.com
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jon Derrick <jonathan.derrick@intel.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 2 insertions, 9 deletions

diff --git a/drivers/pci/controller/pcie-xilinx.c b/drivers/pci/controller/pcie-xilinx.c
index 8523be61bba5..fa5baeb82653 100644
--- a/drivers/pci/controller/pcie-xilinx.c
+++ b/drivers/pci/controller/pcie-xilinx.c
@@ -21,6 +21,7 @@
 #include <linux/of_platform.h>
 #include <linux/of_irq.h>
 #include <linux/pci.h>
+#include <linux/pci-ecam.h>
 #include <linux/platform_device.h>
 
 #include "../pci.h"
@@ -86,10 +87,6 @@
 /* Phy Status/Control Register definitions */
 #define XILINX_PCIE_REG_PSCR_LNKUP	BIT(11)
 
-/* ECAM definitions */
-#define ECAM_BUS_NUM_SHIFT		20
-#define ECAM_DEV_NUM_SHIFT		12
-
 /* Number of MSI IRQs */
 #define XILINX_NUM_MSI_IRQS		128
 
@@ -183,15 +180,11 @@ static void __iomem *xilinx_pcie_map_bus(struct pci_bus *bus,
 					 unsigned int devfn, int where)
 {
 	struct xilinx_pcie_port *port = bus->sysdata;
-	int relbus;
 
 	if (!xilinx_pcie_valid_device(bus, devfn))
 		return NULL;
 
-	relbus = (bus->number << ECAM_BUS_NUM_SHIFT) |
-		 (devfn << ECAM_DEV_NUM_SHIFT);
-
-	return port->reg_base + relbus + where;
+	return port->reg_base + PCIE_ECAM_OFFSET(bus->number, devfn, where);
 }
 
 /* PCIe operations */