Commit 012b7105 authored by Alex Chiang's avatar Alex Chiang Committed by Tony Luck
Browse files

[IA64] prevent MCA when performing MMIO mmap to PCI config space 



Example memory map (HP rx7640 with 'default' acpiconfig setting, VGA disabled):
   0x00000000 - 0x3FFFBFFF  supports only WB (cacheable) access

If a user attempts to perform an MMIO mmap (using the PCIIOC_MMAP_IS_MEM ioctl)
to PCI config space (like mmap'ing and accessing memory at 0xA0000),
we will MCA because the kernel will attempt to use a mapping with the UC
attribute.

So check the memory attribute in kern_mmap and the EFI memmap. If WC is
requested, and WC or UC access is supported for the region, allow it.
Otherwise, use the same attribute the kernel uses.

Updates documentation and test cases as well.

Signed-off-by: default avatarAlex Chiang <achiang@hp.com>
Signed-off-by: default avatarBjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 9e121327

Documentation/ia64/aliasing-test.c

+19 −7
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <sys/mman.h>

#include <sys/stat.h>

#include <unistd.h>

#include <linux/pci.h>



int sum;
@@ -34,13 +35,19 @@ int map_mem(char *path, off_t offset, size_t length, int touch) 
		return -1;

	}



	if (fnmatch("/proc/bus/pci/*", path, 0) == 0) {

		rc = ioctl(fd, PCIIOC_MMAP_IS_MEM);

		if (rc == -1)

			perror("PCIIOC_MMAP_IS_MEM ioctl");

	}



	addr = mmap(NULL, length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, offset);

	if (addr == MAP_FAILED)

		return 1;



	if (touch) {

		c = (int *) addr;

		while (c < (int *) (offset + length))

		while (c < (int *) (addr + length))

			sum += *c++;

	}
@@ -54,7 +61,7 @@ int map_mem(char *path, off_t offset, size_t length, int touch) 
	return 0;

}



int scan_sysfs(char *path, char *file, off_t offset, size_t length, int touch)

int scan_tree(char *path, char *file, off_t offset, size_t length, int touch)

{

	struct dirent **namelist;

	char *name, *path2;
@@ -93,7 +100,7 @@ int scan_sysfs(char *path, char *file, off_t offset, size_t length, int touch) 
		} else {

			r = lstat(path2, &buf);

			if (r == 0 && S_ISDIR(buf.st_mode)) {

				rc = scan_sysfs(path2, file, offset, length, touch);

				rc = scan_tree(path2, file, offset, length, touch);

				if (rc < 0)

					return rc;

			}
@@ -238,10 +245,15 @@ int main() 
	else

		fprintf(stderr, "FAIL: /dev/mem 0x0-0x100000 not accessible\n");



	scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0, 0xA0000, 1);

	scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0xA0000, 0x20000, 0);

	scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0xC0000, 0x40000, 1);

	scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0, 1024*1024, 0);

	scan_tree("/sys/class/pci_bus", "legacy_mem", 0, 0xA0000, 1);

	scan_tree("/sys/class/pci_bus", "legacy_mem", 0xA0000, 0x20000, 0);

	scan_tree("/sys/class/pci_bus", "legacy_mem", 0xC0000, 0x40000, 1);

	scan_tree("/sys/class/pci_bus", "legacy_mem", 0, 1024*1024, 0);



	scan_rom("/sys/devices", "rom");



	scan_tree("/proc/bus/pci", "??.?", 0, 0xA0000, 1);

	scan_tree("/proc/bus/pci", "??.?", 0xA0000, 0x20000, 0);

	scan_tree("/proc/bus/pci", "??.?", 0xC0000, 0x40000, 1);

	scan_tree("/proc/bus/pci", "??.?", 0, 1024*1024, 0);

}

Documentation/ia64/aliasing.txt

+12 −0
Original line number Diff line number Diff line
@@ -112,6 +112,18 @@ POTENTIAL ATTRIBUTE ALIASING CASES 


	The /dev/mem mmap constraints apply.



    mmap of /proc/bus/pci/.../??.?



    	This is an MMIO mmap of PCI functions, which additionally may or

	may not be requested as using the WC attribute.



	If WC is requested, and the region in kern_memmap is either WC

	or UC, and the EFI memory map designates the region as WC, then

	the WC mapping is allowed.



	Otherwise, the user mapping must use the same attribute as the

	kernel mapping.



    read/write of /dev/mem



	This uses copy_from_user(), which implicitly uses a kernel

arch/ia64/pci/pci.c

+17 −5
Original line number Diff line number Diff line
@@ -591,6 +591,9 @@ int 
pci_mmap_page_range (struct pci_dev *dev, struct vm_area_struct *vma,

		     enum pci_mmap_state mmap_state, int write_combine)

{

	unsigned long size = vma->vm_end - vma->vm_start;

	pgprot_t prot;



	/*

	 * I/O space cannot be accessed via normal processor loads and

	 * stores on this platform.
@@ -604,15 +607,24 @@ pci_mmap_page_range (struct pci_dev *dev, struct vm_area_struct *vma, 
		 */

		return -EINVAL;



	if (!valid_mmap_phys_addr_range(vma->vm_pgoff, size))

		return -EINVAL;



	prot = phys_mem_access_prot(NULL, vma->vm_pgoff, size,

				    vma->vm_page_prot);



	/*

	 * Leave vm_pgoff as-is, the PCI space address is the physical

	 * address on this platform.

	 * If the user requested WC, the kernel uses UC or WC for this region,

	 * and the chipset supports WC, we can use WC. Otherwise, we have to

	 * use the same attribute the kernel uses.

	 */

	if (write_combine && efi_range_is_wc(vma->vm_start,

					     vma->vm_end - vma->vm_start))

	if (write_combine &&

	    ((pgprot_val(prot) & _PAGE_MA_MASK) == _PAGE_MA_UC ||

	     (pgprot_val(prot) & _PAGE_MA_MASK) == _PAGE_MA_WC) &&

	    efi_range_is_wc(vma->vm_start, vma->vm_end - vma->vm_start))

		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

	else

		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

		vma->vm_page_prot = prot;



	if (remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,

			     vma->vm_end - vma->vm_start, vma->vm_page_prot))

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