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Subject[patch 03/13] x86: PAT Avoid aliasing in /dev/mem read/write
Add xlate and unxlate around /dev/mem read/write. This sets up the mapping
that can be used for /dev/mem read and write without aliasing worries.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>

Index: linux-2.6-x86.git/arch/x86/mm/ioremap.c
===================================================================
--- linux-2.6-x86.git.orig/arch/x86/mm/ioremap.c 2008-03-18 02:16:08.000000000 -0700
+++ linux-2.6-x86.git/arch/x86/mm/ioremap.c 2008-03-18 09:20:38.000000000 -0700
@@ -284,6 +284,35 @@
}
EXPORT_SYMBOL(iounmap);

+/*
+ * Convert a physical pointer to a virtual kernel pointer for /dev/mem
+ * access
+ */
+void *xlate_dev_mem_ptr(unsigned long phys)
+{
+ void *addr;
+ unsigned long start = phys & PAGE_MASK;
+
+ /* If page is RAM, we can use __va. Otherwise ioremap and unmap. */
+ if (page_is_ram(start >> PAGE_SHIFT))
+ return __va(phys);
+
+ addr = (void *)ioremap(start, PAGE_SIZE);
+ if (addr)
+ addr = (void *)((unsigned long)addr | (phys & ~PAGE_MASK));
+
+ return addr;
+}
+
+void unxlate_dev_mem_ptr(unsigned long phys, void *addr)
+{
+ if (page_is_ram(phys >> PAGE_SHIFT))
+ return;
+
+ iounmap((void __iomem *)((unsigned long)addr & PAGE_MASK));
+ return;
+}
+
#ifdef CONFIG_X86_32

int __initdata early_ioremap_debug;
Index: linux-2.6-x86.git/drivers/char/mem.c
===================================================================
--- linux-2.6-x86.git.orig/drivers/char/mem.c 2008-03-18 02:16:08.000000000 -0700
+++ linux-2.6-x86.git/drivers/char/mem.c 2008-03-18 09:20:34.000000000 -0700
@@ -134,6 +134,10 @@
}
#endif

+void __attribute__((weak)) unxlate_dev_mem_ptr(unsigned long phys, void *addr)
+{
+}
+
/*
* This funcion reads the *physical* memory. The f_pos points directly to the
* memory location.
@@ -176,17 +180,25 @@

sz = min_t(unsigned long, sz, count);

+ if (!range_is_allowed(p >> PAGE_SHIFT, count))
+ return -EPERM;
+
/*
* On ia64 if a page has been mapped somewhere as
* uncached, then it must also be accessed uncached
* by the kernel or data corruption may occur
*/
ptr = xlate_dev_mem_ptr(p);
+ if (!ptr)
+ return -EFAULT;

- if (!range_is_allowed(p >> PAGE_SHIFT, count))
- return -EPERM;
- if (copy_to_user(buf, ptr, sz))
+ if (copy_to_user(buf, ptr, sz)) {
+ unxlate_dev_mem_ptr(p, ptr);
return -EFAULT;
+ }
+
+ unxlate_dev_mem_ptr(p, ptr);
+
buf += sz;
p += sz;
count -= sz;
@@ -235,22 +247,32 @@

sz = min_t(unsigned long, sz, count);

+ if (!range_is_allowed(p >> PAGE_SHIFT, sz))
+ return -EPERM;
+
/*
* On ia64 if a page has been mapped somewhere as
* uncached, then it must also be accessed uncached
* by the kernel or data corruption may occur
*/
ptr = xlate_dev_mem_ptr(p);
+ if (!ptr) {
+ if (written)
+ break;
+ return -EFAULT;
+ }

- if (!range_is_allowed(p >> PAGE_SHIFT, sz))
- return -EPERM;
copied = copy_from_user(ptr, buf, sz);
if (copied) {
written += sz - copied;
+ unxlate_dev_mem_ptr(p, ptr);
if (written)
break;
return -EFAULT;
}
+
+ unxlate_dev_mem_ptr(p, ptr);
+
buf += sz;
p += sz;
count -= sz;
Index: linux-2.6-x86.git/include/asm-x86/io_32.h
===================================================================
--- linux-2.6-x86.git.orig/include/asm-x86/io_32.h 2008-03-18 02:16:08.000000000 -0700
+++ linux-2.6-x86.git/include/asm-x86/io_32.h 2008-03-18 03:11:12.000000000 -0700
@@ -49,12 +49,6 @@
#include <linux/vmalloc.h>

/*
- * Convert a physical pointer to a virtual kernel pointer for /dev/mem
- * access
- */
-#define xlate_dev_mem_ptr(p) __va(p)
-
-/*
* Convert a virtual cached pointer to an uncached pointer
*/
#define xlate_dev_kmem_ptr(p) p
Index: linux-2.6-x86.git/include/asm-x86/io_64.h
===================================================================
--- linux-2.6-x86.git.orig/include/asm-x86/io_64.h 2008-03-18 02:16:08.000000000 -0700
+++ linux-2.6-x86.git/include/asm-x86/io_64.h 2008-03-18 03:11:12.000000000 -0700
@@ -282,12 +282,6 @@
#define BIO_VMERGE_BOUNDARY iommu_bio_merge

/*
- * Convert a physical pointer to a virtual kernel pointer for /dev/mem
- * access
- */
-#define xlate_dev_mem_ptr(p) __va(p)
-
-/*
* Convert a virtual cached pointer to an uncached pointer
*/
#define xlate_dev_kmem_ptr(p) p
Index: linux-2.6-x86.git/include/asm-x86/io.h
===================================================================
--- linux-2.6-x86.git.orig/include/asm-x86/io.h 2008-03-18 02:16:08.000000000 -0700
+++ linux-2.6-x86.git/include/asm-x86/io.h 2008-03-18 09:20:38.000000000 -0700
@@ -1,5 +1,13 @@
+#ifndef _ASM_X86_IO_H
+#define _ASM_X86_IO_H
+
#ifdef CONFIG_X86_32
# include "io_32.h"
#else
# include "io_64.h"
#endif
+
+extern void *xlate_dev_mem_ptr(unsigned long phys);
+extern void unxlate_dev_mem_ptr(unsigned long phys, void *addr);
+
+#endif /* _ASM_X86_IO_H */
--


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