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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 3a4baf9..caac7d56 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -336,6 +336,35 @@
}
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;
