3 files changed, 56 insertions, 11 deletions

diff --git a/arch/x86/include/asm/iomap.h b/arch/x86/include/asm/iomap.h
index c1f06289b14b..86af26091d6c 100644
--- a/arch/x86/include/asm/iomap.h
+++ b/arch/x86/include/asm/iomap.h
@@ -23,6 +23,9 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 
+int
+is_io_mapping_possible(resource_size_t base, unsigned long size);
+
 void *
 iomap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot);
 
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index ca53224fc56c..6c2b1af16926 100644
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -20,6 +20,24 @@
 #include <asm/pat.h>
 #include <linux/module.h>
 
+#ifdef CONFIG_X86_PAE
+int
+is_io_mapping_possible(resource_size_t base, unsigned long size)
+{
+        return 1;
+}
+#else
+int
+is_io_mapping_possible(resource_size_t base, unsigned long size)
+{
+        /* There is no way to map greater than 1 << 32 address without PAE */
+        if (base + size > 0x100000000ULL)
+                return 0;
+
+        return 1;
+}
+#endif
+
 /* Map 'pfn' using fixed map 'type' and protections 'prot'
  */
 void *
diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
index 82df31726a54..cbc2f0cd631b 100644
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -30,11 +30,14 @@
  * See Documentation/io_mapping.txt
  */
 
-/* this struct isn't actually defined anywhere */
-struct io_mapping;
-
 #ifdef CONFIG_HAVE_ATOMIC_IOMAP
 
+struct io_mapping {
+        resource_size_t base;
+        unsigned long size;
+        pgprot_t prot;
+};
+
 /*
  * For small address space machines, mapping large objects
  * into the kernel virtual space isn't practical. Where
@@ -43,23 +46,40 @@ struct io_mapping;
  */
 
 static inline struct io_mapping *
-io_mapping_create_wc(unsigned long base, unsigned long size)
+io_mapping_create_wc(resource_size_t base, unsigned long size)
 {
-        return (struct io_mapping *) base;
+        struct io_mapping *iomap;
+
+        if (!is_io_mapping_possible(base, size))
+                return NULL;
+
+        iomap = kmalloc(sizeof(*iomap), GFP_KERNEL);
+        if (!iomap)
+                return NULL;
+
+        iomap->base = base;
+        iomap->size = size;
+        iomap->prot = pgprot_writecombine(__pgprot(__PAGE_KERNEL));
+        return iomap;
 }
 
 static inline void
 io_mapping_free(struct io_mapping *mapping)
 {
+        kfree(mapping);
 }
 
 /* Atomic map/unmap */
 static inline void *
 io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset)
 {
-        offset += (unsigned long) mapping;
-        return iomap_atomic_prot_pfn(offset >> PAGE_SHIFT, KM_USER0,
-                                     __pgprot(__PAGE_KERNEL_WC));
+        resource_size_t phys_addr;
+        unsigned long pfn;
+
+        BUG_ON(offset >= mapping->size);
+        phys_addr = mapping->base + offset;
+        pfn = (unsigned long) (phys_addr >> PAGE_SHIFT);
+        return iomap_atomic_prot_pfn(pfn, KM_USER0, mapping->prot);
 }
 
 static inline void
@@ -71,8 +91,9 @@ io_mapping_unmap_atomic(void *vaddr)
 static inline void *
 io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset)
 {
-        offset += (unsigned long) mapping;
-        return ioremap_wc(offset, PAGE_SIZE);
+        BUG_ON(offset >= mapping->size);
+        resource_size_t phys_addr = mapping->base + offset;
+        return ioremap_wc(phys_addr, PAGE_SIZE);
 }
 
 static inline void
@@ -83,9 +104,12 @@ io_mapping_unmap(void *vaddr)
 
 #else
 
+/* this struct isn't actually defined anywhere */
+struct io_mapping;
+
 /* Create the io_mapping object*/
 static inline struct io_mapping *
-io_mapping_create_wc(unsigned long base, unsigned long size)
+io_mapping_create_wc(resource_size_t base, unsigned long size)
 {
         return (struct io_mapping *) ioremap_wc(base, size);
 }