mm: add a io_mapping_map_user helper

[linux-2.6-microblaze.git] / mm / io-mapping.c

diff --git a/mm/io-mapping.c b/mm/io-mapping.c
new file mode 100644 (file)
index 0000000..01b3627
--- /dev/null
+++ b/mm/io-mapping.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/mm.h>
+#include <linux/io-mapping.h>
+
+/**
+ * io_mapping_map_user - remap an I/O mapping to userspace
+ * @iomap: the source io_mapping
+ * @vma: user vma to map to
+ * @addr: target user address to start at
+ * @pfn: physical address of kernel memory
+ * @size: size of map area
+ *
+ *  Note: this is only safe if the mm semaphore is held when called.
+ */
+int io_mapping_map_user(struct io_mapping *iomap, struct vm_area_struct *vma,
+               unsigned long addr, unsigned long pfn, unsigned long size)
+{
+       vm_flags_t expected_flags = VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
+
+       if (WARN_ON_ONCE((vma->vm_flags & expected_flags) != expected_flags))
+               return -EINVAL;
+
+       /* We rely on prevalidation of the io-mapping to skip track_pfn(). */
+       return remap_pfn_range_notrack(vma, addr, pfn, size,
+               __pgprot((pgprot_val(iomap->prot) & _PAGE_CACHE_MASK) |
+                        (pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK)));
+}
+EXPORT_SYMBOL_GPL(io_mapping_map_user);