binder: add functions to copy to/from binder buffers

Avoid vm_area when copying to or from binder buffers.
Instead, new copy functions are added that copy from
kernel space to binder buffer space. These use
kmap_atomic() and kunmap_atomic() to create temporary
mappings and then memcpy() is used to copy within
that page.

Also, kmap_atomic() / kunmap_atomic() use the appropriate
cache flushing to support VIVT cache architectures.
Allow binder to build if CPU_CACHE_VIVT is defined.

Several uses of the new functions are added here. More
to follow in subsequent patches.

Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 94c0d85c4e75..2eebff4be83e 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1166,3 +1166,62 @@ binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
 	}
 	return 0;
 }
+
+static void binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
+					bool to_buffer,
+					struct binder_buffer *buffer,
+					binder_size_t buffer_offset,
+					void *ptr,
+					size_t bytes)
+{
+	/* All copies must be 32-bit aligned and 32-bit size */
+	BUG_ON(!check_buffer(alloc, buffer, buffer_offset, bytes));
+
+	while (bytes) {
+		unsigned long size;
+		struct page *page;
+		pgoff_t pgoff;
+		void *tmpptr;
+		void *base_ptr;
+
+		page = binder_alloc_get_page(alloc, buffer,
+					     buffer_offset, &pgoff);
+		size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
+		base_ptr = kmap_atomic(page);
+		tmpptr = base_ptr + pgoff;
+		if (to_buffer)
+			memcpy(tmpptr, ptr, size);
+		else
+			memcpy(ptr, tmpptr, size);
+		/*
+		 * kunmap_atomic() takes care of flushing the cache
+		 * if this device has VIVT cache arch
+		 */
+		kunmap_atomic(base_ptr);
+		bytes -= size;
+		pgoff = 0;
+		ptr = ptr + size;
+		buffer_offset += size;
+	}
+}
+
+void binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
+				 struct binder_buffer *buffer,
+				 binder_size_t buffer_offset,
+				 void *src,
+				 size_t bytes)
+{
+	binder_alloc_do_buffer_copy(alloc, true, buffer, buffer_offset,
+				    src, bytes);
+}
+
+void binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
+				   void *dest,
+				   struct binder_buffer *buffer,
+				   binder_size_t buffer_offset,
+				   size_t bytes)
+{
+	binder_alloc_do_buffer_copy(alloc, false, buffer, buffer_offset,
+				    dest, bytes);
+}
+