3 files changed, 130 insertions, 3 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index c895146c1444..8cf9547a881c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2393,14 +2393,14 @@ static inline bool can_mmap_file(struct file *file)
 	return true;
 }
 
-int __compat_vma_mmap_prepare(const struct file_operations *f_op,
+int __compat_vma_mmap(const struct file_operations *f_op,
 		struct file *file, struct vm_area_struct *vma);
-int compat_vma_mmap_prepare(struct file *file, struct vm_area_struct *vma);
+int compat_vma_mmap(struct file *file, struct vm_area_struct *vma);
 
 static inline int vfs_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	if (file->f_op->mmap_prepare)
-		return compat_vma_mmap_prepare(file, vma);
+		return compat_vma_mmap(file, vma);
 
 	return file->f_op->mmap(file, vma);
 }
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4441ceec913f..2d060081caa5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3608,6 +3608,80 @@ static inline unsigned long vma_desc_pages(const struct vm_area_desc *desc)
 	return vma_desc_size(desc) >> PAGE_SHIFT;
 }
 
+/**
+ * mmap_action_remap - helper for mmap_prepare hook to specify that a pure PFN
+ * remap is required.
+ * @desc: The VMA descriptor for the VMA requiring remap.
+ * @start: The virtual address to start the remap from, must be within the VMA.
+ * @start_pfn: The first PFN in the range to remap.
+ * @size: The size of the range to remap, in bytes, at most spanning to the end
+ * of the VMA.
+ */
+static inline void mmap_action_remap(struct vm_area_desc *desc,
+				     unsigned long start,
+				     unsigned long start_pfn,
+				     unsigned long size)
+{
+	struct mmap_action *action = &desc->action;
+
+	/* [start, start + size) must be within the VMA. */
+	WARN_ON_ONCE(start < desc->start || start >= desc->end);
+	WARN_ON_ONCE(start + size > desc->end);
+
+	action->type = MMAP_REMAP_PFN;
+	action->remap.start = start;
+	action->remap.start_pfn = start_pfn;
+	action->remap.size = size;
+	action->remap.pgprot = desc->page_prot;
+}
+
+/**
+ * mmap_action_remap_full - helper for mmap_prepare hook to specify that the
+ * entirety of a VMA should be PFN remapped.
+ * @desc: The VMA descriptor for the VMA requiring remap.
+ * @start_pfn: The first PFN in the range to remap.
+ */
+static inline void mmap_action_remap_full(struct vm_area_desc *desc,
+					  unsigned long start_pfn)
+{
+	mmap_action_remap(desc, desc->start, start_pfn, vma_desc_size(desc));
+}
+
+/**
+ * mmap_action_ioremap - helper for mmap_prepare hook to specify that a pure PFN
+ * I/O remap is required.
+ * @desc: The VMA descriptor for the VMA requiring remap.
+ * @start: The virtual address to start the remap from, must be within the VMA.
+ * @start_pfn: The first PFN in the range to remap.
+ * @size: The size of the range to remap, in bytes, at most spanning to the end
+ * of the VMA.
+ */
+static inline void mmap_action_ioremap(struct vm_area_desc *desc,
+				       unsigned long start,
+				       unsigned long start_pfn,
+				       unsigned long size)
+{
+	mmap_action_remap(desc, start, start_pfn, size);
+	desc->action.type = MMAP_IO_REMAP_PFN;
+}
+
+/**
+ * mmap_action_ioremap_full - helper for mmap_prepare hook to specify that the
+ * entirety of a VMA should be PFN I/O remapped.
+ * @desc: The VMA descriptor for the VMA requiring remap.
+ * @start_pfn: The first PFN in the range to remap.
+ */
+static inline void mmap_action_ioremap_full(struct vm_area_desc *desc,
+					  unsigned long start_pfn)
+{
+	mmap_action_ioremap(desc, desc->start, start_pfn, vma_desc_size(desc));
+}
+
+void mmap_action_prepare(struct mmap_action *action,
+			 struct vm_area_desc *desc);
+int mmap_action_complete(struct mmap_action *action,
+			 struct vm_area_struct *vma);
+
 /* Look up the first VMA which exactly match the interval vm_start ... vm_end */
 static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
 				unsigned long vm_start, unsigned long vm_end)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 90e5790c318f..5021047485a9 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -773,6 +773,56 @@ struct pfnmap_track_ctx {
 };
 #endif
 
+/* What action should be taken after an .mmap_prepare call is complete? */
+enum mmap_action_type {
+	MMAP_NOTHING,		/* Mapping is complete, no further action. */
+	MMAP_REMAP_PFN,		/* Remap PFN range. */
+	MMAP_IO_REMAP_PFN,	/* I/O remap PFN range. */
+};
+
+/*
+ * Describes an action an mmap_prepare hook can instruct to be taken to complete
+ * the mapping of a VMA. Specified in vm_area_desc.
+ */
+struct mmap_action {
+	union {
+		/* Remap range. */
+		struct {
+			unsigned long start;
+			unsigned long start_pfn;
+			unsigned long size;
+			pgprot_t pgprot;
+		} remap;
+	};
+	enum mmap_action_type type;
+
+	/*
+	 * If specified, this hook is invoked after the selected action has been
+	 * successfully completed. Note that the VMA write lock still held.
+	 *
+	 * The absolute minimum ought to be done here.
+	 *
+	 * Returns 0 on success, or an error code.
+	 */
+	int (*success_hook)(const struct vm_area_struct *vma);
+
+	/*
+	 * If specified, this hook is invoked when an error occurred when
+	 * attempting the selection action.
+	 *
+	 * The hook can return an error code in order to filter the error, but
+	 * it is not valid to clear the error here.
+	 */
+	int (*error_hook)(int err);
+
+	/*
+	 * This should be set in rare instances where the operation required
+	 * that the rmap should not be able to access the VMA until
+	 * completely set up.
+	 */
+	bool hide_from_rmap_until_complete :1;
+};
+
 /*
  * Describes a VMA that is about to be mmap()'ed. Drivers may choose to
  * manipulate mutable fields which will cause those fields to be updated in the
@@ -796,6 +846,9 @@ struct vm_area_desc {
 	/* Write-only fields. */
 	const struct vm_operations_struct *vm_ops;
 	void *private_data;
+
+	/* Take further action? */
+	struct mmap_action action;
 };
 
 /*