vfio: Add capability chain helpers
Allow sub-modules to easily reallocate a buffer for managing
capability chains for info ioctls.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 4cc961b..6fd6fa5 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1729,6 +1729,60 @@
EXPORT_SYMBOL_GPL(vfio_external_check_extension);
/**
+ * Sub-module support
+ */
+/*
+ * Helper for managing a buffer of info chain capabilities, allocate or
+ * reallocate a buffer with additional @size, filling in @id and @version
+ * of the capability. A pointer to the new capability is returned.
+ *
+ * NB. The chain is based at the head of the buffer, so new entries are
+ * added to the tail, vfio_info_cap_shift() should be called to fixup the
+ * next offsets prior to copying to the user buffer.
+ */
+struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
+ size_t size, u16 id, u16 version)
+{
+ void *buf;
+ struct vfio_info_cap_header *header, *tmp;
+
+ buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
+ if (!buf) {
+ kfree(caps->buf);
+ caps->size = 0;
+ return ERR_PTR(-ENOMEM);
+ }
+
+ caps->buf = buf;
+ header = buf + caps->size;
+
+ /* Eventually copied to user buffer, zero */
+ memset(header, 0, size);
+
+ header->id = id;
+ header->version = version;
+
+ /* Add to the end of the capability chain */
+ for (tmp = caps->buf; tmp->next; tmp = (void *)tmp + tmp->next)
+ ; /* nothing */
+
+ tmp->next = caps->size;
+ caps->size += size;
+
+ return header;
+}
+EXPORT_SYMBOL_GPL(vfio_info_cap_add);
+
+void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset)
+{
+ struct vfio_info_cap_header *tmp;
+
+ for (tmp = caps->buf; tmp->next; tmp = (void *)tmp + tmp->next - offset)
+ tmp->next += offset;
+}
+EXPORT_SYMBOL_GPL(vfio_info_cap_shift);
+
+/**
* Module/class support
*/
static char *vfio_devnode(struct device *dev, umode_t *mode)