[PATCH 09/12] xen/hypfs: add support for id-based dynamic directories

[Juergen Gross <jgross@xxxxxxxx>]

Add some helpers to hypfs.c to support dynamic directories with a
numerical id as name.

The dynamic directory is based on a template specified by the user
allowing to use specific access functions and having a predefined
set of entries in the directory.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/hypfs.c      | 76 +++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/hypfs.h | 14 ++++++++
 2 files changed, 90 insertions(+)

diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
index 4c226a06b4..12be2f6d16 100644
--- a/xen/common/hypfs.c
+++ b/xen/common/hypfs.c
@@ -257,6 +257,82 @@ unsigned int hypfs_getsize(const struct hypfs_entry *entry)
     return entry->size;
 }
 
+int hypfs_read_dyndir_id_entry(struct hypfs_entry_dir *template,
+                               unsigned int id, bool is_last,
+                               XEN_GUEST_HANDLE_PARAM(void) *uaddr)
+{
+    struct xen_hypfs_dirlistentry direntry;
+    char name[12];
+    unsigned int e_namelen, e_len;
+
+    e_namelen = snprintf(name, sizeof(name), "%u", id);
+    e_len = HYPFS_DIRENTRY_SIZE(e_namelen);
+    direntry.e.pad = 0;
+    direntry.e.type = template->e.type;
+    direntry.e.encoding = template->e.encoding;
+    direntry.e.content_len = template->e.funcs->getsize(&template->e);
+    direntry.e.max_write_len = template->e.max_size;
+    direntry.off_next = is_last ? 0 : e_len;
+    if ( copy_to_guest(*uaddr, &direntry, 1) )
+        return -EFAULT;
+    if ( copy_to_guest_offset(*uaddr, HYPFS_DIRENTRY_NAME_OFF, name,
+                              e_namelen + 1) )
+        return -EFAULT;
+
+    guest_handle_add_offset(*uaddr, e_len);
+
+    return 0;
+}
+
+static struct hypfs_entry *hypfs_dyndir_findentry(struct hypfs_entry_dir *dir,
+                                                  const char *name,
+                                                  unsigned int name_len)
+{
+    struct hypfs_dyndir_id *data;
+
+    data = hypfs_get_dyndata();
+    if ( !data )
+        return ERR_PTR(-ENOENT);
+
+    /* Use template with original findentry function. */
+    return data->template->e.funcs->findentry(data->template, name, name_len);
+}
+
+static int hypfs_read_dyndir(const struct hypfs_entry *entry,
+                             XEN_GUEST_HANDLE_PARAM(void) uaddr)
+{
+    struct hypfs_dyndir_id *data;
+
+    data = hypfs_get_dyndata();
+    if ( !data )
+        return -ENOENT;
+
+    /* Use template with original read function. */
+    return data->template->e.funcs->read(&data->template->e, uaddr);
+}
+
+struct hypfs_entry *hypfs_gen_dyndir_entry_id(struct hypfs_entry_dir *template,
+                                              unsigned int id)
+{
+    struct hypfs_dyndir_id *data;
+
+    data = hypfs_alloc_dyndata(sizeof(*data), alignof(*data));
+    if ( !data )
+        return ERR_PTR(-ENOMEM);
+
+    data->template = template;
+    data->id = id;
+    snprintf(data->name, sizeof(data->name), "%u", id);
+    data->dir = *template;
+    data->dir.e.name = data->name;
+    data->dir.e.funcs = &data->funcs;
+    data->funcs = *template->e.funcs;
+    data->funcs.findentry = hypfs_dyndir_findentry;
+    data->funcs.read = hypfs_read_dyndir;
+
+    return &data->dir.e;
+}
+
 int hypfs_read_dir(const struct hypfs_entry *entry,
                    XEN_GUEST_HANDLE_PARAM(void) uaddr)
 {
diff --git a/xen/include/xen/hypfs.h b/xen/include/xen/hypfs.h
index c8999b5381..adfb522496 100644
--- a/xen/include/xen/hypfs.h
+++ b/xen/include/xen/hypfs.h
@@ -50,6 +50,15 @@ struct hypfs_entry_dir {
     struct list_head dirlist;
 };
 
+struct hypfs_dyndir_id {
+    struct hypfs_entry_dir dir;       /* Modified copy of template. */
+    struct hypfs_funcs funcs;         /* Dynamic functions. */
+    struct hypfs_entry_dir *template; /* Template used. */
+    char name[12];                    /* Name of hypfs entry. */
+
+    unsigned int id;                  /* Numerical id. */
+};
+
 #define HYPFS_DIRENTRY_NAME_OFF offsetof(struct xen_hypfs_dirlistentry, name)
 #define HYPFS_DIRENTRY_SIZE(name_len) \
     (HYPFS_DIRENTRY_NAME_OFF +        \
@@ -150,6 +159,11 @@ struct hypfs_entry *hypfs_dir_findentry(struct 
hypfs_entry_dir *dir,
                                         unsigned int name_len);
 void *hypfs_alloc_dyndata(unsigned long size, unsigned long align);
 void *hypfs_get_dyndata(void);
+int hypfs_read_dyndir_id_entry(struct hypfs_entry_dir *template,
+                               unsigned int id, bool is_last,
+                               XEN_GUEST_HANDLE_PARAM(void) *uaddr);
+struct hypfs_entry *hypfs_gen_dyndir_entry_id(struct hypfs_entry_dir *template,
+                                              unsigned int id);
 #endif
 
 #endif /* __XEN_HYPFS_H__ */
-- 
2.26.2