libust ABI: export streams

[lttng-ust.git] / libringbuffer / shm.h

diff --git a/libringbuffer/shm.h b/libringbuffer/shm.h
index 9f72a5a248657f73c3176877d2e6357930dd10db..5785b71d8483d26c3684bdd8875c70aa13f00ca2 100644 (file)
--- a/libringbuffer/shm.h
+++ b/libringbuffer/shm.h
@@ -17,6 +17,11 @@
 /*
  * Pointer dereferencing. We don't trust the shm_ref, so we validate
  * both the index and offset with known boundaries.
+ *
+ * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
+ * target type, even in the occurrence of shm_ref modification by an
+ * untrusted process having write access to the shm_ref. We return a
+ * NULL pointer if the ranges are invalid.
  */
 static inline
 char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
@@ -98,4 +103,22 @@ int shm_get_wait_fd(struct shm_handle *handle, struct shm_ref *ref)
        return obj->wait_fd[0];
 }
 
+static inline
+int shm_get_object_data(struct shm_handle *handle, struct shm_ref *ref,
+               int *shm_fd, int *wait_fd, uint64_t *memory_map_size)
+{
+       struct shm_object_table *table = handle->table;
+       struct shm_object *obj;
+       size_t index;
+
+       index = (size_t) ref->index;
+       if (unlikely(index >= table->allocated_len))
+               return -EPERM;
+       obj = &table->objects[index];
+       *shm_fd = obj->shm_fd;
+       *wait_fd = obj->wait_fd[0];
+       *memory_map_size = obj->memory_map_size;
+       return 0;
+}
+
 #endif /* _LIBRINGBUFFER_SHM_H */