int mdb_layered_walk(const char *name, mdb_walk_state_t *wsp);
Layer the walk denoted by wsp on top of a walk initiated using the specified walker name. The name can be scoped using the backquote (`) operator if there are naming conflicts. Layered walks can be used, for example, to facilitate constructing walkers for data structures that are embedded in other data structures.
For example, suppose that each CPU structure in the kernel contains a pointer to an embedded structure. To write a walker for the embedded structure type, you could replicate the code to iterate over CPU structures and dereference the appropriate member of each CPU structure, or you could layer the embedded structure's walker on top of the existing CPU walker.
The mdb_layered_walk() function is used from within a walker's init routine to add a new layer to the current walk. The underlying layer is initialized as part of the call to mdb_layered_walk(). The calling walk routine passes in a pointer to its current walk state; this state is used to construct the layered walk. Each layered walk is cleaned up after the caller's walk fini function is called. If more than one layer is added to a walk, the caller's walk step function will step through each element returned by the first layer, then the second layer, and so forth.
The mdb_layered_walk() function returns 0 for success, or -1 for error. The function fails if the specified walker name is not known to the debugger, if the wsp pointer is not a valid, active walk state pointer, if the layered walker itself fails to initialize, or if the caller attempts to layer the walker on top of itself.