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c652655bcb
The new Rom_session::update function can be used to request the update of an existing ROM dataspace. If the new data fits into the existing dataspace, a subsequent call of 'dataspace' can be omitted. This way, ROM dataspace updates don't suffer from page-fault-handling costs that would occur when replacing the dataspace with each update.
107 lines
3.4 KiB
C++
107 lines
3.4 KiB
C++
/*
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* \brief ROM session interface
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* \author Norman Feske
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* \date 2006-07-06
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*
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* A ROM session corresponds to a ROM module. The module name is specified as
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* an argument on session creation.
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*/
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/*
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* Copyright (C) 2006-2014 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__ROM_SESSION__ROM_SESSION_H_
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#define _INCLUDE__ROM_SESSION__ROM_SESSION_H_
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#include <dataspace/capability.h>
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#include <session/session.h>
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#include <base/signal.h>
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namespace Genode {
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struct Rom_dataspace : Dataspace { };
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struct Rom_session;
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typedef Capability<Rom_dataspace> Rom_dataspace_capability;
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}
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struct Genode::Rom_session : Session
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{
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static const char *service_name() { return "ROM"; }
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virtual ~Rom_session() { }
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/**
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* Request dataspace containing the ROM session data
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*
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* \return capability to ROM dataspace
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*
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* The capability may be invalid.
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*
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* Consecutive calls of this functions are not guaranteed to return the
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* same dataspace as dynamic ROM sessions may update the ROM data
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* during the lifetime of the session. When calling the function, the
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* server may destroy the old dataspace and replace it with a new one
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* containing the updated data. Hence, prior calling this function, the
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* client should make sure to detach the previously requested dataspace
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* from its local address space.
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*/
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virtual Rom_dataspace_capability dataspace() = 0;
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/**
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* Update ROM dataspace content
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*
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* This function is an optimization for use cases where ROM dataspaces
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* are updated at a high rate. In such cases, requesting a new
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* dataspace for each update induces a large overhead because
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* memory mappings must be revoked and updated (e.g., handling the
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* page faults referring to the dataspace). If the updated content
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* fits in the existing dataspace, those costly operations can be
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* omitted.
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*
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* When this function is called, the server may replace the dataspace
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* content with new data.
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*
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* \return true if the existing dataspace contains up-to-date content,
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* or false if a new dataspace must be requested via the
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* 'dataspace' function
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*/
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virtual bool update() { return false; }
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/**
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* Register signal handler to be notified of ROM data changes
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*
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* The ROM session interface allows for the implementation of ROM
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* services that dynamically update the data exported as ROM dataspace
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* during the lifetime of the session. This is useful in scenarios
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* where this data is generated rather than originating from a static
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* file, for example to update a program's configuration at runtime.
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*
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* By installing a signal handler using the 'sigh()' function, the
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* client will receive a notification each time the data changes at the
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* server. From the client's perspective, the original data contained
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* in the currently used dataspace remains unchanged until the client
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* calls 'dataspace()' the next time.
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*/
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virtual void sigh(Signal_context_capability sigh) = 0;
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/*********************
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** RPC declaration **
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*********************/
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GENODE_RPC(Rpc_dataspace, Rom_dataspace_capability, dataspace);
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GENODE_RPC(Rpc_sigh, void, sigh, Signal_context_capability);
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GENODE_RPC(Rpc_update, bool, update);
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GENODE_RPC_INTERFACE(Rpc_dataspace, Rpc_update, Rpc_sigh);
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};
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#endif /* _INCLUDE__ROM_SESSION__ROM_SESSION_H_ */
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