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genode/base-linux/include/linux_pd_session/client.h

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Linux: move process creation into core Genode used to create new processes by directly forking from the respective Genode parent using the process library. The forking process created a PD session at core merely for propagating the PID of the new process into core (for later destruction). This traditional mechanisms has the following disadvantages: First, the PID reported by the creating process to core cannot easily be validated by core. Therefore core has to trust the PD client to not specify a PID of an existing process, which would happen to be killed once the PD session gets destructed. This problem is documented by issue #318. Second, there is no way for a Genode process to detect the failure of its any grandchildren. The immediate parent of a faulting process could use the SIGCHLD-and-waitpid mechanism to observe its children but this mechanism does not work transitively. By performing the process creation exclusively within core, all Genode processes become immediate child processes of core. Hence, core can respond to failures of any of those processes and reflect such conditions via core's session interfaces. Furthermore, the PID associated to a PD session is locally known within core and cannot be forged anymore. In fact, there is actually no need at all to make processes aware of any PIDs of other processes. Please note that this patch breaks the 'chroot' mechanism that comes in the form of the 'os/src/app/chroot' program. Because all processes are forked from core, a chroot'ed process could sneak outside its chroot environment by just creating a new Genode process. To address this issue, the chroot mechanism must be added to core.
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/*
* \brief Client-side PD session interface
* \author Norman Feske
* \date 2012-08-15
*/
/*
Update copyright headers to 2013
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* Copyright (C) 2012-2013 Genode Labs GmbH
Linux: move process creation into core Genode used to create new processes by directly forking from the respective Genode parent using the process library. The forking process created a PD session at core merely for propagating the PID of the new process into core (for later destruction). This traditional mechanisms has the following disadvantages: First, the PID reported by the creating process to core cannot easily be validated by core. Therefore core has to trust the PD client to not specify a PID of an existing process, which would happen to be killed once the PD session gets destructed. This problem is documented by issue #318. Second, there is no way for a Genode process to detect the failure of its any grandchildren. The immediate parent of a faulting process could use the SIGCHLD-and-waitpid mechanism to observe its children but this mechanism does not work transitively. By performing the process creation exclusively within core, all Genode processes become immediate child processes of core. Hence, core can respond to failures of any of those processes and reflect such conditions via core's session interfaces. Furthermore, the PID associated to a PD session is locally known within core and cannot be forged anymore. In fact, there is actually no need at all to make processes aware of any PIDs of other processes. Please note that this patch breaks the 'chroot' mechanism that comes in the form of the 'os/src/app/chroot' program. Because all processes are forked from core, a chroot'ed process could sneak outside its chroot environment by just creating a new Genode process. To address this issue, the chroot mechanism must be added to core.
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*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU General Public License version 2.
*/
#ifndef _INCLUDE__LINUX_PD_SESSION__CLIENT_H_
#define _INCLUDE__LINUX_PD_SESSION__CLIENT_H_
#include <linux_pd_session/linux_pd_session.h>
#include <base/rpc_client.h>
namespace Genode {
struct Linux_pd_session_client : Rpc_client<Linux_pd_session>
{
explicit Linux_pd_session_client(Capability<Linux_pd_session> session)
: Rpc_client<Linux_pd_session>(session) { }
int bind_thread(Thread_capability thread) {
return call<Rpc_bind_thread>(thread); }
int assign_parent(Parent_capability parent) {
return call<Rpc_assign_parent>(parent); }
/*****************************
* Linux-specific extension **
*****************************/
Propagate process labels to PD sessions On Linux, we use the session label for naming the corresponding Linux process. When looking up the processes via 'ps', the Genode process hierarchy becomes immediately visible.
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void start(Capability<Dataspace> binary) {
call<Rpc_start>(binary); }
Linux: move process creation into core Genode used to create new processes by directly forking from the respective Genode parent using the process library. The forking process created a PD session at core merely for propagating the PID of the new process into core (for later destruction). This traditional mechanisms has the following disadvantages: First, the PID reported by the creating process to core cannot easily be validated by core. Therefore core has to trust the PD client to not specify a PID of an existing process, which would happen to be killed once the PD session gets destructed. This problem is documented by issue #318. Second, there is no way for a Genode process to detect the failure of its any grandchildren. The immediate parent of a faulting process could use the SIGCHLD-and-waitpid mechanism to observe its children but this mechanism does not work transitively. By performing the process creation exclusively within core, all Genode processes become immediate child processes of core. Hence, core can respond to failures of any of those processes and reflect such conditions via core's session interfaces. Furthermore, the PID associated to a PD session is locally known within core and cannot be forged anymore. In fact, there is actually no need at all to make processes aware of any PIDs of other processes. Please note that this patch breaks the 'chroot' mechanism that comes in the form of the 'os/src/app/chroot' program. Because all processes are forked from core, a chroot'ed process could sneak outside its chroot environment by just creating a new Genode process. To address this issue, the chroot mechanism must be added to core.
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};
}
#endif /* _INCLUDE__LINUX_PD_SESSION__CLIENT_H_ */
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