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genode/os/include/init/child_policy.h
Norman Feske 959df5d46b Generalize handling of PD-session arguments 
On Linux, we want to attach additional attributes to processes, i.e.,
the chroot location, the designated UID, and GID. Instead of polluting
the generic code with such Linux-specific platform details, I introduced
the new 'Native_pd_args' type, which can be customized for each
platform. The platform-dependent policy of init is factored out in the
new 'pd_args' library.

The new 'base-linux/run/lx_pd_args.run' script can be used to validate
the propagation of those attributes into core.

Note that this patch does not add the interpretation of the new UID and
PID attributes by core. This will be subject of a follow-up patch.

Related to #510.
2012-11-21 20:04:07 +01:00

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/*
* \brief Policy applied to all children of the init process
* \author Norman Feske
* \date 2010-04-29
*/
/*
* Copyright (C) 2010-2012 Genode Labs GmbH
*
* 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__INIT__CHILD_POLICY_H_
#define _INCLUDE__INIT__CHILD_POLICY_H_
/* Genode includes */
#include <base/service.h>
#include <base/child.h>
#include <base/rpc_server.h>
#include <util/arg_string.h>
#include <rom_session/connection.h>
namespace Init {
/**
* Policy for prepending the child name to the 'label' argument
*
* By applying this policy, the identity of the child becomes imprinted
* with each session request.
*/
class Child_policy_enforce_labeling
{
const char *_name;
public:
Child_policy_enforce_labeling(const char *name) : _name(name) { }
/**
* Filter arguments of session request
*
* This function modifies the 'label' argument and leaves all other
* session arguments intact.
*/
void filter_session_args(const char *, char *args,
Genode::size_t args_len)
{
using namespace Genode;
char label_buf[Parent::Session_args::MAX_SIZE];
Arg_string::find_arg(args, "label").string(label_buf, sizeof(label_buf), "");
char value_buf[Parent::Session_args::MAX_SIZE];
Genode::snprintf(value_buf, sizeof(value_buf),
"\"%s%s%s\"",
_name,
Genode::strcmp(label_buf, "") == 0 ? "" : " -> ",
label_buf);
Arg_string::set_arg(args, args_len, "label", value_buf);
}
};
/**
* Policy for handling platform-specific PD-session arguments
*
* This policy is used onthe Linux base platform for prepending the chroot
* path of the child. By applying this policy, the chroot path of the child
* gets supplied to PD session requests.
*/
class Child_policy_pd_args
{
private:
Genode::Native_pd_args const *_pd_args;
public:
Child_policy_pd_args(Genode::Native_pd_args const *pd_args)
: _pd_args(pd_args) { }
void filter_session_args(const char *session, char *args,
Genode::size_t args_len);
};
class Child_policy_handle_cpu_priorities
{
/* priority parameters */
long _prio_levels_log2;
long _priority;
public:
Child_policy_handle_cpu_priorities(long prio_levels_log2, long priority)
: _prio_levels_log2(prio_levels_log2), _priority(priority) { }
void filter_session_args(const char *service, char *args, Genode::size_t args_len)
{
using namespace Genode;
/* intercept only CPU session requests to scale priorities */
if (Genode::strcmp(service, "CPU") || _prio_levels_log2 == 0)
return;
long priority = Arg_string::find_arg(args, "priority").long_value(0);
long discarded_prio_lsb_bits_mask = (1 << _prio_levels_log2) - 1;
if (priority & discarded_prio_lsb_bits_mask) {
PWRN("priority band too small, losing least-significant priority bits");
}
priority >>= _prio_levels_log2;
/* assign child priority to the most significant priority bits */
priority |= _priority*(Cpu_session::PRIORITY_LIMIT >> _prio_levels_log2);
/* override priority when delegating the session request to the parent */
char value_buf[64];
Genode::snprintf(value_buf, sizeof(value_buf), "0x%lx", priority);
Arg_string::set_arg(args, args_len, "priority", value_buf);
}
};
class Child_policy_provide_rom_file
{
private:
struct Local_rom_session_component : Genode::Rpc_object<Genode::Rom_session>
{
Genode::Dataspace_capability ds_cap;
/**
* Constructor
*/
Local_rom_session_component(Genode::Dataspace_capability ds)
: ds_cap(ds) { }
/***************************
** ROM session interface **
***************************/
Genode::Rom_dataspace_capability dataspace() {
return Genode::static_cap_cast<Genode::Rom_dataspace>(ds_cap); }
void sigh(Genode::Signal_context_capability) { }
} _local_rom_session;
Genode::Rpc_entrypoint *_ep;
Genode::Rom_session_capability _rom_session_cap;
enum { FILENAME_MAX_LEN = 32 };
char _filename[FILENAME_MAX_LEN];
struct Local_rom_service : public Genode::Service
{
Genode::Rom_session_capability _rom_cap;
bool _valid;
/**
* Constructor
*
* \param rom_cap capability to return on session requests
* \param valid true if local rom service is backed by a
* valid dataspace
*/
Local_rom_service(Genode::Rom_session_capability rom_cap, bool valid)
: Genode::Service("ROM"), _rom_cap(rom_cap), _valid(valid) { }
Genode::Session_capability session(const char *args)
{
if (!_valid)
throw Invalid_args();
return _rom_cap;
}
void upgrade(Genode::Session_capability, const char *args) { }
void close(Genode::Session_capability) { }
} _local_rom_service;
public:
/**
* Constructor
*/
Child_policy_provide_rom_file(const char *filename,
Genode::Dataspace_capability ds_cap,
Genode::Rpc_entrypoint *ep)
:
_local_rom_session(ds_cap), _ep(ep),
_rom_session_cap(_ep->manage(&_local_rom_session)),
_local_rom_service(_rom_session_cap, ds_cap.valid())
{
Genode::strncpy(_filename, filename, sizeof(_filename));
}
/**
* Destructor
*/
~Child_policy_provide_rom_file() { _ep->dissolve(&_local_rom_session); }
Genode::Service *resolve_session_request(const char *service_name,
const char *args)
{
/* ignore session requests for non-ROM services */
if (Genode::strcmp(service_name, "ROM")) return 0;
/* drop out if request refers to another file name */
char buf[FILENAME_MAX_LEN];
Genode::Arg_string::find_arg(args, "filename").string(buf, sizeof(buf), "");
return !Genode::strcmp(buf, _filename) ? &_local_rom_service : 0;
}
};
class Child_policy_redirect_rom_file
{
private:
char const *_from;
char const *_to;
public:
Child_policy_redirect_rom_file(const char *from, const char *to)
: _from(from), _to(to) { }
void filter_session_args(const char *service,
char *args, Genode::size_t args_len)
{
if (!_from || !_to) return;
/* ignore session requests for non-ROM services */
if (Genode::strcmp(service, "ROM")) return;
/* drop out if request refers to another file name */
enum { FILENAME_MAX_LEN = 32 };
char buf[FILENAME_MAX_LEN];
Genode::Arg_string::find_arg(args, "filename").string(buf, sizeof(buf), "");
if (Genode::strcmp(_from, buf) != 0) return;
/* replace filename argument */
Genode::snprintf(buf, sizeof(buf), "\"%s\"", _to);
Genode::Arg_string::set_arg(args, args_len, "filename", buf);
}
};
class Traditional_child_policy : public Genode::Child_policy,
public Genode::Client
{
protected:
enum { NAME_LEN = 64 };
char _name[NAME_LEN];
char const *_root;
Genode::Server *_server;
Genode::Service_registry *_parent_services;
Genode::Service_registry *_child_services;
Genode::Dataspace_capability _config_ds;
Genode::Rpc_entrypoint *_parent_entrypoint;
Child_policy_enforce_labeling _labeling_policy;
Child_policy_handle_cpu_priorities _priority_policy;
Child_policy_provide_rom_file _config_policy;
Child_policy_provide_rom_file _binary_policy;
public:
/**
* Constructor
*/
Traditional_child_policy(const char *name,
Genode::Server *server,
Genode::Service_registry *parent_services,
Genode::Service_registry *child_services,
Genode::Dataspace_capability config_ds,
Genode::Dataspace_capability binary_ds,
long prio_levels_log2,
long priority,
char const *root,
Genode::Rpc_entrypoint *parent_entrypoint)
:
_root(root),
_server(server),
_parent_services(parent_services),
_child_services(child_services),
_config_ds(config_ds),
_parent_entrypoint(parent_entrypoint),
_labeling_policy(_name),
_priority_policy(prio_levels_log2, priority),
_config_policy("config", config_ds, _parent_entrypoint),
_binary_policy("binary", binary_ds, _parent_entrypoint)
{
Genode::strncpy(_name, name, sizeof(_name));
}
const char *name() const { return _name; }
Genode::Service *resolve_session_request(const char *service_name,
const char *args)
{
Genode::Service *service;
/* check for config file request */
if ((service = _config_policy.resolve_session_request(service_name, args)))
return service;
/* check for binary file request */
if ((service = _binary_policy.resolve_session_request(service_name, args)))
return service;
/* check for services provided by the parent */
if ((service = _parent_services->find(service_name)))
return service;
/*
* If the service is provided by one of our children use it,
* or wait for the service to become available.
*/
return _child_services->wait_for_service(service_name, this,
name());
}
void filter_session_args(const char *service, char *args,
Genode::size_t args_len)
{
_labeling_policy.filter_session_args(service, args, args_len);
_priority_policy.filter_session_args(service, args, args_len);
}
bool announce_service(const char *service_name,
Genode::Root_capability root,
Genode::Allocator *alloc,
Genode::Server *server)
{
if (_child_services->find(service_name)) {
PWRN("%s: service %s is already registered",
name(), service_name);
return false;
}
/* XXX remove potential race between checking for and inserting service */
_child_services->insert(new (alloc)
Genode::Child_service(service_name, root, _server));
Genode::printf("%s registered service %s\n", name(), service_name);
return true;
}
void unregister_services()
{
Genode::Service *rs;
while ((rs = _child_services->find_by_server(_server)))
_child_services->remove(rs);
}
};
}
#endif /* _INCLUDE__INIT__CHILD_POLICY_H_ */
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