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genode/os/include/init/child.h
Norman Feske fcca4f3466 Init: handle reconfiguration 
With this change, init becomes able to respond to config changes by
restarting the scenario with the new config. To make this feature useful
in practice, init must not fail under any circumstances. Even on
conditions that were considered as fatal previously and led to the abort
of init (such as ambiguous names of the children or misconfiguration in
general), init must stay alive and responsive to config changes.
2013-01-15 10:18:12 +01:00

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/*
* \brief Representation used for children of the init process
* \author Norman Feske
* \date 2010-05-04
*/
/*
* Copyright (C) 2010-2013 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_H_
#define _INCLUDE__INIT__CHILD_H_
/* Genode includes */
#include <ram_session/connection.h>
#include <cpu_session/connection.h>
#include <cap_session/connection.h>
#include <base/printf.h>
#include <base/child.h>
/* init includes */
#include <init/child_config.h>
#include <init/child_policy.h>
namespace Init {
extern bool config_verbose;
/***************
** Utilities **
***************/
inline long read_priority(Genode::Xml_node start_node)
{
long priority = Genode::Cpu_session::DEFAULT_PRIORITY;
try { start_node.attribute("priority").value(&priority); }
catch (...) { }
/*
* All priority declarations in the config file are
* negative because child priorities can never be higher
* than parent priorities. To simplify priority
* calculations, we use inverted values. Lower values
* correspond to higher priorities.
*/
return -priority;
}
inline Genode::size_t read_ram_quota(Genode::Xml_node start_node)
{
Genode::Number_of_bytes ram_quota = 0;
try {
Genode::Xml_node rsc = start_node.sub_node("resource");
for (;; rsc = rsc.next("resource")) {
try {
if (rsc.attribute("name").has_value("RAM")) {
rsc.attribute("quantum").value(&ram_quota);
}
} catch (...) { }
}
} catch (...) { }
/*
* If the configured quota exceeds our own quota, we donate
* all remaining quota to the child but we need to count in
* our allocation of the child meta data from the heap.
* Hence, we preserve some of our own quota.
*/
if (ram_quota > Genode::env()->ram_session()->avail() - 128*1024) {
ram_quota = Genode::env()->ram_session()->avail() - 128*1024;
if (config_verbose)
Genode::printf("Warning: Specified quota exceeds available quota.\n"
" Proceeding with a quota of %zd bytes.\n",
(Genode::size_t)ram_quota);
}
return ram_quota;
}
/**
* Return true if service XML node matches the specified service name
*/
inline bool service_node_matches(Genode::Xml_node service_node, const char *service_name)
{
if (service_node.has_type("any-service"))
return true;
return service_node.has_type("service")
&& service_node.attribute("name").has_value(service_name);
}
/**
* Return sub string of label with the leading child name stripped out
*
*/
inline char const *skip_label_prefix(char const *child_name, char const *label)
{
Genode::size_t const child_name_len = Genode::strlen(child_name);
/*
* If the function was called with a valid "label" string, the
* following condition should be always satisfied. See the
* comment in 'service_node_args_condition_satisfied'.
*/
if (Genode::strcmp(child_name, label, child_name_len) == 0)
label += child_name_len;
/*
* If the original label was empty, the 'Child_policy_enforce_labeling'
* does not append a label separator after the child-name prefix. In
* this case, we resulting label is empty.
*/
if (*label == 0)
return label;
/*
* Skip label separator. This condition should be always satisfied.
*/
if (Genode::strcmp(" -> ", label, 4) == 0)
return label + 4;
PWRN("cannot skip label prefix while processing <if-arg>");
return label;
}
/**
* Check if arguments satisfy the condition specified for the route
*/
inline bool service_node_args_condition_satisfied(Genode::Xml_node service_node,
const char *args,
char const *child_name)
{
try {
Genode::Xml_node if_arg = service_node.sub_node("if-arg");
enum { KEY_MAX_LEN = 64, VALUE_MAX_LEN = 64 };
char key[KEY_MAX_LEN];
char value[VALUE_MAX_LEN];
if_arg.attribute("key").value(key, sizeof(key));
if_arg.attribute("value").value(value, sizeof(value));
char arg_value[VALUE_MAX_LEN];
Genode::Arg_string::find_arg(args, key).string(arg_value, sizeof(arg_value), "");
/*
* Skip child-name prefix if the key is the process "label".
*
* Because 'filter_session_args' is called prior the call of
* 'resolve_session_request' from the 'Child::session' function,
* 'args' contains the filtered arguments, in particular the label
* prefixed with the child's name. For the 'if-args' declaration,
* however, we want to omit specifying this prefix because the
* session route is specific to the named start node anyway. So
* the prefix information is redundant.
*/
if (Genode::strcmp("label", key) == 0)
return Genode::strcmp(value, skip_label_prefix(child_name, arg_value)) == 0;
return Genode::strcmp(value, arg_value) == 0;
} catch (...) { }
/* if no if-arg node exists, the condition is met */
return true;
}
/**
* Init-specific representation of a child service
*
* For init, we introduce this 'Service' variant that distinguishes two
* phases, declared and announced. A 'Routed_service' object is created
* when a '<provides>' declaration is found in init's configuration.
* At that time, however, no children including the server do yet exist.
* If, at this stage, a client tries to open a session to this service,
* the client get enqueued in a list of applicants and blocked. When
* the server officially announces its service and passes over the root
* capability, the 'Routed_service' enters the announced stage and any
* applicants get unblocked.
*/
class Routed_service : public Genode::Service
{
private:
Genode::Root_capability _root;
bool _announced;
Genode::Server *_server;
struct Applicant : public Genode::Cancelable_lock,
public Genode::List<Applicant>::Element
{
Applicant() : Cancelable_lock(Genode::Lock::LOCKED) { }
};
Genode::Lock _applicants_lock;
Genode::List<Applicant> _applicants;
public:
/**
* Constructor
*
* \param name name of service
* \param server server providing the service
*/
Routed_service(const char *name,
Genode::Server *server)
: Service(name), _announced(false), _server(server) { }
Genode::Server *server() const { return _server; }
void announce(Genode::Root_capability root)
{
Genode::Lock::Guard guard(_applicants_lock);
_root = root;
_announced = true;
/* wake up aspiring clients */
for (Applicant *a; (a = _applicants.first()); ) {
_applicants.remove(a);
a->unlock();
}
}
Genode::Session_capability session(const char *args)
{
/*
* This function is called from the context of the client's
* activation thread. If the service is not yet announced,
* we let the client block.
*/
_applicants_lock.lock();
if (!_announced) {
Applicant myself;
_applicants.insert(&myself);
_applicants_lock.unlock();
myself.lock();
} else
_applicants_lock.unlock();
Genode::Session_capability cap;
try { cap = Genode::Root_client(_root).session(args); }
catch (Genode::Root::Invalid_args) { throw Invalid_args(); }
catch (Genode::Root::Unavailable) { throw Unavailable(); }
catch (Genode::Root::Quota_exceeded) { throw Quota_exceeded(); }
if (!cap.valid())
throw Unavailable();
return cap;
}
void upgrade(Genode::Session_capability sc, const char *args)
{
Genode::Root_client(_root).upgrade(sc, args);
}
void close(Genode::Session_capability sc)
{
Genode::Root_client(_root).close(sc);
}
};
/**
* Interface for name database
*/
struct Name_registry
{
virtual ~Name_registry() { }
/**
* Check if specified name is unique
*
* \return false if name already exists
*/
virtual bool is_unique(const char *name) const = 0;
/**
* Find server with specified name
*/
virtual Genode::Server *lookup_server(const char *name) const = 0;
};
class Child_registry;
class Child : Genode::Child_policy
{
public:
/**
* Exception type
*/
class Child_name_is_not_unique { };
private:
friend class Child_registry;
Genode::List_element<Child> _list_element;
Genode::Xml_node _start_node;
Genode::Xml_node _default_route_node;
Name_registry *_name_registry;
/**
* Unique child name and file name of ELF binary
*/
struct Name
{
enum { MAX_NAME_LEN = 64 };
char file[MAX_NAME_LEN];
char unique[MAX_NAME_LEN];
/**
* Constructor
*
* Obtains file name and unique process name from XML node
*
* \param start_node XML start node
* \param registry registry tracking unique names
*/
Name(Genode::Xml_node start_node, Name_registry const *registry) {
try {
start_node.attribute("name").value(unique, sizeof(unique)); }
catch (Genode::Xml_node::Nonexistent_attribute) {
PWRN("Missing 'name' attribute in '<start>' entry.\n");
throw; }
/* check for a name confict with the other children */
if (!registry->is_unique(unique)) {
PERR("Child name \"%s\" is not unique", unique);
throw Child_name_is_not_unique();
}
/* use name as default file name if not declared otherwise */
Genode::strncpy(file, unique, sizeof(file));
/* check for a binary declaration */
try {
Genode::Xml_node binary = start_node.sub_node("binary");
binary.attribute("name").value(file, sizeof(file));
} catch (...) { }
}
} _name;
/**
* Platform-specific PD-session arguments
*/
struct Pd_args : Genode::Native_pd_args
{
Pd_args(Genode::Xml_node start_node);
} _pd_args;
/**
* Resources assigned to the child
*/
struct Resources
{
long prio_levels_log2;
long priority;
Genode::size_t ram_quota;
Genode::Ram_connection ram;
Genode::Cpu_connection cpu;
Genode::Rm_connection rm;
Resources(Genode::Xml_node start_node, const char *label,
long prio_levels_log2)
:
prio_levels_log2(prio_levels_log2),
priority(read_priority(start_node)),
ram_quota(read_ram_quota(start_node)),
ram(label),
cpu(label, priority*(Genode::Cpu_session::PRIORITY_LIMIT >> prio_levels_log2))
{
/* deduce session costs from usable ram quota */
Genode::size_t session_donations = Genode::Rm_connection::RAM_QUOTA +
Genode::Cpu_connection::RAM_QUOTA +
Genode::Ram_connection::RAM_QUOTA;
if (ram_quota > session_donations)
ram_quota -= session_donations;
else ram_quota = 0;
ram.ref_account(Genode::env()->ram_session_cap());
Genode::env()->ram_session()->transfer_quota(ram.cap(), ram_quota);
}
} _resources;
/*
* Entry point used for serving the parent interface and the
* locally provided ROM sessions for the 'config' and 'binary'
* files.
*/
enum { ENTRYPOINT_STACK_SIZE = 12*1024 };
Genode::Rpc_entrypoint _entrypoint;
/**
* ELF binary
*/
Genode::Rom_connection _binary_rom;
/**
* Private child configuration
*/
Init::Child_config _config;
/**
* Each child of init can act as a server
*/
Genode::Server _server;
Genode::Child _child;
Genode::Service_registry *_parent_services;
Genode::Service_registry *_child_services;
/**
* Policy helpers
*/
Init::Child_policy_enforce_labeling _labeling_policy;
Init::Child_policy_handle_cpu_priorities _priority_policy;
Init::Child_policy_provide_rom_file _config_policy;
Init::Child_policy_provide_rom_file _binary_policy;
Init::Child_policy_redirect_rom_file _configfile_policy;
Init::Child_policy_pd_args _pd_args_policy;
public:
Child(Genode::Xml_node start_node,
Genode::Xml_node default_route_node,
Name_registry *name_registry,
long prio_levels_log2,
Genode::Service_registry *parent_services,
Genode::Service_registry *child_services,
Genode::Cap_session *cap_session)
:
_list_element(this),
_start_node(start_node),
_default_route_node(default_route_node),
_name_registry(name_registry),
_name(start_node, name_registry),
_pd_args(start_node),
_resources(start_node, _name.unique, prio_levels_log2),
_entrypoint(cap_session, ENTRYPOINT_STACK_SIZE, _name.unique, false),
_binary_rom(_name.file, _name.unique),
_config(_resources.ram.cap(), start_node),
_server(_resources.ram.cap()),
_child(_binary_rom.dataspace(), _resources.ram.cap(),
_resources.cpu.cap(), _resources.rm.cap(), &_entrypoint, this),
_parent_services(parent_services),
_child_services(child_services),
_labeling_policy(_name.unique),
_priority_policy(_resources.prio_levels_log2, _resources.priority),
_config_policy("config", _config.dataspace(), &_entrypoint),
_binary_policy("binary", _binary_rom.dataspace(), &_entrypoint),
_configfile_policy("config", _config.filename()),
_pd_args_policy(&_pd_args)
{
using namespace Genode;
if (_resources.ram_quota == 0)
PWRN("no valid RAM resource for child \"%s\"", _name.unique);
if (config_verbose) {
Genode::printf("child \"%s\"\n", _name.unique);
Genode::printf(" RAM quota: %zd\n", _resources.ram_quota);
Genode::printf(" ELF binary: %s\n", _name.file);
Genode::printf(" priority: %ld\n", _resources.priority);
}
/*
* Determine services provided by the child
*/
try {
Xml_node service_node = start_node.sub_node("provides").sub_node("service");
for (; ; service_node = service_node.next("service")) {
char name[Genode::Service::MAX_NAME_LEN];
service_node.attribute("name").value(name, sizeof(name));
if (config_verbose)
Genode::printf(" provides service %s\n", name);
child_services->insert(new (_child.heap())
Routed_service(name, &_server));
}
} catch (Xml_node::Nonexistent_sub_node) { }
}
virtual ~Child() { }
/**
* Return true if the child has the specified name
*/
bool has_name(const char *n) const { return !Genode::strcmp(name(), n); }
Genode::Server *server() { return &_server; }
/**
* Start execution of child
*/
void start() { _entrypoint.activate(); }
/****************************
** Child-policy interface **
****************************/
const char *name() const { return _name.unique; }
Genode::Service *resolve_session_request(const char *service_name,
const char *args)
{
Genode::Service *service = 0;
/* 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;
try {
Genode::Xml_node route_node = _default_route_node;
try {
route_node = _start_node.sub_node("route"); }
catch (...) { }
Genode::Xml_node service_node = route_node.sub_node();
for (; ; service_node = service_node.next()) {
bool service_wildcard = service_node.has_type("any-service");
if (!service_node_matches(service_node, service_name))
continue;
if (!service_node_args_condition_satisfied(service_node, args, name()))
continue;
Genode::Xml_node target = service_node.sub_node();
for (; ; target = target.next()) {
if (target.has_type("parent")) {
service = _parent_services->find(service_name);
if (service)
return service;
if (!service_wildcard) {
PWRN("%s: service lookup for \"%s\" at parent failed", name(), service_name);
return 0;
}
}
if (target.has_type("child")) {
char server_name[Name::MAX_NAME_LEN];
server_name[0] = 0;
target.attribute("name").value(server_name, sizeof(server_name));
Genode::Server *server = _name_registry->lookup_server(server_name);
if (!server)
PWRN("%s: invalid route to non-existing server \"%s\"", name(), server_name);
service = _child_services->find(service_name, server);
if (service)
return service;
if (!service_wildcard) {
PWRN("%s: lookup to child service \"%s\" failed", name(), service_name);
return 0;
}
}
if (target.has_type("any-child")) {
if (_child_services->is_ambiguous(service_name)) {
PERR("%s: ambiguous routes to service \"%s\"", name(), service_name);
return 0;
}
service = _child_services->find(service_name);
if (service)
return service;
if (!service_wildcard) {
PWRN("%s: lookup for service \"%s\" failed", name(), service_name);
return 0;
}
}
if (target.is_last())
break;
}
}
} catch (...) {
PWRN("%s: no route to service \"%s\"", name(), service_name);
}
return service;
}
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);
_configfile_policy.filter_session_args(service, args, args_len);
_pd_args_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 (config_verbose)
Genode::printf("child \"%s\" announces service \"%s\"\n",
name(), service_name);
Genode::Service *s = _child_services->find(service_name, &_server);
Routed_service *rs = dynamic_cast<Routed_service *>(s);
if (!s || !rs) {
PERR("%s: illegal announcement of service \"%s\"", name(), service_name);
return false;
}
rs->announce(root);
return true;
}
Genode::Native_pd_args const *pd_args() const { return &_pd_args; }
};
}
#endif /* _INCLUDE__INIT__CHILD_H_ */
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