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genode/repos/os/include/init/child.h
Norman Feske eaac3cc1bd Revised API documentation 
This patch curates the API documentation to become suitable for the
functional specificaton, which is partially generated from the header
files.
2015-04-09 16:04:46 +02:00

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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 {
class Routed_service;
class Name_registry;
class Child_registry;
class Child;
}
/***************
** Utilities **
***************/
namespace Init {
extern bool config_verbose;
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::Affinity::Location
read_affinity_location(Genode::Affinity::Space const &space,
Genode::Xml_node start_node)
{
typedef Genode::Affinity::Location Location;
try {
Genode::Xml_node node = start_node.sub_node("affinity");
/* if no position value is specified, select the whole row/column */
unsigned long const
default_width = node.has_attribute("xpos") ? 1 : space.width(),
default_height = node.has_attribute("ypos") ? 1 : space.height();
unsigned long const
width = node.attribute_value<unsigned long>("width", default_width),
height = node.attribute_value<unsigned long>("height", default_height);
long const x1 = node.attribute_value<long>("xpos", 0),
y1 = node.attribute_value<long>("ypos", 0),
x2 = x1 + width - 1,
y2 = y1 + height - 1;
/* clip location to space boundary */
return Location(Genode::max(x1, 0L), Genode::max(y1, 0L),
Genode::min((unsigned)(x2 - x1 + 1), space.width()),
Genode::min((unsigned)(y2 - y1 + 1), space.height()));
}
catch (...) { return Location(0, 0, space.width(), space.height()); }
}
/**
* Return amount of RAM that is currently unused
*/
static inline Genode::size_t avail_slack_ram_quota()
{
Genode::size_t const preserve = 128*1024;
Genode::size_t const avail = Genode::env()->ram_session()->avail();
return avail > preserve ? avail - preserve : 0;
}
/**
* Return amount of CPU time that is currently unused
*/
static inline Genode::size_t avail_slack_cpu_quota() {
return Genode::env()->cpu_session()->avail(); }
/**
* 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 method 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' method,
* '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 Init::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,
Genode::Affinity const &affinity)
{
/*
* This method 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, affinity); }
catch (Genode::Root::Invalid_args) { throw Invalid_args(); }
catch (Genode::Root::Unavailable) { throw Unavailable(); }
catch (Genode::Root::Quota_exceeded) { throw Quota_exceeded(); }
catch (Genode::Ipc_error) { throw Unavailable(); }
if (!cap.valid())
throw Unavailable();
return cap;
}
void upgrade(Genode::Session_capability sc, const char *args)
{
try { Genode::Root_client(_root).upgrade(sc, args); }
catch (Genode::Root::Invalid_args) { throw Invalid_args(); }
catch (Genode::Ipc_error) { throw Unavailable(); }
}
void close(Genode::Session_capability sc)
{
try { Genode::Root_client(_root).close(sc); }
catch (Genode::Ipc_error) { throw Genode::Blocking_canceled(); }
}
};
/**
* Interface for name database
*/
struct Init::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 Init::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;
struct Read_quota
{
void warn_unsuff_quota(Genode::size_t const avail)
{
using namespace Genode;
if (!config_verbose) { return; }
Genode::printf("Warning: Specified quota exceeds available quota.\n");
Genode::printf(" Proceeding with a quota of %zu.\n", avail);
}
Read_quota(Genode::Xml_node start_node,
Genode::size_t & ram_quota,
Genode::size_t & cpu_quota,
bool & constrain_phys)
{
Genode::Number_of_bytes ram_bytes = 0;
Genode::size_t cpu_percent = 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_bytes);
constrain_phys = rsc.attribute("constrain_phys").has_value("yes");
} else if (rsc.attribute("name").has_value("CPU")) {
rsc.attribute("quantum").value(&cpu_percent); }
} catch (...) { }
}
} catch (...) { }
ram_quota = ram_bytes;
cpu_quota = Genode::Cpu_session::pc_to_quota(cpu_percent);
/*
* If the configured RAM 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.
*/
Genode::size_t const ram_avail = avail_slack_ram_quota();
if (ram_quota > ram_avail) {
ram_quota = ram_avail;
warn_unsuff_quota(ram_avail);
}
Genode::size_t const cpu_avail = avail_slack_cpu_quota();
if (cpu_quota > cpu_avail) {
cpu_quota = cpu_avail;
warn_unsuff_quota(cpu_avail);
}
}
};
/**
* Resources assigned to the child
*/
struct Resources : Read_quota
{
long prio_levels_log2;
long priority;
Genode::Affinity affinity;
Genode::size_t ram_quota;
Genode::size_t cpu_quota;
bool constrain_phys;
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,
Genode::Affinity::Space const &affinity_space)
:
Read_quota(start_node, ram_quota, cpu_quota, constrain_phys),
prio_levels_log2(prio_levels_log2),
priority(read_priority(start_node)),
affinity(affinity_space,
read_affinity_location(affinity_space, start_node)),
ram(label),
cpu(label,
priority*(Genode::Cpu_session::PRIORITY_LIMIT >> prio_levels_log2),
affinity)
{
/* 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);
cpu.ref_account(Genode::env()->cpu_session_cap());
Genode::env()->cpu_session()->transfer_quota(cpu.cap(), cpu_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;
Genode::Dataspace_capability _binary_rom_ds;
/**
* 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;
Init::Child_policy_ram_phys _ram_session_policy;
public:
Child(Genode::Xml_node start_node,
Genode::Xml_node default_route_node,
Name_registry *name_registry,
long prio_levels_log2,
Genode::Affinity::Space const &affinity_space,
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, affinity_space),
_entrypoint(cap_session, ENTRYPOINT_STACK_SIZE, _name.unique, false, _resources.affinity.location()),
_binary_rom(_name.file, _name.unique),
_binary_rom_ds(_binary_rom.dataspace()),
_config(_resources.ram.cap(), start_node),
_server(_resources.ram.cap()),
_child(_binary_rom_ds, _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_ds, &_entrypoint),
_configfile_policy("config", _config.filename()),
_pd_args_policy(&_pd_args),
_ram_session_policy(_resources.constrain_phys)
{
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: %zu\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() {
Genode::Service *s;
while ((s = _child_services->find_by_server(&_server))) {
_child_services->remove(s);
}
}
/**
* 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);
_ram_session_policy.filter_session_args(service, args, args_len);
}
Genode::Affinity filter_session_affinity(Genode::Affinity const &session_affinity)
{
using namespace Genode;
Affinity::Space const &child_space = _resources.affinity.space();
Affinity::Location const &child_location = _resources.affinity.location();
/* check if no valid affinity space was specified */
if (session_affinity.space().total() == 0)
return Affinity(child_space, child_location);
Affinity::Space const &session_space = session_affinity.space();
Affinity::Location const &session_location = session_affinity.location();
/* scale resolution of resulting space */
Affinity::Space space(child_space.multiply(session_space));
/* subordinate session affinity to child affinity subspace */
Affinity::Location location(child_location
.multiply_position(session_space)
.transpose(session_location.xpos(),
session_location.ypos()));
return Affinity(space, location);
}
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;
}
void resource_request(Genode::Parent::Resource_args const &args)
{
Genode::printf("child \"%s\" requests resources: %s\n",
name(), args.string());
Genode::size_t const requested_ram_quota =
Genode::Arg_string::find_arg(args.string(), "ram_quota")
.ulong_value(0);
if (avail_slack_ram_quota() < requested_ram_quota) {
PWRN("Cannot respond to resource request - out of memory");
return;
}
/*
* XXX Synchronize quota transfers from/to env()->ram_session()
*
* If multiple children issue concurrent resource requests, the
* value reported by 'avail_slack_ram_quota' may be out of date
* when calling 'transfer_quota'.
*/
Genode::env()->ram_session()->transfer_quota(_resources.ram.cap(),
requested_ram_quota);
/* wake up child that was starved for resources */
_child.notify_resource_avail();
}
Genode::Native_pd_args const *pd_args() const { return &_pd_args; }
};
#endif /* _INCLUDE__INIT__CHILD_H_ */
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