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438 lines
11 KiB
C++
438 lines
11 KiB
C++
/*
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* \brief IPC message buffer layout for NOVA
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* \author Norman Feske
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* \author Alexander Boettcher
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* \date 2009-10-02
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*
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* On NOVA, we use IPC to transmit plain data and for capability delegation
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* and capability translation.
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* Therefore the message buffer contains three categories of payload. The
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* capability-specific part are the members '_snd_pt*' (sending capability
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* selectors) and '_rcv_pt*' (receiving capability selectors).
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*/
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/*
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* Copyright (C) 2009-2013 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__BASE__IPC_MSGBUF_H_
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#define _INCLUDE__BASE__IPC_MSGBUF_H_
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/* NOVA includes */
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#include <nova/syscalls.h>
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#include <nova/util.h>
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namespace Genode {
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class Msgbuf_base
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{
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public:
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enum {
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MAX_CAP_ARGS_LOG2 = 2,
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MAX_CAP_ARGS = 1 << MAX_CAP_ARGS_LOG2
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};
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protected:
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size_t _size;
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/**
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* Number of portal-capability selectors to send
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*/
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size_t _snd_pt_sel_cnt;
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/**
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* Portal capability selectors to delegate
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*/
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Native_capability _snd_pt_sel [MAX_CAP_ARGS];
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/**
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* Base of portal receive window
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*/
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addr_t _rcv_pt_base;
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struct {
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addr_t sel;
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bool del;
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} _rcv_pt_sel [MAX_CAP_ARGS];
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/**
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* Normally the received capabilities start from the beginning of
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* the receive window (_rcv_pt_base), densely packed ascending.
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* However, a receiver may send invalid caps, which will cause
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* capability-selector gaps in the receiver window. Or a
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* misbehaving sender may even intentionally place a cap at the end
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* of the receive window. The position of a cap within the receive
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* window is fundamentally important to correctly maintain the
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* component-local capability-selector reference count.
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*
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* Additionally, the position is also required to decide whether a
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* kernel capability must be revoked during the receive window
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* cleanup/re-usage. '_rcv_pt_cap_free' is used to track this
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* information in order to free up and revoke selectors
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* (message-buffer cleanup).
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*
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* Meanings of the enums:
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* - FREE_INVALID - invalid cap selector, no cap_map entry
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* - FREE_SEL - valid cap selector, invalid kernel capability
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* - UNUSED_CAP - valid selector and cap, not read/used yet
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* - USED_CAP - valid sel and cap, read/used by stream operator
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*/
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enum { FREE_INVALID, FREE_SEL, UNUSED_CAP, USED_CAP }
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_rcv_pt_cap_free [MAX_CAP_ARGS];
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/**
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* Read counter for unmarshalling portal capability
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* selectors
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*/
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unsigned short _rcv_pt_sel_cnt;
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unsigned short _rcv_pt_sel_max;
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unsigned short _rcv_wnd_log2;
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char _msg_start[]; /* symbol marks start of message */
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public:
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enum { INVALID_INDEX = ~0UL };
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/**
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* Constructor
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*/
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Msgbuf_base()
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: _rcv_pt_base(INVALID_INDEX), _rcv_wnd_log2(MAX_CAP_ARGS_LOG2)
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{
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rcv_reset();
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snd_reset();
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}
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~Msgbuf_base()
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{
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rcv_reset();
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}
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/*
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* Begin of actual message buffer
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*/
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char buf[];
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/**
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* Return size of message buffer
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*/
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inline size_t size() const { return _size; }
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/**
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* Return address of message buffer
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*/
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inline void *addr() { return &_msg_start[0]; }
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/**
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* Reset portal capability selector payload
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*/
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inline void snd_reset() {
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for (unsigned i = 0; i < MAX_CAP_ARGS; i++) {
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+_snd_pt_sel[i];
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_snd_pt_sel[i] = Native_capability();
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}
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_snd_pt_sel_cnt = 0;
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}
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/**
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* Append portal capability selector to message buffer
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*/
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inline bool snd_append_pt_sel(Native_capability const &cap)
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{
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if (_snd_pt_sel_cnt >= MAX_CAP_ARGS - 1)
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return false;
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_snd_pt_sel[_snd_pt_sel_cnt++ ] = cap;
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return true;
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}
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/**
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* Return number of marshalled portal-capability
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* selectors
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*/
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inline size_t snd_pt_sel_cnt() const
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{
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return _snd_pt_sel_cnt;
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}
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/**
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* Return portal capability selector
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*
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* \param i index (0 ... 'pt_sel_cnt()' - 1)
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* \return portal-capability range descriptor
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*
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* The returned object could be a null cap. Use
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* is_null method to check for it.
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*/
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Nova::Obj_crd snd_pt_sel(addr_t i, bool &trans_map) const
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{
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if (i >= _snd_pt_sel_cnt)
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return Nova::Obj_crd();
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trans_map = _snd_pt_sel[i].trans_map();
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return Nova::Obj_crd(_snd_pt_sel[i].local_name(), 0,
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_snd_pt_sel[i].dst().rights());
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}
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/**
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* Request current portal-receive window
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*/
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addr_t rcv_pt_base() const { return _rcv_pt_base; }
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/**
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* Set log2 number of capabilities to be received during reply of
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* a IPC call.
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*/
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void rcv_wnd(unsigned short const caps_log2)
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{
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if (caps_log2 > MAX_CAP_ARGS_LOG2)
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nova_die();
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_rcv_wnd_log2 = caps_log2;
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}
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/**
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* Reset portal-capability receive window
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*/
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void rcv_reset()
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{
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if (!rcv_invalid()) { rcv_cleanup(false); }
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_rcv_pt_sel_cnt = 0;
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_rcv_pt_sel_max = 0;
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_rcv_pt_base = INVALID_INDEX;
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}
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/**
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* Return received portal-capability selector
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*/
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void rcv_pt_sel(Native_capability &cap)
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{
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if (_rcv_pt_sel_cnt >= _rcv_pt_sel_max) {
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cap = Native_capability();
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return;
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}
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/* return only received or translated caps */
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cap = Native_capability(_rcv_pt_sel[_rcv_pt_sel_cnt++].sel);
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}
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/**
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* Return true if receive window must be re-initialized
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*/
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bool rcv_invalid() const
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{
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return _rcv_pt_base == INVALID_INDEX;
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}
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/**
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* Return true if receive window must be re-initialized
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*
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* After reading portal selectors from the message
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* buffer using 'rcv_pt_sel()', we assume that the IDC
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* call populated the current receive window with one
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* or more portal capabilities.
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* To enable the reception of portal capability
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* selectors for the next IDC, we need a fresh receive
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* window.
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*
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* \param keep 'true' - Try to keep receive window if
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* it's clean.
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* 'false' - Free caps of receive window
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* because object is freed
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* afterwards.
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*
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* \result 'true' - receive window must be re-initialized
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* 'false' - portal selectors has been kept
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*/
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bool rcv_cleanup(bool keep, unsigned short const new_max = MAX_CAP_ARGS)
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{
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/* mark used mapped capabilities as used to prevent freeing */
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bool reinit = false;
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for (unsigned i = 0; i < _rcv_pt_sel_cnt; i++) {
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if (!_rcv_pt_sel[i].del)
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continue;
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/* should never happen */
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if (_rcv_pt_sel[i].sel < rcv_pt_base() ||
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(_rcv_pt_sel[i].sel >= rcv_pt_base() + MAX_CAP_ARGS))
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nova_die();
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_rcv_pt_cap_free [_rcv_pt_sel[i].sel - rcv_pt_base()] = USED_CAP;
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reinit = true;
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}
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/* if old receive window was smaller, we need to re-init */
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for (unsigned i = 0; !reinit && i < new_max; i++)
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if (_rcv_pt_cap_free[i] == FREE_INVALID)
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reinit = true;
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_rcv_pt_sel_cnt = 0;
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_rcv_pt_sel_max = 0;
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/* we can keep the cap selectors if none was used */
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if (keep && !reinit) {
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for (unsigned i = 0; i < MAX_CAP_ARGS; i++) {
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/* revoke received caps which are unused */
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if (_rcv_pt_cap_free[i] == UNUSED_CAP)
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Nova::revoke(Nova::Obj_crd(rcv_pt_base() + i, 0), true);
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/* free rest of indexes if new_max is smaller then last window */
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if (i >= new_max && _rcv_pt_cap_free[i] == FREE_SEL)
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cap_map()->remove(rcv_pt_base() + i, 0, false);
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}
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return false;
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}
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/* decrease ref count if valid selector */
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for (unsigned i = 0; i < MAX_CAP_ARGS; i++) {
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if (_rcv_pt_cap_free[i] == FREE_INVALID)
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continue;
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cap_map()->remove(rcv_pt_base() + i, 0, _rcv_pt_cap_free[i] != FREE_SEL);
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}
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return true;
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}
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/**
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* Initialize receive window for portal capability
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* selectors
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*
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* \param utcb - UTCB of designated receiver
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* thread
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* \param rcv_window - If specified - receive exactly
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* one capability at the specified
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* index of rcv_window
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*
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* Depending on the 'rcv_invalid', 'rcv_cleanup(true)'
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* state of the message buffer and the specified
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* rcv_window parameter, this function allocates a
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* fresh receive window and clears 'rcv_invalid'.
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*/
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bool prepare_rcv_window(Nova::Utcb *utcb,
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addr_t rcv_window = INVALID_INDEX)
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{
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/* open maximal translate window */
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utcb->crd_xlt = Nova::Obj_crd(0, ~0UL);
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/* use receive window if specified */
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if (rcv_window != INVALID_INDEX) {
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/* cleanup if receive window already used */
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if (!rcv_invalid()) rcv_cleanup(false);
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_rcv_pt_base = rcv_window;
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/* open receive window */
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utcb->crd_rcv = Nova::Obj_crd(rcv_pt_base(), _rcv_wnd_log2);
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return true;
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}
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/* allocate receive window if necessary, otherwise use old one */
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if (rcv_invalid() || rcv_cleanup(true, 1U << _rcv_wnd_log2))
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{
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_rcv_pt_base = cap_map()->insert(_rcv_wnd_log2);
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if (_rcv_pt_base == INVALID_INDEX) {
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/* no mappings can be received */
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utcb->crd_rcv = Nova::Obj_crd();
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return false;
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}
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}
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/* open receive window */
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utcb->crd_rcv = Nova::Obj_crd(rcv_pt_base(), _rcv_wnd_log2);
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return true;
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}
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/**
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* Post IPC processing.
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*
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* Remember where and which caps have been received
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* respectively have been translated.
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* The information is required to correctly free
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* cap indexes and to revoke unused received caps.
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*
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* \param utcb UTCB of designated receiver thread
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*/
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void post_ipc(Nova::Utcb *utcb, addr_t const rcv_window = INVALID_INDEX)
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{
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using namespace Nova;
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unsigned const rcv_items = (utcb->items >> 16) & 0xffffu;
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_rcv_pt_sel_max = 0;
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_rcv_pt_sel_cnt = 0;
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unsigned short const max = 1U << utcb->crd_rcv.order();
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if (max > MAX_CAP_ARGS)
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nova_die();
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for (unsigned short i = 0; i < MAX_CAP_ARGS; i++)
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_rcv_pt_cap_free [i] = (i >= max) ? FREE_INVALID : FREE_SEL;
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for (unsigned i = 0; i < rcv_items; i++) {
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Nova::Utcb::Item * item = utcb->get_item(i);
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if (!item)
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break;
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Nova::Crd cap(item->crd);
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/* track which items we got mapped */
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if (!cap.is_null() && item->is_del()) {
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/* should never happen */
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if (cap.base() < rcv_pt_base() ||
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(cap.base() >= rcv_pt_base() + max))
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nova_die();
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_rcv_pt_cap_free [cap.base() - rcv_pt_base()] = UNUSED_CAP;
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}
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if (_rcv_pt_sel_max >= max) continue;
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/* track the order of mapped and translated items */
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if (cap.is_null()) {
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_rcv_pt_sel[_rcv_pt_sel_max].sel = INVALID_INDEX;
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_rcv_pt_sel[_rcv_pt_sel_max++].del = false;
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} else {
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_rcv_pt_sel[_rcv_pt_sel_max].sel = cap.base();
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_rcv_pt_sel[_rcv_pt_sel_max++].del = item->is_del();
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}
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}
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/*
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* If a specific rcv_window has been specified,
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* (see prepare_rcv_window) then the caller want to take care
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* about freeing the * selector. Make the _rcv_pt_base invalid
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* so that it is not cleanup twice.
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*/
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if (rcv_window != INVALID_INDEX)
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_rcv_pt_base = INVALID_INDEX;
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utcb->crd_rcv = 0;
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}
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};
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template <unsigned BUF_SIZE>
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class Msgbuf : public Msgbuf_base
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{
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public:
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char buf[BUF_SIZE];
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Msgbuf() { _size = BUF_SIZE; }
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};
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}
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#endif /* _INCLUDE__BASE__IPC_MSGBUF_H_ */
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