154 lines
3.9 KiB
C++
154 lines
3.9 KiB
C++
/*
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* \brief RAM dataspace utility
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* \author Norman Feske
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* \date 2008-03-22
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*
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* The combination of RAM allocation and a local RM attachment
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* is a frequent use case. Each function may fail, which makes
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* error handling inevitable. This utility class encapsulates
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* this functionality to handle both operations as a transaction.
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* When embedded as a member, this class also takes care about
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* freeing and detaching the dataspace at destruction time.
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*/
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/*
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* Copyright (C) 2008-2013 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__OS__ATTACHED_RAM_DATASPACE_H_
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#define _INCLUDE__OS__ATTACHED_RAM_DATASPACE_H_
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#include <ram_session/ram_session.h>
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#include <util/touch.h>
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#include <base/env.h>
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namespace Genode {
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class Attached_ram_dataspace
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{
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private:
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size_t _size;
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Ram_session *_ram_session;
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Ram_dataspace_capability _ds;
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void *_local_addr;
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Cache_attribute const _cached;
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template <typename T>
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static void _swap(T &v1, T &v2) { T tmp = v1; v1 = v2; v2 = tmp; }
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void _detach_and_free_dataspace()
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{
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if (_local_addr)
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env()->rm_session()->detach(_local_addr);
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if (_ram_session && _ds.valid())
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_ram_session->free(_ds);
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}
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void _alloc_and_attach()
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{
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if (!_size || !_ram_session) return;
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try {
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_ds = _ram_session->alloc(_size, _cached);
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_local_addr = env()->rm_session()->attach(_ds);
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/* revert allocation if attaching the dataspace failed */
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} catch (Rm_session::Attach_failed) {
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_ram_session->free(_ds);
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throw;
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}
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/*
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* Eagerly map dataspace if used for DMA
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*
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* On some platforms, namely Fiasco.OC on ARMv7, the handling
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* of page faults interferes with the caching attributes used
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* for uncached DMA memory. See issue #452 for more details
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* (https://github.com/genodelabs/genode/issues/452). As a
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* work-around for this issues, we eagerly map the whole
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* dataspace before writing actual content to it.
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*/
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if (_cached != CACHED) {
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enum { PAGE_SIZE = 4096 };
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unsigned char volatile *base = (unsigned char volatile *)_local_addr;
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for (size_t i = 0; i < _size; i += PAGE_SIZE)
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touch_read_write(base + i);
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}
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}
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public:
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/**
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* Constructor
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*
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* \throw Ram_session::Alloc_failed
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* \throw Rm_session::Attach_failed
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*/
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Attached_ram_dataspace(Ram_session *ram_session, size_t size,
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Cache_attribute cached = CACHED)
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:
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_size(size), _ram_session(ram_session), _local_addr(0),
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_cached(cached)
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{
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_alloc_and_attach();
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}
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/**
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* Destructor
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*/
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~Attached_ram_dataspace() { _detach_and_free_dataspace(); }
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/**
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* Return capability of the used RAM dataspace
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*/
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Ram_dataspace_capability cap() const { return _ds; }
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/**
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* Request local address
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*
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* This is a template to avoid inconvenient casts at
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* the caller. A newly allocated RAM dataspace is
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* untyped memory anyway.
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*/
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template <typename T>
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T *local_addr() const { return static_cast<T *>(_local_addr); }
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/**
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* Return size
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*/
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size_t size() const { return _size; }
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void swap(Attached_ram_dataspace &other)
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{
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_swap(_size, other._size);
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_swap(_ram_session, other._ram_session);
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_swap(_ds, other._ds);
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_swap(_local_addr, other._local_addr);
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}
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/**
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* Re-allocate dataspace with a new size
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*
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* The content of the original dataspace is not retained.
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*/
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void realloc(Ram_session *ram_session, size_t new_size)
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{
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if (new_size < _size) return;
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_detach_and_free_dataspace();
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_size = new_size;
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_ram_session = ram_session;
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_alloc_and_attach();
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}
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};
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}
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#endif /* _INCLUDE__OS__ATTACHED_RAM_DATASPACE_H_ */
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