148 lines
3.1 KiB
C++
148 lines
3.1 KiB
C++
/*
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* \brief Event tracing infrastructure
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* \author Norman Feske
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* \date 2013-08-09
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*/
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/*
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* Copyright (C) 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__TRACE__BUFFER_H_
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#define _INCLUDE__BASE__TRACE__BUFFER_H_
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#include <base/stdint.h>
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#include <base/thread.h>
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#include <cpu_session/cpu_session.h>
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namespace Genode { namespace Trace { class Buffer; } }
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/**
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* Buffer shared between CPU client thread and TRACE client
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*/
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class Genode::Trace::Buffer
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{
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private:
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unsigned volatile _head_offset; /* in bytes, relative to 'entries' */
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unsigned volatile _size; /* in bytes */
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unsigned volatile _wrapped; /* count of buffer wraps */
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struct _Entry
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{
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size_t len;
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char data[0];
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};
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_Entry _entries[0];
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_Entry *_head_entry() { return (_Entry *)((addr_t)_entries + _head_offset); }
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void _buffer_wrapped()
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{
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_head_offset = 0;
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_wrapped++;
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}
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/*
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* The 'entries' member marks the beginning of the trace buffer
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* entries. No other member variables must follow.
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*/
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public:
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/******************************************
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** Functions called from the CPU client **
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******************************************/
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void init(size_t size)
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{
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_head_offset = 0;
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/* compute number of bytes available for tracing data */
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size_t const header_size = (addr_t)&_entries - (addr_t)this;
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_size = size - header_size;
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_wrapped = 0;
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}
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char *reserve(size_t len)
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{
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if (_head_offset + sizeof(_Entry) + len <= _size)
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return _head_entry()->data;
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/* mark last entry with len 0 and wrap */
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if (_head_offset + sizeof(_Entry) <= _size)
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_head_entry()->len = 0;
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_buffer_wrapped();
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return _head_entry()->data;
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}
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void commit(size_t len)
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{
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/* omit empty entries */
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if (len == 0)
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return;
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_head_entry()->len = len;
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/* advance head offset, wrap when reaching buffer boundary */
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_head_offset += sizeof(_Entry) + len;
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if (_head_offset == _size)
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_buffer_wrapped();
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}
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unsigned wrapped() const { return _wrapped; }
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/********************************************
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** Functions called from the TRACE client **
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********************************************/
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class Entry
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{
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private:
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_Entry const *_entry;
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friend class Buffer;
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Entry(_Entry const *entry) : _entry(entry) { }
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public:
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size_t length() const { return _entry->len; }
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char const *data() const { return _entry->data; }
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bool is_last() const { return _entry == 0; }
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};
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Entry first() const
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{
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return _entries->len ? Entry(_entries) : Entry(0);
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}
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Entry next(Entry entry) const
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{
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if (entry.is_last())
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return Entry(0);
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if (entry.length() == 0)
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return Entry(0);
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addr_t const offset = (addr_t)entry._entry - (addr_t)_entries;
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if (offset + entry.length() + sizeof(_Entry) > _size)
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return Entry(0);
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return Entry((_Entry const *)((addr_t)entry.data() + entry.length()));
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}
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};
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#endif /* _INCLUDE__BASE__TRACE__BUFFER_H_ */
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