mirror of
https://github.com/vtil-project/VTIL-Core
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125 lines
3.7 KiB
C++
125 lines
3.7 KiB
C++
// Copyright (c) 2020 Can Boluk and contributors of the VTIL Project
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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// 3. Neither the name of mosquitto nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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#include "critical_section.hpp"
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#if _WIN64
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#include <intrin.h>
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#else
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#include <unistd.h>
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#include <sys/syscall.h>
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#endif
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#include "../io/asserts.hpp"
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namespace vtil
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{
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// Returns the thread identifier in a platform independent way,
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// used instead of std::thread::get_id() as conversion to an integer
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// requires std::hash...
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//
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tid_t get_thread_id()
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{
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#if _WIN64
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static_assert( sizeof( tid_t ) == 8, "Thread identifier must be defined as a quadword." );
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return __readgsqword( 0x48 ) >> 3;
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#else
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return ( tid_t ) syscall( SYS_gettid );
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#endif
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}
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// Tries locking the mutex, returns true on success and false on failure.
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//
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bool critical_section::try_lock()
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{
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// If we could not acquire the mutex ownership:
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//
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if ( !mtx.try_lock() )
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{
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// If thread identifier does not match, report failure.
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//
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if ( owner.load() != get_thread_id() )
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return false;
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// Increment lock count.
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//
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lock_count++;
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return true;
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}
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// This thread now owns this mutex, report success.
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//
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owner.store( get_thread_id() );
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return true;
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}
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// Continously attempts to lock the mutex until it succeeds, returns only
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// when the mutex is acquired.
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//
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void critical_section::lock()
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{
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// If we could not acquire the mutex ownership:
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//
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if ( !mtx.try_lock() )
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{
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// If thread identifier matches, increment counter and return.
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//
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if ( owner.load() == get_thread_id() )
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{
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lock_count++;
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return;
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}
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// Spin until we acquire the mutex.
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//
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mtx.lock();
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}
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// Increment lock count and declare ownership.
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//
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fassert( lock_count++ == 0 );
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owner.store( get_thread_id() );
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}
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// Unlocks the mutex with the assumption that caller currently owns it.
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//
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void critical_section::unlock()
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{
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// Validate sanity.
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//
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fassert( owner.load() == get_thread_id() );
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// If lock count reached zero:
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//
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if ( --lock_count == 0 )
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{
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// Zero-out the owning thread-id and unlock the mutex.
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//
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owner.store( 0 );
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mtx.unlock();
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}
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}
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};
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