mirror of
https://github.com/vtil-project/VTIL-Core
synced 2026-08-17 08:23:03 -04:00
350 lines
No EOL
10 KiB
C++
350 lines
No EOL
10 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 "simplifier.hpp"
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#include "directives.hpp"
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#include "../expressions/expression.hpp"
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#include "../directives/transformer.hpp"
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#include <vtil/io>
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namespace vtil::symbolic
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{
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struct join_depth_exception : std::exception
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{
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const char* what() const throw()
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{
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return "Reached the maximum join depth limit.";
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}
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};
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// Simplifier cache and its accessors.
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//
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static thread_local simplifier_cache_t simplifier_cache;
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void purge_simplifier_cache() { simplifier_cache.clear(); }
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simplifier_cache_t& ref_simplifier_cache() { return simplifier_cache; }
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// Attempts to prettify the expression given.
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//
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static void prettify_expression( expression::reference& exp )
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{
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using namespace logger;
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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scope_padding _p( 1 );
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log<CON_CYN>( "[Prettify] = %s\n", *exp );
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#endif
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// Prettify each operand
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//
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auto pexp = +exp;
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for ( auto* op_ptr : { &pexp->lhs, &pexp->rhs } )
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{
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if ( !op_ptr->is_valid() ) continue;
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prettify_expression( *op_ptr );
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}
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// Update the expression.
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//
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pexp->update( false );
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// Enumerate each pack descriptor:
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//
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for ( auto& [dir_src, dir_dst] : directive::pack_descriptors )
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{
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// If we can transform the expression by the directive set:
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//
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if ( auto exp_new = transform( exp, dir_src, dir_dst, {}, -1 ) )
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{
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_PRP>( "[Pack] %s => %s\n", *dir_src, *dir_dst );
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log<CON_GRN>( "= %s\n", *exp );
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#endif
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exp = exp_new;
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return;
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}
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}
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_YLW>( "= %s\n", *exp );
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#endif
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}
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// Attempts to simplify the expression given, returns whether the simplification
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// succeeded or not.
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//
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bool simplify_expression( expression::reference& exp, bool pretty, int64_t max_depth )
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{
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using namespace logger;
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if ( max_depth == 0 )
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throw join_depth_exception{};
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// If simplify hint is set, only call prettify if requested and return.
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//
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if ( exp->simplify_hint )
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{
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if ( pretty )
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prettify_expression( exp );
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return false;
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}
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// If not an expression, we cannot simplify further.
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//
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if ( !exp->is_expression() ||
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exp->op == math::operator_id::ucast ||
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exp->op == math::operator_id::cast )
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return false;
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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// Log the input.
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//
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scope_padding _p( 1 );
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if ( !state::get()->padding ) log( "\n" );
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log( "[Input] = %s ", *exp );
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log( "(Hash: %s)\n", exp->hash() );
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#endif
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// If we resolved a valid cache entry:
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//
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auto cache_it = simplifier_cache.find( ( boxed_expression& ) *exp );
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if ( cache_it != simplifier_cache.end() )
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{
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// Replace with the cached entry, inherit simplification state.
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//
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if ( cache_it->second.first.is_valid() )
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{
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_YLW>( "= %s (From cache, Success: %d)\n", *cache_it->second.first, cache_it->second.second );
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#endif
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exp = cache_it->second.first;
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return cache_it->second.second;
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}
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_RED>( "Failed as directed by cache...\n" );
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#endif
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return false;
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}
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// Otherwise create a new cache entry with {invalid, false} by default.
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//
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cache_it = simplifier_cache.insert( { ( boxed_expression& ) *exp, { {}, false } } ).first;
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auto& [cache_entry, success_flag] = cache_it->second;
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// Simplify operands first if not done already.
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//
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for ( auto* op_ptr : { &exp->lhs, &exp->rhs } )
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{
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// If invalid or is simplified, skip.
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//
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if ( !op_ptr->is_valid() || op_ptr->get()->simplify_hint )
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continue;
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// If we could simplify the operand:
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//
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expression::reference op_ref = *op_ptr;
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if ( simplify_expression( op_ref, false, max_depth - 1 ) )
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{
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// Own the reference and relocate the pointer.
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//
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auto [exp_new, op_new] = exp.own( op_ptr );
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// Update the expression.
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//
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*op_new = op_ref;
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exp_new->update( false );
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// Recurse, and indicate success.
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//
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simplify_expression( exp, pretty, max_depth - 1 );
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exp_new->simplify_hint = true;
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cache_entry = *exp;
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success_flag = true;
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return true;
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}
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}
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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// Log the bit states.
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//
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log( "[Vector] = %s\n", exp->value );
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#endif
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// If reduced to a constant, replace it.
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//
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if ( exp->value.is_known() )
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{
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cache_entry = expression{ exp->value.known_one(), exp->value.size() };
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success_flag = true;
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exp = cache_entry;
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_CYN>( "= %s [By evaluation]\n", *exp );
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#endif
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return success_flag;
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}
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// Enumerate each universal simplifier:
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//
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for ( auto& [dir_src, dir_dst] : directive::universal_simplifiers )
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{
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// If we can transform the expression by the directive set:
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//
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if ( auto exp_new = transform( exp, dir_src, dir_dst, {}, max_depth ) )
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{
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_GRN>( "[Simplify] %s => %s\n", *dir_src, *dir_dst );
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log<CON_GRN>( "= %s [By simplify directive]\n", *exp_new );
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#endif
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// Recurse, set the hint and return the simplified instance.
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//
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simplify_expression( exp_new, pretty, max_depth );
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( +exp_new )->simplify_hint = true;
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cache_entry = exp_new;
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success_flag = true;
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exp = exp_new;
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return success_flag;
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}
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}
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// Enumerate each join descriptor:
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//
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for ( auto& [dir_src, dir_dst] : directive::join_descriptors )
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{
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// Declare the filter.
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//
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expression_filter_t filter;
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// If no maximum depth was set:
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//
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if ( max_depth < 0 )
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{
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filter = [ & ] ( auto& exp_new )
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{
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// If complexity was reduced already, pass.
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//
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if ( exp_new->complexity < exp->complexity )
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return true;
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// Save current cache iterator.
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//
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auto it0 = simplifier_cache.end();
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// Try simplifying with maximum depth set as expression's
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// depth times two and pass if complexity was reduced.
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//
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try
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{
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simplify_expression( exp_new, false, exp_new->depth * 2 );
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return exp_new->complexity < exp->complexity;
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}
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// If maximum depth was reached, revert any changes to the cache
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// and fail the join directive.
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//
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catch ( join_depth_exception& )
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{
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simplifier_cache.erase( it0, simplifier_cache.end() );
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return false;
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}
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};
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}
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// Else:
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//
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else
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{
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filter = [ & ] ( auto& exp_new )
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{
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// If complexity was reduced already, pass.
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//
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if ( exp_new->complexity < exp->complexity )
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return true;
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// Attempt simplifying with maximum depth decremented by one,
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// fail if complexity was not reduced.
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//
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simplify_expression( exp_new, false, max_depth - 1 );
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return exp_new->complexity < exp->complexity;
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};
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}
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// If we can transform the expression by the directive set:
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//
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if ( auto exp_new = transform( exp, dir_src, dir_dst, filter, max_depth ) )
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{
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_GRN>( "[Join] %s => %s\n", *dir_src, *dir_dst );
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log<CON_GRN>( "= %s [By join directive]\n", *exp_new );
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log<CON_YLW>( "Complexity: %lf => %lf\n", exp->complexity, exp_new->complexity );
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#endif
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// Recurse, set the hint and return the simplified instance.
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//
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simplify_expression( exp_new, pretty, max_depth - 1 );
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( +exp_new )->simplify_hint = true;
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cache_entry = exp_new;
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success_flag = true;
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exp = exp_new;
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return success_flag;
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}
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}
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// Enumerate each unpack descriptor:
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//
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for ( auto& [dir_src, dir_dst] : directive::unpack_descriptors )
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{
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// If we can transform the expression by the directive set:
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//
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if ( auto exp_new = transform( exp, dir_src, dir_dst,
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[ & ] ( auto& exp_new ) { return simplify_expression( exp_new, pretty, max_depth - 1 ) && exp_new->complexity < exp->complexity; }, max_depth ) )
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{
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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log<CON_YLW>( "[Unpack] %s => %s\n", *dir_src, *dir_dst );
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log<CON_GRN>( "= %s [By unpack directive]\n", *exp_new );
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#endif
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// Set the hint and return the simplified instance.
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//
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( +exp_new )->simplify_hint = true;
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cache_entry = exp_new;
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success_flag = true;
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exp = exp_new;
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return success_flag;
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}
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}
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// Prettify the expression if requested.
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//
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if ( pretty )
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prettify_expression( exp );
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#if VTIL_SYMEX_SIMPLIFY_VERBOSE
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// Log the output.
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//
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log( "= %s\n\n", *exp );
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#endif
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return false;
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}
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}; |