mirror of
https://github.com/vtil-project/VTIL-Core
synced 2026-08-17 08:23:03 -04:00
664 lines
No EOL
20 KiB
C++
664 lines
No EOL
20 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 VTIL Project nor the names of its contributors
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// may be used to endorse or promote products derived from this software
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// 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 "boolean_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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#include <vtil/utility>
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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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// Implement lookup-table based dynamic tables.
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//
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using static_directive_table_entry = std::pair<directive::instance, directive::instance>;
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using dynamic_directive_table_entry = std::pair<const directive::instance*, const directive::instance*>;
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using dynamic_directive_table = std::vector<dynamic_directive_table_entry>;
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using organized_directive_table = std::array<dynamic_directive_table, ( size_t ) math::operator_id::max>;
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template<typename T>
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static organized_directive_table build_dynamic_table( const T& container )
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{
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organized_directive_table table;
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for ( auto [table, op] : zip( table, iindices() ) )
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for( auto& directive : container )
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if ( directive.first.op == ( math::operator_id ) op )
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table.emplace_back( &directive.first, &directive.second );
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return table;
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};
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static auto& get_boolean_joiners( math::operator_id op ) { static auto tbl = build_dynamic_table( directive::boolean_joiners ); return tbl[ ( size_t ) op ]; }
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static auto& get_pack_descriptors( math::operator_id op ) { static auto tbl = build_dynamic_table( directive::pack_descriptors ); return tbl[ ( size_t ) op ]; }
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static auto& get_join_descriptors( math::operator_id op ) { static auto tbl = build_dynamic_table( directive::join_descriptors ); return tbl[ ( size_t ) op ]; }
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static auto& get_unpack_descriptors( math::operator_id op ) { static auto tbl = build_dynamic_table( directive::unpack_descriptors ); return tbl[ ( size_t ) op ]; }
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static auto& get_boolean_simplifiers( math::operator_id op ) { static auto boolean_simplifiers = directive::build_boolean_simplifiers(); static auto tbl = build_dynamic_table( boolean_simplifiers ); return tbl[ ( size_t ) op ]; }
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static auto& get_universal_simplifiers( math::operator_id op ) { static auto tbl = build_dynamic_table( directive::universal_simplifiers ); return tbl[ ( size_t ) op ]; }
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// Simplifier cache and its accessors.
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//
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using cache_bucket_t = std::unordered_map<expression::reference, std::pair<expression::reference, bool>,
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expression::reference::hasher,
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expression::reference::if_identical >;
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static constexpr size_t simplifier_bucket_count = 16;
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struct local_cache_t
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{
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cache_bucket_t main_cache[ simplifier_bucket_count ];
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cache_bucket_t spec_cache[ simplifier_bucket_count ];
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bool spec_cache_enabled = false;
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bitmap<simplifier_bucket_count> spec_cache_dirty;
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void begin_speculative()
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{
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spec_cache_enabled = true;
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spec_cache_dirty = {};
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}
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void join_speculative()
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{
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while ( true )
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{
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size_t n = spec_cache_dirty.find( true );
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if ( n == math::bit_npos ) break;
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spec_cache_dirty.set( n, false );
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auto& main = main_cache[ n ];
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auto& spec = spec_cache[ n ];
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main.insert( std::make_move_iterator( spec.begin() ), std::make_move_iterator( spec.end() ) );
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spec.clear();
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}
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spec_cache_enabled = false;
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}
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void trash_speculative()
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{
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while ( true )
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{
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size_t n = spec_cache_dirty.find( true );
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if ( n == math::bit_npos ) break;
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spec_cache_dirty.set( n, false );
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auto& spec = spec_cache[ n ];
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spec.clear();
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}
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spec_cache_enabled = false;
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}
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std::tuple<expression::reference&, bool&, bool> lookup( const expression::reference& exp )
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{
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size_t bucket_id = ( size_t ) exp->op % simplifier_bucket_count;
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if ( spec_cache_enabled )
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{
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if ( auto it = main_cache[ bucket_id ].find( exp ); it != main_cache[ bucket_id ].end() )
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return { it->second.first, it->second.second, true };
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if ( spec_cache_dirty.blocks[ 0 ] == 0 )
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{
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auto [it, inserted] = main_cache[ bucket_id ].emplace( exp, make_default<std::pair<expression::reference, bool>>() );
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return { it->second.first, it->second.second, !inserted };
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}
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auto [it, inserted] = spec_cache[ bucket_id ].emplace( exp, make_default<std::pair<expression::reference, bool>>() );
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spec_cache_dirty.set( bucket_id, true );
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return { it->second.first, it->second.second, !inserted };
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}
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auto [it, inserted] = main_cache[ bucket_id ].emplace( exp, make_default<std::pair<expression::reference, bool>>() );
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return { it->second.first, it->second.second, !inserted };
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}
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void purge()
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{
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for ( auto& bucket : main_cache )
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bucket.clear();
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}
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};
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static thread_local local_cache_t local_cache;
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void purge_simplifier_cache() { local_cache = {}; }
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// Attempts to prettify the expression given.
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//
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static bool 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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// If successful, recurse.
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//
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if ( prettify_expression( *op_ptr ) )
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{
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pexp->update( false );
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simplify_expression( exp, true, -1, false );
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return true;
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}
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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] : get_pack_descriptors( exp->op ) )
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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 true;
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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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return false;
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}
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// Checks if the expression can be interpreted as a vector-boolean expression.
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//
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static std::pair<bool, expression::reference> match_boolean_expression( const expression::reference& exp )
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{
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switch ( exp->op )
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{
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// If constant / variable, indicate success and return self if variable:
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//
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case math::operator_id::invalid:
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{
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if ( exp->is_variable() ) return { true, exp };
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else return { true, nullptr };
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}
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// If bitwise not, continue from rhs.
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//
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case math::operator_id::bitwise_not:
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return match_boolean_expression( exp->rhs );
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// Bitwise OR/AND/XOR match both sides, if both were succesful
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// and had matching/null UIDs, indicate success.
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//
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case math::operator_id::bitwise_or:
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case math::operator_id::bitwise_and:
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case math::operator_id::bitwise_xor:
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{
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auto [m1, p1] = match_boolean_expression( exp->lhs );
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if ( !m1 ) return { false, nullptr };
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auto [m2, p2] = match_boolean_expression( exp->rhs );
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if ( !m2 ) return { false, nullptr };
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if ( !p2 ) return { true, std::move( p1 ) };
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if ( !p1 ) return { true, std::move( p2 ) };
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if ( p1->uid == p2->uid )
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return { true, std::move( p1 ) };
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else
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return { false, nullptr };
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}
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// Illegal operation, fail.
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//
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default:
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return { false, nullptr };
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}
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}
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// Attempts to normalize a vector-boolean expression into a simpler format.
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//
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static bool simplify_boolean_expression( expression::reference& exp )
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{
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// If it does not match a basic boolean expression, return false.
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//
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auto [is_match, uid_base] = match_boolean_expression( exp );
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if ( !is_match ) return false;
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// Evaluate for both states.
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//
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auto r0 = exp->evaluate( [ & ] ( auto& uid ) { return 0ull; } );
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auto r1 = exp->evaluate( [ & ] ( auto& uid ) { return ~0ull; } );
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// Calculate normal form AND/OR/XOR masks.
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//
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uint64_t and_mask = { ~( r0.known_zero() & r1.known_zero() ) };
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uint64_t or_mask = { r0.known_one() & r1.known_one() };
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uint64_t xor_mask = { r0.known_one() & r1.known_zero() };
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// Apply each mask if not no-op.
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//
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expression::reference& exp_new = uid_base;
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if ( and_mask != ~0ull ) exp_new = exp_new & expression{ and_mask, exp->size() };
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if ( xor_mask ) exp_new = exp_new ^ expression{ xor_mask, exp->size() };
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if ( or_mask ) exp_new = exp_new | expression{ or_mask, exp->size() };
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// If complexity was higher or equal, fail.
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//
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if ( exp_new->complexity >= exp->complexity ) return false;
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// Apply and return.
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//
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exp = std::move( exp_new );
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return true;
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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, bool unpack )
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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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// Clear lazy if not done.
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//
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if ( exp->is_lazy )
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( +exp )->is_lazy = false;
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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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return false;
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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 expression has known value, return as is.
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//
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if ( exp->value.is_known() )
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{
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exp = expression{ exp->value.known_one(), exp->value.size() };
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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 true;
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}
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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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// Lookup the expression in the cache.
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//
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auto& lcache = local_cache;
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auto [cache_entry, success_flag, found] = lcache.lookup( exp );
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// If we resolved a valid cache entry:
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//
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if ( found )
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{
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// Replace with the cached entry if simplifies.
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//
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if ( cache_entry && success_flag )
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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_entry, success_flag );
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#endif
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exp = cache_entry;
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return true;
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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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// If trying to simplify resizing:
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//
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if ( exp->op == math::operator_id::ucast ||
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exp->op == math::operator_id::cast )
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{
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// Simplify left hand side with the exact same arguments.
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//
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expression::reference exp_new = exp->lhs;
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bool simplified = simplify_expression( exp_new, pretty, max_depth - 1, unpack );
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bitcnt_t new_size = math::narrow_cast<bitcnt_t>( *exp->rhs->get() );
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// Invoke resize with failure on explicit cast:
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//
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exp_new.resize( new_size, exp->op == math::operator_id::cast, true );
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// If implicit resize failed:
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//
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if ( exp_new->size() != new_size )
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{
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// If operand was simplified, indicate success.
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//
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if ( simplified )
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{
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( +exp )->lhs = exp_new;
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( +exp )->update( false );
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success_flag = true;
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}
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}
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else
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{
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// If operand was simplified or if the complexity reduced, indicate success.
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//
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if ( simplified || exp_new->complexity < exp->complexity )
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{
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exp = exp_new;
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success_flag = true;
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}
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}
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exp->simplify_hint = true;
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cache_entry = exp;
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return success_flag;
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}
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// If expression matches a basic boolean expression, simplify through that first:
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//
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if ( simplify_boolean_expression( exp ) )
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{
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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->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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// 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->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] : get_universal_simplifiers( exp->op ) )
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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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if( success_flag = !exp->is_identical( *exp_new ) )
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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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// If it is a boolean expression:
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//
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if ( exp->size() == 1 )
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{
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// Enumerate each universal simplifier:
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//
|
|
for ( auto [dir_src, dir_dst] : get_boolean_simplifiers( exp->op ) )
|
|
{
|
|
// If we can transform the expression by the directive set:
|
|
//
|
|
if ( auto exp_new = transform( exp, dir_src, dir_dst, max_depth ) )
|
|
{
|
|
#if VTIL_SYMEX_SIMPLIFY_VERBOSE
|
|
log<CON_GRN>( "[Simplify] %s => %s\n", *dir_src, *dir_dst );
|
|
log<CON_GRN>( "= %s [By simplify directive]\n", *exp_new );
|
|
#endif
|
|
// Recurse, set the hint and return the simplified instance.
|
|
//
|
|
simplify_expression( exp_new, pretty, max_depth );
|
|
exp_new->simplify_hint = true;
|
|
cache_entry = exp_new;
|
|
if ( success_flag = !exp->is_identical( *exp_new ) )
|
|
exp = exp_new;
|
|
return success_flag;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Declare the filter.
|
|
//
|
|
auto filter = [ &, max_depth ] ( auto& exp_new )
|
|
{
|
|
if ( max_depth < 0 )
|
|
{
|
|
// If complexity was reduced already, pass.
|
|
//
|
|
if ( exp_new->complexity < exp->complexity )
|
|
return true;
|
|
|
|
// Try simplifying with maximum depth set as expression's
|
|
// depth times two and pass if complexity was reduced.
|
|
//
|
|
try
|
|
{
|
|
lcache.begin_speculative();
|
|
simplify_expression( exp_new, false, exp_new->depth * 2 );
|
|
lcache.join_speculative();
|
|
return exp_new->complexity < exp->complexity;
|
|
}
|
|
// If maximum depth was reached, revert any changes to the cache
|
|
// and fail the join directive.
|
|
//
|
|
catch ( join_depth_exception& )
|
|
{
|
|
lcache.trash_speculative();
|
|
return false;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// If complexity was reduced already, pass.
|
|
//
|
|
if ( exp_new->complexity < exp->complexity )
|
|
return true;
|
|
|
|
// Attempt simplifying with maximum depth decremented by one,
|
|
// fail if complexity was not reduced.
|
|
//
|
|
simplify_expression( exp_new, false, max_depth - 1 );
|
|
return exp_new->complexity < exp->complexity;
|
|
}
|
|
};
|
|
|
|
// Enumerate each join descriptor:
|
|
//
|
|
for ( auto [dir_src, dir_dst] : get_join_descriptors( exp->op ) )
|
|
{
|
|
// If we can transform the expression by the directive set:
|
|
//
|
|
if ( auto exp_new = transform( exp, dir_src, dir_dst, max_depth, filter ) )
|
|
{
|
|
#if VTIL_SYMEX_SIMPLIFY_VERBOSE
|
|
log<CON_GRN>( "[Join] %s => %s\n", *dir_src, *dir_dst );
|
|
log<CON_GRN>( "= %s [By join directive]\n", *exp_new );
|
|
log<CON_YLW>( "Complexity: %lf => %lf\n", exp->complexity, exp_new->complexity );
|
|
#endif
|
|
// Recurse, set the hint and return the simplified instance.
|
|
//
|
|
simplify_expression( exp_new, pretty, max_depth - 1 );
|
|
exp_new->simplify_hint = true;
|
|
cache_entry = exp_new;
|
|
if ( success_flag = !exp->is_identical( *exp_new ) )
|
|
exp = exp_new;
|
|
return success_flag;
|
|
}
|
|
}
|
|
|
|
// If it is a boolean expression:
|
|
//
|
|
if ( exp->size() == 1 )
|
|
{
|
|
// Enumerate each join descriptor:
|
|
//
|
|
for ( auto [dir_src, dir_dst] : get_boolean_joiners( exp->op ) )
|
|
{
|
|
// If we can transform the expression by the directive set:
|
|
//
|
|
if ( auto exp_new = transform( exp, dir_src, dir_dst, max_depth, filter ) )
|
|
{
|
|
#if VTIL_SYMEX_SIMPLIFY_VERBOSE
|
|
log<CON_GRN>( "[Join] %s => %s\n", *dir_src, *dir_dst );
|
|
log<CON_GRN>( "= %s [By join directive]\n", *exp_new );
|
|
log<CON_YLW>( "Complexity: %lf => %lf\n", exp->complexity, exp_new->complexity );
|
|
#endif
|
|
// Recurse, set the hint and return the simplified instance.
|
|
//
|
|
simplify_expression( exp_new, pretty, max_depth - 1 );
|
|
exp_new->simplify_hint = true;
|
|
cache_entry = exp_new;
|
|
if ( success_flag = !exp->is_identical( *exp_new ) )
|
|
exp = exp_new;
|
|
return success_flag;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Unpack the expression if requested:
|
|
//
|
|
if ( unpack )
|
|
{
|
|
// Enumerate each unpack descriptor:
|
|
//
|
|
for ( auto [dir_src, dir_dst] : get_unpack_descriptors( exp->op ) )
|
|
{
|
|
// If we can transform the expression by the directive set:
|
|
//
|
|
if ( auto exp_new = transform( exp, dir_src, dir_dst, max_depth,
|
|
[ & ] ( auto& exp_new ) { simplify_expression( exp_new, true, max_depth - 1 ); return exp_new->complexity < exp->complexity; } ) )
|
|
{
|
|
#if VTIL_SYMEX_SIMPLIFY_VERBOSE
|
|
log<CON_YLW>( "[Unpack] %s => %s\n", *dir_src, *dir_dst );
|
|
log<CON_GRN>( "= %s [By unpack directive]\n", *exp_new );
|
|
#endif
|
|
|
|
// Set the hint and return the simplified instance.
|
|
//
|
|
exp_new->simplify_hint = true;
|
|
cache_entry = exp_new;
|
|
if ( success_flag = !exp->is_identical( *exp_new ) )
|
|
exp = exp_new;
|
|
return success_flag;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Prettify the expression if requested.
|
|
//
|
|
if ( pretty )
|
|
prettify_expression( exp );
|
|
|
|
#if VTIL_SYMEX_SIMPLIFY_VERBOSE
|
|
// Log the output.
|
|
//
|
|
log( "= %s\n\n", *exp );
|
|
#endif
|
|
return false;
|
|
}
|
|
}; |