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Added a depth limit to self-generated pattern matching.

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This commit is contained in:
Can Bölük 2020-07-25 12:16:04 +02:00
parent c6340bd7c4
commit 109ad182df
1 changed files with 39 additions and 23 deletions
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62
VTIL-SymEx/simplifier/simplifier.cpp
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@ -33,6 +33,12 @@
#include <vtil/io>
#include <vtil/utility>
// [Configuration]
// Determine the depth limit after which we start self generated signature matching.
//
#ifndef VTIL_SELFGEN_SIGMATCH_DEPTH_LIM
#define VTIL_SELFGEN_SIGMATCH_DEPTH_LIM 3
#endif
namespace vtil::symbolic
{
struct join_depth_exception : std::exception
@ -150,10 +156,16 @@ namespace vtil::symbolic
expression::uid_relation_table table;
};
inline static thread_local result* signal = nullptr;
inline static thread_local bool match_ptr = false;
bool operator()( const expression::reference& a,
const expression::reference& b ) const noexcept
{
// If pointer matching:
//
if ( match_ptr )
return a == b;
// If identical expressions, return true.
//
if ( a.is_identical( *b ) )
@ -170,9 +182,9 @@ namespace vtil::symbolic
else if ( b == signal->key ) self = b, other = a;
else return false;
// If other's complexity is less than self:
// If other's past depth limit:
//
if ( other->complexity < self->complexity )
if ( other->depth > VTIL_SELFGEN_SIGMATCH_DEPTH_LIM )
{
// If matching signature, save the match.
//
@ -191,7 +203,6 @@ namespace vtil::symbolic
}
};
// Cache entry and map type.
//
struct cache_value;
@ -329,7 +340,7 @@ namespace vtil::symbolic
// Signal signature matcher.
//
signature_matcher::result sig_search = { exp };
signature_matcher::signal = &sig_search;
signature_matcher::signal = exp->depth > VTIL_SELFGEN_SIGMATCH_DEPTH_LIM ? &sig_search : nullptr;
auto [it, inserted] = map.emplace( exp, make_default<cache_value>() );
signature_matcher::signal = nullptr;
@ -339,30 +350,35 @@ namespace vtil::symbolic
{
// If there is a partial match:
//
expression::reference result = nullptr;
if ( sig_search.match )
{
// Transform according to the UID table.
//
result = sig_search.match.make_shared();
result.transform( [ & ] ( expression::delegate& exp )
{
for ( auto& [a, b] : sig_search.table )
{
if ( exp->uid == a->uid )
{
exp = b.make_shared();
return;
}
}
}, true, false );
result->simplify_hint = true;
// Write the new result and clear inserted flag.
//
it->second.result = std::move( result );
it->second.is_simplified = true;
signature_matcher::match_ptr = true;
auto& base = map.find( sig_search.match.make_shared() )->second;
signature_matcher::match_ptr = false;
it->second.result = base.result;
it->second.is_simplified = base.is_simplified;
inserted = false;
// Transform according to the UID table.
//
if ( it->second.result )
{
it->second.result.transform( [ & ] ( expression::delegate& exp )
{
for ( auto& [a, b] : sig_search.table )
{
if ( exp->uid == a->uid )
{
exp = b.make_shared();
return;
}
}
}, true, false );
it->second.result->simplify_hint = true;
}
}
// Initialize it.