Merge pull request #19147 from aschackmull/ssa/writedef-source-refactor

Ssa: Refactor data flow integration to make the input signature simpler

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternals.qll

@@ -956,8 +956,6 @@ class GlobalDef extends Definition {
 private module SsaImpl = SsaImplCommon::Make<Location, SsaInput>;
 
 private module DataFlowIntegrationInput implements SsaImpl::DataFlowIntegrationInputSig {
-  private import codeql.util.Void
-
   class Expr extends Instruction {
     Expr() {
       exists(IRBlock bb, int i |
@@ -977,13 +975,7 @@ private module DataFlowIntegrationInput implements SsaImpl::DataFlowIntegrationI
     )
   }
 
-  predicate ssaDefAssigns(SsaImpl::WriteDefinition def, Expr value) { none() }
-
-  class Parameter extends Void {
-    Location getLocation() { none() }
-  }
-
-  predicate ssaDefInitializesParam(SsaImpl::WriteDefinition def, Parameter p) { none() }
+  predicate ssaDefHasSource(SsaImpl::WriteDefinition def) { none() }
 
   predicate allowFlowIntoUncertainDef(SsaImpl::UncertainWriteDefinition def) { any() }
 

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll

@@ -506,7 +506,7 @@ module SsaFlow {
     result.(Impl::ExprPostUpdateNode).getExpr() =
       n.(PostUpdateNode).getPreUpdateNode().(ExprNode).getControlFlowNode()
     or
-    result.(Impl::ParameterNode).getParameter() = n.(ExplicitParameterNode).getSsaDefinition()
+    result.(Impl::WriteDefSourceNode).getDefinition() = n.(ExplicitParameterNode).getSsaDefinition()
   }
 
   predicate localFlowStep(Ssa::SourceVariable v, Node nodeFrom, Node nodeTo, boolean isUseStep) {

csharp/ql/lib/semmle/code/csharp/dataflow/internal/SsaImpl.qll

@@ -1023,16 +1023,12 @@ private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInpu
 
   Expr getARead(Definition def) { exists(getAReadAtNode(def, result)) }
 
-  predicate ssaDefAssigns(WriteDefinition def, Expr value) {
+  predicate ssaDefHasSource(WriteDefinition def) {
     // exclude flow directly from RHS to SSA definition, as we instead want to
-    // go from RHS to matching assingnable definition, and from there to SSA definition
-    none()
+    // go from RHS to matching assignable definition, and from there to SSA definition
+    def instanceof Ssa::ImplicitParameterDefinition
   }
 
-  class Parameter = Ssa::ImplicitParameterDefinition;
-
-  predicate ssaDefInitializesParam(WriteDefinition def, Parameter p) { def = p }
-
   /**
    * Allows for flow into uncertain defintions that are not call definitions,
    * as we, conservatively, consider such definitions to be certain.

java/ql/lib/semmle/code/java/dataflow/internal/DataFlowNodes.qll

@@ -26,6 +26,14 @@ private predicate deadcode(Expr e) {
 module SsaFlow {
   module Impl = SsaImpl::DataFlowIntegration;
 
+  private predicate ssaDefAssigns(SsaExplicitUpdate def, Expr value) {
+    exists(VariableUpdate upd | upd = def.getDefiningExpr() |
+      value = upd.(VariableAssign).getSource() or
+      value = upd.(AssignOp) or
+      value = upd.(RecordBindingVariableExpr)
+    )
+  }
+
   Impl::Node asNode(Node n) {
     n = TSsaNode(result)
     or
@@ -33,7 +41,12 @@ module SsaFlow {
     or
     result.(Impl::ExprPostUpdateNode).getExpr() = n.(PostUpdateNode).getPreUpdateNode().asExpr()
     or
-    TExplicitParameterNode(result.(Impl::ParameterNode).getParameter()) = n
+    exists(Parameter p |
+      n = TExplicitParameterNode(p) and
+      result.(Impl::WriteDefSourceNode).getDefinition().(SsaImplicitInit).isParameterDefinition(p)
+    )
+    or
+    ssaDefAssigns(result.(Impl::WriteDefSourceNode).getDefinition(), n.asExpr())
   }
 
   predicate localFlowStep(SsaSourceVariable v, Node nodeFrom, Node nodeTo, boolean isUseStep) {

java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll

@@ -647,22 +647,8 @@ private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInpu
 
   Expr getARead(Definition def) { result = getAUse(def) }
 
-  class Parameter = J::Parameter;
-
-  predicate ssaDefAssigns(Impl::WriteDefinition def, Expr value) {
-    exists(VariableUpdate upd | upd = def.(SsaExplicitUpdate).getDefiningExpr() |
-      value = upd.(VariableAssign).getSource() or
-      value = upd.(AssignOp) or
-      value = upd.(RecordBindingVariableExpr)
-    )
-  }
-
-  predicate ssaDefInitializesParam(Impl::WriteDefinition def, Parameter p) {
-    def.(SsaImplicitInit).getSourceVariable() =
-      any(SsaSourceVariable v |
-        v.getVariable() = p and
-        v.getEnclosingCallable() = p.getCallable()
-      )
+  predicate ssaDefHasSource(WriteDefinition def) {
+    def instanceof SsaExplicitUpdate or def.(SsaImplicitInit).isParameterDefinition(_)
   }
 
   predicate allowFlowIntoUncertainDef(UncertainWriteDefinition def) {

javascript/ql/lib/semmle/javascript/dataflow/internal/sharedlib/Ssa.qll

@@ -56,14 +56,7 @@ module SsaDataflowInput implements DataFlowIntegrationInputSig {
     predicate hasCfgNode(js::BasicBlock bb, int i) { this = bb.getNode(i) }
   }
 
-  predicate ssaDefAssigns(WriteDefinition def, Expr value) {
-    // This library only handles use-use flow after a post-update, there are no definitions, only uses.
-    none()
-  }
-
-  class Parameter = js::Parameter;
-
-  predicate ssaDefInitializesParam(WriteDefinition def, Parameter p) {
+  predicate ssaDefHasSource(WriteDefinition def) {
     // This library only handles use-use flow after a post-update, there are no definitions, only uses.
     none()
   }

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -108,7 +108,12 @@ module SsaFlow {
     or
     result.(Impl::ExprPostUpdateNode).getExpr() = n.(PostUpdateNode).getPreUpdateNode().asExpr()
     or
-    n = toParameterNode(result.(Impl::ParameterNode).getParameter())
+    exists(SsaImpl::ParameterExt p |
+      n = toParameterNode(p) and
+      p.isInitializedBy(result.(Impl::WriteDefSourceNode).getDefinition())
+    )
+    or
+    result.(Impl::WriteDefSourceNode).getDefinition().(Ssa::WriteDefinition).assigns(n.asExpr())
   }
 
   predicate localFlowStep(

ruby/ql/lib/codeql/ruby/dataflow/internal/SsaImpl.qll

@@ -473,20 +473,16 @@ class ParameterExt extends TParameterExt {
 private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInputSig {
   private import codeql.ruby.controlflow.internal.Guards as Guards
 
-  class Parameter = ParameterExt;
-
   class Expr extends Cfg::CfgNodes::ExprCfgNode {
     predicate hasCfgNode(SsaInput::BasicBlock bb, int i) { this = bb.getNode(i) }
   }
 
   Expr getARead(Definition def) { result = Cached::getARead(def) }
 
-  predicate ssaDefAssigns(WriteDefinition def, Expr value) {
-    def.(Ssa::WriteDefinition).assigns(value)
+  predicate ssaDefHasSource(WriteDefinition def) {
+    any(ParameterExt p).isInitializedBy(def) or def.(Ssa::WriteDefinition).assigns(_)
   }
 
-  predicate ssaDefInitializesParam(WriteDefinition def, Parameter p) { p.isInitializedBy(def) }
-
   class Guard extends Cfg::CfgNodes::AstCfgNode {
     /**
      * Holds if the control flow branching from `bb1` is dependent on this guard,

rust/ql/lib/codeql/rust/dataflow/internal/DataFlowImpl.qll

@@ -172,10 +172,6 @@ predicate isArgumentForCall(ExprCfgNode arg, CallExprBaseCfgNode call, Parameter
 module SsaFlow {
   private module SsaFlow = SsaImpl::DataFlowIntegration;
 
-  private ParameterNode toParameterNode(ParamCfgNode p) {
-    result.(SourceParameterNode).getParameter() = p
-  }
-
   /** Converts a control flow node into an SSA control flow node. */
   SsaFlow::Node asNode(Node n) {
     n = TSsaNode(result)
@@ -183,8 +179,6 @@ module SsaFlow {
     result.(SsaFlow::ExprNode).getExpr() = n.asExpr()
     or
     result.(SsaFlow::ExprPostUpdateNode).getExpr() = n.(PostUpdateNode).getPreUpdateNode().asExpr()
-    or
-    n = toParameterNode(result.(SsaFlow::ParameterNode).getParameter())
   }
 
   predicate localFlowStep(

rust/ql/lib/codeql/rust/dataflow/internal/SsaImpl.qll

@@ -340,10 +340,7 @@ private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInpu
 
   Expr getARead(Definition def) { result = Cached::getARead(def) }
 
-  /** Holds if SSA definition `def` assigns `value` to the underlying variable. */
-  predicate ssaDefAssigns(WriteDefinition def, Expr value) {
-    none() // handled in `DataFlowImpl.qll` instead
-  }
+  predicate ssaDefHasSource(WriteDefinition def) { none() } // handled in `DataFlowImpl.qll` instead
 
   private predicate isArg(CfgNodes::CallExprBaseCfgNode call, CfgNodes::ExprCfgNode e) {
     call.getArgument(_) = e
@@ -364,13 +361,6 @@ private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInpu
     )
   }
 
-  class Parameter = CfgNodes::ParamBaseCfgNode;
-
-  /** Holds if SSA definition `def` initializes parameter `p` at function entry. */
-  predicate ssaDefInitializesParam(WriteDefinition def, Parameter p) {
-    none() // handled in `DataFlowImpl.qll` instead
-  }
-
   class Guard extends CfgNodes::AstCfgNode {
     /**
      * Holds if the control flow branching from `bb1` is dependent on this guard,

shared/ssa/codeql/ssa/Ssa.qll

@@ -1459,20 +1459,14 @@ module Make<LocationSig Location, InputSig<Location> Input> {
       )
     }
 
-    /** Holds if SSA definition `def` assigns `value` to the underlying variable. */
-    predicate ssaDefAssigns(WriteDefinition def, Expr value);
-
-    /** A parameter. */
-    class Parameter {
-      /** Gets a textual representation of this parameter. */
-      string toString();
-
-      /** Gets the location of this parameter. */
-      Location getLocation();
-    }
-
-    /** Holds if SSA definition `def` initializes parameter `p` at function entry. */
-    predicate ssaDefInitializesParam(WriteDefinition def, Parameter p);
+    /**
+     * Holds if `def` has some form of input flow. For example, the right-hand
+     * side of an assignment or a parameter of an SSA entry definition.
+     *
+     * For such definitions, a flow step is added from a synthetic node
+     * representing the source to the definition.
+     */
+    default predicate ssaDefHasSource(WriteDefinition def) { any() }
 
     /**
      * Holds if flow should be allowed into uncertain SSA definition `def` from
@@ -1665,17 +1659,8 @@ module Make<LocationSig Location, InputSig<Location> Input> {
 
     cached
     private newtype TNode =
-      TParamNode(DfInput::Parameter p) {
-        exists(WriteDefinition def | DfInput::ssaDefInitializesParam(def, p))
-      } or
-      TExprNode(DfInput::Expr e, Boolean isPost) {
-        e = DfInput::getARead(_)
-        or
-        exists(DefinitionExt def |
-          DfInput::ssaDefAssigns(def, e) and
-          isPost = false
-        )
-      } or
+      TWriteDefSource(WriteDefinition def) { DfInput::ssaDefHasSource(def) } or
+      TExprNode(DfInput::Expr e, Boolean isPost) { e = DfInput::getARead(_) } or
       TSsaDefinitionNode(DefinitionExt def) { not phiHasUniqNextNode(def) } or
       TSsaInputNode(SsaPhiExt phi, BasicBlock input) { relevantPhiInputNode(phi, input) }
 
@@ -1696,21 +1681,21 @@ module Make<LocationSig Location, InputSig<Location> Input> {
 
     final class Node = NodeImpl;
 
-    /** A parameter node. */
-    private class ParameterNodeImpl extends NodeImpl, TParamNode {
-      private DfInput::Parameter p;
+    /** A source of a write definition. */
+    private class WriteDefSourceNodeImpl extends NodeImpl, TWriteDefSource {
+      private WriteDefinition def;
 
-      ParameterNodeImpl() { this = TParamNode(p) }
+      WriteDefSourceNodeImpl() { this = TWriteDefSource(def) }
 
-      /** Gets the underlying parameter. */
-      DfInput::Parameter getParameter() { result = p }
+      /** Gets the underlying definition. */
+      WriteDefinition getDefinition() { result = def }
 
-      override string toString() { result = p.toString() }
+      override string toString() { result = "[source] " + def.toString() }
 
-      override Location getLocation() { result = p.getLocation() }
+      override Location getLocation() { result = def.getLocation() }
     }
 
-    final class ParameterNode = ParameterNodeImpl;
+    final class WriteDefSourceNode = WriteDefSourceNodeImpl;
 
     /** A (post-update) expression node. */
     abstract private class ExprNodePreOrPostImpl extends NodeImpl, TExprNode {
@@ -1976,12 +1961,8 @@ module Make<LocationSig Location, InputSig<Location> Input> {
      */
     predicate localFlowStep(SourceVariable v, Node nodeFrom, Node nodeTo, boolean isUseStep) {
       exists(Definition def |
-        // Flow from assignment into SSA definition
-        DfInput::ssaDefAssigns(def, nodeFrom.(ExprNode).getExpr())
-        or
-        // Flow from parameter into entry definition
-        DfInput::ssaDefInitializesParam(def, nodeFrom.(ParameterNode).getParameter())
-      |
+        // Flow from write definition source into SSA definition
+        nodeFrom = TWriteDefSource(def) and
         isUseStep = false and
         if DfInput::includeWriteDefsInFlowStep()
         then
@@ -2012,12 +1993,8 @@ module Make<LocationSig Location, InputSig<Location> Input> {
     /** Holds if the value of `nodeTo` is given by `nodeFrom`. */
     predicate localMustFlowStep(SourceVariable v, Node nodeFrom, Node nodeTo) {
       exists(Definition def |
-        // Flow from assignment into SSA definition
-        DfInput::ssaDefAssigns(def, nodeFrom.(ExprNode).getExpr())
-        or
-        // Flow from parameter into entry definition
-        DfInput::ssaDefInitializesParam(def, nodeFrom.(ParameterNode).getParameter())
-      |
+        // Flow from write definition source into SSA definition
+        nodeFrom = TWriteDefSource(def) and
         v = def.getSourceVariable() and
         if DfInput::includeWriteDefsInFlowStep()
         then nodeTo.(SsaDefinitionNode).getDefinition() = def