kc3-lang/angle/src/compiler/timing/RestrictVertexShaderTiming.cpp

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• Hash : 66ebd014
  Author :
  Date : 2012-05-30T22:18:11
  

  Add the SH_TIMING_RESTRICTIONS compile flag and dependency graph implementation.
  
  Description of the algorithm:
  http://code.google.com/p/mvujovic/wiki/ShaderControlFlowAnalysis
  
  This flag is one potential solution to timing attacks on textures containing cross-domain content
  or user agent data.
  This kind of analysis could be useful for both WebGL and CSS Shaders.
  
  The SH_TIMING_RESTRICTIONS flag will reject a shader if it uses texture dependent data to affect
  control flow.
  
  Other ways of affecting shader timing such as using NaNs in basic arithmetic operations or using
  built-in functions (e.g. atan) with different inputs are still under investigation.
  
  Issue=329
  Review URL: http://codereview.appspot.com/6195062/
  
  
  
  git-svn-id: https://angleproject.googlecode.com/svn/trunk@1101 736b8ea6-26fd-11df-bfd4-992fa37f6226
  

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• src/compiler/timing/RestrictVertexShaderTiming.cpp

• //
  // Copyright (c) 2012 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  
  #include "compiler/timing/RestrictVertexShaderTiming.h"
  
  void RestrictVertexShaderTiming::visitSymbol(TIntermSymbol* node)
  {
      if (node->getQualifier() == EvqUniform &&
          node->getBasicType() == EbtSampler2D &&
          node->getSymbol() == mRestrictedSymbol) {
          mFoundRestrictedSymbol = true;
          mSink.prefix(EPrefixError);
          mSink.location(node->getLine());
          mSink << "Definition of a uniform sampler2D by the name '" << mRestrictedSymbol
                << "' is not permitted in vertex shaders.\n";
      }
  }
  
  bool RestrictVertexShaderTiming::visitAggregate(Visit visit, TIntermAggregate* node)
  {
      // Don't keep exploring if we've found the restricted symbol, and don't explore anything besides
      // the global scope (i.e. don't explore function definitions).
      if (mFoundRestrictedSymbol || node->getOp() == EOpFunction)
          return false;
  
      return true;
  }
  

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