1    :  // Copyright 2012 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  //
  15    :  // Utilities for dealing with block-graphs and blocks.
  16    :  
  17    :  #ifndef SYZYGY_BLOCK_GRAPH_BLOCK_UTIL_H_
  18    :  #define SYZYGY_BLOCK_GRAPH_BLOCK_UTIL_H_
  19    :  
  20    :  #include "syzygy/block_graph/basic_block.h"
  21    :  #include "syzygy/block_graph/block_graph.h"
  22    :  
  23  m :  namespace block_graph {
  24    :  
  25    :  // Determines whether @p block's attributes preclude basic-block
  26    :  // decomposition.
  27    :  // @param block the code block whose attributes are to be inspected.
  28    :  // @returns true if the block attributes are safe for decomposition to basic-
  29    :  //     blocks, false otherwise.
  30    :  // @pre block has type CODE_BLOCK.
  31  m :  bool CodeBlockAttributesAreBasicBlockSafe(const BlockGraph::Block* block);
  32    :  
  33    :  // Determines whether @p bb's instructions and successors comprise a contiguous
  34    :  // source range, and return it if so.
  35    :  // @param bb the basic block to inspect.
  36    :  // @param source_range returns @p bb's source range on success.
  37    :  // @returns true iff @p bb's instructions and successors comprise a contiguous
  38    :  //     source range.
  39    :  // @note @p bb's source range is deemed contiguous if at least one instruction
  40    :  //     or successor has a source range, and if all the source ranges constitute
  41    :  //     a single contiguous range, irrespective order. This means that this
  42    :  //     function may succeed even if instructions in @p bb have been added,
  43    :  //     reordered or mutated.
  44  m :  bool GetBasicBlockSourceRange(const BasicCodeBlock& bb,
  45  m :                                BlockGraph::Block::SourceRange* source_range);
  46    :  
  47    :  // Returns true if the given references @p ref from @p referrer may not safely
  48    :  // be redirected. If both the referrer and the referenced blocks are irregular
  49    :  // in any way (i.e., inline assembly, not generated by cl.exe, etc) we cannot
  50    :  // safely assume that @p ref has call semantics, i.e., where a return address
  51    :  // is at the top of stack at entry. Ideally we would decide this on the basis
  52    :  // of a full stack analysis, but beggars can't be choosers; plus, for
  53    :  // hand-coded assembly that's the halting problem :).
  54    :  // For any instrumentation or manipulation that uses return address swizzling,
  55    :  // instrumenting an unsafe reference generally leads to crashes.
  56  m :  bool IsUnsafeReference(const BlockGraph::Block* referrer,
  57  m :                         const BlockGraph::Reference& ref);
  58    :  
  59  m :  }  // namespace block_graph
  60    :  
  61    :  #endif  // SYZYGY_BLOCK_GRAPH_BLOCK_UTIL_H_