Move Courgette...

courgette/encoded_program.cc

+// Copyright (c) 2009 The Chromium 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 "courgette/encoded_program.h"
+
+#include <algorithm>
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/sys_info.h"
+
+#include "courgette/courgette.h"
+#include "courgette/streams.h"
+
+namespace courgette {
+
+// Stream indexes.
+const int kStreamMisc    = 0;
+const int kStreamOps     = 1;
+const int kStreamBytes   = 2;
+const int kStreamAbs32Indexes = 3;
+const int kStreamRel32Indexes = 4;
+const int kStreamAbs32Addresses = 5;
+const int kStreamRel32Addresses = 6;
+const int kStreamCopyCounts = 7;
+const int kStreamOriginAddresses = kStreamMisc;
+
+const int kStreamLimit = 9;
+
+// Binary assembly language operations.
+enum EncodedProgram::OP {
+  ORIGIN,    // ORIGIN <rva> - set address for subsequent assembly.
+  COPY,      // COPY <count> <bytes> - copy bytes to output.
+  COPY1,     // COPY1 <byte> - same as COPY 1 <byte>.
+  REL32,     // REL32 <index> - emit rel32 encoded reference to address at
+             // address table offset <index>
+  ABS32,     // ABS32 <index> - emit abs32 encoded reference to address at
+             // address table offset <index>
+  MAKE_BASE_RELOCATION_TABLE,  // Emit base relocation table blocks.
+  OP_LAST
+};
+
+
+// Constructor is here rather than in the header.  Although the constructor
+// appears to do nothing it is fact quite large because of the implict calls to
+// field constructors.  Ditto for the destructor.
+EncodedProgram::EncodedProgram() {}
+EncodedProgram::~EncodedProgram() {}
+
+// Serializes a vector of integral values using Varint32 coding.
+template<typename T>
+void WriteVector(const std::vector<T>& items, SinkStream* buffer) {
+  size_t count = items.size();
+  buffer->WriteVarint32(count);
+  for (size_t i = 0;  i < count;  ++i) {
+    COMPILE_ASSERT(sizeof(T) <= sizeof(uint32), T_must_fit_in_uint32);
+    buffer->WriteVarint32(static_cast<uint32>(items[i]));
+  }
+}
+
+template<typename T>
+bool ReadVector(std::vector<T>* items, SourceStream* buffer) {
+  uint32 count;
+  if (!buffer->ReadVarint32(&count))
+    return false;
+
+  items->clear();
+  items->reserve(count);
+  for (size_t i = 0;  i < count;  ++i) {
+    uint32 item;
+    if (!buffer->ReadVarint32(&item))
+      return false;
+    items->push_back(static_cast<T>(item));
+  }
+
+  return true;
+}
+
+// Serializes a vector, using delta coding followed by Varint32 coding.
+void WriteU32Delta(const std::vector<uint32>& set, SinkStream* buffer) {
+  size_t count = set.size();
+  buffer->WriteVarint32(count);
+  uint32 prev = 0;
+  for (size_t i = 0;  i < count;  ++i) {
+    uint32 current = set[i];
+    uint32 delta = current - prev;
+    buffer->WriteVarint32(delta);
+    prev = current;
+  }
+}
+
+static bool ReadU32Delta(std::vector<uint32>* set, SourceStream* buffer) {
+  uint32 count;
+
+  if (!buffer->ReadVarint32(&count))
+    return false;
+
+  set->clear();
+  set->reserve(count);
+  uint32 prev = 0;
+
+  for (size_t i = 0;  i < count;  ++i) {
+    uint32 delta;
+    if (!buffer->ReadVarint32(&delta))
+      return false;
+    uint32 current = prev + delta;
+    set->push_back(current);
+    prev = current;
+  }
+
+  return true;
+}
+
+// Write a vector as the byte representation of the contents.
+//
+// (This only really makes sense for a type T that has sizeof(T)==1, otherwise
+// serilized representation is not endian-agnositic.  But it is useful to keep
+// the possibility of a greater size for experiments comparing Varint32 encoding
+// of a vector of larger integrals vs a plain form.)
+//
+template<typename T>
+void WriteVectorU8(const std::vector<T>& items, SinkStream* buffer) {
+  uint32 count = items.size();
+  buffer->WriteVarint32(count);
+  if (count != 0) {
+    size_t byte_count = count * sizeof(T);
+    buffer->Write(static_cast<const void*>(&items[0]), byte_count);
+  }
+}
+
+template<typename T>
+bool ReadVectorU8(std::vector<T>* items, SourceStream* buffer) {
+  uint32 count;
+  if (!buffer->ReadVarint32(&count))
+    return false;
+
+  items->clear();
+  items->resize(count);
+  if (count != 0) {
+    size_t byte_count = count * sizeof(T);
+    return buffer->Read(static_cast<void*>(&((*items)[0])), byte_count);
+  }
+  return true;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+void EncodedProgram::DefineRel32Label(int index, RVA value) {
+  DefineLabelCommon(&rel32_rva_, index, value);
+}
+
+void EncodedProgram::DefineAbs32Label(int index, RVA value) {
+  DefineLabelCommon(&abs32_rva_, index, value);
+}
+
+static const RVA kUnassignedRVA = static_cast<RVA>(-1);
+
+void EncodedProgram::DefineLabelCommon(std::vector<RVA>* rvas,
+                                       int index,
+                                       RVA rva) {
+  if (static_cast<int>(rvas->size()) <= index) {
+    rvas->resize(index + 1, kUnassignedRVA);
+  }
+  if ((*rvas)[index] != kUnassignedRVA) {
+    NOTREACHED() << "DefineLabel double assigned " << index;
+  }
+  (*rvas)[index] = rva;
+}
+
+void EncodedProgram::EndLabels() {
+  FinishLabelsCommon(&abs32_rva_);
+  FinishLabelsCommon(&rel32_rva_);
+}
+
+void EncodedProgram::FinishLabelsCommon(std::vector<RVA>* rvas) {
+  // Replace all unassigned slots with the value at the previous index so they
+  // delta-encode to zero.  (There might be better values than zero.  The way to
+  // get that is have the higher level assembly program assign the unassigned
+  // slots.)
+  RVA previous = 0;
+  size_t size = rvas->size();
+  for (size_t i = 0;  i < size;  ++i) {
+    if ((*rvas)[i] == kUnassignedRVA)
+      (*rvas)[i] = previous;
+    else
+      previous = (*rvas)[i];
+  }
+}
+
+void EncodedProgram::AddOrigin(RVA origin) {
+  ops_.push_back(ORIGIN);
+  origins_.push_back(origin);
+}
+
+void EncodedProgram::AddCopy(int count, const void* bytes) {
+  const uint8* source = static_cast<const uint8*>(bytes);
+
+  // Fold adjacent COPY instructions into one.  This nearly halves the size of
+  // an EncodedProgram with only COPY1 instructions since there are approx plain
+  // 16 bytes per reloc.  This has a working-set benefit during decompression.
+  // For compression of files with large differences this makes a small (4%)
+  // improvement in size.  For files with small differences this degrades the
+  // compressed size by 1.3%
+  if (ops_.size() > 0) {
+    if (ops_.back() == COPY1) {
+      ops_.back() = COPY;
+      copy_counts_.push_back(1);
+    }
+    if (ops_.back() == COPY) {
+      copy_counts_.back() += count;
+      for (int i = 0;  i < count;  ++i) {
+        copy_bytes_.push_back(source[i]);
+      }
+      return;
+    }
+  }
+
+  if (count == 1) {
+    ops_.push_back(COPY1);
+    copy_bytes_.push_back(source[0]);
+  } else {
+    ops_.push_back(COPY);
+    copy_counts_.push_back(count);
+    for (int i = 0;  i < count;  ++i) {
+      copy_bytes_.push_back(source[i]);
+    }
+  }
+}
+
+void EncodedProgram::AddAbs32(int label_index) {
+  ops_.push_back(ABS32);
+  abs32_ix_.push_back(label_index);
+}
+
+void EncodedProgram::AddRel32(int label_index) {
+  ops_.push_back(REL32);
+  rel32_ix_.push_back(label_index);
+}
+
+void EncodedProgram::AddMakeRelocs() {
+  ops_.push_back(MAKE_BASE_RELOCATION_TABLE);
+}
+
+void EncodedProgram::DebuggingSummary() {
+  LOG(INFO) << "EncodedProgram Summary";
+  LOG(INFO) << "  image base  " << image_base_;
+  LOG(INFO) << "  abs32 rvas  " << abs32_rva_.size();
+  LOG(INFO) << "  rel32 rvas  " << rel32_rva_.size();
+  LOG(INFO) << "  ops         " << ops_.size();
+  LOG(INFO) << "  origins     " << origins_.size();
+  LOG(INFO) << "  copy_counts " << copy_counts_.size();
+  LOG(INFO) << "  copy_bytes  " << copy_bytes_.size();
+  LOG(INFO) << "  abs32_ix    " << abs32_ix_.size();
+  LOG(INFO) << "  rel32_ix    " << rel32_ix_.size();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+// For algorithm refinement purposes it is useful to write subsets of the file
+// format.  This gives us the ability to estimate the entropy of the
+// differential compression of the individual streams, which can provide
+// invaluable insights.  The default, of course, is to include all the streams.
+//
+enum FieldSelect {
+  INCLUDE_ABS32_ADDRESSES = 0x0001,
+  INCLUDE_REL32_ADDRESSES = 0x0002,
+  INCLUDE_ABS32_INDEXES   = 0x0010,
+  INCLUDE_REL32_INDEXES   = 0x0020,
+  INCLUDE_OPS             = 0x0100,
+  INCLUDE_BYTES           = 0x0200,
+  INCLUDE_COPY_COUNTS     = 0x0400,
+  INCLUDE_MISC            = 0x1000
+};
+
+static FieldSelect GetFieldSelect() {
+#if 1
+  // TODO(sra): Use better configuration.
+  std::wstring s = base::SysInfo::GetEnvVar(L"A_FIELDS");
+  if (!s.empty()) {
+    return static_cast<FieldSelect>(wcstoul(s.c_str(), 0, 0));
+  }
+#endif
+  return  static_cast<FieldSelect>(~0);
+}
+
+void EncodedProgram::WriteTo(SinkStreamSet* streams) {
+  FieldSelect select = GetFieldSelect();
+
+  // The order of fields must be consistent in WriteTo and ReadFrom, regardless
+  // of the streams used.  The code can be configured with all kStreamXXX
+  // constants the same.
+  //
+  // If we change the code to pipeline reading with assembly (to avoid temporary
+  // storage vectors by consuming operands directly from the stream) then we
+  // need to read the base address and the random access address tables first,
+  // the rest can be interleaved.
+
+  if (select & INCLUDE_MISC) {
+    // TODO(sra): write 64 bits.
+    streams->stream(kStreamMisc)->WriteVarint32(
+      static_cast<uint32>(image_base_));
+  }
+
+  if (select & INCLUDE_ABS32_ADDRESSES)
+    WriteU32Delta(abs32_rva_, streams->stream(kStreamAbs32Addresses));
+  if (select & INCLUDE_REL32_ADDRESSES)
+    WriteU32Delta(rel32_rva_, streams->stream(kStreamRel32Addresses));
+  if (select & INCLUDE_MISC)
+    WriteVector(origins_, streams->stream(kStreamOriginAddresses));
+  if (select & INCLUDE_OPS) {
+    streams->stream(kStreamOps)->Reserve(ops_.size() + 5);  // 5 for length.
+    WriteVector(ops_, streams->stream(kStreamOps));
+  }
+  if (select & INCLUDE_COPY_COUNTS)
+    WriteVector(copy_counts_, streams->stream(kStreamCopyCounts));
+  if (select & INCLUDE_BYTES)
+    WriteVectorU8(copy_bytes_, streams->stream(kStreamBytes));
+  if (select & INCLUDE_ABS32_INDEXES)
+    WriteVector(abs32_ix_, streams->stream(kStreamAbs32Indexes));
+  if (select & INCLUDE_REL32_INDEXES)
+    WriteVector(rel32_ix_, streams->stream(kStreamRel32Indexes));
+}
+
+bool EncodedProgram::ReadFrom(SourceStreamSet* streams) {
+  // TODO(sra): read 64 bits.
+  uint32 temp;
+  if (!streams->stream(kStreamMisc)->ReadVarint32(&temp))
+    return false;
+  image_base_ = temp;
+
+  if (!ReadU32Delta(&abs32_rva_, streams->stream(kStreamAbs32Addresses)))
+    return false;
+  if (!ReadU32Delta(&rel32_rva_, streams->stream(kStreamRel32Addresses)))
+    return false;
+  if (!ReadVector(&origins_, streams->stream(kStreamOriginAddresses)))
+    return false;
+  if (!ReadVector(&ops_, streams->stream(kStreamOps)))
+    return false;
+  if (!ReadVector(&copy_counts_, streams->stream(kStreamCopyCounts)))
+    return false;
+  if (!ReadVectorU8(&copy_bytes_, streams->stream(kStreamBytes)))
+    return false;
+  if (!ReadVector(&abs32_ix_, streams->stream(kStreamAbs32Indexes)))
+    return false;
+  if (!ReadVector(&rel32_ix_, streams->stream(kStreamRel32Indexes)))
+    return false;
+
+  // Check that streams have been completely consumed.
+  for (int i = 0;  i < kStreamLimit;  ++i) {
+    if (streams->stream(i)->Remaining() > 0)
+      return false;
+  }
+
+  return true;
+}
+
+// Safe, non-throwing version of std::vector::at().  Returns 'true' for success,
+// 'false' for out-of-bounds index error.
+template<typename T>
+bool VectorAt(const std::vector<T>& v, size_t index, T* output) {
+  if (index >= v.size())
+    return false;
+  *output = v[index];
+  return true;
+}
+
+bool EncodedProgram::AssembleTo(SinkStream* final_buffer) {
+  // For the most part, the assembly process walks the various tables.
+  // ix_mumble is the index into the mumble table.
+  size_t ix_origins = 0;
+  size_t ix_copy_counts = 0;
+  size_t ix_copy_bytes = 0;
+  size_t ix_abs32_ix = 0;
+  size_t ix_rel32_ix = 0;
+
+  RVA current_rva = 0;
+
+  bool pending_base_relocation_table = false;
+  SinkStream bytes_following_base_relocation_table;
+
+  SinkStream* output = final_buffer;
+
+  for (size_t ix_ops = 0;  ix_ops < ops_.size();  ++ix_ops) {
+    OP op = ops_[ix_ops];
+
+    switch (op) {
+      default:
+        return false;
+
+      case ORIGIN: {
+        RVA section_rva;
+        if (!VectorAt(origins_, ix_origins, &section_rva))
+          return false;
+        ++ix_origins;
+        current_rva = section_rva;
+        break;
+      }
+
+      case COPY: {
+        int count;
+        if (!VectorAt(copy_counts_, ix_copy_counts, &count))
+          return false;
+        ++ix_copy_counts;
+        for (int i = 0;  i < count;  ++i) {
+          uint8 b;
+          if (!VectorAt(copy_bytes_, ix_copy_bytes, &b))
+            return false;
+          ++ix_copy_bytes;
+          output->Write(&b, 1);
+        }
+        current_rva += count;
+        break;
+      }
+
+      case COPY1: {
+        uint8 b;
+        if (!VectorAt(copy_bytes_, ix_copy_bytes, &b))
+          return false;
+        ++ix_copy_bytes;
+        output->Write(&b, 1);
+        current_rva += 1;
+        break;
+      }
+
+      case REL32: {
+        uint32 index;
+        if (!VectorAt(rel32_ix_, ix_rel32_ix, &index))
+          return false;
+        ++ix_rel32_ix;
+        RVA rva;
+        if (!VectorAt(rel32_rva_, index, &rva))
+          return false;
+        uint32 offset = (rva - (current_rva + 4));
+        output->Write(&offset, 4);
+        current_rva += 4;
+        break;
+      }
+
+      case ABS32: {
+        uint32 index;
+        if (!VectorAt(abs32_ix_, ix_abs32_ix, &index))
+          return false;
+        ++ix_abs32_ix;
+        RVA rva;
+        if (!VectorAt(abs32_rva_, index, &rva))
+          return false;
+        uint32 abs32 = static_cast<uint32>(rva + image_base_);
+        abs32_relocs_.push_back(current_rva);
+        output->Write(&abs32, 4);
+        current_rva += 4;
+        break;
+      }
+
+      case MAKE_BASE_RELOCATION_TABLE: {
+        // We can see the base relocation anywhere, but we only have the
+        // information to generate it at the very end.  So we divert the bytes
+        // we are generating to a temporary stream.
+        if (pending_base_relocation_table)  // Can't have two base relocation
+                                            // tables.
+          return false;
+
+        pending_base_relocation_table = true;
+        output = &bytes_following_base_relocation_table;
+        break;
+        // There is a potential problem *if* the instruction stream contains
+        // some REL32 relocations following the base relocation and in the same
+        // section.  We don't know the size of the table, so 'current_rva' will
+        // be wrong, causing REL32 offsets to be miscalculated.  This never
+        // happens; the base relocation table is usually in a section of its
+        // own, a data-only section, and following everything else in the
+        // executable except some padding zero bytes.  We could fix this by
+        // emitting an ORIGIN after the MAKE_BASE_RELOCATION_TABLE.
+      }
+    }
+  }
+
+  if (pending_base_relocation_table) {
+    GenerateBaseRelocations(final_buffer);
+    final_buffer->Append(&bytes_following_base_relocation_table);
+  }
+
+  // Final verification check: did we consume all lists?
+  if (ix_copy_counts != copy_counts_.size())
+    return false;
+  if (ix_copy_bytes != copy_bytes_.size())
+    return false;
+  if (ix_abs32_ix != abs32_ix_.size())
+    return false;
+  if (ix_rel32_ix != rel32_ix_.size())
+    return false;
+
+  return true;
+}
+
+
+// RelocBlock has the layout of a block of relocations in the base relocation
+// table file format.
+//
+class RelocBlock {
+ public:
+  uint32 page_rva;
+  uint32 block_size;
+  uint16 relocs[4096];  // Allow up to one relocation per byte of a 4k page.
+
+  RelocBlock() : page_rva(~0), block_size(8) {}
+
+  void Add(uint16 item) {
+    relocs[(block_size-8)/2] = item;
+    block_size += 2;
+  }
+
+  void Flush(SinkStream* buffer) {
+    if (block_size != 8) {
+      if (block_size % 4 != 0) {  // Pad to make size multiple of 4 bytes.
+        Add(0);
+      }
+      buffer->Write(this, block_size);
+      block_size = 8;
+    }
+  }
+};
+
+COMPILE_ASSERT(offsetof(RelocBlock, relocs) == 8, reloc_block_header_size);
+
+void EncodedProgram::GenerateBaseRelocations(SinkStream* buffer) {
+  std::sort(abs32_relocs_.begin(), abs32_relocs_.end());
+
+  RelocBlock block;
+
+  for (size_t i = 0;  i < abs32_relocs_.size();  ++i) {
+    uint32 rva = abs32_relocs_[i];
+    uint32 page_rva = rva & ~0xFFF;
+    if (page_rva != block.page_rva) {
+      block.Flush(buffer);
+      block.page_rva = page_rva;
+    }
+    block.Add(0x3000 | (rva & 0xFFF));
+  }
+  block.Flush(buffer);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+Status WriteEncodedProgram(EncodedProgram* encoded, SinkStreamSet* sink) {
+  encoded->WriteTo(sink);
+  return C_OK;
+}
+
+Status ReadEncodedProgram(SourceStreamSet* streams, EncodedProgram** output) {
+  EncodedProgram* encoded = new EncodedProgram();
+  if (encoded->ReadFrom(streams)) {
+    *output = encoded;
+    return C_OK;
+  }
+  delete encoded;
+  return C_DESERIALIZATION_FAILED;
+}
+
+Status Assemble(EncodedProgram* encoded, SinkStream* buffer) {
+  bool assembled = encoded->AssembleTo(buffer);
+  if (assembled)
+    return C_OK;
+  return C_ASSEMBLY_FAILED;
+}
+
+void DeleteEncodedProgram(EncodedProgram* encoded) {
+  delete encoded;
+}
+
+}  // end namespace