[Courgette] Add and use AddressTranslator::PointerToTargetRVA(); Update comments.

Addresses in Courgette (abs32 and rel32) are represented in these forms:
 (1) Location RVA.
 (2) Location FileOffset.
 (3) Pointer in image.
 (4) Target VA.
 (5) Target RVA.
We already have (1) -> (2), (2) -> (1), (2) -> (3), (1) -> (3) for
existing usage. Now we add (3) -> (5) and refactor accordingly (with
helpers to do (4) -> (5) for PE files). PointerToTargetRVA() will
be used again we apply LabelManager to save 25% peak RAM.

Review URL: https://codereview.chromium.org/1807293003

Cr-Commit-Position: refs/heads/master@{#382920}

1 files changed, 27 insertions, 18 deletions

diff --git a/courgette/disassembler_win32_x64.cc b/courgette/disassembler_win32_x64.cc
index 6604268..ffa6c36 100644
--- a/courgette/disassembler_win32_x64.cc
+++ b/courgette/disassembler_win32_x64.cc
@@ -41,6 +41,21 @@ DisassemblerWin32X64::DisassemblerWin32X64(const void* start, size_t length)
       number_of_data_directories_(0) {
 }
 
+RVA DisassemblerWin32X64::FileOffsetToRVA(FileOffset file_offset) const {
+  for (int i = 0; i < number_of_sections_; ++i) {
+    const Section* section = &sections_[i];
+    if (file_offset >= section->file_offset_of_raw_data) {
+      FileOffset offset_in_section =
+          file_offset - section->file_offset_of_raw_data;
+      if (offset_in_section < section->size_of_raw_data)
+        return static_cast<RVA>(section->virtual_address + offset_in_section);
+    }
+  }
+
+  NOTREACHED();
+  return kNoRVA;
+}
+
 FileOffset DisassemblerWin32X64::RVAToFileOffset(RVA rva) const {
   const Section* section = RVAToSection(rva);
   if (section != nullptr) {
@@ -65,19 +80,8 @@ FileOffset DisassemblerWin32X64::RVAToFileOffset(RVA rva) const {
   return kNoFileOffset;
 }
 
-RVA DisassemblerWin32X64::FileOffsetToRVA(FileOffset file_offset) const {
-  for (int i = 0; i < number_of_sections_; ++i) {
-    const Section* section = &sections_[i];
-    if (file_offset >= section->file_offset_of_raw_data) {
-      FileOffset offset_in_section =
-          file_offset - section->file_offset_of_raw_data;
-      if (offset_in_section < section->size_of_raw_data)
-        return static_cast<RVA>(section->virtual_address + offset_in_section);
-    }
-  }
-
-  NOTREACHED();
-  return kNoRVA;
+RVA DisassemblerWin32X64::PointerToTargetRVA(const uint8_t* p) const {
+  return Address64ToRVA(Read64LittleEndian(p));
 }
 
 // ParseHeader attempts to match up the buffer with the Windows data
@@ -338,6 +342,12 @@ const Section* DisassemblerWin32X64::RVAToSection(RVA rva) const {
   return nullptr;
 }
 
+RVA DisassemblerWin32X64::Address64ToRVA(uint64_t address) const {
+  if (address < image_base() || address >= image_base() + size_of_image_)
+    return kNoRVA;
+  return base::checked_cast<RVA>(address - image_base());
+}
+
 std::string DisassemblerWin32X64::SectionName(const Section* section) {
   if (section == nullptr)
     return "<none>";
@@ -389,9 +399,8 @@ bool DisassemblerWin32X64::ParseAbs32Relocs() {
 #if COURGETTE_HISTOGRAM_TARGETS
   for (size_t i = 0; i < abs32_locations_.size(); ++i) {
     RVA rva = abs32_locations_[i];
-    // The 4 bytes at the relocation are a reference to some address.
-    uint32_t target_address = Read32LittleEndian(RVAToPointer(rva));
-    ++abs32_target_rvas_[target_address - image_base()];
+    // The 8 bytes at the relocation are a reference to some address.
+    ++abs32_target_rvas_[PointerToTargetRVA(RVAToPointer(rva))];
   }
 #endif
   return true;
@@ -601,8 +610,8 @@ CheckBool DisassemblerWin32X64::ParseFileRegion(const Section* section,
       ++abs32_pos;
 
     if (abs32_pos != abs32_locations_.end() && *abs32_pos == current_rva) {
-      uint64_t target_address = Read64LittleEndian(p);
-      RVA target_rva = base::checked_cast<RVA>(target_address - image_base());
+      RVA target_rva = PointerToTargetRVA(p);
+      DCHECK_NE(kNoRVA, target_rva);
       // TODO(sra): target could be Label+offset.  It is not clear how to guess
       // which it might be.  We assume offset==0.
       if (!program->EmitAbs64(program->FindOrMakeAbs32Label(target_rva)))