[Zucchini] Disassemblers: Fix abs32 width for ELF; cleanup Traits template param.

Previously DisassemblerElfIntel<TRAITS>::ParseExecSection() passes a
hard-coded 4 to Abs32GapFinder's |abs32_width| CTOR param. This is
wrong for X64, which has abs32 pointer width of 8 bytes. This can lead
to lower quality rel32 extraction.

This CL fixes the above by replacing 4 with Traits::kVAWidth, and also
cleans up TRAITS / Traits template parameter for Disassembler:
* For template param, "template <class TRAITS>" is used throughout.
  * This means function params needs to use TRAITS.
* For usage, each Disassembler class with TRAITS declares
    using Traits = TRAITS;
  (and variant) and uses Traits in the body of all functions. Reason:
  Specialized derive classes won't have TRAITS available , so:
  * Function params can use DisassemblerBase::Traits.
  * Function bodies can use Traits.
  * For consistency, even if TRAITS is available, still use Traits.

Bug: 1233831
Change-Id: Ie796c867fb238eca462b2fb6b4e68a965996c25a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3063919
Commit-Queue: Samuel Huang <huangs@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#908261}
NOKEYCHECK=True
GitOrigin-RevId: 294860c47cd3678c46422ce57da366724e1dc629

1 files changed, 5 insertions, 3 deletions

diff --git a/disassembler_elf.h b/disassembler_elf.h
index 17e7523..ffd1690 100644
--- a/disassembler_elf.h
+++ b/disassembler_elf.h
@@ -65,9 +65,10 @@ struct Elf64IntelTraits : public Elf64Traits {
 };
 
 // Disassembler for ELF.
-template <class Traits>
+template <class TRAITS>
 class DisassemblerElf : public Disassembler {
  public:
+  using Traits = TRAITS;
   // Applies quick checks to determine whether |image| *may* point to the start
   // of an executable. Returns true iff the check passes.
   static bool QuickDetect(ConstBufferView image);
@@ -155,9 +156,10 @@ class DisassemblerElf : public Disassembler {
 };
 
 // Disassembler for ELF with Intel architectures.
-template <class Traits>
-class DisassemblerElfIntel : public DisassemblerElf<Traits> {
+template <class TRAITS>
+class DisassemblerElfIntel : public DisassemblerElf<TRAITS> {
  public:
+  using Traits = TRAITS;
   enum ReferenceType : uint8_t { kReloc, kAbs32, kRel32, kTypeCount };
 
   DisassemblerElfIntel();