[Zucchini] Fix patch apply failure from untranslatable abs32 references.

Disassembler (Win32 and ELF) uses reloc to find abs32 locations, which
are stored in (1) |abs32_locations_|. Later on, (1) is filtered to
generate (2) actual abs32 locations.

A patching failure case was discovered: Equivalence blocks must never
cut across reference boundaries. However, it turns out blocks generated
using (2) were subject to checks using (1), which triggers a failure
since (1) - (2) is nonempty.

One way for (1) != (2) to happen is from CURRENT_MODULE() usage, which
creates an abs32 reference outside a section. This results in an abs32
target whose RVA does not map to an offset using section data, and
gets rejected by filtering logic for (2).

Fix: Apply the filtering logic direcly to (1), so (1) == (2). Details:
* Add RemoveUntranslatableAbs32() (abs32_utils.h), which uses the
  filtering logic for (2) to preemptively remove problematic RVAs
  from (1), so |abs32_locations_| matches (2). Extensive unit tests
  are added.
* DisassemblerWin32<Traits>::ParseAndStoreAbs32(): Initialize
  |abs32_locations_| with 3 steps: Naive extraction from relocs,
  RemoveUntranslatableAbs32(), and RemoveOverlappingAbs32Locations().
* DisassemblerElf<Traits>::GetAbs32FromRelocSections(): Do the same,
  noting that ELF's image base is always 0.

Additional fixes:
* address_translator.h: kInvalidRva was -1, but it should be -2 to
  better match kInvalidOffset.
* Abs32RvaExtractorWin32::Abs32RvaExtractorWin32: The lambda
  |find_and_check| binds |addr|, which has been std::move()'ed.
  Better to just bind |this| and use |addr_|.

Bug: 892284
Change-Id: I628f4668ea231c7e06f35bd924652ca4d74bb848
Reviewed-on: https://chromium-review.googlesource.com/c/1263877
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598342}
NOKEYCHECK=True
GitOrigin-RevId: b6d108f1cabab2a9f3fe46a7cdeb92685a2c790e

1 files changed, 8 insertions, 1 deletions

diff --git a/abs32_utils.h b/abs32_utils.h
index a97aa38..5bc9cf2 100644
--- a/abs32_utils.h
+++ b/abs32_utils.h
@@ -45,7 +45,7 @@ class AbsoluteAddress {
   // the write and returns true. On failure (invalid |offset|), returns false.
   bool Write(offset_t offset, MutableBufferView* image);
 
-  size_t width() const { return WidthOf(bitness_); }
+  uint32_t width() const { return WidthOf(bitness_); }
 
   // Exposing |value_| for testing.
   uint64_t* mutable_value() { return &value_; }
@@ -126,6 +126,13 @@ class Abs32WriterWin32 : public ReferenceWriter {
   DISALLOW_COPY_AND_ASSIGN(Abs32WriterWin32);
 };
 
+// Given a list of abs32 |locations|, removes all elements whose targets cannot
+// be translated. Returns the number of elements removed.
+size_t RemoveUntranslatableAbs32(ConstBufferView image,
+                                 AbsoluteAddress&& addr,
+                                 const AddressTranslator& translator,
+                                 std::vector<offset_t>* locations);
+
 // Given a sorted list of abs32 |locations|, removes all elements whose body
 // (with |width| given) overlaps with the body of a previous element.
 size_t RemoveOverlappingAbs32Locations(uint32_t width,