[Zucchini]: Fix implicit conversions.

Fix compile error with -Wshorten-64-to-32.

Bug: 881008
Change-Id: I52a1bab9cb7b4cb67ea4c275143390d42b192120
Reviewed-on: https://chromium-review.googlesource.com/1216524Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590285}

components/zucchini/disassembler_elf.cc

@@ -270,7 +270,8 @@ bool DisassemblerElf<Traits>::ParseHeader() {
        segment != segments_ + segments_count_; ++segment) {
     if (!RangeIsBounded(segment->p_offset, segment->p_filesz, kOffsetBound))
       return false;
-    offset_t segment_end = segment->p_offset + segment->p_filesz;
+    offset_t segment_end =
+        base::checked_cast<offset_t>(segment->p_offset + segment->p_filesz);
     offset_bound = std::max(offset_bound, segment_end);
   }
 
@@ -366,8 +367,10 @@ void DisassemblerElfIntel<Traits>::ParseExecSection(
   auto& abs32_locations_ = this->abs32_locations_;
 
   std::ptrdiff_t from_offset_to_rva = section.sh_addr - section.sh_offset;
-  rva_t start_rva = section.sh_addr;
-  rva_t end_rva = start_rva + section.sh_size;
+
+  // Range of values was ensured in ParseHeader().
+  rva_t start_rva = base::checked_cast<rva_t>(section.sh_addr);
+  rva_t end_rva = base::checked_cast<rva_t>(start_rva + section.sh_size);
 
   AddressTranslator::RvaToOffsetCache target_rva_checker(this->translator_);
 
@@ -380,7 +383,8 @@ void DisassemblerElfIntel<Traits>::ParseExecSection(
     finder->Reset(gap.value());
     for (auto rel32 = finder->GetNext(); rel32.has_value();
          rel32 = finder->GetNext()) {
-      offset_t rel32_offset = offset_t(rel32->location - image_.begin());
+      offset_t rel32_offset =
+          base::checked_cast<offset_t>(rel32->location - image_.begin());
       rva_t rel32_rva = rva_t(rel32_offset + from_offset_to_rva);
       rva_t target_rva = rel32_rva + 4 + image_.read<uint32_t>(rel32_offset);
       if (target_rva_checker.IsValid(target_rva) &&

components/zucchini/disassembler_ztf.cc

@@ -7,11 +7,13 @@
 #include <algorithm>
 #include <cmath>
 #include <iterator>
+#include <limits>
 #include <numeric>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/numerics/checked_math.h"
+#include "base/numerics/safe_conversions.h"
 #include "components/zucchini/algorithm.h"
 #include "components/zucchini/buffer_source.h"
 #include "components/zucchini/buffer_view.h"
@@ -384,6 +386,8 @@ bool ReadZtfHeader(ConstBufferView image) {
   // Reject empty images and "ZTxtxTZ\n" (missing 't').
   if (source.size() < kTotalMagicSize)
     return false;
+  if (source.size() > std::numeric_limits<offset_t>::max())
+    return false;
   return source.CheckNextBytes({'Z', 'T', 'x', 't'});
 }
 
@@ -405,7 +409,7 @@ bool ZtfTranslator::Init(ConstBufferView image) {
       // sentinel.
       if (line_starts_.size() >= ztf::kMaxDimValue)
         return false;
-      line_starts_.push_back(i + 1);
+      line_starts_.push_back(base::checked_cast<offset_t>(i + 1));
       // Check that the line length is reachable from an absolute reference.
       if (line_starts_.back() - *std::next(line_starts_.rbegin()) >=
           ztf::kMaxDimValue) {

components/zucchini/rel32_finder.cc

@@ -6,6 +6,8 @@
 
 #include <algorithm>
 
+#include "base/numerics/safe_conversions.h"
+
 namespace zucchini {
 
 /******** Abs32GapFinder ********/
@@ -22,7 +24,8 @@ Abs32GapFinder::Abs32GapFinder(ConstBufferView image,
   DCHECK_GE(region.begin(), image.begin());
   DCHECK_LE(region.end(), image.end());
 
-  const offset_t begin_offset = region.begin() - image.begin();
+  const offset_t begin_offset =
+      base::checked_cast<offset_t>(region.begin() - image.begin());
   // Find the first |abs32_current_| with |*abs32_current_ >= begin_offset|.
   abs32_current_ = std::lower_bound(abs32_locations.begin(),
                                     abs32_locations.end(), begin_offset);

components/zucchini/reloc_win32.cc

@@ -40,7 +40,8 @@ bool RelocRvaReaderWin32::FindRelocBlocks(
   ConstBufferView reloc_data = image[reloc_region];
   reloc_block_offsets->clear();
   while (reloc_data.size() >= sizeof(pe::RelocHeader)) {
-    reloc_block_offsets->push_back(reloc_data.begin() - image.begin());
+    reloc_block_offsets->push_back(
+        base::checked_cast<offset_t>(reloc_data.begin() - image.begin()));
     auto size = reloc_data.read<pe::RelocHeader>(0).size;
     // |size| must be aligned to 4-bytes.
     if (size < sizeof(pe::RelocHeader) || size % 4 || size > reloc_data.size())
@@ -78,7 +79,8 @@ RelocRvaReaderWin32::RelocRvaReaderWin32(
     return;  // Nothing left.
 
   // Skip |cur_reloc_units_| to |lo|, truncating up.
-  offset_t cur_reloc_units_offset = cur_reloc_units_.begin() - image_.begin();
+  offset_t cur_reloc_units_offset =
+      base::checked_cast<offset_t>(cur_reloc_units_.begin() - image_.begin());
   if (lo > cur_reloc_units_offset) {
     offset_t delta =
         AlignCeil<offset_t>(lo - cur_reloc_units_offset, kRelocUnitSize);
@@ -100,7 +102,8 @@ base::Optional<RelocUnitWin32> RelocRvaReaderWin32::GetNext() {
   if (end_it_ - cur_reloc_units_.begin() < kRelocUnitSize)
     return base::nullopt;
   // "Inner loop" to extract single reloc unit.
-  offset_t location = cur_reloc_units_.begin() - image_.begin();
+  offset_t location =
+      base::checked_cast<offset_t>(cur_reloc_units_.begin() - image_.begin());
   uint16_t entry = cur_reloc_units_.read<uint16_t>(0);
   uint8_t type = static_cast<uint8_t>(entry >> 12);
   rva_t rva = rva_hi_bits_ + (entry & 0xFFF);