diff --git a/compiler/elf_writer.cc b/compiler/elf_writer.cc
index 47402f3..f75638d 100644
--- a/compiler/elf_writer.cc
+++ b/compiler/elf_writer.cc
@@ -39,16 +39,17 @@
 }
 
 void ElfWriter::GetOatElfInformation(File* file,
-                                     size_t& oat_loaded_size,
-                                     size_t& oat_data_offset) {
+                                     size_t* oat_loaded_size,
+                                     size_t* oat_data_offset) {
   std::string error_msg;
   std::unique_ptr<ElfFile> elf_file(ElfFile::Open(file, false, false, &error_msg));
   CHECK(elf_file.get() != nullptr) << error_msg;
 
-  oat_loaded_size = elf_file->GetLoadedSize();
-  CHECK_NE(0U, oat_loaded_size);
-  oat_data_offset = GetOatDataAddress(elf_file.get());
-  CHECK_NE(0U, oat_data_offset);
+  bool success = elf_file->GetLoadedSize(oat_loaded_size, &error_msg);
+  CHECK(success) << error_msg;
+  CHECK_NE(0U, *oat_loaded_size);
+  *oat_data_offset = GetOatDataAddress(elf_file.get());
+  CHECK_NE(0U, *oat_data_offset);
 }
 
 bool ElfWriter::Fixup(File* file, uintptr_t oat_data_begin) {
diff --git a/compiler/elf_writer.h b/compiler/elf_writer.h
index 033c1f8..8e13b51 100644
--- a/compiler/elf_writer.h
+++ b/compiler/elf_writer.h
@@ -38,8 +38,8 @@
   // Looks up information about location of oat file in elf file container.
   // Used for ImageWriter to perform memory layout.
   static void GetOatElfInformation(File* file,
-                                   size_t& oat_loaded_size,
-                                   size_t& oat_data_offset);
+                                   size_t* oat_loaded_size,
+                                   size_t* oat_data_offset);
 
   // Returns runtime oat_data runtime address for an opened ElfFile.
   static uintptr_t GetOatDataAddress(ElfFile* elf_file);
diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index 4dc7509..195949b 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -166,7 +166,7 @@
 
   size_t oat_loaded_size = 0;
   size_t oat_data_offset = 0;
-  ElfWriter::GetOatElfInformation(oat_file.get(), oat_loaded_size, oat_data_offset);
+  ElfWriter::GetOatElfInformation(oat_file.get(), &oat_loaded_size, &oat_data_offset);
 
   Thread::Current()->TransitionFromSuspendedToRunnable();
   CreateHeader(oat_loaded_size, oat_data_offset);
diff --git a/patchoat/patchoat.cc b/patchoat/patchoat.cc
index 4dc0967..ef84a17 100644
--- a/patchoat/patchoat.cc
+++ b/patchoat/patchoat.cc
@@ -650,29 +650,34 @@
 template <typename ElfFileImpl>
 bool PatchOat::PatchElf(ElfFileImpl* oat_file) {
   TimingLogger::ScopedTiming t("Fixup Elf Text Section", timings_);
+
+  // Fix up absolute references to locations within the boot image.
   if (!oat_file->ApplyOatPatchesTo(".text", delta_)) {
     return false;
   }
 
+  // Update the OatHeader fields referencing the boot image.
   if (!PatchOatHeader<ElfFileImpl>(oat_file)) {
     return false;
   }
 
-  bool need_fixup = false;
+  bool need_boot_oat_fixup = true;
   for (unsigned int i = 0; i < oat_file->GetProgramHeaderNum(); ++i) {
     auto hdr = oat_file->GetProgramHeader(i);
-    if ((hdr->p_vaddr != 0 && hdr->p_vaddr != hdr->p_offset) ||
-        (hdr->p_paddr != 0 && hdr->p_paddr != hdr->p_offset)) {
-      need_fixup = true;
+    if (hdr->p_type == PT_LOAD && hdr->p_vaddr == 0u) {
+      need_boot_oat_fixup = false;
       break;
     }
   }
-  if (!need_fixup) {
-    // This was never passed through ElfFixup so all headers/symbols just have their offset as
-    // their addr. Therefore we do not need to update these parts.
+  if (!need_boot_oat_fixup) {
+    // This is an app oat file that can be loaded at an arbitrary address in memory.
+    // Boot image references were patched above and there's nothing else to do.
     return true;
   }
 
+  // This is a boot oat file that's loaded at a particular address and we need
+  // to patch all absolute addresses, starting with ELF program headers.
+
   t.NewTiming("Fixup Elf Headers");
   // Fixup Phdr's
   oat_file->FixupProgramHeaders(delta_);
diff --git a/runtime/elf_file.cc b/runtime/elf_file.cc
index e909e64..0c5210d 100644
--- a/runtime/elf_file.cc
+++ b/runtime/elf_file.cc
@@ -1080,9 +1080,9 @@
 
 // Base on bionic phdr_table_get_load_size
 template <typename ElfTypes>
-size_t ElfFileImpl<ElfTypes>::GetLoadedSize() const {
-  Elf_Addr min_vaddr = 0xFFFFFFFFu;
-  Elf_Addr max_vaddr = 0x00000000u;
+bool ElfFileImpl<ElfTypes>::GetLoadedSize(size_t* size, std::string* error_msg) const {
+  Elf_Addr min_vaddr = static_cast<Elf_Addr>(-1);
+  Elf_Addr max_vaddr = 0u;
   for (Elf_Word i = 0; i < GetProgramHeaderNum(); i++) {
     Elf_Phdr* program_header = GetProgramHeader(i);
     if (program_header->p_type != PT_LOAD) {
@@ -1093,6 +1093,15 @@
        min_vaddr = begin_vaddr;
     }
     Elf_Addr end_vaddr = program_header->p_vaddr + program_header->p_memsz;
+    if (UNLIKELY(begin_vaddr > end_vaddr)) {
+      std::ostringstream oss;
+      oss << "Program header #" << i << " has overflow in p_vaddr+p_memsz: 0x" << std::hex
+          << program_header->p_vaddr << "+0x" << program_header->p_memsz << "=0x" << end_vaddr
+          << " in ELF file \"" << file_->GetPath() << "\"";
+      *error_msg = oss.str();
+      *size = static_cast<size_t>(-1);
+      return false;
+    }
     if (end_vaddr > max_vaddr) {
       max_vaddr = end_vaddr;
     }
@@ -1100,8 +1109,18 @@
   min_vaddr = RoundDown(min_vaddr, kPageSize);
   max_vaddr = RoundUp(max_vaddr, kPageSize);
   CHECK_LT(min_vaddr, max_vaddr) << file_->GetPath();
-  size_t loaded_size = max_vaddr - min_vaddr;
-  return loaded_size;
+  Elf_Addr loaded_size = max_vaddr - min_vaddr;
+  // Check that the loaded_size fits in size_t.
+  if (UNLIKELY(loaded_size > std::numeric_limits<size_t>::max())) {
+    std::ostringstream oss;
+    oss << "Loaded size is 0x" << std::hex << loaded_size << " but maximum size_t is 0x"
+        << std::numeric_limits<size_t>::max() << " for ELF file \"" << file_->GetPath() << "\"";
+    *error_msg = oss.str();
+    *size = static_cast<size_t>(-1);
+    return false;
+  }
+  *size = loaded_size;
+  return true;
 }
 
 template <typename ElfTypes>
@@ -1164,9 +1183,14 @@
       }
       std::string reservation_name("ElfFile reservation for ");
       reservation_name += file_->GetPath();
+      size_t loaded_size;
+      if (!GetLoadedSize(&loaded_size, error_msg)) {
+        DCHECK(!error_msg->empty());
+        return false;
+      }
       std::unique_ptr<MemMap> reserve(MemMap::MapAnonymous(reservation_name.c_str(),
                                                            reserve_base_override,
-                                                           GetLoadedSize(), PROT_NONE, false, false,
+                                                           loaded_size, PROT_NONE, false, false,
                                                            error_msg));
       if (reserve.get() == nullptr) {
         *error_msg = StringPrintf("Failed to allocate %s: %s",
@@ -1915,8 +1939,8 @@
   DELEGATE_TO_IMPL(FindSymbolAddress, section_type, symbol_name, build_map);
 }
 
-size_t ElfFile::GetLoadedSize() const {
-  DELEGATE_TO_IMPL(GetLoadedSize);
+bool ElfFile::GetLoadedSize(size_t* size, std::string* error_msg) const {
+  DELEGATE_TO_IMPL(GetLoadedSize, size, error_msg);
 }
 
 bool ElfFile::Strip(File* file, std::string* error_msg) {
diff --git a/runtime/elf_file.h b/runtime/elf_file.h
index fe6896d..48cb4b8 100644
--- a/runtime/elf_file.h
+++ b/runtime/elf_file.h
@@ -66,7 +66,7 @@
                              const std::string& symbol_name,
                              bool build_map);
 
-  size_t GetLoadedSize() const;
+  bool GetLoadedSize(size_t* size, std::string* error_msg) const;
 
   // Strip an ELF file of unneeded debugging information.
   // Returns true on success, false on failure.
diff --git a/runtime/elf_file_impl.h b/runtime/elf_file_impl.h
index 80950c6..3ad096f 100644
--- a/runtime/elf_file_impl.h
+++ b/runtime/elf_file_impl.h
@@ -106,8 +106,8 @@
   Elf_Word GetRelaNum(Elf_Shdr&) const;
   Elf_Rela& GetRela(Elf_Shdr&, Elf_Word) const;
 
-  // Returns the expected size when the file is loaded at runtime
-  size_t GetLoadedSize() const;
+  // Retrieves the expected size when the file is loaded at runtime. Returns true if successful.
+  bool GetLoadedSize(size_t* size, std::string* error_msg) const;
 
   // Load segments into memory based on PT_LOAD program headers.
   // executable is true at run time, false at compile time.