diff --git a/libunwindstack/DwarfMemory.cpp b/libunwindstack/DwarfMemory.cpp
index 901f492..6ffdc0d 100644
--- a/libunwindstack/DwarfMemory.cpp
+++ b/libunwindstack/DwarfMemory.cpp
@@ -27,7 +27,7 @@
 namespace unwindstack {
 
 bool DwarfMemory::ReadBytes(void* dst, size_t num_bytes) {
-  if (!memory_->Read(cur_offset_, dst, num_bytes)) {
+  if (!memory_->ReadFully(cur_offset_, dst, num_bytes)) {
     return false;
   }
   cur_offset_ += num_bytes;
diff --git a/libunwindstack/DwarfOp.cpp b/libunwindstack/DwarfOp.cpp
index b3fd0df..3b3d340 100644
--- a/libunwindstack/DwarfOp.cpp
+++ b/libunwindstack/DwarfOp.cpp
@@ -141,7 +141,7 @@
   // Read the address and dereference it.
   AddressType addr = StackPop();
   AddressType value;
-  if (!regular_memory()->Read(addr, &value, sizeof(value))) {
+  if (!regular_memory()->ReadFully(addr, &value, sizeof(value))) {
     last_error_ = DWARF_ERROR_MEMORY_INVALID;
     return false;
   }
@@ -159,7 +159,7 @@
   // Read the address and dereference it.
   AddressType addr = StackPop();
   AddressType value = 0;
-  if (!regular_memory()->Read(addr, &value, bytes_to_read)) {
+  if (!regular_memory()->ReadFully(addr, &value, bytes_to_read)) {
     last_error_ = DWARF_ERROR_MEMORY_INVALID;
     return false;
   }
diff --git a/libunwindstack/DwarfSection.cpp b/libunwindstack/DwarfSection.cpp
index 805dcd3..0954187 100644
--- a/libunwindstack/DwarfSection.cpp
+++ b/libunwindstack/DwarfSection.cpp
@@ -142,7 +142,7 @@
         return false;
       }
       if (loc->type == DWARF_LOCATION_EXPRESSION) {
-        if (!regular_memory->Read(value, &cfa, sizeof(AddressType))) {
+        if (!regular_memory->ReadFully(value, &cfa, sizeof(AddressType))) {
           last_error_ = DWARF_ERROR_MEMORY_INVALID;
           return false;
         }
@@ -175,7 +175,8 @@
     const DwarfLocation* loc = &entry.second;
     switch (loc->type) {
       case DWARF_LOCATION_OFFSET:
-        if (!regular_memory->Read(cfa + loc->values[0], &(*cur_regs)[reg], sizeof(AddressType))) {
+        if (!regular_memory->ReadFully(cfa + loc->values[0], &(*cur_regs)[reg],
+                                       sizeof(AddressType))) {
           last_error_ = DWARF_ERROR_MEMORY_INVALID;
           return false;
         }
@@ -210,7 +211,7 @@
           return false;
         }
         if (loc->type == DWARF_LOCATION_EXPRESSION) {
-          if (!regular_memory->Read(value, &(*cur_regs)[reg], sizeof(AddressType))) {
+          if (!regular_memory->ReadFully(value, &(*cur_regs)[reg], sizeof(AddressType))) {
             last_error_ = DWARF_ERROR_MEMORY_INVALID;
             return false;
           }
diff --git a/libunwindstack/Elf.cpp b/libunwindstack/Elf.cpp
index 48e33ee..97ade56 100644
--- a/libunwindstack/Elf.cpp
+++ b/libunwindstack/Elf.cpp
@@ -136,7 +136,7 @@
 
   // Verify that this is a valid elf file.
   uint8_t e_ident[SELFMAG + 1];
-  if (!memory->Read(0, e_ident, SELFMAG)) {
+  if (!memory->ReadFully(0, e_ident, SELFMAG)) {
     return false;
   }
 
@@ -156,7 +156,7 @@
 
   // Now read the section header information.
   uint8_t class_type;
-  if (!memory->Read(EI_CLASS, &class_type, 1)) {
+  if (!memory->ReadFully(EI_CLASS, &class_type, 1)) {
     return;
   }
   if (class_type == ELFCLASS32) {
@@ -174,12 +174,12 @@
   }
 
   std::unique_ptr<ElfInterface> interface;
-  if (!memory->Read(EI_CLASS, &class_type_, 1)) {
+  if (!memory->ReadFully(EI_CLASS, &class_type_, 1)) {
     return nullptr;
   }
   if (class_type_ == ELFCLASS32) {
     Elf32_Half e_machine;
-    if (!memory->Read(EI_NIDENT + sizeof(Elf32_Half), &e_machine, sizeof(e_machine))) {
+    if (!memory->ReadFully(EI_NIDENT + sizeof(Elf32_Half), &e_machine, sizeof(e_machine))) {
       return nullptr;
     }
 
@@ -200,7 +200,7 @@
     }
   } else if (class_type_ == ELFCLASS64) {
     Elf64_Half e_machine;
-    if (!memory->Read(EI_NIDENT + sizeof(Elf64_Half), &e_machine, sizeof(e_machine))) {
+    if (!memory->ReadFully(EI_NIDENT + sizeof(Elf64_Half), &e_machine, sizeof(e_machine))) {
       return nullptr;
     }
     if (e_machine != EM_AARCH64 && e_machine != EM_X86_64) {
diff --git a/libunwindstack/ElfInterface.cpp b/libunwindstack/ElfInterface.cpp
index d5d158f..9bdb094 100644
--- a/libunwindstack/ElfInterface.cpp
+++ b/libunwindstack/ElfInterface.cpp
@@ -53,7 +53,7 @@
   Crc64GenerateTable();
 
   std::vector<uint8_t> src(gnu_debugdata_size_);
-  if (!memory_->Read(gnu_debugdata_offset_, src.data(), gnu_debugdata_size_)) {
+  if (!memory_->ReadFully(gnu_debugdata_offset_, src.data(), gnu_debugdata_size_)) {
     gnu_debugdata_offset_ = 0;
     gnu_debugdata_size_ = static_cast<uint64_t>(-1);
     return nullptr;
@@ -131,7 +131,7 @@
 template <typename EhdrType, typename PhdrType, typename ShdrType>
 bool ElfInterface::ReadAllHeaders(uint64_t* load_bias) {
   EhdrType ehdr;
-  if (!memory_->Read(0, &ehdr, sizeof(ehdr))) {
+  if (!memory_->ReadFully(0, &ehdr, sizeof(ehdr))) {
     return false;
   }
 
@@ -242,7 +242,7 @@
     }
 
     if (shdr.sh_type == SHT_SYMTAB || shdr.sh_type == SHT_DYNSYM) {
-      if (!memory_->Read(offset, &shdr, sizeof(shdr))) {
+      if (!memory_->ReadFully(offset, &shdr, sizeof(shdr))) {
         return false;
       }
       // Need to go get the information about the section that contains
@@ -324,7 +324,7 @@
   uint64_t offset = dynamic_offset_;
   uint64_t max_offset = offset + dynamic_size_;
   for (uint64_t offset = dynamic_offset_; offset < max_offset; offset += sizeof(DynType)) {
-    if (!memory_->Read(offset, &dyn, sizeof(dyn))) {
+    if (!memory_->ReadFully(offset, &dyn, sizeof(dyn))) {
       return false;
     }
 
@@ -388,7 +388,7 @@
 template <typename EhdrType>
 void ElfInterface::GetMaxSizeWithTemplate(Memory* memory, uint64_t* size) {
   EhdrType ehdr;
-  if (!memory->Read(0, &ehdr, sizeof(ehdr))) {
+  if (!memory->ReadFully(0, &ehdr, sizeof(ehdr))) {
     return;
   }
   if (ehdr.e_shnum == 0) {
diff --git a/libunwindstack/MapInfo.cpp b/libunwindstack/MapInfo.cpp
index 5417659..8a7ad9c 100644
--- a/libunwindstack/MapInfo.cpp
+++ b/libunwindstack/MapInfo.cpp
@@ -102,7 +102,7 @@
   if (!(flags & PROT_READ)) {
     return nullptr;
   }
-  return new MemoryRange(process_memory, start, end);
+  return new MemoryRange(process_memory, start, end - start, 0);
 }
 
 Elf* MapInfo::GetElf(const std::shared_ptr<Memory>& process_memory, bool init_gnu_debugdata) {
diff --git a/libunwindstack/Memory.cpp b/libunwindstack/Memory.cpp
index 32753df..2479655 100644
--- a/libunwindstack/Memory.cpp
+++ b/libunwindstack/Memory.cpp
@@ -32,14 +32,69 @@
 
 #include "Check.h"
 
+static size_t ProcessVmRead(pid_t pid, void* dst, uint64_t remote_src, size_t len) {
+  struct iovec dst_iov = {
+      .iov_base = dst,
+      .iov_len = len,
+  };
+
+  // Split up the remote read across page boundaries.
+  // From the manpage:
+  //   A partial read/write may result if one of the remote_iov elements points to an invalid
+  //   memory region in the remote process.
+  //
+  //   Partial transfers apply at the granularity of iovec elements.  These system calls won't
+  //   perform a partial transfer that splits a single iovec element.
+  constexpr size_t kMaxIovecs = 64;
+  struct iovec src_iovs[kMaxIovecs];
+  size_t iovecs_used = 0;
+
+  uint64_t cur = remote_src;
+  while (len > 0) {
+    if (iovecs_used == kMaxIovecs) {
+      errno = EINVAL;
+      return 0;
+    }
+
+    // struct iovec uses void* for iov_base.
+    if (cur >= UINTPTR_MAX) {
+      errno = EFAULT;
+      return 0;
+    }
+
+    src_iovs[iovecs_used].iov_base = reinterpret_cast<void*>(cur);
+
+    uintptr_t misalignment = cur & (getpagesize() - 1);
+    size_t iov_len = getpagesize() - misalignment;
+    iov_len = std::min(iov_len, len);
+
+    len -= iov_len;
+    if (__builtin_add_overflow(cur, iov_len, &cur)) {
+      errno = EFAULT;
+      return 0;
+    }
+
+    src_iovs[iovecs_used].iov_len = iov_len;
+    ++iovecs_used;
+  }
+
+  ssize_t rc = process_vm_readv(pid, &dst_iov, 1, src_iovs, iovecs_used, 0);
+  return rc == -1 ? 0 : rc;
+}
+
 namespace unwindstack {
 
+bool Memory::ReadFully(uint64_t addr, void* dst, size_t size) {
+  size_t rc = Read(addr, dst, size);
+  return rc == size;
+}
+
 bool Memory::ReadString(uint64_t addr, std::string* string, uint64_t max_read) {
   string->clear();
   uint64_t bytes_read = 0;
   while (bytes_read < max_read) {
     uint8_t value;
-    if (!Read(addr, &value, sizeof(value))) {
+    if (!ReadFully(addr, &value, sizeof(value))) {
       return false;
     }
     if (value == '\0') {
@@ -59,16 +114,17 @@
   return std::shared_ptr<Memory>(new MemoryRemote(pid));
 }
 
-bool MemoryBuffer::Read(uint64_t addr, void* dst, size_t size) {
-  uint64_t last_read_byte;
-  if (__builtin_add_overflow(size, addr, &last_read_byte)) {
-    return false;
+size_t MemoryBuffer::Read(uint64_t addr, void* dst, size_t size) {
+  if (addr >= raw_.size()) {
+    return 0;
   }
-  if (last_read_byte > raw_.size()) {
-    return false;
-  }
-  memcpy(dst, &raw_[addr], size);
-  return true;
+
+  size_t bytes_left = raw_.size() - static_cast<size_t>(addr);
+  const unsigned char* actual_base = static_cast<const unsigned char*>(raw_.data()) + addr;
+  size_t actual_len = std::min(bytes_left, size);
+
+  memcpy(dst, actual_base, actual_len);
+  return actual_len;
 }
 
 uint8_t* MemoryBuffer::GetPtr(size_t offset) {
@@ -129,145 +185,77 @@
   return true;
 }
 
-bool MemoryFileAtOffset::Read(uint64_t addr, void* dst, size_t size) {
-  uint64_t max_size;
-  if (__builtin_add_overflow(addr, size, &max_size) || max_size > size_) {
-    return false;
+size_t MemoryFileAtOffset::Read(uint64_t addr, void* dst, size_t size) {
+  if (addr >= size_) {
+    return 0;
   }
-  memcpy(dst, &data_[addr], size);
-  return true;
+
+  size_t bytes_left = size_ - static_cast<size_t>(addr);
+  const unsigned char* actual_base = static_cast<const unsigned char*>(data_) + addr;
+  size_t actual_len = std::min(bytes_left, size);
+
+  memcpy(dst, actual_base, actual_len);
+  return actual_len;
 }
 
-bool MemoryRemote::PtraceRead(uint64_t addr, long* value) {
-#if !defined(__LP64__)
-  // Cannot read an address greater than 32 bits.
-  if (addr > UINT32_MAX) {
-    return false;
-  }
-#endif
-  // ptrace() returns -1 and sets errno when the operation fails.
-  // To disambiguate -1 from a valid result, we clear errno beforehand.
-  errno = 0;
-  *value = ptrace(PTRACE_PEEKTEXT, pid_, reinterpret_cast<void*>(addr), nullptr);
-  if (*value == -1 && errno) {
-    return false;
-  }
-  return true;
+size_t MemoryRemote::Read(uint64_t addr, void* dst, size_t size) {
+  return ProcessVmRead(pid_, dst, addr, size);
 }
 
-bool MemoryRemote::Read(uint64_t addr, void* dst, size_t bytes) {
-  // Make sure that there is no overflow.
-  uint64_t max_size;
-  if (__builtin_add_overflow(addr, bytes, &max_size)) {
-    return false;
-  }
-
-  size_t bytes_read = 0;
-  long data;
-  size_t align_bytes = addr & (sizeof(long) - 1);
-  if (align_bytes != 0) {
-    if (!PtraceRead(addr & ~(sizeof(long) - 1), &data)) {
-      return false;
-    }
-    size_t copy_bytes = std::min(sizeof(long) - align_bytes, bytes);
-    memcpy(dst, reinterpret_cast<uint8_t*>(&data) + align_bytes, copy_bytes);
-    addr += copy_bytes;
-    dst = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(dst) + copy_bytes);
-    bytes -= copy_bytes;
-    bytes_read += copy_bytes;
-  }
-
-  for (size_t i = 0; i < bytes / sizeof(long); i++) {
-    if (!PtraceRead(addr, &data)) {
-      return false;
-    }
-    memcpy(dst, &data, sizeof(long));
-    dst = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(dst) + sizeof(long));
-    addr += sizeof(long);
-    bytes_read += sizeof(long);
-  }
-
-  size_t left_over = bytes & (sizeof(long) - 1);
-  if (left_over) {
-    if (!PtraceRead(addr, &data)) {
-      return false;
-    }
-    memcpy(dst, &data, left_over);
-    bytes_read += left_over;
-  }
-  return true;
+size_t MemoryLocal::Read(uint64_t addr, void* dst, size_t size) {
+  return ProcessVmRead(getpid(), dst, addr, size);
 }
 
-bool MemoryLocal::Read(uint64_t addr, void* dst, size_t size) {
-  // Make sure that there is no overflow.
-  uint64_t max_size;
-  if (__builtin_add_overflow(addr, size, &max_size)) {
-    return false;
+MemoryRange::MemoryRange(const std::shared_ptr<Memory>& memory, uint64_t begin, uint64_t length,
+                         uint64_t offset)
+    : memory_(memory), begin_(begin), length_(length), offset_(offset) {}
+
+size_t MemoryRange::Read(uint64_t addr, void* dst, size_t size) {
+  if (addr < offset_) {
+    return 0;
   }
 
-  // The process_vm_readv call will not always work on remote
-  // processes, so only use it for reads from the current pid.
-  // Use this method to avoid crashes if an address is invalid since
-  // unwind data could try to access any part of the address space.
-  struct iovec local_io;
-  local_io.iov_base = dst;
-  local_io.iov_len = size;
-
-  struct iovec remote_io;
-  remote_io.iov_base = reinterpret_cast<void*>(static_cast<uintptr_t>(addr));
-  remote_io.iov_len = size;
-
-  ssize_t bytes_read = process_vm_readv(getpid(), &local_io, 1, &remote_io, 1, 0);
-  if (bytes_read == -1) {
-    return false;
+  uint64_t read_offset = addr - offset_;
+  if (read_offset >= length_) {
+    return 0;
   }
-  return static_cast<size_t>(bytes_read) == size;
+
+  uint64_t read_length = std::min(static_cast<uint64_t>(size), length_ - read_offset);
+  uint64_t read_addr;
+  if (__builtin_add_overflow(read_offset, begin_, &read_addr)) {
+    return 0;
+  }
+
+  return memory_->Read(read_addr, dst, read_length);
 }
 
 bool MemoryOffline::Init(const std::string& file, uint64_t offset) {
-  if (!MemoryFileAtOffset::Init(file, offset)) {
+  auto memory_file = std::make_shared<MemoryFileAtOffset>();
+  if (!memory_file->Init(file, offset)) {
     return false;
   }
+
   // The first uint64_t value is the start of memory.
-  if (!MemoryFileAtOffset::Read(0, &start_, sizeof(start_))) {
+  uint64_t start;
+  if (!memory_file->ReadFully(0, &start, sizeof(start))) {
     return false;
   }
-  // Subtract the first 64 bit value from the total size.
-  size_ -= sizeof(start_);
+
+  uint64_t size = memory_file->Size();
+  if (__builtin_sub_overflow(size, sizeof(start), &size)) {
+    return false;
+  }
+
+  memory_ = std::make_unique<MemoryRange>(memory_file, sizeof(start), size, start);
   return true;
 }
 
-bool MemoryOffline::Read(uint64_t addr, void* dst, size_t size) {
-  uint64_t max_size;
-  if (__builtin_add_overflow(addr, size, &max_size)) {
-    return false;
+size_t MemoryOffline::Read(uint64_t addr, void* dst, size_t size) {
+  if (!memory_) {
+    return 0;
   }
 
-  uint64_t real_size;
-  if (__builtin_add_overflow(start_, offset_, &real_size) ||
-      __builtin_add_overflow(real_size, size_, &real_size)) {
-    return false;
-  }
-
-  if (addr < start_ || max_size > real_size) {
-    return false;
-  }
-  memcpy(dst, &data_[addr + offset_ - start_ + sizeof(start_)], size);
-  return true;
-}
-
-MemoryRange::MemoryRange(const std::shared_ptr<Memory>& memory, uint64_t begin, uint64_t end)
-    : memory_(memory), begin_(begin), length_(end - begin) {
-  CHECK(end > begin);
-}
-
-bool MemoryRange::Read(uint64_t addr, void* dst, size_t size) {
-  uint64_t max_read;
-  if (__builtin_add_overflow(addr, size, &max_read) || max_read > length_) {
-    return false;
-  }
-  // The check above guarantees that addr + begin_ will not overflow.
-  return memory_->Read(addr + begin_, dst, size);
+  return memory_->Read(addr, dst, size);
 }
 
 }  // namespace unwindstack
diff --git a/libunwindstack/Regs.cpp b/libunwindstack/Regs.cpp
index 36b8e25..28a77dc 100644
--- a/libunwindstack/Regs.cpp
+++ b/libunwindstack/Regs.cpp
@@ -58,7 +58,7 @@
   if (adjusted_rel_pc & 1) {
     // This is a thumb instruction, it could be 2 or 4 bytes.
     uint32_t value;
-    if (rel_pc < 5 || !elf->memory()->Read(adjusted_rel_pc - 5, &value, sizeof(value)) ||
+    if (rel_pc < 5 || !elf->memory()->ReadFully(adjusted_rel_pc - 5, &value, sizeof(value)) ||
         (value & 0xe000f000) != 0xe000f000) {
       return rel_pc - 2;
     }
@@ -193,7 +193,7 @@
 bool RegsX86::SetPcFromReturnAddress(Memory* process_memory) {
   // Attempt to get the return address from the top of the stack.
   uint32_t new_pc;
-  if (!process_memory->Read(sp_, &new_pc, sizeof(new_pc)) || new_pc == pc()) {
+  if (!process_memory->ReadFully(sp_, &new_pc, sizeof(new_pc)) || new_pc == pc()) {
     return false;
   }
 
@@ -240,7 +240,7 @@
 bool RegsX86_64::SetPcFromReturnAddress(Memory* process_memory) {
   // Attempt to get the return address from the top of the stack.
   uint64_t new_pc;
-  if (!process_memory->Read(sp_, &new_pc, sizeof(new_pc)) || new_pc == pc()) {
+  if (!process_memory->ReadFully(sp_, &new_pc, sizeof(new_pc)) || new_pc == pc()) {
     return false;
   }
 
@@ -474,7 +474,7 @@
   Memory* elf_memory = elf->memory();
   // Read from elf memory since it is usually more expensive to read from
   // process memory.
-  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {
+  if (!elf_memory->ReadFully(rel_pc, &data, sizeof(data))) {
     return false;
   }
 
@@ -493,7 +493,7 @@
     // Form 3 (thumb):
     // 0x77 0x27              movs r7, #77
     // 0x00 0xdf              svc 0
-    if (!process_memory->Read(sp(), &data, sizeof(data))) {
+    if (!process_memory->ReadFully(sp(), &data, sizeof(data))) {
       return false;
     }
     if (data == 0x5ac3c35a) {
@@ -517,7 +517,7 @@
     // Form 3 (thumb):
     // 0xad 0x27              movs r7, #ad
     // 0x00 0xdf              svc 0
-    if (!process_memory->Read(sp(), &data, sizeof(data))) {
+    if (!process_memory->ReadFully(sp(), &data, sizeof(data))) {
       return false;
     }
     if (data == sp() + 8) {
@@ -532,7 +532,7 @@
     return false;
   }
 
-  if (!process_memory->Read(offset, regs_.data(), sizeof(uint32_t) * ARM_REG_LAST)) {
+  if (!process_memory->ReadFully(offset, regs_.data(), sizeof(uint32_t) * ARM_REG_LAST)) {
     return false;
   }
   SetFromRaw();
@@ -544,7 +544,7 @@
   Memory* elf_memory = elf->memory();
   // Read from elf memory since it is usually more expensive to read from
   // process memory.
-  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {
+  if (!elf_memory->ReadFully(rel_pc, &data, sizeof(data))) {
     return false;
   }
 
@@ -557,8 +557,8 @@
   }
 
   // SP + sizeof(siginfo_t) + uc_mcontext offset + X0 offset.
-  if (!process_memory->Read(sp() + 0x80 + 0xb0 + 0x08, regs_.data(),
-                            sizeof(uint64_t) * ARM64_REG_LAST)) {
+  if (!process_memory->ReadFully(sp() + 0x80 + 0xb0 + 0x08, regs_.data(),
+                                 sizeof(uint64_t) * ARM64_REG_LAST)) {
     return false;
   }
 
@@ -571,7 +571,7 @@
   Memory* elf_memory = elf->memory();
   // Read from elf memory since it is usually more expensive to read from
   // process memory.
-  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {
+  if (!elf_memory->ReadFully(rel_pc, &data, sizeof(data))) {
     return false;
   }
 
@@ -587,7 +587,7 @@
     //   int signum
     //   struct sigcontext (same format as mcontext)
     struct x86_mcontext_t context;
-    if (!process_memory->Read(sp() + 4, &context, sizeof(context))) {
+    if (!process_memory->ReadFully(sp() + 4, &context, sizeof(context))) {
       return false;
     }
     regs_[X86_REG_EBP] = context.ebp;
@@ -613,12 +613,12 @@
 
     // Get the location of the sigcontext data.
     uint32_t ptr;
-    if (!process_memory->Read(sp() + 8, &ptr, sizeof(ptr))) {
+    if (!process_memory->ReadFully(sp() + 8, &ptr, sizeof(ptr))) {
       return false;
     }
     // Only read the portion of the data structure we care about.
     x86_ucontext_t x86_ucontext;
-    if (!process_memory->Read(ptr + 0x14, &x86_ucontext.uc_mcontext, sizeof(x86_mcontext_t))) {
+    if (!process_memory->ReadFully(ptr + 0x14, &x86_ucontext.uc_mcontext, sizeof(x86_mcontext_t))) {
       return false;
     }
     SetFromUcontext(&x86_ucontext);
@@ -632,12 +632,12 @@
   Memory* elf_memory = elf->memory();
   // Read from elf memory since it is usually more expensive to read from
   // process memory.
-  if (!elf_memory->Read(rel_pc, &data, sizeof(data)) || data != 0x0f0000000fc0c748) {
+  if (!elf_memory->ReadFully(rel_pc, &data, sizeof(data)) || data != 0x0f0000000fc0c748) {
     return false;
   }
 
   uint16_t data2;
-  if (!elf_memory->Read(rel_pc + 8, &data2, sizeof(data2)) || data2 != 0x0f05) {
+  if (!elf_memory->ReadFully(rel_pc + 8, &data2, sizeof(data2)) || data2 != 0x0f05) {
     return false;
   }
 
@@ -649,7 +649,8 @@
   // Read the mcontext data from the stack.
   // sp points to the ucontext data structure, read only the mcontext part.
   x86_64_ucontext_t x86_64_ucontext;
-  if (!process_memory->Read(sp() + 0x28, &x86_64_ucontext.uc_mcontext, sizeof(x86_64_mcontext_t))) {
+  if (!process_memory->ReadFully(sp() + 0x28, &x86_64_ucontext.uc_mcontext,
+                                 sizeof(x86_64_mcontext_t))) {
     return false;
   }
   SetFromUcontext(&x86_64_ucontext);
diff --git a/libunwindstack/Symbols.cpp b/libunwindstack/Symbols.cpp
index 42d816a..b4b92d6 100644
--- a/libunwindstack/Symbols.cpp
+++ b/libunwindstack/Symbols.cpp
@@ -71,7 +71,7 @@
   bool return_value = false;
   while (cur_offset_ + entry_size_ <= end_) {
     SymType entry;
-    if (!elf_memory->Read(cur_offset_, &entry, sizeof(entry))) {
+    if (!elf_memory->ReadFully(cur_offset_, &entry, sizeof(entry))) {
       // Stop all processing, something looks like it is corrupted.
       cur_offset_ = UINT64_MAX;
       return false;
diff --git a/libunwindstack/include/unwindstack/Memory.h b/libunwindstack/include/unwindstack/Memory.h
index 183b899..8163152 100644
--- a/libunwindstack/include/unwindstack/Memory.h
+++ b/libunwindstack/include/unwindstack/Memory.h
@@ -36,7 +36,9 @@
 
   virtual bool ReadString(uint64_t addr, std::string* string, uint64_t max_read = UINT64_MAX);
 
-  virtual bool Read(uint64_t addr, void* dst, size_t size) = 0;
+  virtual size_t Read(uint64_t addr, void* dst, size_t size) = 0;
+
+  bool ReadFully(uint64_t addr, void* dst, size_t size);
 
   inline bool ReadField(uint64_t addr, void* start, void* field, size_t size) {
     if (reinterpret_cast<uintptr_t>(field) < reinterpret_cast<uintptr_t>(start)) {
@@ -47,12 +49,16 @@
       return false;
     }
     // The read will check if offset + size overflows.
-    return Read(offset, field, size);
+    return ReadFully(offset, field, size);
   }
 
-  inline bool Read32(uint64_t addr, uint32_t* dst) { return Read(addr, dst, sizeof(uint32_t)); }
+  inline bool Read32(uint64_t addr, uint32_t* dst) {
+    return ReadFully(addr, dst, sizeof(uint32_t));
+  }
 
-  inline bool Read64(uint64_t addr, uint64_t* dst) { return Read(addr, dst, sizeof(uint64_t)); }
+  inline bool Read64(uint64_t addr, uint64_t* dst) {
+    return ReadFully(addr, dst, sizeof(uint64_t));
+  }
 };
 
 class MemoryBuffer : public Memory {
@@ -60,7 +66,7 @@
   MemoryBuffer() = default;
   virtual ~MemoryBuffer() = default;
 
-  bool Read(uint64_t addr, void* dst, size_t size) override;
+  size_t Read(uint64_t addr, void* dst, size_t size) override;
 
   uint8_t* GetPtr(size_t offset);
 
@@ -79,7 +85,9 @@
 
   bool Init(const std::string& file, uint64_t offset, uint64_t size = UINT64_MAX);
 
-  bool Read(uint64_t addr, void* dst, size_t size) override;
+  size_t Read(uint64_t addr, void* dst, size_t size) override;
+
+  size_t Size() { return size_; }
 
   void Clear();
 
@@ -89,31 +97,15 @@
   uint8_t* data_ = nullptr;
 };
 
-class MemoryOffline : public MemoryFileAtOffset {
- public:
-  MemoryOffline() = default;
-  virtual ~MemoryOffline() = default;
-
-  bool Init(const std::string& file, uint64_t offset);
-
-  bool Read(uint64_t addr, void* dst, size_t size) override;
-
- private:
-  uint64_t start_;
-};
-
 class MemoryRemote : public Memory {
  public:
   MemoryRemote(pid_t pid) : pid_(pid) {}
   virtual ~MemoryRemote() = default;
 
-  bool Read(uint64_t addr, void* dst, size_t size) override;
+  size_t Read(uint64_t addr, void* dst, size_t size) override;
 
   pid_t pid() { return pid_; }
 
- protected:
-  virtual bool PtraceRead(uint64_t addr, long* value);
-
  private:
   pid_t pid_;
 };
@@ -123,20 +115,38 @@
   MemoryLocal() = default;
   virtual ~MemoryLocal() = default;
 
-  bool Read(uint64_t addr, void* dst, size_t size) override;
+  size_t Read(uint64_t addr, void* dst, size_t size) override;
 };
 
+// MemoryRange maps one address range onto another.
+// The range [src_begin, src_begin + length) in the underlying Memory is mapped onto offset,
+// such that range.read(offset) is equivalent to underlying.read(src_begin).
 class MemoryRange : public Memory {
  public:
-  MemoryRange(const std::shared_ptr<Memory>& memory, uint64_t begin, uint64_t end);
+  MemoryRange(const std::shared_ptr<Memory>& memory, uint64_t begin, uint64_t length,
+              uint64_t offset);
   virtual ~MemoryRange() = default;
 
-  bool Read(uint64_t addr, void* dst, size_t size) override;
+  size_t Read(uint64_t addr, void* dst, size_t size) override;
 
  private:
   std::shared_ptr<Memory> memory_;
   uint64_t begin_;
   uint64_t length_;
+  uint64_t offset_;
+};
+
+class MemoryOffline : public Memory {
+ public:
+  MemoryOffline() = default;
+  virtual ~MemoryOffline() = default;
+
+  bool Init(const std::string& file, uint64_t offset);
+
+  size_t Read(uint64_t addr, void* dst, size_t size) override;
+
+ private:
+  std::unique_ptr<MemoryRange> memory_;
 };
 
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/MapInfoCreateMemoryTest.cpp b/libunwindstack/tests/MapInfoCreateMemoryTest.cpp
index bdcb652..866b5b4 100644
--- a/libunwindstack/tests/MapInfoCreateMemoryTest.cpp
+++ b/libunwindstack/tests/MapInfoCreateMemoryTest.cpp
@@ -120,14 +120,14 @@
 
   // Read the entire file.
   std::vector<uint8_t> buffer(1024);
-  ASSERT_TRUE(memory->Read(0, buffer.data(), 1024));
+  ASSERT_TRUE(memory->ReadFully(0, buffer.data(), 1024));
   ASSERT_TRUE(memcmp(buffer.data(), ELFMAG, SELFMAG) == 0);
   ASSERT_EQ(ELFCLASS32, buffer[EI_CLASS]);
   for (size_t i = EI_CLASS + 1; i < buffer.size(); i++) {
     ASSERT_EQ(0, buffer[i]) << "Failed at byte " << i;
   }
 
-  ASSERT_FALSE(memory->Read(1024, buffer.data(), 1));
+  ASSERT_FALSE(memory->ReadFully(1024, buffer.data(), 1));
 }
 
 // Verify that if the offset is non-zero and there is an elf at that
@@ -141,14 +141,14 @@
 
   // Read the valid part of the file.
   std::vector<uint8_t> buffer(0x100);
-  ASSERT_TRUE(memory->Read(0, buffer.data(), 0x100));
+  ASSERT_TRUE(memory->ReadFully(0, buffer.data(), 0x100));
   ASSERT_TRUE(memcmp(buffer.data(), ELFMAG, SELFMAG) == 0);
   ASSERT_EQ(ELFCLASS64, buffer[EI_CLASS]);
   for (size_t i = EI_CLASS + 1; i < buffer.size(); i++) {
     ASSERT_EQ(0, buffer[i]) << "Failed at byte " << i;
   }
 
-  ASSERT_FALSE(memory->Read(0x100, buffer.data(), 1));
+  ASSERT_FALSE(memory->ReadFully(0x100, buffer.data(), 1));
 }
 
 // Verify that if the offset is non-zero and there is an elf at that
@@ -164,11 +164,11 @@
 
   // Verify the memory is a valid elf.
   uint8_t e_ident[SELFMAG + 1];
-  ASSERT_TRUE(memory->Read(0, e_ident, SELFMAG));
+  ASSERT_TRUE(memory->ReadFully(0, e_ident, SELFMAG));
   ASSERT_EQ(0, memcmp(e_ident, ELFMAG, SELFMAG));
 
   // Read past the end of what would normally be the size of the map.
-  ASSERT_TRUE(memory->Read(0x1000, e_ident, 1));
+  ASSERT_TRUE(memory->ReadFully(0x1000, e_ident, 1));
 }
 
 TEST_F(MapInfoCreateMemoryTest, file_backed_non_zero_offset_partial_file_whole_elf64) {
@@ -180,11 +180,11 @@
 
   // Verify the memory is a valid elf.
   uint8_t e_ident[SELFMAG + 1];
-  ASSERT_TRUE(memory->Read(0, e_ident, SELFMAG));
+  ASSERT_TRUE(memory->ReadFully(0, e_ident, SELFMAG));
   ASSERT_EQ(0, memcmp(e_ident, ELFMAG, SELFMAG));
 
   // Read past the end of what would normally be the size of the map.
-  ASSERT_TRUE(memory->Read(0x1000, e_ident, 1));
+  ASSERT_TRUE(memory->ReadFully(0x1000, e_ident, 1));
 }
 
 // Verify that device file names will never result in Memory object creation.
@@ -221,13 +221,13 @@
   ASSERT_TRUE(memory.get() != nullptr);
 
   memset(buffer.data(), 0, buffer.size());
-  ASSERT_TRUE(memory->Read(0, buffer.data(), buffer.size()));
+  ASSERT_TRUE(memory->ReadFully(0, buffer.data(), buffer.size()));
   for (size_t i = 0; i < buffer.size(); i++) {
     ASSERT_EQ(i % 256, buffer[i]) << "Failed at byte " << i;
   }
 
   // Try to read outside of the map size.
-  ASSERT_FALSE(memory->Read(buffer.size(), buffer.data(), 1));
+  ASSERT_FALSE(memory->ReadFully(buffer.size(), buffer.data(), 1));
 }
 
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/MapInfoGetElfTest.cpp b/libunwindstack/tests/MapInfoGetElfTest.cpp
index 9973794..948597b 100644
--- a/libunwindstack/tests/MapInfoGetElfTest.cpp
+++ b/libunwindstack/tests/MapInfoGetElfTest.cpp
@@ -216,13 +216,13 @@
 
   // Read the entire file.
   memset(buffer.data(), 0, buffer.size());
-  ASSERT_TRUE(elf->memory()->Read(0, buffer.data(), buffer.size()));
+  ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), buffer.size()));
   ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
   for (size_t i = sizeof(ehdr); i < buffer.size(); i++) {
     ASSERT_EQ(0, buffer[i]) << "Failed at byte " << i;
   }
 
-  ASSERT_FALSE(elf->memory()->Read(buffer.size(), buffer.data(), 1));
+  ASSERT_FALSE(elf->memory()->ReadFully(buffer.size(), buffer.data(), 1));
 }
 
 // Verify that if the offset is non-zero and there is an elf at that
@@ -244,13 +244,13 @@
   ASSERT_EQ(0U, info.elf_offset);
 
   // Read the valid part of the file.
-  ASSERT_TRUE(elf->memory()->Read(0, buffer.data(), 0x1000));
+  ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), 0x1000));
   ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
   for (size_t i = sizeof(ehdr); i < 0x1000; i++) {
     ASSERT_EQ(0, buffer[i]) << "Failed at byte " << i;
   }
 
-  ASSERT_FALSE(elf->memory()->Read(0x1000, buffer.data(), 1));
+  ASSERT_FALSE(elf->memory()->ReadFully(0x1000, buffer.data(), 1));
 }
 
 // Verify that if the offset is non-zero and there is an elf at that
@@ -278,11 +278,11 @@
 
   // Verify the memory is a valid elf.
   memset(buffer.data(), 0, buffer.size());
-  ASSERT_TRUE(elf->memory()->Read(0, buffer.data(), 0x1000));
+  ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), 0x1000));
   ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
 
   // Read past the end of what would normally be the size of the map.
-  ASSERT_TRUE(elf->memory()->Read(0x1000, buffer.data(), 1));
+  ASSERT_TRUE(elf->memory()->ReadFully(0x1000, buffer.data(), 1));
 }
 
 TEST_F(MapInfoGetElfTest, file_backed_non_zero_offset_partial_file_whole_elf64) {
@@ -306,11 +306,11 @@
 
   // Verify the memory is a valid elf.
   memset(buffer.data(), 0, buffer.size());
-  ASSERT_TRUE(elf->memory()->Read(0, buffer.data(), 0x1000));
+  ASSERT_TRUE(elf->memory()->ReadFully(0, buffer.data(), 0x1000));
   ASSERT_EQ(0, memcmp(buffer.data(), &ehdr, sizeof(ehdr)));
 
   // Read past the end of what would normally be the size of the map.
-  ASSERT_TRUE(elf->memory()->Read(0x1000, buffer.data(), 1));
+  ASSERT_TRUE(elf->memory()->ReadFully(0x1000, buffer.data(), 1));
 }
 
 TEST_F(MapInfoGetElfTest, process_memory_not_read_only) {
diff --git a/libunwindstack/tests/MemoryBufferTest.cpp b/libunwindstack/tests/MemoryBufferTest.cpp
index 50a8a1b..28e0e76 100644
--- a/libunwindstack/tests/MemoryBufferTest.cpp
+++ b/libunwindstack/tests/MemoryBufferTest.cpp
@@ -36,7 +36,7 @@
 TEST_F(MemoryBufferTest, empty) {
   ASSERT_EQ(0U, memory_->Size());
   std::vector<uint8_t> buffer(1024);
-  ASSERT_FALSE(memory_->Read(0, buffer.data(), 1));
+  ASSERT_FALSE(memory_->ReadFully(0, buffer.data(), 1));
   ASSERT_EQ(nullptr, memory_->GetPtr(0));
   ASSERT_EQ(nullptr, memory_->GetPtr(1));
 }
@@ -55,7 +55,7 @@
   }
 
   std::vector<uint8_t> buffer(memory_->Size());
-  ASSERT_TRUE(memory_->Read(0, buffer.data(), buffer.size()));
+  ASSERT_TRUE(memory_->ReadFully(0, buffer.data(), buffer.size()));
   for (size_t i = 0; i < buffer.size(); i++) {
     ASSERT_EQ(i, buffer[i]) << "Failed at byte " << i;
   }
@@ -64,18 +64,38 @@
 TEST_F(MemoryBufferTest, read_failures) {
   memory_->Resize(100);
   std::vector<uint8_t> buffer(200);
-  ASSERT_FALSE(memory_->Read(0, buffer.data(), 101));
-  ASSERT_FALSE(memory_->Read(100, buffer.data(), 1));
-  ASSERT_FALSE(memory_->Read(101, buffer.data(), 2));
-  ASSERT_FALSE(memory_->Read(99, buffer.data(), 2));
-  ASSERT_TRUE(memory_->Read(99, buffer.data(), 1));
+  ASSERT_FALSE(memory_->ReadFully(0, buffer.data(), 101));
+  ASSERT_FALSE(memory_->ReadFully(100, buffer.data(), 1));
+  ASSERT_FALSE(memory_->ReadFully(101, buffer.data(), 2));
+  ASSERT_FALSE(memory_->ReadFully(99, buffer.data(), 2));
+  ASSERT_TRUE(memory_->ReadFully(99, buffer.data(), 1));
 }
 
 TEST_F(MemoryBufferTest, read_failure_overflow) {
   memory_->Resize(100);
   std::vector<uint8_t> buffer(200);
 
-  ASSERT_FALSE(memory_->Read(UINT64_MAX - 100, buffer.data(), 200));
+  ASSERT_FALSE(memory_->ReadFully(UINT64_MAX - 100, buffer.data(), 200));
+}
+
+TEST_F(MemoryBufferTest, Read) {
+  memory_->Resize(256);
+  ASSERT_EQ(256U, memory_->Size());
+  ASSERT_TRUE(memory_->GetPtr(0) != nullptr);
+  ASSERT_TRUE(memory_->GetPtr(1) != nullptr);
+  ASSERT_TRUE(memory_->GetPtr(255) != nullptr);
+  ASSERT_TRUE(memory_->GetPtr(256) == nullptr);
+
+  uint8_t* data = memory_->GetPtr(0);
+  for (size_t i = 0; i < memory_->Size(); i++) {
+    data[i] = i;
+  }
+
+  std::vector<uint8_t> buffer(memory_->Size());
+  ASSERT_EQ(128U, memory_->Read(128, buffer.data(), buffer.size()));
+  for (size_t i = 0; i < 128; i++) {
+    ASSERT_EQ(128 + i, buffer[i]) << "Failed at byte " << i;
+  }
 }
 
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/MemoryFake.cpp b/libunwindstack/tests/MemoryFake.cpp
index 2026acc..60936cd 100644
--- a/libunwindstack/tests/MemoryFake.cpp
+++ b/libunwindstack/tests/MemoryFake.cpp
@@ -35,16 +35,16 @@
   }
 }
 
-bool MemoryFake::Read(uint64_t addr, void* memory, size_t size) {
+size_t MemoryFake::Read(uint64_t addr, void* memory, size_t size) {
   uint8_t* dst = reinterpret_cast<uint8_t*>(memory);
   for (size_t i = 0; i < size; i++, addr++) {
     auto value = data_.find(addr);
     if (value == data_.end()) {
-      return false;
+      return i;
     }
     dst[i] = value->second;
   }
-  return true;
+  return size;
 }
 
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/MemoryFake.h b/libunwindstack/tests/MemoryFake.h
index d374261..764a6c3 100644
--- a/libunwindstack/tests/MemoryFake.h
+++ b/libunwindstack/tests/MemoryFake.h
@@ -32,7 +32,7 @@
   MemoryFake() = default;
   virtual ~MemoryFake() = default;
 
-  bool Read(uint64_t addr, void* buffer, size_t size) override;
+  size_t Read(uint64_t addr, void* buffer, size_t size) override;
 
   void SetMemory(uint64_t addr, const void* memory, size_t length);
 
@@ -71,21 +71,9 @@
   MemoryFakeAlwaysReadZero() = default;
   virtual ~MemoryFakeAlwaysReadZero() = default;
 
-  bool Read(uint64_t, void* buffer, size_t size) override {
+  size_t Read(uint64_t, void* buffer, size_t size) override {
     memset(buffer, 0, size);
-    return true;
-  }
-};
-
-class MemoryFakeRemote : public MemoryRemote {
- public:
-  MemoryFakeRemote() : MemoryRemote(0) {}
-  virtual ~MemoryFakeRemote() = default;
-
- protected:
-  bool PtraceRead(uint64_t, long* value) override {
-    *value = 0;
-    return true;
+    return size;
   }
 };
 
diff --git a/libunwindstack/tests/MemoryFileTest.cpp b/libunwindstack/tests/MemoryFileTest.cpp
index a204bae..d7d1ace 100644
--- a/libunwindstack/tests/MemoryFileTest.cpp
+++ b/libunwindstack/tests/MemoryFileTest.cpp
@@ -49,7 +49,7 @@
 
   ASSERT_TRUE(memory_.Init(tf_->path, 0));
   std::vector<char> buffer(11);
-  ASSERT_TRUE(memory_.Read(0, buffer.data(), 10));
+  ASSERT_TRUE(memory_.ReadFully(0, buffer.data(), 10));
   buffer[10] = '\0';
   ASSERT_STREQ("0123456789", buffer.data());
 }
@@ -59,7 +59,7 @@
 
   ASSERT_TRUE(memory_.Init(tf_->path, 10));
   std::vector<char> buffer(11);
-  ASSERT_TRUE(memory_.Read(0, buffer.data(), 10));
+  ASSERT_TRUE(memory_.ReadFully(0, buffer.data(), 10));
   buffer[10] = '\0';
   ASSERT_STREQ("abcdefghij", buffer.data());
 }
@@ -75,7 +75,7 @@
 
   ASSERT_TRUE(memory_.Init(tf_->path, pagesize + 15));
   std::vector<char> buffer(9);
-  ASSERT_TRUE(memory_.Read(0, buffer.data(), 8));
+  ASSERT_TRUE(memory_.ReadFully(0, buffer.data(), 8));
   buffer[8] = '\0';
   ASSERT_STREQ("abcdefgh", buffer.data());
 }
@@ -91,7 +91,7 @@
 
   ASSERT_TRUE(memory_.Init(tf_->path, 2 * pagesize));
   std::vector<char> buffer(11);
-  ASSERT_TRUE(memory_.Read(0, buffer.data(), 10));
+  ASSERT_TRUE(memory_.ReadFully(0, buffer.data(), 10));
   buffer[10] = '\0';
   std::string expected_str;
   for (size_t i = 0; i < 5; i++) {
@@ -112,7 +112,7 @@
 
   ASSERT_TRUE(memory_.Init(tf_->path, 2 * pagesize + 10));
   std::vector<char> buffer(11);
-  ASSERT_TRUE(memory_.Read(0, buffer.data(), 10));
+  ASSERT_TRUE(memory_.ReadFully(0, buffer.data(), 10));
   buffer[10] = '\0';
   std::string expected_str;
   for (size_t i = 0; i < 5; i++) {
@@ -149,19 +149,19 @@
   std::vector<char> buffer(100);
 
   // Read before init.
-  ASSERT_FALSE(memory_.Read(0, buffer.data(), 10));
+  ASSERT_FALSE(memory_.ReadFully(0, buffer.data(), 10));
 
   ASSERT_TRUE(memory_.Init(tf_->path, 0));
 
-  ASSERT_FALSE(memory_.Read(10000, buffer.data(), 10));
-  ASSERT_FALSE(memory_.Read(5000, buffer.data(), 10));
-  ASSERT_FALSE(memory_.Read(4990, buffer.data(), 11));
-  ASSERT_TRUE(memory_.Read(4990, buffer.data(), 10));
-  ASSERT_FALSE(memory_.Read(4999, buffer.data(), 2));
-  ASSERT_TRUE(memory_.Read(4999, buffer.data(), 1));
+  ASSERT_FALSE(memory_.ReadFully(10000, buffer.data(), 10));
+  ASSERT_FALSE(memory_.ReadFully(5000, buffer.data(), 10));
+  ASSERT_FALSE(memory_.ReadFully(4990, buffer.data(), 11));
+  ASSERT_TRUE(memory_.ReadFully(4990, buffer.data(), 10));
+  ASSERT_FALSE(memory_.ReadFully(4999, buffer.data(), 2));
+  ASSERT_TRUE(memory_.ReadFully(4999, buffer.data(), 1));
 
   // Check that overflow fails properly.
-  ASSERT_FALSE(memory_.Read(UINT64_MAX - 100, buffer.data(), 200));
+  ASSERT_FALSE(memory_.ReadFully(UINT64_MAX - 100, buffer.data(), 200));
 }
 
 TEST_F(MemoryFileTest, read_past_file_within_mapping) {
@@ -178,7 +178,8 @@
 
   for (size_t i = 0; i < 100; i++) {
     uint8_t value;
-    ASSERT_FALSE(memory_.Read(buffer.size() + i, &value, 1)) << "Should have failed at value " << i;
+    ASSERT_FALSE(memory_.ReadFully(buffer.size() + i, &value, 1))
+        << "Should have failed at value " << i;
   }
 }
 
@@ -195,8 +196,8 @@
 
   std::vector<uint8_t> read_buffer(pagesize * 2);
   // Make sure that reading after mapped data is a failure.
-  ASSERT_FALSE(memory_.Read(pagesize * 2, read_buffer.data(), 1));
-  ASSERT_TRUE(memory_.Read(0, read_buffer.data(), pagesize * 2));
+  ASSERT_FALSE(memory_.ReadFully(pagesize * 2, read_buffer.data(), 1));
+  ASSERT_TRUE(memory_.ReadFully(0, read_buffer.data(), pagesize * 2));
   for (size_t i = 0; i < pagesize; i++) {
     ASSERT_EQ(2, read_buffer[i]) << "Failed at byte " << i;
   }
@@ -219,8 +220,8 @@
 
   std::vector<uint8_t> read_buffer(pagesize * 2);
   // Make sure that reading after mapped data is a failure.
-  ASSERT_FALSE(memory_.Read(pagesize * 2, read_buffer.data(), 1));
-  ASSERT_TRUE(memory_.Read(0, read_buffer.data(), pagesize * 2));
+  ASSERT_FALSE(memory_.ReadFully(pagesize * 2, read_buffer.data(), 1));
+  ASSERT_TRUE(memory_.ReadFully(0, read_buffer.data(), pagesize * 2));
   for (size_t i = 0; i < pagesize - 0x100; i++) {
     ASSERT_EQ(2, read_buffer[i]) << "Failed at byte " << i;
   }
@@ -245,8 +246,8 @@
   ASSERT_TRUE(memory_.Init(tf_->path, pagesize + 0x100, UINT64_MAX));
 
   std::vector<uint8_t> read_buffer(pagesize * 10);
-  ASSERT_FALSE(memory_.Read(pagesize * 9 - 0x100 + 1, read_buffer.data(), 1));
-  ASSERT_TRUE(memory_.Read(0, read_buffer.data(), pagesize * 9 - 0x100));
+  ASSERT_FALSE(memory_.ReadFully(pagesize * 9 - 0x100 + 1, read_buffer.data(), 1));
+  ASSERT_TRUE(memory_.ReadFully(0, read_buffer.data(), pagesize * 9 - 0x100));
 }
 
 TEST_F(MemoryFileTest, init_reinit) {
@@ -259,14 +260,14 @@
 
   ASSERT_TRUE(memory_.Init(tf_->path, 0));
   std::vector<uint8_t> read_buffer(buffer.size());
-  ASSERT_TRUE(memory_.Read(0, read_buffer.data(), pagesize));
+  ASSERT_TRUE(memory_.ReadFully(0, read_buffer.data(), pagesize));
   for (size_t i = 0; i < pagesize; i++) {
     ASSERT_EQ(1, read_buffer[i]) << "Failed at byte " << i;
   }
 
   // Now reinit.
   ASSERT_TRUE(memory_.Init(tf_->path, pagesize));
-  ASSERT_TRUE(memory_.Read(0, read_buffer.data(), pagesize));
+  ASSERT_TRUE(memory_.ReadFully(0, read_buffer.data(), pagesize));
   for (size_t i = 0; i < pagesize; i++) {
     ASSERT_EQ(2, read_buffer[i]) << "Failed at byte " << i;
   }
diff --git a/libunwindstack/tests/MemoryLocalTest.cpp b/libunwindstack/tests/MemoryLocalTest.cpp
index 73eebdd..5a389d0 100644
--- a/libunwindstack/tests/MemoryLocalTest.cpp
+++ b/libunwindstack/tests/MemoryLocalTest.cpp
@@ -16,6 +16,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <sys/mman.h>
 
 #include <vector>
 
@@ -32,14 +33,14 @@
   MemoryLocal local;
 
   std::vector<uint8_t> dst(1024);
-  ASSERT_TRUE(local.Read(reinterpret_cast<uint64_t>(src.data()), dst.data(), 1024));
+  ASSERT_TRUE(local.ReadFully(reinterpret_cast<uint64_t>(src.data()), dst.data(), 1024));
   ASSERT_EQ(0, memcmp(src.data(), dst.data(), 1024));
   for (size_t i = 0; i < 1024; i++) {
     ASSERT_EQ(0x4cU, dst[i]);
   }
 
   memset(src.data(), 0x23, 512);
-  ASSERT_TRUE(local.Read(reinterpret_cast<uint64_t>(src.data()), dst.data(), 1024));
+  ASSERT_TRUE(local.ReadFully(reinterpret_cast<uint64_t>(src.data()), dst.data(), 1024));
   ASSERT_EQ(0, memcmp(src.data(), dst.data(), 1024));
   for (size_t i = 0; i < 512; i++) {
     ASSERT_EQ(0x23U, dst[i]);
@@ -53,8 +54,8 @@
   MemoryLocal local;
 
   std::vector<uint8_t> dst(100);
-  ASSERT_FALSE(local.Read(0, dst.data(), 1));
-  ASSERT_FALSE(local.Read(0, dst.data(), 100));
+  ASSERT_FALSE(local.ReadFully(0, dst.data(), 1));
+  ASSERT_FALSE(local.ReadFully(0, dst.data(), 100));
 }
 
 TEST(MemoryLocalTest, read_overflow) {
@@ -64,7 +65,47 @@
   // version will always go through the overflow check.
   std::vector<uint8_t> dst(100);
   uint64_t value;
-  ASSERT_FALSE(local.Read(reinterpret_cast<uint64_t>(&value), dst.data(), SIZE_MAX));
+  ASSERT_FALSE(local.ReadFully(reinterpret_cast<uint64_t>(&value), dst.data(), SIZE_MAX));
+}
+
+TEST(MemoryLocalTest, Read) {
+  char* mapping = static_cast<char*>(
+      mmap(nullptr, 2 * getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
+
+  ASSERT_NE(MAP_FAILED, mapping);
+
+  mprotect(mapping + getpagesize(), getpagesize(), PROT_NONE);
+  memset(mapping + getpagesize() - 1024, 0x4c, 1024);
+
+  MemoryLocal local;
+
+  std::vector<uint8_t> dst(4096);
+  ASSERT_EQ(1024U, local.Read(reinterpret_cast<uint64_t>(mapping + getpagesize() - 1024),
+                              dst.data(), 4096));
+  for (size_t i = 0; i < 1024; i++) {
+    ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
+  }
+
+  ASSERT_EQ(0, munmap(mapping, 2 * getpagesize()));
+}
+
+TEST(MemoryLocalTest, read_hole) {
+  void* mapping =
+      mmap(nullptr, 3 * 4096, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  ASSERT_NE(MAP_FAILED, mapping);
+  memset(mapping, 0xFF, 3 * 4096);
+  mprotect(static_cast<char*>(mapping) + 4096, 4096, PROT_NONE);
+
+  MemoryLocal local;
+  std::vector<uint8_t> dst(4096 * 3, 0xCC);
+  ASSERT_EQ(4096U, local.Read(reinterpret_cast<uintptr_t>(mapping), dst.data(), 4096 * 3));
+  for (size_t i = 0; i < 4096; ++i) {
+    ASSERT_EQ(0xFF, dst[i]);
+  }
+  for (size_t i = 4096; i < 4096 * 3; ++i) {
+    ASSERT_EQ(0xCC, dst[i]);
+  }
+  ASSERT_EQ(0, munmap(mapping, 3 * 4096));
 }
 
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/MemoryRangeTest.cpp b/libunwindstack/tests/MemoryRangeTest.cpp
index 680fae9..cb1a0c9 100644
--- a/libunwindstack/tests/MemoryRangeTest.cpp
+++ b/libunwindstack/tests/MemoryRangeTest.cpp
@@ -35,10 +35,10 @@
   std::shared_ptr<Memory> process_memory(memory_fake);
   memory_fake->SetMemory(9001, src);
 
-  MemoryRange range(process_memory, 9001, 9001 + src.size());
+  MemoryRange range(process_memory, 9001, src.size(), 0);
 
   std::vector<uint8_t> dst(1024);
-  ASSERT_TRUE(range.Read(0, dst.data(), src.size()));
+  ASSERT_TRUE(range.ReadFully(0, dst.data(), src.size()));
   for (size_t i = 0; i < 1024; i++) {
     ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
   }
@@ -51,29 +51,44 @@
   std::shared_ptr<Memory> process_memory(memory_fake);
   memory_fake->SetMemory(1000, src);
 
-  MemoryRange range(process_memory, 1000, 2024);
+  MemoryRange range(process_memory, 1000, 1024, 0);
 
   std::vector<uint8_t> dst(1024);
-  ASSERT_TRUE(range.Read(1020, dst.data(), 4));
+  ASSERT_TRUE(range.ReadFully(1020, dst.data(), 4));
   for (size_t i = 0; i < 4; i++) {
     ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
   }
 
   // Verify that reads outside of the range will fail.
-  ASSERT_FALSE(range.Read(1020, dst.data(), 5));
-  ASSERT_FALSE(range.Read(1024, dst.data(), 1));
-  ASSERT_FALSE(range.Read(1024, dst.data(), 1024));
+  ASSERT_FALSE(range.ReadFully(1020, dst.data(), 5));
+  ASSERT_FALSE(range.ReadFully(1024, dst.data(), 1));
+  ASSERT_FALSE(range.ReadFully(1024, dst.data(), 1024));
 
   // Verify that reading up to the end works.
-  ASSERT_TRUE(range.Read(1020, dst.data(), 4));
+  ASSERT_TRUE(range.ReadFully(1020, dst.data(), 4));
 }
 
 TEST(MemoryRangeTest, read_overflow) {
   std::vector<uint8_t> buffer(100);
 
   std::shared_ptr<Memory> process_memory(new MemoryFakeAlwaysReadZero);
-  std::unique_ptr<MemoryRange> overflow(new MemoryRange(process_memory, 100, 200));
-  ASSERT_FALSE(overflow->Read(UINT64_MAX - 10, buffer.data(), 100));
+  std::unique_ptr<MemoryRange> overflow(new MemoryRange(process_memory, 100, 200, 0));
+  ASSERT_FALSE(overflow->ReadFully(UINT64_MAX - 10, buffer.data(), 100));
+}
+
+TEST(MemoryRangeTest, Read) {
+  std::vector<uint8_t> src(4096);
+  memset(src.data(), 0x4c, 4096);
+  MemoryFake* memory_fake = new MemoryFake;
+  std::shared_ptr<Memory> process_memory(memory_fake);
+  memory_fake->SetMemory(1000, src);
+
+  MemoryRange range(process_memory, 1000, 1024, 0);
+  std::vector<uint8_t> dst(1024);
+  ASSERT_EQ(4U, range.Read(1020, dst.data(), 1024));
+  for (size_t i = 0; i < 4; i++) {
+    ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
+  }
 }
 
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/MemoryRemoteTest.cpp b/libunwindstack/tests/MemoryRemoteTest.cpp
index a66d0c5..8aa4c3f 100644
--- a/libunwindstack/tests/MemoryRemoteTest.cpp
+++ b/libunwindstack/tests/MemoryRemoteTest.cpp
@@ -71,7 +71,7 @@
   MemoryRemote remote(pid);
 
   std::vector<uint8_t> dst(1024);
-  ASSERT_TRUE(remote.Read(reinterpret_cast<uint64_t>(src.data()), dst.data(), 1024));
+  ASSERT_TRUE(remote.ReadFully(reinterpret_cast<uint64_t>(src.data()), dst.data(), 1024));
   for (size_t i = 0; i < 1024; i++) {
     ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
   }
@@ -79,6 +79,39 @@
   ASSERT_TRUE(Detach(pid));
 }
 
+TEST_F(MemoryRemoteTest, Read) {
+  char* mapping = static_cast<char*>(
+      mmap(nullptr, 2 * getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
+
+  ASSERT_NE(MAP_FAILED, mapping);
+
+  mprotect(mapping + getpagesize(), getpagesize(), PROT_NONE);
+  memset(mapping + getpagesize() - 1024, 0x4c, 1024);
+
+  pid_t pid;
+  if ((pid = fork()) == 0) {
+    while (true)
+      ;
+    exit(1);
+  }
+  ASSERT_LT(0, pid);
+  TestScopedPidReaper reap(pid);
+
+  ASSERT_TRUE(Attach(pid));
+
+  MemoryRemote remote(pid);
+
+  std::vector<uint8_t> dst(4096);
+  ASSERT_EQ(1024U, remote.Read(reinterpret_cast<uint64_t>(mapping + getpagesize() - 1024),
+                               dst.data(), 4096));
+  for (size_t i = 0; i < 1024; i++) {
+    ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
+  }
+
+  ASSERT_TRUE(Detach(pid));
+  ASSERT_EQ(0, munmap(mapping, 2 * getpagesize()));
+}
+
 TEST_F(MemoryRemoteTest, read_fail) {
   int pagesize = getpagesize();
   void* src = mmap(nullptr, pagesize * 2, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE,-1, 0);
@@ -101,17 +134,17 @@
   MemoryRemote remote(pid);
 
   std::vector<uint8_t> dst(pagesize);
-  ASSERT_TRUE(remote.Read(reinterpret_cast<uint64_t>(src), dst.data(), pagesize));
+  ASSERT_TRUE(remote.ReadFully(reinterpret_cast<uint64_t>(src), dst.data(), pagesize));
   for (size_t i = 0; i < 1024; i++) {
     ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
   }
 
-  ASSERT_FALSE(remote.Read(reinterpret_cast<uint64_t>(src) + pagesize, dst.data(), 1));
-  ASSERT_TRUE(remote.Read(reinterpret_cast<uint64_t>(src) + pagesize - 1, dst.data(), 1));
-  ASSERT_FALSE(remote.Read(reinterpret_cast<uint64_t>(src) + pagesize - 4, dst.data(), 8));
+  ASSERT_FALSE(remote.ReadFully(reinterpret_cast<uint64_t>(src) + pagesize, dst.data(), 1));
+  ASSERT_TRUE(remote.ReadFully(reinterpret_cast<uint64_t>(src) + pagesize - 1, dst.data(), 1));
+  ASSERT_FALSE(remote.ReadFully(reinterpret_cast<uint64_t>(src) + pagesize - 4, dst.data(), 8));
 
   // Check overflow condition is caught properly.
-  ASSERT_FALSE(remote.Read(UINT64_MAX - 100, dst.data(), 200));
+  ASSERT_FALSE(remote.ReadFully(UINT64_MAX - 100, dst.data(), 200));
 
   ASSERT_EQ(0, munmap(src, pagesize));
 
@@ -119,11 +152,24 @@
 }
 
 TEST_F(MemoryRemoteTest, read_overflow) {
-  MemoryFakeRemote remote;
+  pid_t pid;
+  if ((pid = fork()) == 0) {
+    while (true)
+      ;
+    exit(1);
+  }
+  ASSERT_LT(0, pid);
+  TestScopedPidReaper reap(pid);
+
+  ASSERT_TRUE(Attach(pid));
+
+  MemoryRemote remote(pid);
 
   // Check overflow condition is caught properly.
   std::vector<uint8_t> dst(200);
-  ASSERT_FALSE(remote.Read(UINT64_MAX - 100, dst.data(), 200));
+  ASSERT_FALSE(remote.ReadFully(UINT64_MAX - 100, dst.data(), 200));
+
+  ASSERT_TRUE(Detach(pid));
 }
 
 TEST_F(MemoryRemoteTest, read_illegal) {
@@ -140,10 +186,38 @@
   MemoryRemote remote(pid);
 
   std::vector<uint8_t> dst(100);
-  ASSERT_FALSE(remote.Read(0, dst.data(), 1));
-  ASSERT_FALSE(remote.Read(0, dst.data(), 100));
+  ASSERT_FALSE(remote.ReadFully(0, dst.data(), 1));
+  ASSERT_FALSE(remote.ReadFully(0, dst.data(), 100));
 
   ASSERT_TRUE(Detach(pid));
 }
 
+TEST_F(MemoryRemoteTest, read_hole) {
+  void* mapping =
+      mmap(nullptr, 3 * 4096, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  ASSERT_NE(MAP_FAILED, mapping);
+  memset(mapping, 0xFF, 3 * 4096);
+  mprotect(static_cast<char*>(mapping) + 4096, 4096, PROT_NONE);
+
+  pid_t pid;
+  if ((pid = fork()) == 0) {
+    while (true);
+    exit(1);
+  }
+  ASSERT_LT(0, pid);
+  TestScopedPidReaper reap(pid);
+
+  ASSERT_TRUE(Attach(pid));
+
+  MemoryRemote remote(pid);
+  std::vector<uint8_t> dst(4096 * 3, 0xCC);
+  ASSERT_EQ(4096U, remote.Read(reinterpret_cast<uintptr_t>(mapping), dst.data(), 4096 * 3));
+  for (size_t i = 0; i < 4096; ++i) {
+    ASSERT_EQ(0xFF, dst[i]);
+  }
+  for (size_t i = 4096; i < 4096 * 3; ++i) {
+    ASSERT_EQ(0xCC, dst[i]);
+  }
+}
+
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/UnwindTest.cpp b/libunwindstack/tests/UnwindTest.cpp
index 66c8ba6..b372fd0 100644
--- a/libunwindstack/tests/UnwindTest.cpp
+++ b/libunwindstack/tests/UnwindTest.cpp
@@ -174,7 +174,7 @@
       MemoryRemote memory(pid);
       // Read the remote value to see if we are ready.
       bool value;
-      if (memory.Read(addr, &value, sizeof(value)) && value) {
+      if (memory.ReadFully(addr, &value, sizeof(value)) && value) {
         *completed = true;
       }
       if (!*completed || !leave_attached) {