Move Windows Sandbox, trybots version (don't commit me!)

sandbox/src/sidestep/preamble_patcher_with_stub.cpp

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Implementation of PreamblePatcher
-
-#include "sandbox/src/sidestep/preamble_patcher.h"
-
-#include "sandbox/src/sandbox_nt_util.h"
-#include "sandbox/src/sidestep/mini_disassembler.h"
-
-// Definitions of assembly statements we need
-#define ASM_JMP32REL 0xE9
-#define ASM_INT3 0xCC
-
-namespace {
-
-// Very basic memcpy. We are copying 4 to 12 bytes most of the time, so there
-// is no attempt to optimize this code or have a general purpose function.
-// We don't want to call the crt from this code.
-inline void* RawMemcpy(void* destination, const void* source, size_t bytes) {
-  const char* from = reinterpret_cast<const char*>(source);
-  char* to = reinterpret_cast<char*>(destination);
-
-  for (size_t i = 0; i < bytes ; i++)
-    to[i] = from[i];
-
-  return destination;
-}
-
-// Very basic memset. We are filling 1 to 7 bytes most of the time, so there
-// is no attempt to optimize this code or have a general purpose function.
-// We don't want to call the crt from this code.
-inline void* RawMemset(void* destination, int value, size_t bytes) {
-  char* to = reinterpret_cast<char*>(destination);
-
-  for (size_t i = 0; i < bytes ; i++)
-    to[i] = static_cast<char>(value);
-
-  return destination;
-}
-
-}  // namespace
-
-#define ASSERT(a, b) DCHECK_NT(a)
-
-namespace sidestep {
-
-SideStepError PreamblePatcher::RawPatchWithStub(
-    void* target_function,
-    void* replacement_function,
-    unsigned char* preamble_stub,
-    size_t stub_size,
-    size_t* bytes_needed) {
-  if ((NULL == target_function) ||
-      (NULL == replacement_function) ||
-      (NULL == preamble_stub)) {
-    ASSERT(false, (L"Invalid parameters - either pTargetFunction or "
-                   L"pReplacementFunction or pPreambleStub were NULL."));
-    return SIDESTEP_INVALID_PARAMETER;
-  }
-
-  // TODO(V7:joi) Siggi and I just had a discussion and decided that both
-  // patching and unpatching are actually unsafe.  We also discussed a
-  // method of making it safe, which is to freeze all other threads in the
-  // process, check their thread context to see if their eip is currently
-  // inside the block of instructions we need to copy to the stub, and if so
-  // wait a bit and try again, then unfreeze all threads once we've patched.
-  // Not implementing this for now since we're only using SideStep for unit
-  // testing, but if we ever use it for production code this is what we
-  // should do.
-  //
-  // NOTE: Stoyan suggests we can write 8 or even 10 bytes atomically using
-  // FPU instructions, and on newer processors we could use cmpxchg8b or
-  // cmpxchg16b. So it might be possible to do the patching/unpatching
-  // atomically and avoid having to freeze other threads.  Note though, that
-  // doing it atomically does not help if one of the other threads happens
-  // to have its eip in the middle of the bytes you change while you change
-  // them.
-  unsigned char* target = reinterpret_cast<unsigned char*>(target_function);
-
-  // Let's disassemble the preamble of the target function to see if we can
-  // patch, and to see how much of the preamble we need to take.  We need 5
-  // bytes for our jmp instruction, so let's find the minimum number of
-  // instructions to get 5 bytes.
-  MiniDisassembler disassembler;
-  unsigned int preamble_bytes = 0;
-  while (preamble_bytes < 5) {
-    InstructionType instruction_type =
-      disassembler.Disassemble(target + preamble_bytes, &preamble_bytes);
-    if (IT_JUMP == instruction_type) {
-      ASSERT(false, (L"Unable to patch because there is a jump instruction "
-                     L"in the first 5 bytes."));
-      return SIDESTEP_JUMP_INSTRUCTION;
-    } else if (IT_RETURN == instruction_type) {
-      ASSERT(false, (L"Unable to patch because function is too short"));
-      return SIDESTEP_FUNCTION_TOO_SMALL;
-    } else if (IT_GENERIC != instruction_type) {
-      ASSERT(false, (L"Disassembler encountered unsupported instruction "
-                     L"(either unused or unknown"));
-      return SIDESTEP_UNSUPPORTED_INSTRUCTION;
-    }
-  }
-
-  if (NULL != bytes_needed)
-    *bytes_needed = preamble_bytes + 5;
-
-  // Inv: preamble_bytes is the number of bytes (at least 5) that we need to
-  // take from the preamble to have whole instructions that are 5 bytes or more
-  // in size total. The size of the stub required is cbPreamble + size of
-  // jmp (5)
-  if (preamble_bytes + 5 > stub_size) {
-    NOTREACHED_NT();
-    return SIDESTEP_INSUFFICIENT_BUFFER;
-  }
-
-  // First, copy the preamble that we will overwrite.
-  RawMemcpy(reinterpret_cast<void*>(preamble_stub),
-            reinterpret_cast<void*>(target), preamble_bytes);
-
-  // Now, make a jmp instruction to the rest of the target function (minus the
-  // preamble bytes we moved into the stub) and copy it into our preamble-stub.
-  // find address to jump to, relative to next address after jmp instruction
-#pragma warning(push)
-#pragma warning(disable:4244)
-  // This assignment generates a warning because it is 32 bit specific.
-  int relative_offset_to_target_rest
-    = ((reinterpret_cast<unsigned char*>(target) + preamble_bytes) -
-        (preamble_stub + preamble_bytes + 5));
-#pragma warning(pop)
-  // jmp (Jump near, relative, displacement relative to next instruction)
-  preamble_stub[preamble_bytes] = ASM_JMP32REL;
-  // copy the address
-  RawMemcpy(reinterpret_cast<void*>(preamble_stub + preamble_bytes + 1),
-            reinterpret_cast<void*>(&relative_offset_to_target_rest), 4);
-
-  // Inv: preamble_stub points to assembly code that will execute the
-  // original function by first executing the first cbPreamble bytes of the
-  // preamble, then jumping to the rest of the function.
-
-  // Overwrite the first 5 bytes of the target function with a jump to our
-  // replacement function.
-  // (Jump near, relative, displacement relative to next instruction)
-  target[0] = ASM_JMP32REL;
-
-  // Find offset from instruction after jmp, to the replacement function.
-#pragma warning(push)
-#pragma warning(disable:4244)
-  int offset_to_replacement_function =
-    reinterpret_cast<unsigned char*>(replacement_function) -
-    reinterpret_cast<unsigned char*>(target) - 5;
-#pragma warning(pop)
-  // complete the jmp instruction
-  RawMemcpy(reinterpret_cast<void*>(target + 1),
-            reinterpret_cast<void*>(&offset_to_replacement_function), 4);
-  // Set any remaining bytes that were moved to the preamble-stub to INT3 so
-  // as not to cause confusion (otherwise you might see some strange
-  // instructions if you look at the disassembly, or even invalid
-  // instructions). Also, by doing this, we will break into the debugger if
-  // some code calls into this portion of the code.  If this happens, it
-  // means that this function cannot be patched using this patcher without
-  // further thought.
-  if (preamble_bytes > 5) {
-    RawMemset(reinterpret_cast<void*>(target + 5), ASM_INT3,
-              preamble_bytes - 5);
-  }
-
-  // Inv: The memory pointed to by target_function now points to a relative
-  // jump instruction that jumps over to the preamble_stub.  The preamble
-  // stub contains the first stub_size bytes of the original target
-  // function's preamble code, followed by a relative jump back to the next
-  // instruction after the first cbPreamble bytes.
-
-  return SIDESTEP_SUCCESS;
-}
-
-};  // namespace sidestep
-
-#undef ASSERT