path: root/js/src/jit/x86-shared/AssemblerBuffer-x86-shared.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
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 * 1. Redistributions of source code must retain the above copyright
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 * 2. Redistributions in binary form must reproduce the above copyright
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 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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#ifndef jit_x86_shared_AssemblerBuffer_x86_shared_h
#define jit_x86_shared_AssemblerBuffer_x86_shared_h

#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"
#include "mozilla/Vector.h"

#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>

#include "jit/JitContext.h"
#include "jit/JitSpewer.h"
#include "jit/ProcessExecutableMemory.h"
#include "js/AllocPolicy.h"
#include "js/Vector.h"

// Spew formatting helpers.
#define PRETTYHEX(x)      \
  (((x) < 0) ? "-" : ""), \
      ((unsigned)((x) ^ ((x) >> 31)) + ((unsigned)(x) >> 31))

#define MEM_o "%s0x%x"
#define MEM_os MEM_o "(,%s,%d)"
#define MEM_ob MEM_o "(%s)"
#define MEM_obs MEM_o "(%s,%s,%d)"

#define MEM_o32 "%s0x%04x"
#define MEM_o32s MEM_o32 "(,%s,%d)"
#define MEM_o32b MEM_o32 "(%s)"
#define MEM_o32bs MEM_o32 "(%s,%s,%d)"
#define MEM_o32r ".Lfrom%d(%%rip)"

#define ADDR_o(offset) PRETTYHEX(offset)
#define ADDR_os(offset, index, scale) \
  ADDR_o(offset), GPRegName((index)), (1 << (scale))
#define ADDR_ob(offset, base) ADDR_o(offset), GPRegName((base))
#define ADDR_obs(offset, base, index, scale) \
  ADDR_ob(offset, base), GPRegName((index)), (1 << (scale))

#define ADDR_o32(offset) ADDR_o(offset)
#define ADDR_o32s(offset, index, scale) ADDR_os(offset, index, scale)
#define ADDR_o32b(offset, base) ADDR_ob(offset, base)
#define ADDR_o32bs(offset, base, index, scale) \
  ADDR_obs(offset, base, index, scale)
#define ADDR_o32r(offset) (offset)

namespace js {

class JS_PUBLIC_API Sprinter;

namespace jit {

// AllocPolicy for AssemblerBuffer. OOMs when trying to allocate more than
// MaxCodeBytesPerProcess bytes. Use private inheritance to make sure we
// explicitly have to expose SystemAllocPolicy methods.
class AssemblerBufferAllocPolicy : private SystemAllocPolicy {
 public:
  using SystemAllocPolicy::checkSimulatedOOM;
  using SystemAllocPolicy::free_;
  using SystemAllocPolicy::reportAllocOverflow;

  template <typename T>
  T* pod_realloc(T* p, size_t oldSize, size_t newSize) {
    static_assert(
        sizeof(T) == 1,
        "AssemblerBufferAllocPolicy should only be used with byte vectors");
    MOZ_ASSERT(oldSize <= MaxCodeBytesPerProcess);
    if (MOZ_UNLIKELY(newSize > MaxCodeBytesPerProcess)) {
      return nullptr;
    }
    return SystemAllocPolicy::pod_realloc<T>(p, oldSize, newSize);
  }
  template <typename T>
  T* pod_malloc(size_t numElems) {
    static_assert(
        sizeof(T) == 1,
        "AssemblerBufferAllocPolicy should only be used with byte vectors");
    if (MOZ_UNLIKELY(numElems > MaxCodeBytesPerProcess)) {
      return nullptr;
    }
    return SystemAllocPolicy::pod_malloc<T>(numElems);
  }
};

class AssemblerBuffer {
  template <size_t size, typename T>
  MOZ_ALWAYS_INLINE void sizedAppendUnchecked(T value) {
    m_buffer.infallibleAppend(reinterpret_cast<unsigned char*>(&value), size);
  }

  template <size_t size, typename T>
  MOZ_ALWAYS_INLINE void sizedAppend(T value) {
    if (MOZ_UNLIKELY(
            !m_buffer.append(reinterpret_cast<unsigned char*>(&value), size))) {
      oomDetected();
    }
  }

 public:
  AssemblerBuffer() : m_oom(false) {}

  void ensureSpace(size_t space) {
    // This should only be called with small |space| values to ensure
    // we don't overflow below.
    MOZ_ASSERT(space <= 16);
    if (MOZ_UNLIKELY(!m_buffer.reserve(m_buffer.length() + space))) {
      oomDetected();
    }
  }

  bool isAligned(size_t alignment) const {
    return !(m_buffer.length() & (alignment - 1));
  }

  MOZ_ALWAYS_INLINE void putByteUnchecked(int value) {
    sizedAppendUnchecked<1>(value);
  }
  MOZ_ALWAYS_INLINE void putShortUnchecked(int value) {
    sizedAppendUnchecked<2>(value);
  }
  MOZ_ALWAYS_INLINE void putIntUnchecked(int value) {
    sizedAppendUnchecked<4>(value);
  }
  MOZ_ALWAYS_INLINE void putInt64Unchecked(int64_t value) {
    sizedAppendUnchecked<8>(value);
  }

  MOZ_ALWAYS_INLINE void putByte(int value) { sizedAppend<1>(value); }
  MOZ_ALWAYS_INLINE void putShort(int value) { sizedAppend<2>(value); }
  MOZ_ALWAYS_INLINE void putInt(int value) { sizedAppend<4>(value); }
  MOZ_ALWAYS_INLINE void putInt64(int64_t value) { sizedAppend<8>(value); }

  [[nodiscard]] bool append(const unsigned char* values, size_t size) {
    if (MOZ_UNLIKELY(!m_buffer.append(values, size))) {
      oomDetected();
      return false;
    }
    return true;
  }

  size_t size() const { return m_buffer.length(); }

  bool oom() const { return m_oom; }

  bool reserve(size_t size) { return !m_oom && m_buffer.reserve(size); }

  bool swap(Vector<uint8_t, 0, SystemAllocPolicy>& bytes);

  const unsigned char* buffer() const {
    MOZ_RELEASE_ASSERT(!m_oom);
    return m_buffer.begin();
  }

  unsigned char* data() { return m_buffer.begin(); }

 protected:
  /*
   * OOM handling: This class can OOM in the ensureSpace() method trying
   * to allocate a new buffer. In response to an OOM, we need to avoid
   * crashing and report the error. We also want to make it so that
   * users of this class need to check for OOM only at certain points
   * and not after every operation.
   *
   * Our strategy for handling an OOM is to set m_oom, and then clear (but
   * not free) m_buffer, preserving the current buffer. This way, the user
   * can continue assembling into the buffer, deferring OOM checking
   * until the user wants to read code out of the buffer.
   *
   * See also the |buffer| method.
   */
  void oomDetected() {
    m_oom = true;
    m_buffer.clear();
#ifdef DEBUG
    JitContext* context = MaybeGetJitContext();
    if (context) {
      context->setOOM();
    }
#endif
  }

  mozilla::Vector<unsigned char, 256, AssemblerBufferAllocPolicy> m_buffer;
  bool m_oom;
};

class GenericAssembler {
#ifdef JS_JITSPEW
  Sprinter* printer;
#endif
 public:
  GenericAssembler()
#ifdef JS_JITSPEW
      : printer(nullptr)
#endif
  {
  }

  void setPrinter(Sprinter* sp) {
#ifdef JS_JITSPEW
    printer = sp;
#endif
  }

#ifdef JS_JITSPEW
  inline void spew(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3) {
    if (MOZ_UNLIKELY(printer || JitSpewEnabled(JitSpew_Codegen))) {
      va_list va;
      va_start(va, fmt);
      spew(fmt, va);
      va_end(va);
    }
  }
#else
  MOZ_ALWAYS_INLINE void spew(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3) {}
#endif

#ifdef JS_JITSPEW
  MOZ_COLD void spew(const char* fmt, va_list va) MOZ_FORMAT_PRINTF(2, 0);
#endif
};

}  // namespace jit
}  // namespace js

#endif /* jit_x86_shared_AssemblerBuffer_x86_shared_h */