// Copyright 2017 The Abseil Authors.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

//

// Functions for directly invoking mmap() via syscall, avoiding the case where

// mmap() has been locally overridden.

#ifndef ABSL_BASE_INTERNAL_DIRECT_MMAP_H_

#define ABSL_BASE_INTERNAL_DIRECT_MMAP_H_

#include "absl/base/config.h"

#ifdef ABSL_HAVE_MMAP

#include <sys/mman.h>

#ifdef __linux__

#include <sys/types.h>

#ifdef __BIONIC__

#include <sys/syscall.h>

#else

#include <syscall.h>

#endif

#include <linux/unistd.h>

#include <unistd.h>

#include <cerrno>

#include <cstdarg>

#include <cstddef>

#include <cstdint>

#ifdef __mips__

// Include definitions of the ABI currently in use.

#if defined(__BIONIC__) || !defined(__GLIBC__)

// Android doesn't have sgidefs.h, but does have asm/sgidefs.h, which has the

// definitions we need.

#include <asm/sgidefs.h>

#else

#include <sgidefs.h>

#endif  // __BIONIC__ || !__GLIBC__

#endif  // __mips__

// SYS_mmap and SYS_munmap are not defined in Android.

#ifdef __BIONIC__

#pragma GCC visibility push(default)

extern "C" void* __mmap2(void*, size_t, int, int, int, size_t);

#pragma GCC visibility pop

#if defined(__NR_mmap) && !defined(SYS_mmap)

#define SYS_mmap __NR_mmap

#endif

#ifndef SYS_munmap

#define SYS_munmap __NR_munmap

#endif

#endif  // __BIONIC__

#if defined(__NR_mmap2) && !defined(SYS_mmap2)

#define SYS_mmap2 __NR_mmap2

#endif

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace base_internal {

// Platform specific logic extracted from

// https://chromium.googlesource.com/linux-syscall-support/+/master/linux_syscall_support.h

inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,

                        off_t offset) noexcept {

#if defined(__i386__) || defined(__ARM_ARCH_3__) || defined(__ARM_EABI__) || \

    defined(__m68k__) || defined(__sh__) ||                                  \

    (defined(__hppa__) && !defined(__LP64__)) ||                             \

    (defined(__mips__) && _MIPS_SIM == _MIPS_SIM_ABI32) ||                   \

    (defined(__PPC__) && !defined(__PPC64__)) ||                             \

    (defined(__riscv) && __riscv_xlen == 32) ||                              \

    (defined(__s390__) && !defined(__s390x__)) ||                            \

    (defined(__sparc__) && !defined(__arch64__))

  // On these architectures, implement mmap with mmap2.

  static int pagesize = 0;

  if (pagesize == 0) {

#if defined(__wasm__) || defined(__asmjs__)

    pagesize = getpagesize();

#else

    pagesize = sysconf(_SC_PAGESIZE);

#endif

  }

  if (offset < 0 || offset % pagesize != 0) {

    errno = EINVAL;

    return MAP_FAILED;

  }

#ifdef __BIONIC__

  // SYS_mmap2 has problems on Android API level <= 16.

  // Workaround by invoking __mmap2() instead.

  return __mmap2(start, length, prot, flags, fd,

                 static_cast<size_t>(offset / pagesize));

#else

  return reinterpret_cast<void*>(

      syscall(SYS_mmap2, start, length, prot, flags, fd,

              static_cast<unsigned long>(offset / pagesize)));  // NOLINT

#endif

#elif defined(__s390x__)

  // On s390x, mmap() arguments are passed in memory.

  unsigned long buf[6] = {reinterpret_cast<unsigned long>(start),  // NOLINT

                          static_cast<unsigned long>(length),      // NOLINT

                          static_cast<unsigned long>(prot),        // NOLINT

                          static_cast<unsigned long>(flags),       // NOLINT

                          static_cast<unsigned long>(fd),          // NOLINT

                          static_cast<unsigned long>(offset)};     // NOLINT

  return reinterpret_cast<void*>(syscall(SYS_mmap, buf));

#elif defined(__x86_64__)

// The x32 ABI has 32 bit longs, but the syscall interface is 64 bit.

// We need to explicitly cast to an unsigned 64 bit type to avoid implicit

// sign extension.  We can't cast pointers directly because those are

// 32 bits, and gcc will dump ugly warnings about casting from a pointer

// to an integer of a different size. We also need to make sure __off64_t

// isn't truncated to 32-bits under x32.

#define MMAP_SYSCALL_ARG(x) ((uint64_t)(uintptr_t)(x))

  return reinterpret_cast<void*>(

      syscall(SYS_mmap, MMAP_SYSCALL_ARG(start), MMAP_SYSCALL_ARG(length),

              MMAP_SYSCALL_ARG(prot), MMAP_SYSCALL_ARG(flags),

              MMAP_SYSCALL_ARG(fd), static_cast<uint64_t>(offset)));

#undef MMAP_SYSCALL_ARG

#else  // Remaining 64-bit aritectures.

  static_assert(sizeof(unsigned long) == 8, "Platform is not 64-bit");

  return reinterpret_cast<void*>(

      syscall(SYS_mmap, start, length, prot, flags, fd, offset));

#endif

}

inline int DirectMunmap(void* start, size_t length) {

  return static_cast<int>(syscall(SYS_munmap, start, length));

}

}  // namespace base_internal

ABSL_NAMESPACE_END

}  // namespace absl

#else  // !__linux__

// For non-linux platforms where we have mmap, just dispatch directly to the

// actual mmap()/munmap() methods.

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace base_internal {

inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,

                        off_t offset) {

  return mmap(start, length, prot, flags, fd, offset);

}

inline int DirectMunmap(void* start, size_t length) {

  return munmap(start, length);

}

}  // namespace base_internal

ABSL_NAMESPACE_END

}  // namespace absl

#endif  // __linux__

#endif  // ABSL_HAVE_MMAP

#endif  // ABSL_BASE_INTERNAL_DIRECT_MMAP_H_