libc/bionic/legacy_32_bit_support.cpp

/*
 * Copyright (C) 2008 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#undef _FORTIFY_SOURCE

#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/vfs.h>
#include <unistd.h>

#if defined(__LP64__)
#error This code is only needed on 32-bit systems!
#endif

// System calls we need.
extern "C" int __fcntl64(int, int, void*);
extern "C" int __llseek(int, unsigned long, unsigned long, off64_t*, int);
extern "C" int __preadv64(int, const struct iovec*, int, long, long);
extern "C" int __pwritev64(int, const struct iovec*, int, long, long);

// For fcntl we use the fcntl64 system call to signal that we're using struct flock64.
int fcntl(int fd, int cmd, ...) {
  va_list ap;

  va_start(ap, cmd);
  void* arg = va_arg(ap, void*);
  va_end(ap);

  return __fcntl64(fd, cmd, arg);
}

// For lseek64 we need to use the llseek system call which splits the off64_t in two and
// returns the off64_t result via a pointer because 32-bit kernels can't return 64-bit results.
off64_t lseek64(int fd, off64_t off, int whence) {
  off64_t result;
  unsigned long off_hi = static_cast<unsigned long>(off >> 32);
  unsigned long off_lo = static_cast<unsigned long>(off);
  if (__llseek(fd, off_hi, off_lo, &result, whence) < 0) {
    return -1;
  }
  return result;
}

// There is no pread for 32-bit off_t, so we need to widen and call pread64.
ssize_t pread(int fd, void* buf, size_t byte_count, off_t offset) {
  return pread64(fd, buf, byte_count, static_cast<off64_t>(offset));
}

// There is no pwrite for 32-bit off_t, so we need to widen and call pwrite64.
ssize_t pwrite(int fd, const void* buf, size_t byte_count, off_t offset) {
  return pwrite64(fd, buf, byte_count, static_cast<off64_t>(offset));
}

// On LP32, there is no off_t preadv/pwritev, and even the 64-bit preadv/pwritev
// don't use off64_t (see SYSCALLS.TXT for more). Here, this means that we need
// to implement all four functions because the two system calls don't match any
// of the userspace functions. Unlike llseek, the pair is split lo-hi, not hi-lo.
ssize_t preadv(int fd, const struct iovec* ios, int count, off_t offset) {
  return __preadv64(fd, ios, count, offset, 0);
}
ssize_t preadv64(int fd, const struct iovec* ios, int count, off64_t offset) {
  return __preadv64(fd, ios, count, offset, offset >> 32);
}
ssize_t pwritev(int fd, const struct iovec* ios, int count, off_t offset) {
  return __pwritev64(fd, ios, count, offset, 0);
}
ssize_t pwritev64(int fd, const struct iovec* ios, int count, off64_t offset) {
  return __pwritev64(fd, ios, count, offset, offset >> 32);
}

// There is no fallocate for 32-bit off_t, so we need to widen and call fallocate64.
int fallocate(int fd, int mode, off_t offset, off_t length) {
  return fallocate64(fd, mode, static_cast<off64_t>(offset), static_cast<off64_t>(length));
}

// There is no getrlimit64 system call, so we need to use prlimit64.
int getrlimit64(int resource, rlimit64* limits64) {
  return prlimit64(0, resource, NULL, limits64);
}

// There is no setrlimit64 system call, so we need to use prlimit64.
int setrlimit64(int resource, const rlimit64* limits64) {
  return prlimit64(0, resource, limits64, NULL);
}

// There is no prlimit system call, so we need to use prlimit64.
int prlimit(pid_t pid, int resource, const rlimit* n32, rlimit* o32) {
  rlimit64 n64;
  if (n32 != nullptr) {
    n64.rlim_cur = (n32->rlim_cur == RLIM_INFINITY) ? RLIM64_INFINITY : n32->rlim_cur;
    n64.rlim_max = (n32->rlim_max == RLIM_INFINITY) ? RLIM64_INFINITY : n32->rlim_max;
  }

  rlimit64 o64;
  int result = prlimit64(pid, resource,
                         (n32 != nullptr) ? &n64 : nullptr,
                         (o32 != nullptr) ? &o64 : nullptr);
  if (result != -1 && o32 != nullptr) {
    o32->rlim_cur = (o64.rlim_cur == RLIM64_INFINITY) ? RLIM_INFINITY : o64.rlim_cur;
    o32->rlim_max = (o64.rlim_max == RLIM64_INFINITY) ? RLIM_INFINITY : o64.rlim_max;
  }
  return result;
}