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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #undef _FORTIFY_SOURCE
     30 
     31 #include <errno.h>
     32 #include <fcntl.h>
     33 #include <stdarg.h>
     34 #include <sys/resource.h>
     35 #include <sys/types.h>
     36 #include <sys/uio.h>
     37 #include <sys/vfs.h>
     38 #include <unistd.h>
     39 
     40 #if __LP64__
     41 #error This code is only needed on 32-bit systems!
     42 #endif
     43 
     44 // System calls we need.
     45 extern "C" int __fcntl64(int, int, void*);
     46 extern "C" int __llseek(int, unsigned long, unsigned long, off64_t*, int);
     47 extern "C" int __preadv64(int, const struct iovec*, int, long, long);
     48 extern "C" int __pwritev64(int, const struct iovec*, int, long, long);
     49 
     50 // For fcntl we use the fcntl64 system call to signal that we're using struct flock64.
     51 int fcntl(int fd, int cmd, ...) {
     52   va_list ap;
     53 
     54   va_start(ap, cmd);
     55   void* arg = va_arg(ap, void*);
     56   va_end(ap);
     57 
     58   return __fcntl64(fd, cmd, arg);
     59 }
     60 
     61 // For lseek64 we need to use the llseek system call which splits the off64_t in two and
     62 // returns the off64_t result via a pointer because 32-bit kernels can't return 64-bit results.
     63 off64_t lseek64(int fd, off64_t off, int whence) {
     64   off64_t result;
     65   unsigned long off_hi = static_cast<unsigned long>(off >> 32);
     66   unsigned long off_lo = static_cast<unsigned long>(off);
     67   if (__llseek(fd, off_hi, off_lo, &result, whence) < 0) {
     68     return -1;
     69   }
     70   return result;
     71 }
     72 
     73 // There is no pread for 32-bit off_t, so we need to widen and call pread64.
     74 ssize_t pread(int fd, void* buf, size_t byte_count, off_t offset) {
     75   return pread64(fd, buf, byte_count, static_cast<off64_t>(offset));
     76 }
     77 
     78 // There is no pwrite for 32-bit off_t, so we need to widen and call pwrite64.
     79 ssize_t pwrite(int fd, const void* buf, size_t byte_count, off_t offset) {
     80   return pwrite64(fd, buf, byte_count, static_cast<off64_t>(offset));
     81 }
     82 
     83 // On LP32, there is no off_t preadv/pwritev, and even the 64-bit preadv/pwritev
     84 // don't use off64_t (see SYSCALLS.TXT for more). Here, this means that we need
     85 // to implement all four functions because the two system calls don't match any
     86 // of the userspace functions. Unlike llseek, the pair is split lo-hi, not hi-lo.
     87 ssize_t preadv(int fd, const struct iovec* ios, int count, off_t offset) {
     88   return __preadv64(fd, ios, count, offset, 0);
     89 }
     90 ssize_t preadv64(int fd, const struct iovec* ios, int count, off64_t offset) {
     91   return __preadv64(fd, ios, count, offset, offset >> 32);
     92 }
     93 ssize_t pwritev(int fd, const struct iovec* ios, int count, off_t offset) {
     94   return __pwritev64(fd, ios, count, offset, 0);
     95 }
     96 ssize_t pwritev64(int fd, const struct iovec* ios, int count, off64_t offset) {
     97   return __pwritev64(fd, ios, count, offset, offset >> 32);
     98 }
     99 
    100 // There is no fallocate for 32-bit off_t, so we need to widen and call fallocate64.
    101 int fallocate(int fd, int mode, off_t offset, off_t length) {
    102   return fallocate64(fd, mode, static_cast<off64_t>(offset), static_cast<off64_t>(length));
    103 }
    104 
    105 // There is no getrlimit64 system call, so we need to use prlimit64.
    106 int getrlimit64(int resource, rlimit64* limits64) {
    107   return prlimit64(0, resource, NULL, limits64);
    108 }
    109 
    110 // There is no setrlimit64 system call, so we need to use prlimit64.
    111 int setrlimit64(int resource, const rlimit64* limits64) {
    112   return prlimit64(0, resource, limits64, NULL);
    113 }
    114 
    115 // There is no prlimit system call, so we need to use prlimit64.
    116 int prlimit(pid_t pid, int resource, const rlimit* n32, rlimit* o32) {
    117   rlimit64 n64;
    118   if (n32 != nullptr) {
    119     n64.rlim_cur = (n32->rlim_cur == RLIM_INFINITY) ? RLIM64_INFINITY : n32->rlim_cur;
    120     n64.rlim_max = (n32->rlim_max == RLIM_INFINITY) ? RLIM64_INFINITY : n32->rlim_max;
    121   }
    122 
    123   rlimit64 o64;
    124   int result = prlimit64(pid, resource,
    125                          (n32 != nullptr) ? &n64 : nullptr,
    126                          (o32 != nullptr) ? &o64 : nullptr);
    127   if (result != -1 && o32 != nullptr) {
    128     o32->rlim_cur = (o64.rlim_cur == RLIM64_INFINITY) ? RLIM_INFINITY : o64.rlim_cur;
    129     o32->rlim_max = (o64.rlim_max == RLIM64_INFINITY) ? RLIM_INFINITY : o64.rlim_max;
    130   }
    131   return result;
    132 }
    133