libc/src/__support/OSUtil/linux/fcntl.cpp

   1 //===-- Implementation of internal fcntl ----------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "src/__support/OSUtil/fcntl.h"
  10
  11 #include "hdr/fcntl_macros.h"
  12 #include "hdr/types/off_t.h"
  13 #include "hdr/types/struct_f_owner_ex.h"
  14 #include "hdr/types/struct_flock.h"
  15 #include "hdr/types/struct_flock64.h"
  16 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
  17 #include "src/__support/common.h"
  18 #include "src/__support/macros/config.h"
  19 #include "src/errno/libc_errno.h"
  20
  21 #include <stdarg.h>
  22 #include <sys/syscall.h> // For syscall numbers.
  23
  24 namespace LIBC_NAMESPACE_DECL {
  25 namespace internal {
  26
  27 int fcntl(int fd, int cmd, void *arg) {
  28 #if SYS_fcntl
  29   constexpr auto FCNTL_SYSCALL_ID = SYS_fcntl;
  30 #elif defined(SYS_fcntl64)
  31   constexpr auto FCNTL_SYSCALL_ID = SYS_fcntl64;
  32 #else
  33 #error "fcntl and fcntl64 syscalls not available."
  34 #endif
  35
  36   int new_cmd = cmd;
  37   switch (new_cmd) {
  38   case F_OFD_SETLKW: {
  39     struct flock *flk = reinterpret_cast<struct flock *>(arg);
  40     // convert the struct to a flock64
  41     struct flock64 flk64;
  42     flk64.l_type = flk->l_type;
  43     flk64.l_whence = flk->l_whence;
  44     flk64.l_start = flk->l_start;
  45     flk64.l_len = flk->l_len;
  46     flk64.l_pid = flk->l_pid;
  47     // create a syscall
  48     return LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd, new_cmd,
  49                                              &flk64);
  50   }
  51   case F_OFD_GETLK:
  52   case F_OFD_SETLK: {
  53     struct flock *flk = reinterpret_cast<struct flock *>(arg);
  54     // convert the struct to a flock64
  55     struct flock64 flk64;
  56     flk64.l_type = flk->l_type;
  57     flk64.l_whence = flk->l_whence;
  58     flk64.l_start = flk->l_start;
  59     flk64.l_len = flk->l_len;
  60     flk64.l_pid = flk->l_pid;
  61     // create a syscall
  62     int retVal = LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd,
  63                                                    new_cmd, &flk64);
  64     // On failure, return
  65     if (retVal == -1)
  66       return -1;
  67     // Check for overflow, i.e. the offsets are not the same when cast
  68     // to off_t from off64_t.
  69     if (static_cast<off_t>(flk64.l_len) != flk64.l_len ||
  70         static_cast<off_t>(flk64.l_start) != flk64.l_start) {
  71       libc_errno = EOVERFLOW;
  72       return -1;
  73     }
  74     // Now copy back into flk, in case flk64 got modified
  75     flk->l_type = flk64.l_type;
  76     flk->l_whence = flk64.l_whence;
  77     flk->l_start = static_cast<decltype(flk->l_start)>(flk64.l_start);
  78     flk->l_len = static_cast<decltype(flk->l_len)>(flk64.l_len);
  79     flk->l_pid = flk64.l_pid;
  80     return retVal;
  81   }
  82   case F_GETOWN: {
  83     struct f_owner_ex fex;
  84     int ret = LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd,
  85                                                 F_GETOWN_EX, &fex);
  86     if (ret >= 0)
  87       return fex.type == F_OWNER_PGRP ? -fex.pid : fex.pid;
  88     libc_errno = -ret;
  89     return -1;
  90   }
  91 #ifdef SYS_fcntl64
  92   case F_GETLK: {
  93     if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
  94       new_cmd = F_GETLK64;
  95     break;
  96   }
  97   case F_SETLK: {
  98     if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
  99       new_cmd = F_SETLK64;
 100     break;
 101   }
 102   case F_SETLKW: {
 103     if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
 104       new_cmd = F_SETLKW64;
 105     break;
 106   }
 107 #endif
 108   }
 109   int retVal = LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd, new_cmd,
 110                                                  reinterpret_cast<void *>(arg));
 111   if (retVal >= 0) {
 112     return retVal;
 113   }
 114   libc_errno = -retVal;
 115   return -1;
 116 }
 117
 118 } // namespace internal
 119 } // namespace LIBC_NAMESPACE_DECL