libc/src/unistd/linux/readlink.cpp

   1 //===-- Linux implementation of readlink ----------------------------------===//
   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/unistd/readlink.h"
  10
  11 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
  12 #include "src/__support/common.h"
  13
  14 #include "src/errno/libc_errno.h"
  15 #include <fcntl.h>
  16 #include <sys/syscall.h> // For syscall numbers.
  17
  18 namespace LIBC_NAMESPACE {
  19
  20 LLVM_LIBC_FUNCTION(ssize_t, readlink,
  21                    (const char *__restrict path, char *__restrict buf,
  22                     size_t bufsize)) {
  23 #ifdef SYS_readlink
  24   ssize_t ret =
  25       LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_readlink, path, buf, bufsize);
  26 #elif defined(SYS_readlinkat)
  27   ssize_t ret = LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_readlinkat, AT_FDCWD,
  28                                                       path, buf, bufsize);
  29 #else
  30 #error "readlink or readlinkat syscalls not available."
  31 #endif
  32   if (ret < 0) {
  33     libc_errno = static_cast<int>(-ret);
  34     return -1;
  35   }
  36   return ret;
  37 }
  38
  39 } // namespace LIBC_NAMESPACE