| //===-- Linux implementation of dup2 --------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "src/unistd/dup2.h" |
| |
| #include "src/__support/OSUtil/syscall.h" // For internal syscall function. |
| #include "src/__support/common.h" |
| |
| #include "src/errno/libc_errno.h" |
| #include <fcntl.h> |
| #include <sys/syscall.h> // For syscall numbers. |
| |
| namespace LIBC_NAMESPACE { |
| |
| LLVM_LIBC_FUNCTION(int, dup2, (int oldfd, int newfd)) { |
| #ifdef SYS_dup2 |
| // If dup2 syscall is available, we make use of directly. |
| int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_dup2, oldfd, newfd); |
| #elif defined(SYS_dup3) |
| // If dup2 syscall is not available, we try using the dup3 syscall. However, |
| // dup3 fails if oldfd is the same as newfd. So, we handle that case |
| // separately before making the dup3 syscall. |
| if (oldfd == newfd) { |
| // Check if oldfd is actually a valid file descriptor. |
| #if SYS_fcntl |
| int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_fcntl, oldfd, F_GETFD); |
| #elif defined(SYS_fcntl64) |
| // Same as fcntl but can handle large offsets |
| static_assert(sizeof(off_t) == 8); |
| int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_fcntl64, oldfd, F_GETFD); |
| #else |
| #error "SYS_fcntl and SYS_fcntl64 syscalls not available." |
| #endif |
| if (ret >= 0) |
| return oldfd; |
| libc_errno = -ret; |
| return -1; |
| } |
| int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_dup3, oldfd, newfd, 0); |
| #else |
| #error "dup2 and dup3 syscalls not available." |
| #endif |
| if (ret < 0) { |
| libc_errno = -ret; |
| return -1; |
| } |
| return ret; |
| } |
| |
| } // namespace LIBC_NAMESPACE |