mirror of
https://github.com/jart/cosmopolitan.git
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104 lines
4.7 KiB
C
104 lines
4.7 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/calls/internal.h"
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#include "libc/calls/state.internal.h"
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#include "libc/calls/syscall-nt.internal.h"
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#include "libc/calls/syscall-sysv.internal.h"
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#include "libc/dce.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/intrin/strace.h"
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#include "libc/intrin/weaken.h"
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#include "libc/runtime/zipos.internal.h"
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#include "libc/str/str.h"
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#include "libc/sysv/errfuns.h"
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/**
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* Duplicates file descriptor, granting it specific number.
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*
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* Unlike dup3(), the dup2() function permits oldfd and newfd to be the
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* same, in which case the only thing this function does is test if
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* oldfd is open.
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*
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* The `O_CLOEXEC` flag shall be cleared from the resulting file
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* descriptor; see dup3() to preserve it.
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*
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* One use case for duplicating file descriptors is to be able to
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* reassign an open()'d file or pipe() to the stdio of an executed
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* subprocess. On Windows, in order for this to work, the subprocess
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* needs to be a Cosmopolitan program that has socket() linked.
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*
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* Only small programs should duplicate sockets. That's because this
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* implementation uses DuplicateHandle() on Windows, which Microsoft
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* says might cause its resources to leak internally. Thus it likely
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* isn't a good idea to design a server that does it a lot and lives
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* a long time, without contributing a patch to this implementation.
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*
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* @param oldfd isn't closed afterwards
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* @param newfd if already assigned, is silently closed beforehand;
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* unless it's equal to oldfd, in which case dup2() is a no-op
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* @return new file descriptor, or -1 w/ errno
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* @raise EPERM if pledge() is in play without stdio
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* @raise EMFILE if `RLIMIT_NOFILE` has been reached
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* @raise ENOTSUP if `oldfd` is on zip file system
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* @raise EINTR if a signal handler was called
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* @raise EBADF is `newfd` negative or too big
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* @raise EBADF is `oldfd` isn't open
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* @asyncsignalsafe
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* @vforksafe
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*/
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int dup2(int oldfd, int newfd) {
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int rc;
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// helps guarantee stderr log gets duplicated before user closes
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if (_weaken(kloghandle))
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_weaken(kloghandle)();
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#ifdef __aarch64__
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if (oldfd == newfd) {
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// linux aarch64 defines dup3() but not dup2(), which wasn't such a
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// great decision, since the two syscalls don't behave the same way
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if (!(rc = read(oldfd, 0, 0)))
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rc = oldfd;
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} else
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#endif
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if (!IsWindows()) {
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if (__isfdkind(oldfd, kFdZip) || __isfdkind(newfd, kFdZip)) {
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if (__vforked) {
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return enotsup();
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}
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rc = sys_dup2(oldfd, newfd, 0);
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if (rc != -1) {
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_weaken(__zipos_postdup)(oldfd, newfd);
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}
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} else {
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rc = sys_dup2(oldfd, newfd, 0);
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}
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} else if (newfd < 0) {
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rc = ebadf();
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} else if (oldfd == newfd) {
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if (__isfdopen(oldfd)) {
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rc = newfd;
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} else {
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rc = ebadf();
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}
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} else {
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rc = sys_dup_nt(oldfd, newfd, 0, -1);
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}
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STRACE("dup2(%d, %d) → %d% m", oldfd, newfd, rc);
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return rc;
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}
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