mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
3f0bcdc3ef
- Exhaustively document cancellation points - Rename SIGCANCEL to SIGTHR just like BSDs - Further improve POSIX thread cancellations - Ensure asynchronous cancellations work correctly - Elevate the quality of getrandom() and getentropy() - Make futexes cancel correctly on OpenBSD 6.x and 7.x - Add reboot.com and shutdown.com to examples directory - Remove underscore prefix from awesome timespec_*() APIs - Create assertions that help verify our cancellation points - Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)
115 lines
4.5 KiB
C
115 lines
4.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net 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/dce.h"
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#include "libc/errno.h"
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#include "libc/runtime/runtime.h"
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#include "libc/stdio/rand.h"
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#include "libc/stdio/temp.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/o.h"
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#define _O_TMPFILE 000020200000
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/**
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* Returns file descriptor of open anonymous file, e.g.
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*
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* int fd;
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* if ((fd = tmpfd()) == -1) {
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* perror("tmpfd");
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* exit(1);
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* }
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* // do stuff
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* close(f);
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*
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* This creates a secure temporary file inside $TMPDIR. If it isn't
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* defined, then /tmp is used on UNIX and GetTempPath() is used on the
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* New Technology. This resolution of $TMPDIR happens once in a ctor,
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* which is copied to the `kTmpDir` global.
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*
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* Once close() is called, the returned file is guaranteed to be deleted
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* automatically. On UNIX the file is unlink()'d before this function
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* returns. On the New Technology it happens upon close().
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*
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* On newer Linux only (c. 2013) it's possible to turn the anonymous
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* returned file back into a real file, by doing this:
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*
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* linkat(AT_FDCWD, _gc(xasprintf("/proc/self/fd/%d", fd)),
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* AT_FDCWD, "real.txt", AT_SYMLINK_FOLLOW)
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*
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* On the New Technology, temporary files created by this function
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* should have better performance, because `kNtFileAttributeTemporary`
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* asks the kernel to more aggressively cache and reduce i/o ops.
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*
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* The tmpfd() function should be favored over `open(O_TMPFILE)` because
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* the latter only works on Linux, and will cause open() failures on all
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* other platforms.
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*
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* @return file descriptor on success, or -1 w/ errno
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* @raise ECANCELED if thread was cancelled in masked mode
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* @raise EINTR if signal was delivered
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* @see tmpfile() for stdio version
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* @cancellationpoint
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* @asyncsignalsafe
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* @threadsafe
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* @vforksafe
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*/
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int tmpfd(void) {
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FILE *f;
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unsigned x;
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int fd, i, j, e;
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char path[PATH_MAX], *p;
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e = errno;
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if (IsLinux() && (fd = open(kTmpPath, O_RDWR | _O_TMPFILE, 0600)) != -1) {
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return fd;
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}
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errno = e;
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p = path;
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p = stpcpy(p, kTmpPath);
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p = stpcpy(p, "tmp.");
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if (program_invocation_short_name &&
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strlen(program_invocation_short_name) < 128) {
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p = stpcpy(p, program_invocation_short_name);
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*p++ = '.';
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}
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for (i = 0; i < 10; ++i) {
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x = _rand64();
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for (j = 0; j < 6; ++j) {
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p[j] = "0123456789abcdefghijklmnopqrstuvwxyz"[x % 36];
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x /= 36;
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}
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p[j] = 0;
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e = errno;
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if ((fd = open(path,
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O_RDWR | O_CREAT | O_EXCL | (IsWindows() ? _O_TMPFILE : 0),
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0600)) != -1) {
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if (!IsWindows()) {
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if (unlink(path)) {
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notpossible;
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}
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}
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return fd;
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} else if (errno == EEXIST) {
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errno = e;
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} else {
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break;
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}
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}
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return -1;
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}
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