mirror of
https://github.com/jart/cosmopolitan.git
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100 lines
4.3 KiB
C
100 lines
4.3 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/sysv/consts/msync.h"
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#include "libc/assert.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/cp.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/describeflags.h"
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#include "libc/intrin/strace.h"
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#include "libc/macros.internal.h"
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#include "libc/sysv/errfuns.h"
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/**
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* Synchronize memory mapping changes to disk.
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*
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* Without this, there's no guarantee memory is written back to disk.
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* Particularly on RHEL5, OpenBSD, and Windows NT.
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*
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* @param addr needs to be 4096-byte page aligned
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* @param flags needs MS_ASYNC or MS_SYNC and can have MS_INVALIDATE
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* @return 0 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 we needed to block and a signal was delivered instead
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* @raise EINVAL if `MS_SYNC` and `MS_ASYNC` were both specified
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* @raise EINVAL if unknown `flags` were passed
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* @cancelationpoint
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*/
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int msync(void *addr, size_t size, int flags) {
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int rc;
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if ((flags & ~(MS_SYNC | MS_ASYNC | MS_INVALIDATE)) ||
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(flags & (MS_SYNC | MS_ASYNC)) == (MS_SYNC | MS_ASYNC)) {
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rc = einval();
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goto Finished;
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}
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// According to POSIX, either MS_SYNC or MS_ASYNC must be specified
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// in flags, and indeed failure to include one of these flags will
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// cause msync() to fail on some systems. However, Linux permits a
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// call to msync() that specifies neither of these flags, with
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// semantics that are (currently) equivalent to specifying MS_ASYNC.
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// ──Quoth msync(2) of Linux Programmer's Manual
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int sysflags = flags;
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sysflags = flags;
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if (flags & MS_ASYNC) {
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sysflags = MS_ASYNC;
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} else if (flags & MS_SYNC) {
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sysflags = MS_SYNC;
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} else {
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sysflags = MS_ASYNC;
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}
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if (flags & MS_INVALIDATE) {
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sysflags |= MS_INVALIDATE;
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}
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// FreeBSD's manual says "The flags argument was both MS_ASYNC and
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// MS_INVALIDATE. Only one of these flags is allowed." which makes
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// following the POSIX recommendation somewhat difficult.
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if (IsFreebsd()) {
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if (sysflags == (MS_ASYNC | MS_INVALIDATE)) {
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sysflags = MS_INVALIDATE;
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}
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}
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// FreeBSD specifies MS_SYNC as 0 so we shift the Cosmo constants
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if (IsFreebsd()) {
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sysflags >>= 1;
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}
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BEGIN_CANCELATION_POINT;
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if (!IsWindows()) {
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rc = sys_msync(addr, size, sysflags);
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} else {
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rc = sys_msync_nt(addr, size, sysflags);
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}
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END_CANCELATION_POINT;
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Finished:
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STRACE("msync(%p, %'zu, %s) → %d% m", addr, size, DescribeMsyncFlags(flags),
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rc);
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return rc;
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}
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