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Fix msync() flags on FreeBSD

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Justine Tunney 2023-08-21 04:15:05 -07:00
parent ebf784d4f5
commit fffcd98b0e
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GPG key ID: BE714B4575D6E328
7 changed files with 95 additions and 15 deletions
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54
libc/runtime/msync.c
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@ -25,6 +25,7 @@
#include "libc/dce.h"
#include "libc/intrin/strace.internal.h"
#include "libc/macros.internal.h"
#include "libc/sysv/errfuns.h"
/**
* Synchronize memory mapping changes to disk.
@ -37,20 +38,61 @@
* @return 0 on success or -1 w/ errno
* @raise ECANCELED if thread was cancelled in masked mode
* @raise EINTR if we needed to block and a signal was delivered instead
* @raise EINVAL if `MS_SYNC` and `MS_ASYNC` were both specified
* @raise EINVAL if unknown `flags` were passed
* @cancellationpoint
*/
int msync(void *addr, size_t size, int flags) {
int rc;
BEGIN_CANCELLATION_POINT;
unassert(((flags & MS_SYNC) ^ (flags & MS_ASYNC)) || !(MS_SYNC && MS_ASYNC));
if (!IsWindows()) {
rc = sys_msync(addr, size, flags);
} else {
rc = sys_msync_nt(addr, size, flags);
if ((flags & ~(MS_SYNC | MS_ASYNC | MS_INVALIDATE)) ||
(flags & (MS_SYNC | MS_ASYNC)) == (MS_SYNC | MS_ASYNC)) {
rc = einval();
goto Finished;
}
// According to POSIX, either MS_SYNC or MS_ASYNC must be specified
// in flags, and indeed failure to include one of these flags will
// cause msync() to fail on some systems. However, Linux permits a
// call to msync() that specifies neither of these flags, with
// semantics that are (currently) equivalent to specifying MS_ASYNC.
// ──Quoth msync(2) of Linux Programmer's Manual
int sysflags = flags;
sysflags = flags;
if (flags & MS_ASYNC) {
sysflags = MS_ASYNC;
} else if (flags & MS_SYNC) {
sysflags = MS_SYNC;
} else {
sysflags = MS_ASYNC;
}
if (flags & MS_INVALIDATE) {
sysflags |= MS_INVALIDATE;
}
// FreeBSD's manual says "The flags argument was both MS_ASYNC and
// MS_INVALIDATE. Only one of these flags is allowed." which makes
// following the POSIX recommendation somewhat difficult.
if (IsFreebsd()) {
if (sysflags == (MS_ASYNC | MS_INVALIDATE)) {
sysflags = MS_INVALIDATE;
}
}
// FreeBSD specifies MS_SYNC as 0 so we shift the Cosmo constants
if (IsFreebsd()) {
sysflags >>= 1;
}
BEGIN_CANCELLATION_POINT;
if (!IsWindows()) {
rc = sys_msync(addr, size, sysflags);
} else {
rc = sys_msync_nt(addr, size, sysflags);
}
END_CANCELLATION_POINT;
Finished:
STRACE("msync(%p, %'zu, %#x) → %d% m", addr, size, flags, rc);
return rc;
}