On Tue, 23 Aug 2005, Ulrich Drepper wrote: > Linus Torvalds wrote: > > Actually, it should be pretty much as valid as using mremap - ie it works > > on Linux. > > > > Especially if you use MAP_SHARED, you don't even need to mprotect > > anything: you'll get a nice SIGBUS if you ever try to access past the last > > page that maps the file. > > If you guarantee this (and test for this) it's fine with me. The POSIX > spec explicitly leaves this undefined and requiring to use mremap() > would be a nice way to work around this without allowing the > introduction of undefined behavior into programs. I probably would > prefer to use mremap() since this makes it clear what should happen but > I can live with using the too-large mapping.
I don't have spec to hand to quote, but at least 10 years ago the SIGBUS beyond end of file was required behaviour, on both MAP_SHARED and more surprisingly MAP_PRIVATE mappings of a file. Well, you don't get SIGBUS on any part of the page that covers the end of the file: perhaps what you read as undefined in the spec is addressing that tail page issue. We guarantee it: it's a kernel bug if it doesn't work. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
