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Date: Fri, 30 Mar 2007 21:44:24 +0800 From: "Aubrey Li" <aubreylee@...il.com> To: "David Howells" <dhowells@...hat.com> Cc: vapier.adi@...il.com, jie.zhang@...log.com, bryan.wu@...log.com, "Andrew Morton" <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] nommu arch dont zero the anonymous mapping by adding UNINITIALIZE flag On 3/30/07, David Howells <dhowells@...hat.com> wrote: > Aubrey Li <aubreylee@...il.com> wrote: > > > malloc() allocates size bytes and returns a pointer to the allocated memory. > > ****The memory is not cleared.**** > > But this is *not* malloc(). It's mmap(). Are you prepared to guarantee that > there are no applications out there that don't rely on anon mmap() giving > zeroed memory? I can't find mmap must give zeroed memory in the mmap manual. Is there any reason relying on anon mmap() giving zerod memory? Can you show me an example? > > The MMU-mode clearing is done for security reasons - there shouldn't be any > leakage between processes, and because the zero page can just be faulted in. > NO-MMU can't do this clearing. Performance is down. > Personally, I'd prefer to maintain compatibility with MMU-mode wherever > possible, but I'm happy with overrides like the MAP_UNINITIALISED flag > suggested. > Not necessary IMHO. -Aubrey - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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