Date: Tue, 18 Oct 2011 12:26:36 -0400 From: Arnaud Lacombe <lacombar@gmail.com> To: Garrett Cooper <yanegomi@gmail.com> Cc: Kostik Belousov <kostikbel@gmail.com>, current@freebsd.org, Oliver Pinter <oliver.pntr@gmail.com> Subject: Re: [RFC] Enable nxstack by default Message-ID: <CACqU3MWOXTMfu0LySukcwAz=NGSzyN=ettiY0fQj3Ehp5MONug@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1110180838200.38610@toaster.local> References: <CAPjTQNFCT5LBKwVQFf9FHk4aTzrJ243j2uN1nPmMeFp=cTdMUA@mail.gmail.com> <20111018090750.GG50300@deviant.kiev.zoral.com.ua> <CACqU3MWftO=FG4GbnKCFjTcKg1narJWuYnCwv-Mcu=WGriScwA@mail.gmail.com> <alpine.BSF.2.00.1110180838200.38610@toaster.local>
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Hi, On Tue, Oct 18, 2011 at 11:44 AM, Garrett Cooper <yanegomi@gmail.com> wrote= : > On Tue, 18 Oct 2011, Arnaud Lacombe wrote: > >> Hi, >> >> On Tue, Oct 18, 2011 at 5:07 AM, Kostik Belousov <kostikbel@gmail.com> >> wrote: >>> >>> On Mon, Oct 17, 2011 at 09:30:56PM +0200, Oliver Pinter wrote: >>>> >>>> Hi all! >>>> >>>> I think, it's the time to enable the nxstack feature. Any comments, >>>> pros, cons? >>> >>> I dragged the change long enough for it to miss the 9.0. >>> After the 9.0 is released, I will flip the switch with the following >>> change. >>> >>> diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c >>> index 8455f48..926fe64 100644 >>> --- a/sys/kern/imgact_elf.c >>> +++ b/sys/kern/imgact_elf.c >>> @@ -118,7 +118,12 @@ static int elf_legacy_coredump =3D 0; >>> =A0SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, >>> =A0 =A0 &elf_legacy_coredump, 0, ""); >>> >>> -static int __elfN(nxstack) =3D 0; >>> +int __elfN(nxstack) =3D >>> +#if defined(__amd64__) || defined(__powerpc64__) /* both 64 and 32 bit >>> */ >>> >> Why leaving 32bits x86 CPU supporting the NX feature behind ? > > Most likely because it was assumed that i386 doesn't fully support it. > According to ye great Wikipedia, NX support didn't roll into i386 until > Prescott, which was pretty late in the non-64-bit capable family of CPUs,= as > its successor -- Conroe -- was 64-bit. Intel detuned some of the early Du= al > Core Pentiums, e.g. the Yonahs to not talk 64-bit. Not sure about AMD. > > There are probably more details in binutils, gcc, etc, that I'm missing a= nd > Kostik can expound on. > NX support is advertised in the cpuid flags, just add the logic to handle this interface. Kostik's patch is just incomplete, but he's got a commit bit so he can commit it as-is, as he will. If nonexec_stack becomes the default, it should be on every CPU supporting the feature, not just the low-hanging one. - Arnaud
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