Date: Tue, 18 Oct 2011 09:35:00 -0700 From: Garrett Cooper <yanegomi@gmail.com> To: Arnaud Lacombe <lacombar@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: <F10D8DB1-C693-4D0B-BB2D-C3A8F0302DC5@gmail.com> In-Reply-To: <CACqU3MWOXTMfu0LySukcwAz=NGSzyN=ettiY0fQj3Ehp5MONug@mail.gmail.com> 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> <CACqU3MWOXTMfu0LySukcwAz=NGSzyN=ettiY0fQj3Ehp5MONug@mail.gmail.com>
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On Oct 18, 2011, at 9:26 AM, Arnaud Lacombe wrote: > Hi, >=20 > On Tue, Oct 18, 2011 at 11:44 AM, Garrett Cooper <yanegomi@gmail.com> = wrote: >> On Tue, 18 Oct 2011, Arnaud Lacombe wrote: >>=20 >>> Hi, >>>=20 >>> On Tue, Oct 18, 2011 at 5:07 AM, Kostik Belousov = <kostikbel@gmail.com> >>> wrote: >>>>=20 >>>> On Mon, Oct 17, 2011 at 09:30:56PM +0200, Oliver Pinter wrote: >>>>>=20 >>>>> Hi all! >>>>>=20 >>>>> I think, it's the time to enable the nxstack feature. Any = comments, >>>>> pros, cons? >>>>=20 >>>> 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. >>>>=20 >>>> 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; >>>> SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, >>>> &elf_legacy_coredump, 0, ""); >>>>=20 >>>> -static int __elfN(nxstack) =3D 0; >>>> +int __elfN(nxstack) =3D >>>> +#if defined(__amd64__) || defined(__powerpc64__) /* both 64 and 32 = bit >>>> */ >>>>=20 >>> Why leaving 32bits x86 CPU supporting the NX feature behind ? >>=20 >> 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 Dual >> Core Pentiums, e.g. the Yonahs to not talk 64-bit. Not sure about = AMD. >>=20 >> There are probably more details in binutils, gcc, etc, that I'm = missing and >> Kostik can expound on. >>=20 > 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. >=20 > If nonexec_stack becomes the default, it should be on every CPU > supporting the feature, not just the low-hanging one. It gets a bit trickier because now you're putting MD code into MI code, = but that should be easy enough to abstract out into amd64, i386, etc. Still wondering if the toolchain is lacking support though, because I = remember a few committers (dim?, kib?) making some modifications in = order to get NX working about a year ago. -Garrett=
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