Adding a MACHINE_ARCH note

[Warner Losh]

On Jul 9, 2013, at 7:08 PM, Peter Wemm wrote:

> On Tue, Jul 9, 2013 at 5:56 PM, Adrian Chadd <adrian at freebsd.org> wrote:
>> ... boy I'd like to see this particular x86 hiccup fixed before this
>> stuff is mainstream.
> 
> I'm not entirely sure how much support there is behind "x32".  I don't
> know if its much more than an academic curiosity or if there's real
> demand for it.  gcc-4.8 and clang have it, or have patches for it.
> 
> https://sites.google.com/site/x32abi/
> 
> http://www.phoronix.com/scan.php?page=news_item&px=MTExNDE

If FreeBSD ever does support x32, we'd do what we do on MIPS for the odd-ball n32 where we have mipsn32 as the uname -p.

Warner

> 
>> adrian
>> 
>> On 9 July 2013 17:54, Peter Wemm <peter at wemm.org> wrote:
>>> On Tue, Jul 9, 2013 at 5:40 PM, Adrian Chadd <adrian at freebsd.org> wrote:
>>>> Someone pointed out there's dirty people running 32-bit binaries using
>>>> the 64-bit intel/amd instruction set.
>>>> 
>>>> Is this also able to represent that?
>>> 
>>> That would be "X32", so there's 3 x86 ABI variants:
>>> i386 - 32 bit
>>> amd64 - 32 bit
>>> amd64 - 64 bit
>>> 
>>> Incidentally, pkgng has a issues with this.  For some reason it lumps
>>> both i386 and amd64 into a single pseudo-arch called "x86" with a 32
>>> and 64 bit variant.  It doesn't leave room for distinguishing the two
>>> incompatible 32 bit architectures.
>>> 
>>> "x32" is where the compiler generates code where "long" and "pointer"
>>> are 32 bit, but the instruction set is otherwise amd64 and has all 16
>>> general purpose registers available.   "long long" is a 64 bit
>>> register instead of a pair of 32 bit registers like on i386.
>>> 
>>>> -adrian
>>>> 
>>>> On 9 July 2013 15:48, Andrew Turner <andrew at fubar.geek.nz> wrote:
>>>>> On Tue, 9 Jul 2013 08:19:46 -0600
>>>>> Warner Losh <imp at bsdimp.com> wrote:
>>>>>> I thought that the ELF headers gave us all the data we needed to know
>>>>>> how things were built...
>>>>> 
>>>>> It will tell us if it was for e.g. an ARM or MIPS ELF file, but I'm not
>>>>> sure how we can tell the difference between an arm and an armv6 ELF.
>>>>> 
>>>>> With armv6 there are a few changes in the userland/kernel
>>>>> interface, e.g. reading the thread local storage pointer is different
>>>>> such that an armv6 static binary would not run on an ARMv5 core as it
>>>>> uses newer instructions.
>>>>> 
>>>>> Andrew
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>>> 
>>> 
>>> 
>>> --
>>> Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com; KI6FJV
>>> UTF-8: So you can \342\200\231 .. for when a ' just won't do
>>> <brueffer> ZFS must be the bacon of file systems. "everything's better with ZFS"
> 
> 
> 
> -- 
> Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com; KI6FJV
> UTF-8: So you can \342\200\231 .. for when a ' just won't do
> <brueffer> ZFS must be the bacon of file systems. "everything's better with ZFS"
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