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Re: RFC: Add 32bit x86-64 support to binutils
On Thu, Dec 30, 2010 at 12:27 PM, David Daney <ddaney@caviumnetworks.com> wrote:
> On 12/30/2010 12:12 PM, H. Peter Anvin wrote:
>>
>> On 12/30/2010 11:34 AM, David Daney wrote:
>>>
>>> My suggestion: ?Since people already spend a great deal of effort
>>> maintaining the existing i386 compatible Linux syscall infrastructure,
>>> make your new 32-bit x86-64 Linux syscall ABI identical to the existing
>>> i386 syscall ABI. ?This means that the psABI must use the same size and
>>> alignment rules for in-memory structures as the i386 does.
>>>
>>
>> No, it doesn't. ?It just means it need to do so *for the types used by
>> the kernel*. ?The kernel uses types like __u64, which would indeed have
>> to be declared aligned(4).
>>
>
> Some legacy interfaces don't use fixed width types. ?There almost certainly
> are some ioctls that don't use your fancy __u64.
>
> Then there are things like ppoll() that take a pointer to:
>
> ? ? ? ? ? struct timespec {
> ? ? ? ? ? ? ? long ? ?tv_sec; ? ? ? ? /* seconds */
> ? ? ? ? ? ? ? long ? ?tv_nsec; ? ? ? ?/* nanoseconds */
> ? ? ? ? ? };
>
> There are no fields in there that are controlled by __u64 either. Admittedly
> this case might not differ between the two 32-bit ABIs, but it shows that
> __u64/__u32 are not universally used in the Linux syscall ABIs.
>
> If you are happy with potential memory layout differences between the two
> 32-bit ABIs, then don't specify that they are the same. ?But don't claim
> that use of __u64/__u32 covers all cases.
We can put a syscall wrapper to translate it.
--
H.J.