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.
David Daney
