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SubjectRe: RFD: x32 ABI system call numbers
On 08/31/2011 08:09 PM, H. Peter Anvin wrote:
> > I really think that "x32" should try to aim *VERY* hard at using the
> > 64-bit system calls, and seeing itself as being a "32-bit application
> > in a 64-bit world". That's not just true for time_t (which I think
> > should be 64-bit on anything new that expects to survive for any
> > amount of time), but in general.
> We're trying for it. The things we're trying to avoid is to muck (too
> much) with the compat layer for the mega-multiplex system calls like
> ioctl. We can't just use the 64-bit ioctl because ioctl structures
> generally contain pointers.

struct iovec
void __user *iov_base; /* BSD uses caddr_t (1003.1g requires
void *) */
__kernel_size_t iov_len; /* Must be size_t (1003.1g) */
} __attribute__((x32_abi_64));

typedef long time_t __attribute__((x32_abi_64));

The x32_abi_64 attribute converts pointers and longs back to 64-bit and
adjusts the alignment accordingly. If we tag all userspace visible
structures with this attribute, we can use the 64-bit ABI without changes.

&my_iovec->iov_base yields something that is not a void ** (reads of a
64-bit pointer decay to a 32-bit pointer, writes zero extend).
printf formats will break
if someone embeds an iovec in a structure, it will occupy more space
than expected

error compiling committee.c: too many arguments to function

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