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    SubjectRE: X32 project status update
    I'll look at it but possibly not until the weekend.

    -----Original Message-----
    From: H.J. Lu [<>]
    Sent: Saturday, May 21, 2011 12:39 PM Pacific Standard Time
    To: Anvin, H Peter
    Cc:; Arnd Bergmann; GCC Development; GNU C Library; LKML
    Subject: Re: X32 project status update

    On Sat, May 21, 2011 at 11:55 AM, H. Peter Anvin
    <> wrote:
    > On 05/21/2011 09:27 AM, H.J. Lu wrote:
    >> On Sat, May 21, 2011 at 8:34 AM, H.J. Lu <> wrote:
    >>> On Sat, May 21, 2011 at 8:27 AM, Arnd Bergmann <> wrote:
    >>>> On Saturday 21 May 2011 17:01:33 H.J. Lu wrote:
    >>>>> This is the x32 project status update:
    >>>> I've had another look at the kernel patch. It basically
    >>>> looks all good, but the system call table appears to
    >>>> diverge from the x86_64 list for no (documented) reason,
    >>>> in the calls above 302. Is that intentional?
    >>>> I can see why you might want to keep the numbers identical,
    >>>> but if they are already different, why not use the generic
    >>>> system call table from asm-generic/unistd.h for the new
    >>>> ABI?
    >>> We can sort it out when we start merging x32 kernel changes.
    >> Peter, is that possible to use the single syscall table for
    >> both x86-64 and x32 system calls? Out of 300+ system
    >> calls, only 84 are different for x86-64 and x32. That
    >> is additional 8*84 == 672 bytes in syscall table.
    > Sort of... remember we talked about merging system calls at the tail
    > end? The problem with that is that some system calls (like read()!)
    > actually are different system calls in very subtle situations, due to
    > abuse in some subsystems of the is_compat() construct. I think that may
    > mean we have to have an unambiguous flag after all...
    > Now, perhaps we can use a high bit for that and mask it before dispatch,
    > then we don't need the additional table. A bit of a hack, but it should
    > work.

    How about this patch?

    Merge x32 system calls with x86-64 system calls

    Implemented with

    1. Mark all x86-64 specific system calls with __NR_64_.
    2. Mark all x32 specific system calls with __NR_x32_.
    3. Include unistd_64_compat.h, instead of unistd_x32.h for kernel
    build, which provides __NR_ versions of x86-64 specific system calls.
    4. Append x32 specific system calls after the current x86-64 system
    5. Generate unistd_x32.h from unistd_64.h, replacing __NR_x32_ with
    6. Install user-space unistd_64.h, replacing __NR_64_ with _NR_.

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