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Re: [Question] New mmap64 syscall?

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  Re: [Question] New mmap64 syscall? Florian Weimer <fweimer@redhat.com> - 2016-12-07 14:30 +0100
    Re: [Question] New mmap64 syscall? Florian Weimer <fweimer@redhat.com> - 2016-12-08 17:00 +0100

#1537747 — Re: [Question] New mmap64 syscall?

On 12/06/2016 07:54 PM, Yury Norov wrote:
> 3. Introduce new mmap64() syscall like this:
> sys_mmap64(void *addr, size_t len, int prot, int flags, int fd, struct off_pair *off);
> (The pointer here because otherwise we have 7 args, if simply pass off_hi and
> off_lo in registers.)

I would prefer a batched mmap/munmap/mremap/mprotect/madvise interface, 
so that VM changes can be coalesced and the output reduced.  This 
interface could then be used to implement mmap on 32-bit architectures 
as well because the offset restrictions would not apply there.

Thanks,
Florian

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#1538656

On 12/07/2016 04:48 PM, Yury Norov wrote:
> On Wed, Dec 07, 2016 at 02:23:55PM +0100, Florian Weimer wrote:
>> On 12/06/2016 07:54 PM, Yury Norov wrote:
>>> 3. Introduce new mmap64() syscall like this:
>>> sys_mmap64(void *addr, size_t len, int prot, int flags, int fd, struct off_pair *off);
>>> (The pointer here because otherwise we have 7 args, if simply pass off_hi and
>>> off_lo in registers.)
>>
>> I would prefer a batched mmap/munmap/mremap/mprotect/madvise interface, so
>> that VM changes can be coalesced and the output reduced.  This interface
>> could then be used to implement mmap on 32-bit architectures as well because
>> the offset restrictions would not apply there.
>
> Hi Florian,
>
> I frankly don't understand what you mean, All syscalls you mentioned
> doesn't take off_t or other 64-bit arguments. 'VM changes' - virtual
> memory? If so, I don't see any changes in VM with this approach, just
> correct handling of big offsets.

What I was trying to suggest is a completely different interface which 
is not subject to register size constraints and which has been requested 
before (a mechanism for batching mm updates).

Thanks,
Florian

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