Re: futex(2) man page update help request

["H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>]

On 05/15/2014 08:42 AM, chrubis-AlSwsSmVLrQ@public.gmane.org wrote:
> Hi!
>> People have a number of times noted that there are problems
>> with syscall(), but I'm not knowledgeable on the details.
>> I'd happily take a patch to the man page (which, for historical
>> reasons, is actually syscall(2)) that explains the the problems 
>> (and ideally notes those platforms where there are no problems).
> 
> Have a look at this commit that tries to deal with passing 64 bit
> numbers to syscalls. On 32 bit ABI (but not on X32) these needs to be
> split up (accordingly to machine endianity).
> 
> https://github.com/linux-test-project/ltp/commit/04afb02b4280a20c262054e8f99a3fad4ad54916
> 

That is wrong, too.  That assumes that there will never be padding
words, which isn't true in the general case, either.

I really believe the proper fix is to use assembly syscall stubs.  In
klibc I build a fairly elaborate machinery to autogenerate such syscall
stubs for a variety of architectures.

	-hpa

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