[PATCH] Add SYSCALL_LONG/SYSCALL_ULONG to pass long to syscall [BZ #25810]

[Florian Weimer]

* H. J. Lu:

> On Sat, Apr 11, 2020 at 7:45 AM Florian Weimer <fw@deneb.enyo.de> wrote:
>>
>> * H. J. Lu:
>>
>> > On Sat, Apr 11, 2020 at 3:01 AM Florian Weimer <fw@deneb.enyo.de> wrote:
>> >>
>> >> * H. J. Lu via Libc-alpha:
>> >>
>> >> > For inline syscalls, SYSCALL_LONG and SYSCALL_ULONG are introduced as
>> >> > wrappers for long and unsigned long arguments.
>> >>
>> >> Do the arguments have the correct types?  Then I think you can do the
>> >
>> > Yes, they have correct types.  But it is not the problem.  Take this example:
>> >
>> > int munmap(void *addr, size_t length);
>> >
>> > The type of length is unsigned int (size_t) for x32 and is unsigned long
>> > (64bit) in kernel.  We have no way to know the type which kernel expects.
>>
>> Is it possible to extend all 32-bit arguments?  Ot is this incorrect
>> for negative int arguments, which must not have their upper bits set?
>
>       ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp,
>                       int msgflg);
>
>       * If msgtyp is 0, then the first message in the queue is read.
>
>        * If  msgtyp  is greater than 0, then the first message in the queue of
>          type msgtyp is read, unless MSG_EXCEPT was specified  in  msgflg,  in
>          which case the first message in the queue of type not equal to msgtyp
>          will be read.
>
>        * If msgtyp is less than 0, then the first message in  the  queue  with
>          the  lowest  type  less than or equal to the absolute value of msgtyp
>          will be read.
>
> In this syscall, msgtyp should be sign-extended to 64-bit.

As far as I can tell, this is not a problematic exception.