Re: Why is the bit size different between a syscall and its wrapper?

[Bhaskar Chowdhury]

On 11:48 Fri 12 Mar 2021, Masahiro Yamada wrote:
> Hi.
>
> I think I am missing something, but
> is there any particular reason to
> use a different bit size between
> a syscall and its userspace wrapper?
>
>
>
> For example, for the unshare syscall,
>
> unshare(2) says the parameter is int.
>
>
> SYNOPSIS
>       #define _GNU_SOURCE
>       #include <sched.h>
>
>       int unshare(int flags);
>
>
>
>
> In the kernel, it is unsigned long.
>
>
> SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
> {
>        return ksys_unshare(unshare_flags);
> }
>
>
>
>
> I guess the upper 32-bit will be
> zeroed out in the c library when
> sizeof(int) != sizeof(unsigned long)
> (i.e. 64-bit system), but I'd like to know
> why we do it this way.
Small nit! never mind ...but eye catching, Masahiro :) ...are you typing this
on narrowed device, which allow only this much line length?? It's bloody
narrow...don't you think so?

Sorry, for the deviation.

~Bhaskar
> --
> Best Regards
> Masahiro Yamada

Attachment: signature.asc
Description: PGP signature