Re: [Minios-devel] [UNIKRAFT PATCH] lib/vfscore: sys_ioctl() - Fix build with nolibc

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

Hello Costin,

Also noticed a checkpatch error with this patch.

Thanks & Regards

Sharan


On 9/11/19 6:44 PM, Costin Lupu wrote:
> On 9/11/19 6:27 PM, Sharan Santhanam wrote:
> > On 9/11/19 3:38 PM, Costin Lupu wrote:
> > > Hi Sharan,
> > >
> > > On 9/11/19 3:56 PM, Sharan Santhanam wrote:
> > > > Hello Costin,
> > > >
> > > > The fix seems fine. Please find the question inline.
> > > >
> > > > Thanks & Regards
> > > >
> > > > Sharan
> > > >
> > > > On 9/11/19 1:56 PM, Costin Lupu wrote:
> > > > > Commit 3dcccd04 introduced handling of FIOCLEX and FIONCLEX requests.
> > > > > However,
> > > > > these flags are not defined in nolibc.
> > > > >
> > > > > Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
> > > > > ---
> > > > >     lib/nolibc/include/sys/ioctl.h | 0
> > > > Why do we introduce a empty file? In newlib we introduces a header
> > > > imported from musl.
> > > I didn't get that completely, does it build on your side? Do you get any
> > > errors/warnings?
> > No, but I guess with a review process you do clarify why you made
> > certain choices.
> > > > Why don't we use the same file here?
> > > This is an open question. The thing is that newlib itself seems to be a
> > > poor choice if we do copy so much code from musl. Now getting back to
> > > nolibc, if we do add more and more code from musl then we can simply get
> > > rid of it too and use musl instead. In conclusion, I fail to see why we
> > > should copy code to nolibc instead using musl directly.
> > But in this case we are introducing the FIONCLEX and FIOCLEX within the
> > core Unikraft and it is expected to work with nolibc. Instead of adding
> > #ifdef it would be better to make it feature complete.
> Now why would you say it is expected to work with nolibc? The two flags
> are actually related with close-on-exec logic. Why would any app running
> on top of Unikraft and which would not use a libc implementation need to
> call exec() since this is not possible? Besides this, there is no exec()
> function in nolibc.
From my perspective,

fcntl(fd, F_SETFD, FD_CLOEXEC);

and

ioctl(fd, FIOCLEX);

is functionally equivalent. The former is supported in nolibc while the 
latter is not. As far as exec call is concerned, we don't support exec 
family in either of the libc except for glue to compile it. So when exec 
family is available we can decide on the libcs to support the exec.
> Cheers,
> Costin
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