Re: [musl] [PATCH 1/1] uapi: Don't include <linux/sysinfo.h> in <linux/kernel.h>

[Petr Vorel]

Hi,

> On Thu, Oct 01, 2020 at 10:27:03PM +0200, Petr Vorel wrote:
> > Hi Rich,

> > > On Thu, Oct 01, 2020 at 09:52:31PM +0200, Petr Vorel wrote:
> > > > + update code where needed (include <linux/sysinfo.h> in code which
> > > > included <linux/kernel.h> only to get struct sysinfo or SI_LOAD_SHIFT).

> > > > The reason is to avoid indirect <linux/sysinfo.h> include when using
> > > > some network headers: <linux/netlink.h> or others [1] ->
> > > > <linux/kernel.h> -> <linux/sysinfo.h>.

> > > > This indirect include causes redefinition of struct sysinfo when
> > > > included both <sys/sysinfo.h> and some of network headers:

> > > > In file included from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/kernel.h:5,
> > > >                  from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/netlink.h:5,
> > > >                  from ../include/tst_netlink.h:14,
> > > >                  from tst_crypto.c:13:
> > > > x86_64-buildroot-linux-musl/sysroot/usr/include/linux/sysinfo.h:8:8: error: redefinition of ‘struct sysinfo’
> > > >  struct sysinfo {
> > > >         ^~~~~~~
> > > > In file included from ../include/tst_safe_macros.h:15,
> > > >                  from ../include/tst_test.h:93,
> > > >                  from tst_crypto.c:11:
> > > > x86_64-buildroot-linux-musl/sysroot/usr/include/sys/sysinfo.h:10:8: note: originally defined here

> > > > [1] or <linux/sysctl.h>, <linux/ethtool.h>, <linux/mroute6.h>, <linux/ethtool.h>

> > > > Suggested-by: Rich Felker <dalias@xxxxxxxxxx>
> > > > Signed-off-by: Petr Vorel <petr.vorel@xxxxxxxxx>
> > > > ---
> > > > Hi,

> > > > this looks to be long standing problem: python-psutil [2], iproute2 [3],
> > > > even for glibc in the past [4] and it tried to be solved before [5].

> > > > This will require glibc fix after:

> > > You can't do this; it breaks the existing contract with glibc. New
> > > kernel headers can't force a glibc upgrade.
> > Right, got that.

> > > You just have to get rid
> > > of use of <linux/kernel.h> elsewhere in the uapi headers. It was a
> > > mistake that <linux/sysinfo.h> was ever separated out of
> > > <linux/kernel.h> since it didn't (and couldn't) fix the contract that
> > > <linux/kernel.h> exposes struct sysinfo (and that it's misnamed). But
> > > it's no big deal. This can all be fixed without any breakage anywhere
> > > just by not using it.
> > Back to your original suggestion to move the alignment macros to a separate
> > header. I was trying to avoid it not sure if introducing new header is
> > acceptable, but we'll see.

> Isn't there already another similar header with that type of macro
> that they belong in?
The only one I've found is const.h. Not sure it'd be better to move things
there.

Kind regards,
Petr

> Rich