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

  + 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@aerifal.cx>
Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
---
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:

+++ sysdeps/unix/sysv/linux/sys/sysinfo.h
@@ -21,7 +21,7 @@
 #include <features.h>

 /* Get sysinfo structure from kernel header.  */
-#include <linux/kernel.h>
+#include <linux/sysinfo.h>

 __BEGIN_DECLS


Kind regards,
Petr

[2] https://git.buildroot.net/buildroot/commit/?id=ab930190d7754b7f5fdda115b2069d00f1320861
[3] http://patchwork.ozlabs.org/project/netdev/patch/602128d22db86bd67e11dec8fe40a73832c222c9.1559230347.git.baruch@tkos.co.il/
[4] https://www.mail-archive.com/busybox@busybox.net/msg15363.html
[5] https://lore.kernel.org/patchwork/patch/449607/

 drivers/scsi/mpt3sas/mpt3sas_base.c | 2 +-
 fs/eventpoll.c                      | 2 +-
 fs/proc/meminfo.c                   | 2 +-
 include/linux/mm.h                  | 1 +
 include/uapi/linux/kernel.h         | 2 --
 kernel/debug/kdb/kdb_main.c         | 2 +-
 kernel/sys.c                        | 2 +-
 mm/page_alloc.c                     | 2 +-
 net/ipv4/inetpeer.c                 | 2 +-
 net/rds/ib_recv.c                   | 2 +-
 10 files changed, 9 insertions(+), 10 deletions(-)
  

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@aerifal.cx>
> Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> ---
> 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. 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.

Rich
  

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@aerifal.cx>
> > Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> > ---
> > 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.

> Rich

Kind regards,
Petr
  

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@aerifal.cx>
> > > Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> > > ---
> > > 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?

Rich
  

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@aerifal.cx>
> > > > Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> > > > ---
> > > > 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