[RFC PATCH v2 1/1] uapi: Introduce <linux/align.h>

[Petr Vorel]

move there code from <linux/kernel.h>,
and include it in UAPI headers instead of <linux/kernel.h>.

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

This indirect include causes on MUSL redefinition of struct sysinfo when
included both <sys/sysinfo.h> and some of UAPI 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

Suggested-by: Rich Felker <dalias@xxxxxxxxxx>
Signed-off-by: Petr Vorel <petr.vorel@xxxxxxxxx>
---
Changes v1->v2:
* Move kernel.h content into new header in order not break the existing
contract with glibc.

Background: long standing problem: python-psutil [1], iproute2 [2],
even for glibc in the past [3].

Kind regards,
Petr

[1] https://git.buildroot.net/buildroot/commit/?id=ab930190d7754b7f5fdda115b2069d00f1320861
[2] http://patchwork.ozlabs.org/project/netdev/patch/602128d22db86bd67e11dec8fe40a73832c222c9.1559230347.git.baruch@xxxxxxxxxx/
[3] https://www.mail-archive.com/busybox@xxxxxxxxxxx/msg15363.html

 include/uapi/linux/align.h              | 10 ++++++++++
 include/uapi/linux/ethtool.h            |  2 +-
 include/uapi/linux/kernel.h             |  9 +--------
 include/uapi/linux/lightnvm.h           |  2 +-
 include/uapi/linux/mroute6.h            |  2 +-
 include/uapi/linux/netfilter/x_tables.h |  2 +-
 include/uapi/linux/netlink.h            |  2 +-
 include/uapi/linux/sysctl.h             |  2 +-
 8 files changed, 17 insertions(+), 14 deletions(-)
 create mode 100644 include/uapi/linux/align.h

diff --git a/include/uapi/linux/align.h b/include/uapi/linux/align.h
new file mode 100644
index 000000000000..6d2fef859d03
--- /dev/null
+++ b/include/uapi/linux/align.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_LINUX_ALIGN_H
+#define _UAPI_LINUX_ALIGN_H
+
+#define __ALIGN_KERNEL(x, a)		__ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
+#define __ALIGN_KERNEL_MASK(x, mask)	(((x) + (mask)) & ~(mask))
+
+#define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
+
+#endif /* _UAPI_LINUX_ALIGN_H */
diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index b4f2d134e713..73ca97a6ec86 100644
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -14,7 +14,7 @@
 #ifndef _UAPI_LINUX_ETHTOOL_H
 #define _UAPI_LINUX_ETHTOOL_H
 
-#include <linux/kernel.h>
+#include <linux/align.h>
 #include <linux/types.h>
 #include <linux/if_ether.h>
 
diff --git a/include/uapi/linux/kernel.h b/include/uapi/linux/kernel.h
index 0ff8f7477847..15f70c510311 100644
--- a/include/uapi/linux/kernel.h
+++ b/include/uapi/linux/kernel.h
@@ -3,13 +3,6 @@
 #define _UAPI_LINUX_KERNEL_H
 
 #include <linux/sysinfo.h>
-
-/*
- * 'kernel.h' contains some often-used function prototypes etc
- */
-#define __ALIGN_KERNEL(x, a)		__ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1)
-#define __ALIGN_KERNEL_MASK(x, mask)	(((x) + (mask)) & ~(mask))
-
-#define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
+#include <linux/align.h>
 
 #endif /* _UAPI_LINUX_KERNEL_H */
diff --git a/include/uapi/linux/lightnvm.h b/include/uapi/linux/lightnvm.h
index f9a1be7fc696..d686cd576a24 100644
--- a/include/uapi/linux/lightnvm.h
+++ b/include/uapi/linux/lightnvm.h
@@ -21,7 +21,7 @@
 #define _UAPI_LINUX_LIGHTNVM_H
 
 #ifdef __KERNEL__
-#include <linux/kernel.h>
+#include <linux/align.h>
 #include <linux/ioctl.h>
 #else /* __KERNEL__ */
 #include <stdio.h>
diff --git a/include/uapi/linux/mroute6.h b/include/uapi/linux/mroute6.h
index c36177a86516..e638aaefbe7f 100644
--- a/include/uapi/linux/mroute6.h
+++ b/include/uapi/linux/mroute6.h
@@ -2,7 +2,7 @@
 #ifndef _UAPI__LINUX_MROUTE6_H
 #define _UAPI__LINUX_MROUTE6_H
 
-#include <linux/kernel.h>
+#include <linux/align.h>
 #include <linux/types.h>
 #include <linux/sockios.h>
 #include <linux/in6.h>		/* For struct sockaddr_in6. */
diff --git a/include/uapi/linux/netfilter/x_tables.h b/include/uapi/linux/netfilter/x_tables.h
index a8283f7dbc51..c49d7a630d05 100644
--- a/include/uapi/linux/netfilter/x_tables.h
+++ b/include/uapi/linux/netfilter/x_tables.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 #ifndef _UAPI_X_TABLES_H
 #define _UAPI_X_TABLES_H
-#include <linux/kernel.h>
+#include <linux/align.h>
 #include <linux/types.h>
 
 #define XT_FUNCTION_MAXNAMELEN 30
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index eac8a6a648ea..2ff384e9bf00 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -2,7 +2,7 @@
 #ifndef _UAPI__LINUX_NETLINK_H
 #define _UAPI__LINUX_NETLINK_H
 
-#include <linux/kernel.h>
+#include <linux/align.h>
 #include <linux/socket.h> /* for __kernel_sa_family_t */
 #include <linux/types.h>
 
diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index 27c1ed2822e6..18360ea6dd4e 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -23,7 +23,7 @@
 #ifndef _UAPI_LINUX_SYSCTL_H
 #define _UAPI_LINUX_SYSCTL_H
 
-#include <linux/kernel.h>
+#include <linux/align.h>
 #include <linux/types.h>
 #include <linux/compiler.h>
 
-- 
2.28.0