The patch titled Subject: Kbuild: always define endianess in kconfig.h has been added to the -mm tree. Its filename is kbuild-always-define-endianess-in-kconfigh.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/kbuild-always-define-endianess-in-k... and later at http://ozlabs.org/~akpm/mmotm/broken-out/kbuild-always-define-endianess-in-k...

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------------------------------------------------------ From: Arnd Bergmann arnd@arndb.de Subject: Kbuild: always define endianess in kconfig.h

Build testing with LTO found a couple of files that get compiled differently depending on whether asm/byteorder.h gets included early enough or not. In particular, include/asm-generic/qrwlock_types.h is affected by this, but there are probably others as well.

The symptom is a series of LTO link time warnings, including these:

net/netlabel/netlabel_unlabeled.h:223: error: type of 'netlbl_unlhsh_add' does not match original declaration [-Werror=lto-type-mismatch] int netlbl_unlhsh_add(struct net *net, net/netlabel/netlabel_unlabeled.c:377: note: 'netlbl_unlhsh_add' was previously declared here

include/net/ipv6.h:360: error: type of 'ipv6_renew_options_kern' does not match original declaration [-Werror=lto-type-mismatch] ipv6_renew_options_kern(struct sock *sk, net/ipv6/exthdrs.c:1162: note: 'ipv6_renew_options_kern' was previously declared here

net/core/dev.c:761: note: 'dev_get_by_name_rcu' was previously declared here struct net_device *dev_get_by_name_rcu(struct net *net, const char *name) net/core/dev.c:761: note: code may be misoptimized unless -fno-strict-aliasing is used

drivers/gpu/drm/i915/i915_drv.h:3377: error: type of 'i915_gem_object_set_to_wc_domain' does not match original declaration [-Werror=lto-type-mismatch] i915_gem_object_set_to_wc_domain(struct drm_i915_gem_object *obj, bool write); drivers/gpu/drm/i915/i915_gem.c:3639: note: 'i915_gem_object_set_to_wc_domain' was previously declared here

include/linux/debugfs.h:92:9: error: type of 'debugfs_attr_read' does not match original declaration [-Werror=lto-type-mismatch] ssize_t debugfs_attr_read(struct file *file, char __user *buf, fs/debugfs/file.c:318: note: 'debugfs_attr_read' was previously declared here

include/linux/rwlock_api_smp.h:30: error: type of '_raw_read_unlock' does not match original declaration [-Werror=lto-type-mismatch] void __lockfunc _raw_read_unlock(rwlock_t *lock) __releases(lock); kernel/locking/spinlock.c:246:26: note: '_raw_read_unlock' was previously declared here

include/linux/fs.h:3308:5: error: type of 'simple_attr_open' does not match original declaration [-Werror=lto-type-mismatch] int simple_attr_open(struct inode *inode, struct file *file, fs/libfs.c:795: note: 'simple_attr_open' was previously declared here

All of the above are caused by include/asm-generic/qrwlock_types.h failing to include asm/byteorder.h after commit e0d02285f16e ("locking/qrwlock: Use 'struct qrwlock' instead of 'struct __qrwlock'") in linux-4.15.

Similar bugs may or may not exist in older kernels as well, but there is no easy way to test those with link-time optimizations, and kernels before 4.14 are harder to fix because they don't have Babu's patch series

We had similar issues with CONFIG_ symbols in the past and ended up always including the configuration headers though linux/kconfig.h. This works around the issue through that same file, defining either __BIG_ENDIAN or __LITTLE_ENDIAN depending on CONFIG_CPU_BIG_ENDIAN, which is now always set on all architectures since commit 4c97a0c8fee3 ("arch: define CPU_BIG_ENDIAN for all fixed big endian archs").

Link: http://lkml.kernel.org/r/20180202154104.1522809-2-arnd@arndb.de Signed-off-by: Arnd Bergmann arnd@arndb.de Cc: Babu Moger babu.moger@oracle.com Cc: Andi Kleen ak@linux.intel.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Masahiro Yamada yamada.masahiro@socionext.com Cc: Nicolas Pitre nico@linaro.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Will Deacon will.deacon@arm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

include/linux/kconfig.h | 6 ++++++ 1 file changed, 6 insertions(+)

diff -puN include/linux/kconfig.h~kbuild-always-define-endianess-in-kconfigh include/linux/kconfig.h --- a/include/linux/kconfig.h~kbuild-always-define-endianess-in-kconfigh +++ a/include/linux/kconfig.h @@ -4,6 +4,12 @@

#include <generated/autoconf.h>

+#ifdef CONFIG_CPU_BIG_ENDIAN +#define __BIG_ENDIAN 4321 +#else +#define __LITTLE_ENDIAN 1234 +#endif + #define __ARG_PLACEHOLDER_1 0, #define __take_second_arg(__ignored, val, ...) val

_

Patches currently in -mm which might be from arnd@arndb.de are

locking-qrwlock-include-asm-byteorderh-as-needed.patch kbuild-always-define-endianess-in-kconfigh.patch kasan-added-functions-for-unpoisoning-stack-variables-fix-fix.patch bugh-work-around-gcc-pr82365-in-bug.patch bitmap-replace-bitmap_fromto_u32array-fix.patch nilfs2-use-time64_t-internally.patch pps-parport-use-timespec64-instead-of-timespec.patch kasan-rework-kconfig-settings.patch