[03/16] Kbuild: always define endianess in kconfig.h

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@amd.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(+)