Patch "MIPS: VDSO: Build with `-fno-strict-aliasing'" has been added to the 4.4-stable tree

Patch "MIPS: VDSO: Build with `-fno-strict-aliasing'" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    MIPS: VDSO: Build with `-fno-strict-aliasing'

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-vdso-build-with-fno-strict-aliasing.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 94cc36b84acc29f543b48bc5ed786011b112a666 Mon Sep 17 00:00:00 2001
From: "Maciej W. Rozycki" <macro@imgtec.com>
Date: Thu, 26 May 2016 12:55:45 +0100
Subject: MIPS: VDSO: Build with `-fno-strict-aliasing'

From: Maciej W. Rozycki <macro@imgtec.com>

commit 94cc36b84acc29f543b48bc5ed786011b112a666 upstream.

Avoid an aliasing issue causing a build error in VDSO:

In file included from include/linux/srcu.h:34:0,
                 from include/linux/notifier.h:15,
                 from ./arch/mips/include/asm/uprobes.h:9,
                 from include/linux/uprobes.h:61,
                 from include/linux/mm_types.h:13,
                 from ./arch/mips/include/asm/vdso.h:14,
                 from arch/mips/vdso/vdso.h:27,
                 from arch/mips/vdso/gettimeofday.c:11:
include/linux/workqueue.h: In function 'work_static':
include/linux/workqueue.h:186:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  return *work_data_bits(work) & WORK_STRUCT_STATIC;
  ^
cc1: all warnings being treated as errors
make[2]: *** [arch/mips/vdso/gettimeofday.o] Error 1

with a CONFIG_DEBUG_OBJECTS_WORK configuration and GCC 5.2.0.  Include
`-fno-strict-aliasing' along with compiler options used, as required for
kernel code, fixing a problem present since the introduction of VDSO
with commit ebb5e78cc634 ("MIPS: Initial implementation of a VDSO").

Thanks to Tejun for diagnosing this properly!

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Fixes: ebb5e78cc634 ("MIPS: Initial implementation of a VDSO")
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13357/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/vdso/Makefile |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/mips/vdso/Makefile
+++ b/arch/mips/vdso/Makefile
@@ -9,7 +9,8 @@ ccflags-vdso := \
 	$(filter -march=%,$(KBUILD_CFLAGS))
 cflags-vdso := $(ccflags-vdso) \
 	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
-	-O2 -g -fPIC -fno-common -fno-builtin -G 0 -DDISABLE_BRANCH_PROFILING \
+	-O2 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \
+	-DDISABLE_BRANCH_PROFILING \
 	$(call cc-option, -fno-stack-protector)
 aflags-vdso := $(ccflags-vdso) \
 	$(filter -I%,$(KBUILD_CFLAGS)) \


Patches currently in stable-queue which might be from macro@imgtec.com are

queue-4.4/mips-disable-preemption-during-prctl-pr_set_fp_mode.patch
queue-4.4/mips-ptrace-prevent-writes-to-read-only-fcsr-bits.patch
queue-4.4/mips-msa-fix-a-link-error-on-_init_msa_upper-with-older-gcc.patch
queue-4.4/mips-ptrace-fix-fp-context-restoration-fcsr-regression.patch
queue-4.4/mips-vdso-build-with-fno-strict-aliasing.patch
queue-4.4/mips-math-emu-fix-jalr-emulation-when-rd-0.patch