[Buildroot] [PATCH 1/1] linux: disable SSP on s390 when needed

[Romain Naour]

Hello Fabrice,

For s390 arch you can add Alexander Egorenkov <egorenar at linux.ibm.com> in Cc.

Le 09/05/2021 à 11:18, Fabrice Fontaine a écrit :
> Fix build failure raised since commit
> 810ba387bec3c5b6904e8893fb4cb6f9d3717466 by disabling SSP when needed
> 
> Fixes:
>  - https://gitlab.com/kubu93/buildroot/-/jobs/1247043361
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> ---
>  ...02-arch-s390-disable-SSP-when-needed.patch | 47 +++++++++++++++++++
>  linux/linux.mk                                |  7 +++
>  2 files changed, 54 insertions(+)
>  create mode 100644 linux/0002-arch-s390-disable-SSP-when-needed.patch
> 
> diff --git a/linux/0002-arch-s390-disable-SSP-when-needed.patch b/linux/0002-arch-s390-disable-SSP-when-needed.patch
> new file mode 100644
> index 0000000000..c8199d4fd6
> --- /dev/null
> +++ b/linux/0002-arch-s390-disable-SSP-when-needed.patch
> @@ -0,0 +1,47 @@
> +From 8a054081678ed0b0e56f829bac0a4656e3a198b9 Mon Sep 17 00:00:00 2001
> +From: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> +Date: Sat, 8 May 2021 22:03:11 +0200
> +Subject: [PATCH] arch/s390: disable SSP when needed
> +
> +Though -nostdlib is passed in PURGATORY_LDFLAGS and -ffreestanding in
> +KBUILD_CFLAGS_DECOMPRESSOR, -fno-stack-protector must also be passed to
> +avoid linking errors related to undefined references to
> +'__stack_chk_guard' and '__stack_chk_fail' if toolchain enforces
> +-fstack-protector.
> +
> +Fixes:
> + - https://gitlab.com/kubu93/buildroot/-/jobs/1247043361
> +
> +Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
> +---
> + arch/s390/Makefile           | 1 +
> + arch/s390/purgatory/Makefile | 1 +
> + 2 files changed, 2 insertions(+)
> +
> +diff --git a/arch/s390/Makefile b/arch/s390/Makefile
> +index e443ed9947bd..098abe3a56f3 100644
> +--- a/arch/s390/Makefile
> ++++ b/arch/s390/Makefile
> +@@ -28,6 +28,7 @@ KBUILD_CFLAGS_DECOMPRESSOR += -DDISABLE_BRANCH_PROFILING -D__NO_FORTIFY
> + KBUILD_CFLAGS_DECOMPRESSOR += -fno-delete-null-pointer-checks -msoft-float -mbackchain
> + KBUILD_CFLAGS_DECOMPRESSOR += -fno-asynchronous-unwind-tables
> + KBUILD_CFLAGS_DECOMPRESSOR += -ffreestanding
> ++KBUILD_CFLAGS_DECOMPRESSOR += -fno-stack-protector
> + KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, address-of-packed-member)
> + KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
> + KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))
> +diff --git a/arch/s390/purgatory/Makefile b/arch/s390/purgatory/Makefile
> +index c57f8c40e992..21c4ebe29b9a 100644
> +--- a/arch/s390/purgatory/Makefile
> ++++ b/arch/s390/purgatory/Makefile
> +@@ -24,6 +24,7 @@ KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes
> + KBUILD_CFLAGS += -Wno-pointer-sign -Wno-sign-compare
> + KBUILD_CFLAGS += -fno-zero-initialized-in-bss -fno-builtin -ffreestanding
> + KBUILD_CFLAGS += -c -MD -Os -m64 -msoft-float -fno-common
> ++KBUILD_CFLAGS += -fno-stack-protector
> + KBUILD_CFLAGS += $(CLANG_FLAGS)
> + KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
> + KBUILD_AFLAGS := $(filter-out -DCC_USING_EXPOLINE,$(KBUILD_AFLAGS))
> +-- 
> +2.30.2
> +
> diff --git a/linux/linux.mk b/linux/linux.mk
> index 1457228eb9..338e79d23d 100644
> --- a/linux/linux.mk
> +++ b/linux/linux.mk
> @@ -274,6 +274,13 @@ define LINUX_TRY_PATCH_TIMECONST
>  endef
>  LINUX_POST_PATCH_HOOKS += LINUX_TRY_PATCH_TIMECONST
>  
> +define LINUX_TRY_PATCH_ARCH_S390_SSP
> +	@if patch -p1 --dry-run -f -s -d $(@D) <$(LINUX_PKGDIR)/0002-arch-s390-disable-SSP-when-needed.patch.conditional >/dev/null ; then \
> +		$(APPLY_PATCHES) $(@D) $(LINUX_PKGDIR) 0002-arch-s390-disable-SSP-when-needed.patch.conditional ; \
> +	fi
> +endef
> +LINUX_POST_PATCH_HOOKS += LINUX_TRY_PATCH_ARCH_S390_SSP

I'm not sure if we should fix this in linux.mk
Instead put the patch to board/qemu/s390x/patches/linux/ (as for other kernel
patches for qemu defconfig).

Best regards,
Romain


> +
>  LINUX_KERNEL_CUSTOM_LOGO_PATH = $(call qstrip,$(BR2_LINUX_KERNEL_CUSTOM_LOGO_PATH))
>  ifneq ($(LINUX_KERNEL_CUSTOM_LOGO_PATH),)
>  LINUX_DEPENDENCIES += host-imagemagick
>