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s390: always build relocatable kernel

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Nathan Chancellor reported several link errors on s390 with
CONFIG_RELOCATABLE disabled, after binutils commit 906f69cf65da ("IBM
zSystems: Issue error for *DBL relocs on misaligned symbols"). The binutils
commit reveals potential miscompiles that might have happened already
before with linker script defined symbols at odd addresses.

A similar bug was recently fixed in the kernel with commit c9305b6c1f
("s390: fix nospec table alignments").

See https://github.com/ClangBuiltLinux/linux/issues/1747 for an analysis
from Ulich Weigand.

Therefore always build a relocatable kernel to avoid this problem. There is
hardly any use-case for non-relocatable kernels, so this shouldn't be
controversial.

Link: https://github.com/ClangBuiltLinux/linux/issues/1747
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20221030182202.2062705-1-hca@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2022-10-30 19:22:02 +01:00 committed by Alexander Gordeev
parent 9afea696a0
commit 80ddf5ce1c
4 changed files with 5 additions and 9 deletions
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6
arch/s390/Kconfig
View File

@ -568,8 +568,7 @@ config EXPOLINE_FULL
endchoice
config RELOCATABLE
bool "Build a relocatable kernel"
default y
def_bool y
help
This builds a kernel image that retains relocation information
so it can be loaded at an arbitrary address.
@ -578,10 +577,11 @@ config RELOCATABLE
bootup process.
The relocations make the kernel image about 15% larger (compressed
10%), but are discarded at runtime.
Note: this option exists only for documentation purposes, please do
not remove it.
config RANDOMIZE_BASE
bool "Randomize the address of the kernel image (KASLR)"
depends on RELOCATABLE
default y
help
In support of Kernel Address Space Layout Randomization (KASLR),

2
arch/s390/Makefile
View File

@ -14,10 +14,8 @@ KBUILD_AFLAGS_MODULE += -fPIC
KBUILD_CFLAGS_MODULE += -fPIC
KBUILD_AFLAGS += -m64
KBUILD_CFLAGS += -m64
ifeq ($(CONFIG_RELOCATABLE),y)
KBUILD_CFLAGS += -fPIE
LDFLAGS_vmlinux := -pie
endif
aflags_dwarf := -Wa,-gdwarf-2
KBUILD_AFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -D__ASSEMBLY__
ifndef CONFIG_AS_IS_LLVM

3
arch/s390/boot/Makefile
View File

@ -37,9 +37,8 @@ CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
obj-y := head.o als.o startup.o mem_detect.o ipl_parm.o ipl_report.o
obj-y += string.o ebcdic.o sclp_early_core.o mem.o ipl_vmparm.o cmdline.o
obj-y += version.o pgm_check_info.o ctype.o ipl_data.o
obj-y += version.o pgm_check_info.o ctype.o ipl_data.o machine_kexec_reloc.o
obj-$(findstring y, $(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) $(CONFIG_PGSTE)) += uv.o
obj-$(CONFIG_RELOCATABLE) += machine_kexec_reloc.o
obj-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
obj-y += $(if $(CONFIG_KERNEL_UNCOMPRESSED),,decompressor.o) info.o
obj-$(CONFIG_KERNEL_ZSTD) += clz_ctz.o

3
arch/s390/boot/startup.c
View File

@ -291,8 +291,7 @@ void startup_kernel(void)
clear_bss_section();
copy_bootdata();
if (IS_ENABLED(CONFIG_RELOCATABLE))
handle_relocs(__kaslr_offset);
handle_relocs(__kaslr_offset);
if (__kaslr_offset) {
/*