6.6-stable review patch. If anyone has any objections, please let me know.
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From: Sumanth Korikkar sumanthk@linux.ibm.com
[ Upstream commit 8192a1b3807510d0ed5be1f8988c08f8d41cced9 ]
Gcc recently implemented an optimization [1] for loading symbols without explicit alignment, aligning with the IBM Z ELF ABI. This ABI mandates symbols to reside on a 2-byte boundary, enabling the use of the larl instruction. However, kernel linker scripts may still generate unaligned symbols. To address this, a new -munaligned-symbols option has been introduced [2] in recent gcc versions.
[1] https://gcc.gnu.org/pipermail/gcc-patches/2023-June/622872.html [2] https://gcc.gnu.org/pipermail/gcc-patches/2023-August/625986.html
However, when -munaligned-symbols is used in vdso code, it leads to the following compilation error: `.data.rel.ro.local' referenced in section `.text' of arch/s390/kernel/vdso64/vdso64_generic.o: defined in discarded section `.data.rel.ro.local' of arch/s390/kernel/vdso64/vdso64_generic.o
vdso linker script discards .data section to make it lightweight. However, -munaligned-symbols in vdso object files references literal pool and accesses _vdso_data. Hence, compile vdso code without -munaligned-symbols. This means in the future, vdso code should deal with alignment of newly introduced unaligned linker symbols.
Acked-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sumanth Korikkar sumanthk@linux.ibm.com Link: https://lore.kernel.org/r/20240219132734.22881-2-sumanthk@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Stable-dep-of: 10f705253651 ("s390/vdso: Generate unwind information for C modules") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kernel/vdso64/Makefile | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile index 11f798e6cfea7..aa410a0a141cc 100644 --- a/arch/s390/kernel/vdso64/Makefile +++ b/arch/s390/kernel/vdso64/Makefile @@ -25,6 +25,7 @@ KBUILD_AFLAGS_64 += -m64
KBUILD_CFLAGS_64 := $(filter-out -m64,$(KBUILD_CFLAGS)) KBUILD_CFLAGS_64 := $(filter-out -mno-pic-data-is-text-relative,$(KBUILD_CFLAGS_64)) +KBUILD_CFLAGS_64 := $(filter-out -munaligned-symbols,$(KBUILD_CFLAGS_64)) KBUILD_CFLAGS_64 += -m64 -fPIC -fno-common -fno-builtin ldflags-y := -shared -soname=linux-vdso64.so.1 \ --hash-style=both --build-id=sha1 -T