This is a note to let you know that I've just added the patch titled
s390/vdso64: filter out munaligned-symbols flag for vdso
to the 5.15-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:
s390-vdso64-filter-out-munaligned-symbols-flag-for-v.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b5771731ee3d2b5174053e3c5c144761ca9c74e1
Author: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx>
Date: Mon Feb 19 14:27:31 2024 +0100
s390/vdso64: filter out munaligned-symbols flag for vdso
[ 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@xxxxxxxxxxxxx>
Signed-off-by: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240219132734.22881-2-sumanthk@xxxxxxxxxxxxx
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Stable-dep-of: 10f705253651 ("s390/vdso: Generate unwind information for C modules")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile
index 08e87b083647c..e2e031e4d9243 100644
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -26,6 +26,7 @@ KBUILD_AFLAGS_64 += -m64 -s
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
