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2022-09-28linux/export: use inline assembler to populate symbol CRCsMasahiro Yamada1-2/+4
Since commit 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS"), the module versioning on the (non-upstreamed-yet) kvx Linux port is broken due to unexpected padding for __crc_* symbols. The kvx GCC adds padding so u32 gets 8-byte alignment instead of 4. I do not know if this happens for upstream architectures in general, but any compiler has the freedom to insert padding for faster access. Use the inline assembler to directly specify the wanted data layout. This is how we previously did before the breakage. Link: https://lore.kernel.org/lkml/20220817161438.32039-1-ysionneau@kalray.eu/ Link: https://lore.kernel.org/linux-kbuild/31ce5305-a76b-13d7-ea55-afca82c46cf2@kalray.eu/ Fixes: 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS") Reported-by: Yann Sionneau <ysionneau@kalray.eu> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Yann Sionneau <ysionneau@kalray.eu>
2022-05-24kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCSMasahiro Yamada1-0/+17
include/{linux,asm-generic}/export.h defines a weak symbol, __crc_* as a placeholder. Genksyms writes the version CRCs into the linker script, which will be used for filling the __crc_* symbols. The linker script format depends on CONFIG_MODULE_REL_CRCS. If it is enabled, __crc_* holds the offset to the reference of CRC. It is time to get rid of this complexity. Now that modpost parses text files (.*.cmd) to collect all the CRCs, it can generate C code that will be linked to the vmlinux or modules. Generate a new C file, .vmlinux.export.c, which contains the CRCs of symbols exported by vmlinux. It is compiled and linked to vmlinux in scripts/link-vmlinux.sh. Put the CRCs of symbols exported by modules into the existing *.mod.c files. No additional build step is needed for modules. As before, *.mod.c are compiled and linked to *.ko in scripts/Makefile.modfinal. No linker magic is used here. The new C implementation works in the same way, whether CONFIG_RELOCATABLE is enabled or not. CONFIG_MODULE_REL_CRCS is no longer needed. Previously, Kbuild invoked additional $(LD) to update the CRCs in objects, but this step is unneeded too. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nicolas Schier <nicolas@fjasle.eu> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)