From 6f7b372ec68f9e4edc438b14b91332914d1c433d Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 16 Sep 2022 15:29:53 +0900 Subject: [PATCH] linux/export: use inline assembler to populate symbol CRCs [ Upstream commit f3304ecd7f060db1d4197fbdce5a503259f770d3 ] 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 Signed-off-by: Masahiro Yamada Tested-by: Yann Sionneau Signed-off-by: Sasha Levin --- include/linux/export-internal.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/export-internal.h b/include/linux/export-internal.h index c2b1d4fd59873..fe7e6ba918f10 100644 --- a/include/linux/export-internal.h +++ b/include/linux/export-internal.h @@ -10,8 +10,10 @@ #include #include -/* __used is needed to keep __crc_* for LTO */ #define SYMBOL_CRC(sym, crc, sec) \ - u32 __section("___kcrctab" sec "+" #sym) __used __crc_##sym = crc + asm(".section \"___kcrctab" sec "+" #sym "\",\"a\"" "\n" \ + "__crc_" #sym ":" "\n" \ + ".long " #crc "\n" \ + ".previous" "\n") #endif /* __LINUX_EXPORT_INTERNAL_H__ */ -- 2.47.2