From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Masahiro Yamada Subject: [PATCH v3 06/15] kbuild: record symbol versions in *.cmd files Date: Thu, 5 May 2022 16:22:35 +0900 Message-Id: <20220505072244.1155033-7-masahiroy@kernel.org> In-Reply-To: <20220505072244.1155033-1-masahiroy@kernel.org> References: <20220505072244.1155033-1-masahiroy@kernel.org> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: linux-kbuild@vger.kernel.org Cc: clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org, Nicolas Schier a , Ard Biesheuvel , Luis Chamberlain , Peter Zijlstra , linuxppc-dev@lists.ozlabs.org, linux-um@lists.infradead.org, linux-s390@vger.kernel.org, Nick Desaulniers , Sami Tolvanen , Kees Cook , Masahiro Yamada When CONFIG_MODVERSIONS=y, the output from genksyms is saved in separate *.symversions files, and will be used much later when CONFIG_LTO_CLANG=y because it is impossible to update LLVM bit code here. This approach is not robust because: - *.symversions may or may not exist. If *.symversions does not exist, we never know if it is missing for legitimate reason (i.e. no EXPORT_SYMBOL) or something bad has happened (for example, the user accidentally deleted it). Once it occurs, it is not self-healing because *.symversions is generated as a side effect. - stale (i.e. invalid) *.symversions might be picked up if an object is generated in a non-ordinary way, and corresponding *.symversions (, which was generated by old builds) just happen to exist. A more robust approach is to save symbol versions in *.cmd files because: - *.cmd always exists (if the object is generated by if_changed rule or friends). Even if the user accidentally deletes it, it will be regenerated in the next build. - *.cmd is always re-generated when the object is updated. This avoid stale version information being picked up. I will remove *.symversions later. Signed-off-by: Masahiro Yamada Tested-by: Nicolas Schier Reviewed-by: Nicolas Schier --- (no changes since v2) Changes in v2: - Fix CONFIG_MODULE_REL_CRCS=y case scripts/Makefile.build | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index f6a506318795..a1023868775f 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -171,10 +171,17 @@ ifdef CONFIG_MODVERSIONS # Generate .o.symversions files for each .o with exported symbols, and link these # to the kernel and/or modules at the end. + +genksyms_format_rel_crc := [^_]*__crc_\([^ ]*\) = \.; LONG(\([^)]*\)).* +genksyms_format_normal := __crc_\(.*\) = \(.*\); +genksyms_format := $(if $(CONFIG_MODULE_REL_CRCS),$(genksyms_format_rel_crc),$(genksyms_format_normal)) + gen_symversions = \ if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \ $(call cmd_gensymtypes_$(1),$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \ > $@.symversions; \ + sed -n 's/$(genksyms_format)/$(pound)SYMVER \1 \2/p' $@.symversions \ + >> $(dot-target).cmd; \ else \ rm -f $@.symversions; \ fi -- 2.32.0 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um