From 7b4537199a4a8480b8c3ba37a2d44765ce76cd9b Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 13 May 2022 20:39:22 +0900 Subject: kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS 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 Tested-by: Nathan Chancellor Tested-by: Nicolas Schier Reviewed-by: Nicolas Schier Tested-by: Sedat Dilek # LLVM-14 (x86-64) --- scripts/Makefile.build | 27 ++++----------------------- 1 file changed, 4 insertions(+), 23 deletions(-) (limited to 'scripts/Makefile.build') diff --git a/scripts/Makefile.build b/scripts/Makefile.build index a1023868775f..ddd9080fc028 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -128,7 +128,6 @@ $(obj)/%.i: $(src)/%.c FORCE genksyms = scripts/genksyms/genksyms \ $(if $(1), -T $(2)) \ - $(if $(CONFIG_MODULE_REL_CRCS), -R) \ $(if $(KBUILD_PRESERVE), -p) \ -r $(or $(wildcard $(2:.symtypes=.symref)), /dev/null) @@ -162,19 +161,11 @@ ifdef CONFIG_MODVERSIONS # o if .o doesn't contain a __ksymtab version, i.e. does # not export symbols, it's done. # o otherwise, we calculate symbol versions using the good old -# genksyms on the preprocessed source and postprocess them in a way -# that they are usable as a linker script -# o generate .tmp_.o from .o using the linker to -# replace the unresolved symbols __crc_exported_symbol with -# the actual value of the checksum generated by genksyms -# o remove .tmp_.o to .o +# genksyms on the preprocessed source and dump them into the .cmd file. +# o modpost will extract versions from that file and create *.c files that will +# be compiled and linked to the kernel and/or modules. -# 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)) +genksyms_format := __crc_\(.*\) = \(.*\); gen_symversions = \ if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \ @@ -188,12 +179,6 @@ gen_symversions = \ cmd_gen_symversions_c = $(call gen_symversions,c) -cmd_modversions = \ - if [ -r $@.symversions ]; then \ - $(LD) $(KBUILD_LDFLAGS) -r -o $(@D)/.tmp_$(@F) $@ \ - -T $@.symversions; \ - mv -f $(@D)/.tmp_$(@F) $@; \ - fi endif ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT @@ -273,7 +258,6 @@ define rule_cc_o_c $(call cmd,checkdoc) $(call cmd,gen_objtooldep) $(call cmd,gen_symversions_c) - $(if $(CONFIG_LTO_CLANG),,$(call cmd,modversions)) $(call cmd,record_mcount) endef @@ -282,7 +266,6 @@ define rule_as_o_S $(call cmd,gen_ksymdeps) $(call cmd,gen_objtooldep) $(call cmd,gen_symversions_S) - $(call cmd,modversions) endef # Built-in and composite module parts @@ -296,8 +279,6 @@ ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),) quiet_cmd_cc_prelink_modules = LD [M] $@ cmd_cc_prelink_modules = \ $(LD) $(ld_flags) -r -o $@ \ - $(shell [ -s $(@:.prelink.o=.o.symversions) ] && \ - echo -T $(@:.prelink.o=.o.symversions)) \ --whole-archive $(filter-out FORCE,$^) \ $(cmd_objtool) -- cgit v1.2.3