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authorMasahiro Yamada <masahiroy@kernel.org>2022-05-13 14:39:22 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2022-05-24 10:33:20 +0300
commit7b4537199a4a8480b8c3ba37a2d44765ce76cd9b (patch)
tree0690afa62208ca15fd36069afcbdac85908d0676 /scripts/Makefile.build
parentf292d875d0dc700b3af0bef04c5abc1dc7b3b62c (diff)
downloadlinux-7b4537199a4a8480b8c3ba37a2d44765ce76cd9b.tar.xz
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 <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)
Diffstat (limited to 'scripts/Makefile.build')
-rw-r--r--scripts/Makefile.build27
1 files changed, 4 insertions, 23 deletions
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 <file>.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_<file>.o from <file>.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_<file>.o to <file>.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)