[PATCH v2 19/26] kbuild: embed symbol versions at final link of vmlinux or modules

Masahiro Yamada
2022-05-01T08:43:26Z

Do not update objects with version CRCs while the directory descending.

Do it at the final link stage.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

(no changes since v1)

scripts/Makefile.build | 22 +++-------------------
scripts/Makefile.modfinal | 3 ++-
scripts/link-vmlinux.sh | 4 +++-
3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a1023868775f..cec17b28de42 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -162,15 +162,9 @@ 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
-
-# Generate .o.symversions files for each .o with exported symbols, and link these
-# to the kernel and/or modules at the end.
+# genksyms on the preprocessed source and dump them into the .cmd file.
+# o modpost will extract versions from the .cmd file and create linker
+# scripts used to link the kernel and/or modules.

genksyms_format_rel_crc := [^_]*__crc_\([^ ]*\) = \.; LONG(\([^)]*\)).*
genksyms_format_normal := __crc_\(.*\) = \(.*\);
@@ -188,12 +182,6 @@ 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 +261,6 @@ 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 +269,6 @@ 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 +282,6 @@ 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)

diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 7f39599e9fae..d429e3f9ae1d 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -34,6 +34,7 @@ quiet_cmd_ld_ko_o = LD [M] $@
cmd_ld_ko_o += \
$(LD) -r $(KBUILD_LDFLAGS) \
$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
+ $(addprefix -T, $(filter %.symver.lds, $(real-prereqs)))\
-T scripts/module.lds -o $@ $(filter %.o, $^); \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)

@@ -56,7 +57,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \

# Re-generate module BTFs if either module's .ko or vmlinux changed
-$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
+$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o $(if $(CONFIG_MODVERSIONS), %.symver.lds) scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
+$(call if_changed_except,ld_ko_o,vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+$(if $(newer-prereqs),$(call cmd,btf_ko))
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index eceb3ee7ec06..8da5c0182665 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -90,7 +90,6 @@ modpost_link()

if is_enabled CONFIG_MODVERSIONS; then
gen_symversions
- lds="${lds} -T .tmp_symversions.lds"
fi

# This might take a while, so indicate that we're doing
@@ -196,6 +195,9 @@ vmlinux_link()
fi

ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
+ if is_enabled CONFIG_MODVERSIONS; then
+ ldflags="${ldflags} ${wl}--script=vmlinux.symver.lds"
+ fi

# The kallsyms linking does not need debug symbols included.
if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
--
2.32.0