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authorMasahiro Yamada <masahiroy@kernel.org>2022-05-13 20:39:22 +0900
committerMasahiro Yamada <masahiroy@kernel.org>2022-05-24 16:33:20 +0900
commit7b4537199a4a8480b8c3ba37a2d44765ce76cd9b (patch)
tree0690afa62208ca15fd36069afcbdac85908d0676 /scripts/Makefile.vmlinux
parentf292d875d0dc700b3af0bef04c5abc1dc7b3b62c (diff)
downloadlinux-7b4537199a4a8480b8c3ba37a2d44765ce76cd9b.tar.bz2
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.vmlinux')
-rw-r--r--scripts/Makefile.vmlinux32
1 files changed, 32 insertions, 0 deletions
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
new file mode 100644
index 000000000000..7a63abf22399
--- /dev/null
+++ b/scripts/Makefile.vmlinux
@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+include include/config/auto.conf
+include $(srctree)/scripts/Kbuild.include
+
+# for c_flags
+include $(srctree)/scripts/Makefile.lib
+
+quiet_cmd_cc_o_c = CC $@
+ cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+
+%.o: %.c FORCE
+ $(call if_changed_dep,cc_o_c)
+
+targets := $(MAKECMDGOALS)
+
+# Add FORCE to the prequisites of a target to force it to be always rebuilt.
+# ---------------------------------------------------------------------------
+
+PHONY += FORCE
+FORCE:
+
+# Read all saved command lines and dependencies for the $(targets) we
+# may be building above, using $(if_changed{,_dep}). As an
+# optimization, we don't need to read them if the target does not
+# exist, we will rebuild anyway in that case.
+
+existing-targets := $(wildcard $(sort $(targets)))
+
+-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
+
+.PHONY: $(PHONY)