linux/scripts/Makefile.modfinal
Masahiro Yamada 0d989ac2c9 kbuild: remove libelf checks from top Makefile
I do not see a good reason why only the libelf development package must
be so carefully checked.

Kbuild generally does not check host tools or libraries.

For example, x86_64 defconfig fails to build with no libssl development
package installed.

scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory
   21 | #include <openssl/bio.h>
      |          ^~~~~~~~~~~~~~~

To solve the build error, you need to install libssl-dev or openssl-devel
package, depending on your distribution.

'apt-file search', 'dnf provides', etc. is your frined to find a proper
package to install.

This commit removes all the libelf checks from the top Makefile.

If libelf is missing, objtool will fail to build in a similar pattern:

.../linux/tools/objtool/include/objtool/elf.h:10:10: fatal error: gelf.h: No such file or directory
   10 | #include <gelf.h>

You need to install libelf-dev, libelf-devel, or elfutils-libelf-devel
to proceed.

Another remarkable change is, CONFIG_STACK_VALIDATION (without
CONFIG_UNWINDER_ORC) previously continued to build with a warning,
but now it will treat missing libelf as an error.

This is just a one-time installation, so it should not hurt to break
a build and make a user install the package.

BTW, the traditional way to handle such checks is autotool, but according
to [1], I do not expect the kernel build would have similar scripting
like './configure' does.

[1]: https://lore.kernel.org/lkml/CA+55aFzr2HTZVOuzpHYDwmtRJLsVzE-yqg2DHpHi_9ePsYp5ug@mail.gmail.com/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
2021-05-24 12:06:51 +09:00

99 lines
3.2 KiB
Makefile

# SPDX-License-Identifier: GPL-2.0-only
# ===========================================================================
# Module final link
# ===========================================================================
PHONY := __modfinal
__modfinal:
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
# for c_flags and objtool_args
include $(srctree)/scripts/Makefile.lib
# find all modules listed in modules.order
modules := $(sort $(shell cat $(MODORDER)))
__modfinal: $(modules)
@:
# modname and part-of-module are set to make c_flags define proper module flags
modname = $(notdir $(@:.mod.o=))
part-of-module = y
quiet_cmd_cc_o_c = CC [M] $@
cmd_cc_o_c = $(CC) $(filter-out $(CC_FLAGS_CFI), $(c_flags)) -c -o $@ $<
%.mod.o: %.mod.c FORCE
$(call if_changed_dep,cc_o_c)
ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
ifdef CONFIG_LTO_CLANG
# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to
# avoid a second slow LTO link
prelink-ext := .lto
# ELF processing was skipped earlier because we didn't have native code,
# so let's now process the prelinked binary before we link the module.
ifdef CONFIG_STACK_VALIDATION
cmd_ld_ko_o += \
$(objtree)/tools/objtool/objtool $(objtool_args) \
$(@:.ko=$(prelink-ext).o);
endif # CONFIG_STACK_VALIDATION
endif # CONFIG_LTO_CLANG
quiet_cmd_ld_ko_o = LD [M] $@
cmd_ld_ko_o += \
$(LD) -r $(KBUILD_LDFLAGS) \
$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
-T scripts/module.lds -o $@ $(filter %.o, $^); \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
quiet_cmd_btf_ko = BTF [M] $@
cmd_btf_ko = \
if [ -f vmlinux ]; then \
LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@; \
else \
printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
fi;
# Same as newer-prereqs, but allows to exclude specified extra dependencies
newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
# Same as if_changed, but allows to exclude specified extra dependencies
if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
$(cmd); \
printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
# Re-generate module BTFs if either module's .ko or vmlinux changed
$(modules): %.ko: %$(prelink-ext).o %.mod.o 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))
endif
targets += $(modules) $(modules:.ko=.mod.o)
# 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)