Commit 0d989ac2 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

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: default avatarMasahiro Yamada <masahiroy@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parent 1bb0b18a

Makefile

+22 −56
Original line number Diff line number Diff line
@@ -1081,41 +1081,6 @@ export INSTALL_DTBS_PATH ?= $(INSTALL_PATH)/dtbs/$(KERNELRELEASE) 
MODLIB	= $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)

export MODLIB



HOST_LIBELF_LIBS = $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)



has_libelf = $(call try-run,\

               echo "int main() {}" | $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -xc -o /dev/null $(HOST_LIBELF_LIBS) -,1,0)



ifdef CONFIG_STACK_VALIDATION

  ifeq ($(has_libelf),1)

    objtool_target := tools/objtool FORCE

  else

    SKIP_STACK_VALIDATION := 1

    export SKIP_STACK_VALIDATION

  endif

endif



PHONY += resolve_btfids_clean



resolve_btfids_O = $(abspath $(objtree))/tools/bpf/resolve_btfids



# tools/bpf/resolve_btfids directory might not exist

# in output directory, skip its clean in that case

resolve_btfids_clean:

ifneq ($(wildcard $(resolve_btfids_O)),)

	$(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(resolve_btfids_O) clean

endif



ifdef CONFIG_BPF

ifdef CONFIG_DEBUG_INFO_BTF

  ifeq ($(has_libelf),1)

    resolve_btfids_target := tools/bpf/resolve_btfids FORCE

  else

    ERROR_RESOLVE_BTFIDS := 1

  endif

endif # CONFIG_DEBUG_INFO_BTF

endif # CONFIG_BPF



PHONY += prepare0



export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
@@ -1227,7 +1192,7 @@ prepare0: archprepare 
	$(Q)$(MAKE) $(build)=.



# All the preparing..

prepare: prepare0 prepare-objtool prepare-resolve_btfids

prepare: prepare0



PHONY += remove-stale-files

remove-stale-files:
@@ -1244,26 +1209,6 @@ uapi-asm-generic: 
	$(Q)$(MAKE) $(asm-generic)=arch/$(SRCARCH)/include/generated/uapi/asm \

	generic=include/uapi/asm-generic



PHONY += prepare-objtool prepare-resolve_btfids

prepare-objtool: $(objtool_target)

ifeq ($(SKIP_STACK_VALIDATION),1)

ifdef CONFIG_FTRACE_MCOUNT_USE_OBJTOOL

	@echo "error: Cannot generate __mcount_loc for CONFIG_DYNAMIC_FTRACE=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2

	@false

endif

ifdef CONFIG_UNWINDER_ORC

	@echo "error: Cannot generate ORC metadata for CONFIG_UNWINDER_ORC=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2

	@false

else

	@echo "warning: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2

endif

endif



prepare-resolve_btfids: $(resolve_btfids_target)

ifeq ($(ERROR_RESOLVE_BTFIDS),1)

	@echo "error: Cannot resolve BTF IDs for CONFIG_DEBUG_INFO_BTF, please install libelf-dev, libelf-devel or elfutils-libelf-devel" >&2

	@false

endif

# Generate some files

# ---------------------------------------------------------------------------
@@ -1354,6 +1299,27 @@ scripts_unifdef: scripts_basic 
# ---------------------------------------------------------------------------

# Tools



ifdef CONFIG_STACK_VALIDATION

prepare: tools/objtool

endif



ifdef CONFIG_BPF

ifdef CONFIG_DEBUG_INFO_BTF

prepare: tools/bpf/resolve_btfids

endif

endif



PHONY += resolve_btfids_clean



resolve_btfids_O = $(abspath $(objtree))/tools/bpf/resolve_btfids



# tools/bpf/resolve_btfids directory might not exist

# in output directory, skip its clean in that case

resolve_btfids_clean:

ifneq ($(wildcard $(resolve_btfids_O)),)

	$(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(resolve_btfids_O) clean

endif



# Clear a bunch of variables before executing the submake

ifeq ($(quiet),silent_)

tools_silent=s

scripts/Makefile.build

+0 −2
Original line number Diff line number Diff line
@@ -219,7 +219,6 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT 


ifdef CONFIG_STACK_VALIDATION

ifndef CONFIG_LTO_CLANG

ifneq ($(SKIP_STACK_VALIDATION),1)



__objtool_obj := $(objtree)/tools/objtool/objtool
@@ -233,7 +232,6 @@ objtool_obj = $(if $(patsubst y%,, \ 
	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \

	$(__objtool_obj))



endif # SKIP_STACK_VALIDATION

endif # CONFIG_LTO_CLANG

endif # CONFIG_STACK_VALIDATION

scripts/Makefile.modfinal

+0 −2
Original line number Diff line number Diff line
@@ -39,12 +39,10 @@ prelink-ext := .lto 
# so let's now process the prelinked binary before we link the module.



ifdef CONFIG_STACK_VALIDATION

ifneq ($(SKIP_STACK_VALIDATION),1)

cmd_ld_ko_o +=								\

	$(objtree)/tools/objtool/objtool $(objtool_args)		\

		$(@:.ko=$(prelink-ext).o);



endif # SKIP_STACK_VALIDATION

endif # CONFIG_STACK_VALIDATION



endif # CONFIG_LTO_CLANG