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>
This commit is contained in:
Masahiro Yamada 2021-05-12 15:52:01 +09:00
parent 1bb0b18a06
commit 0d989ac2c9
3 changed files with 22 additions and 60 deletions

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@ -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

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@ -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

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@ -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