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Revert "kbuild: remove libelf checks from top Makefile"

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This reverts commit 0d989ac2c9.

Android kernel isn't ready for this change yet.  Here's why:

There are a couple of different methods for linking the Android
kernel presently, hermetically and not.  When *not* building
hermetically, the kernel is linked against locally installed
libraries (OpenSSL, LibElf, etc), usually installed by the distro.
Since these are usually fully fledged versions, they're usually
sufficient for any possible combination of build options.

However, when building hermetically (the intended default), the kernel
is linked against libraries contained in the `repo` controlled AOSP
repositories.  This is not a problem for the vast majority of the
important builds, but x86 allmodconfig builds require more
functionality than is presently provided.

This revert changes the presence of LibElf to be voluntary again.
Meaning that we do not have to insist on the presence of a locally
installed instance.

Once OpenSSL (currently provided via BoringSSL) is upgraded to a more
featureful offering, we can consider re-inclusion of this patch.

Change-Id: I810139b034e1a6c2db4dc9fa8871279f5edf215d
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Lee Jones
2021-07-14 13:01:24 +01:00
parent 7f3675457d
commit a2480b4d7e
3 changed files with 60 additions and 22 deletions
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78
Makefile
View File

@@ -1117,6 +1117,41 @@ 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)/)
@@ -1266,7 +1301,7 @@ prepare0: archprepare
$(Q)$(MAKE) $(build)=.
# All the preparing..
prepare: prepare0
prepare: prepare0 prepare-objtool prepare-resolve_btfids
PHONY += remove-stale-files
remove-stale-files:
@@ -1283,6 +1318,26 @@ 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
# ---------------------------------------------------------------------------
@@ -1351,27 +1406,6 @@ 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

2
scripts/Makefile.build
View File

@@ -219,6 +219,7 @@ 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
@@ -232,6 +233,7 @@ 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

2
scripts/Makefile.modfinal
View File

@@ -39,10 +39,12 @@ 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