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Subject[PATCH] objtool: Warn if libelf is missing
Date
With CONFIG_STACK_VALIDATION enabled, if the host system doesn't have
a development version of libelf installed, the build fails with errors
like:

elf.h:22:18: fatal error: gelf.h: No such file or directory compilation terminated.

Instead of failing to build, instead just print a warning and disable
stack validation.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
Based on tip/master.

Makefile | 13 ++++++++++++-
scripts/Makefile.build | 2 ++
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 750df29..1fd8328 100644
--- a/Makefile
+++ b/Makefile
@@ -998,8 +998,19 @@ prepare0: archprepare FORCE
# All the preparing..
prepare: prepare0 prepare-objtool

+ifdef CONFIG_STACK_VALIDATION
+ has_libelf := $(shell echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf - &> /dev/null && echo 1 || echo 0)
+ ifeq ($(has_libelf),1)
+ objtool_target := tools/objtool FORCE
+ else
+ $(warning "Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev or elfutils-libelf-devel")
+ SKIP_STACK_VALIDATION := 1
+ export SKIP_STACK_VALIDATION
+ endif
+endif
+
PHONY += prepare-objtool
-prepare-objtool: $(if $(CONFIG_STACK_VALIDATION), tools/objtool FORCE)
+prepare-objtool: $(objtool_target)

# Generate some files
# ---------------------------------------------------------------------------
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 130a452..e1bc190 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -242,6 +242,7 @@ cmd_record_mcount = \
endif

ifdef CONFIG_STACK_VALIDATION
+ifneq ($(SKIP_STACK_VALIDATION),1)

__objtool_obj := $(objtree)/tools/objtool/objtool

@@ -260,6 +261,7 @@ objtool_obj = $(if $(patsubst y%,, \
$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
$(__objtool_obj))

+endif # SKIP_STACK_VALIDATION
endif # CONFIG_STACK_VALIDATION

define rule_cc_o_c
--
2.4.3
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