objtool: Detect and warn if libelf is missing and don't break the build

[linux-2.6-block.git] / Makefile

diff --git a/Makefile b/Makefile
index 2c27a01c42f17e5ea7858fde2a1903ef35c5f946..60b729540785b127c393fa8ccd229b6ca6b6e2e6 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -995,8 +995,19 @@ 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
 # ---------------------------------------------------------------------------