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Commit 3b27a0c8 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

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



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: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-next@vger.kernel.org
Cc: linux@roeck-us.net
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/8c27fe00face60f42e888ddb3142c97e45223165.1457026550.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e17cf3a8

Makefile

+12 −1
Original line number Diff line number Diff line
@@ -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

# ---------------------------------------------------------------------------

scripts/Makefile.build

+2 −0
Original line number Diff line number Diff line
@@ -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