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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: Josh 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2016-03-03 11:39:30 -06:00 committed by Ingo Molnar
parent e17cf3a80d
commit 3b27a0c85d
2 changed files with 14 additions and 1 deletions
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13
Makefile
View File

@ -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
# ---------------------------------------------------------------------------

2
scripts/Makefile.build
View File

@ -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