Commit c1d45c3a authored Mar 02, 2016 by Josh Poimboeuf Committed by Ingo Molnar Mar 03, 2016

objtool: Support CROSS_COMPILE



When building with CONFIG_STACK_VALIDATION on a ppc64le host with an x86
cross-compiler, Stephen Rothwell saw the following objtool build errors:

    DESCEND  objtool
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/builtin-check.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/special.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/elf.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/objtool.o
    MKDIR    /home/sfr/next/x86_64_allmodconfig/tools/objtool/arch/x86/insn/
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/libstring.o
  elf.c:22:23: fatal error: sys/types.h: No such file or directory
  compilation terminated.
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/exec-cmd.o
    CC       /home/sfr/next/x86_64_allmodconfig/tools/objtool/help.o
  builtin-check.c:28:20: fatal error: string.h: No such file or directory
  compilation terminated.
  objtool.c:28:19: fatal error: stdio.h: No such file or directory
  compilation terminated.

It fails to build because it tries to compile objtool with the
cross-compiler instead of the host compiler.

Ensure that it always uses the host compiler by ignoring CROSS_COMPILE.

In order to do that properly, the libsubcmd.a library needs to be built
in tools/objtool/ rather than tools/lib/subcmd/.  The latter directory
contains the cross-compiled version which is needed for perf and
possibly other tools.

Note that cross-compiling for x86 on a _big_ endian system would result
in a bunch of false positive objtool warnings during the kernel build
because it isn't endian-aware.  But that's generally a rare edge case
and there haven't been any reports of anybody needing that.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/55b63eefc347f1bb28573f972d8d1adbf1f1c31d.1456962210.git.jpoimboe@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 19072f23

tools/lib/subcmd/Makefile

+4 −2

Original line number	Diff line number	Diff line
		@@ -8,8 +8,10 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
		#$(info Determined 'srctree' to be $(srctree))
		endif

		CC = $(CROSS_COMPILE)gcc
		AR = $(CROSS_COMPILE)ar
		CC ?= $(CROSS_COMPILE)gcc
		LD ?= $(CROSS_COMPILE)ld
		AR ?= $(CROSS_COMPILE)ar

		RM = rm -f

		MAKEFLAGS += --no-print-directory

tools/objtool/Makefile

+10 −7

Original line number	Diff line number	Diff line
		@@ -7,13 +7,19 @@ ARCH := x86
		endif
		endif

		# always use the host compiler
		CC = gcc
		LD = ld
		AR = ar

		ifeq ($(srctree),)
		srctree := $(patsubst %/,%,$(dir $(shell pwd)))
		srctree := $(patsubst %/,%,$(dir $(srctree)))
		endif

		SUBCMD_SRCDIR = $(srctree)/tools/lib/subcmd/
		LIBSUBCMD = $(if $(OUTPUT),$(OUTPUT),$(SUBCMD_SRCDIR))libsubcmd.a
		LIBSUBCMD_OUTPUT = $(if $(OUTPUT),$(OUTPUT),$(PWD)/)
		LIBSUBCMD = $(LIBSUBCMD_OUTPUT)libsubcmd.a

		OBJTOOL := $(OUTPUT)objtool
		OBJTOOL_IN := $(OBJTOOL)-in.o
		@@ -45,12 +51,9 @@ $(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN)


		$(LIBSUBCMD): fixdep FORCE
		$(Q)$(MAKE) -C $(SUBCMD_SRCDIR)

		$(LIBSUBCMD)-clean:
		$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) clean > /dev/null
		$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) OUTPUT=$(LIBSUBCMD_OUTPUT)

		clean: $(LIBSUBCMD)-clean
		clean:
		$(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
		$(Q)find $(OUTPUT) -name '.o' -delete -o -name '\..cmd' -delete -o -name '\.*.d' -delete
		$(Q)$(RM) $(OUTPUT)arch/x86/insn/inat-tables.c $(OUTPUT)fixdep

Admin message