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>
c1d45c3abd