Subject: Re: [PATCH/RFC] Re: linux-next: build failure after merge of the luto-misc tree

From: Josh Poimboeuf <[email-masked]>
Date: Fri, 22 Jul 2016 14:19:20 -0500

On Fri, Jul 22, 2016 at 11:37:39AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jul 21, 2016 at 10:41:18PM -0500, Josh Poimboeuf escreveu:
> > On Fri, Jul 22, 2016 at 09:23:02AM +1000, Stephen Rothwell wrote:
> > > It just looks like objtool was not written with cross compilation in
> > > mind?
>  
> > I don't know yet what the specific problem is, but objtool should work
> > fine in a cross-compiled environment.  It needs to be compiled with the
> > host (powerpc) compiler, but then it needs to disassemble target (x86)
> > files.  It worked fine before the bitsperlong.h files were merged.
> 
> So, trying to summarize from the various messages in this thread:
> 
> In Tue, Jul 19, 2016 at 01:26:08PM +1000, Stephen Rothwell wrote:
> 
> > It produces these errors (from the x86_64 allmodconfig build):
> >
> > In file included from
> > /home/sfr/next/next/tools/arch/x86/include/uapi/asm/bitsperlong.h:10:0,
> >                  from /usr/include/asm-generic/int-ll64.h:11,
> >                  from /usr/include/powerpc64le-linux-gnu/asm/types.h:27,
> >                  from /home/sfr/next/next/tools/include/linux/types.h:9,
> >                  from /home/sfr/next/next/tools/include/linux/list.h:4,
> >                  from elf.h:23,
> >                  from elf.c:30:
> > /home/sfr/next/next/tools/include/asm-generic/bitsperlong.h:13:2:
> > error: #error Inconsistent word size. Check asm/bitsperlong.h
> >  #error Inconsistent word size. Check asm/bitsperlong.h
> >   ^
> 
> So it starts at tools/arch/x86/include/uapi/asm/bitsperlong.h, and as
> you mention, this should've instead be using the host headers, i.e.:
> 
>    tools/arch/powerpc/include/uapi/asm/bitsperlong.h
> 
> Which it will if it uses HOSTARCH in tools/objtool/Makefile when setting
> up the header search path, I have two csets in my perf/core branch that
> fixes this, and that are equivalent to the last patch Stephen tried:
> 
>   $ git log --oneline -2
>   87f7dc54366a objtool: Use tools/scripts/Makefile.arch to get ARCH and HOSTARCH
>   0eec6770ab60 tools build: Add HOSTARCH Makefile variable
>   $ 
> 
> Ok, so now it uses the right file, see the whole sequence at the end of this
> e-mail, but it boils down to:
> 
> -----------------------------------------------------------------------------
> #if defined(__powerpc64__)
> # define __BITS_PER_LONG 64
> #else
> # define __BITS_PER_LONG 32
> #endif
> 
> #ifdef __SIZEOF_LONG__
> #define BITS_PER_LONG (__CHAR_BIT__ * __SIZEOF_LONG__)
> #else
> #define BITS_PER_LONG __WORDSIZE
> #endif
> 
> #if BITS_PER_LONG != __BITS_PER_LONG
> #error Inconsistent word size. Check asm/bitsperlong.h
> #endif
> -----------------------------------------------------------------------------
> 
> Which I think has no problems, right? The last problem reported ty Stephen now is:
> 
> In Fri, 22 Jul 2016 09:23:02 +1000, Stephen Rothwell wrote:
> 
> > That gets me this errors from the x86_64 allmodconfig build:
> 
> > tools/objtool/objtool-in.o: In function `decode_instructions':
> > tools/objtool/builtin-check.c:276: undefined reference to `arch_decode_instruction'
> 
> Should work, since ARCH should be x86 and then tools/objtool/Build will have
> this:
> 
> objtool-y += arch/$(ARCH)/
> 
> Turned into:
> 
> objtool-y += arch/x86/
> 
> Which will build tools/objtool/arch/x86/decode.c, that will provide that
> arch_decode_instruction() function :-\
> 
> I.e. with the two patches I mentioned, that are equivalent to the last patch I
> sent to Stephen for testing, we would end up with HOSTARCH=powerpc and
> ARCH=x86, no?

Thanks for spelling it out, that helped a lot.

I'm guessing Stephen is setting ARCH=x86_64 on the command-line rather
than ARCH=x86.  How about the following patch?  Stephen, can you confirm
this fixes it?  This is on top of Arnaldo's other two fixes here:

  https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git perf/core

From: Josh Poimboeuf <[email-masked]>
Subject: [PATCH] tools build: fix objtool build with ARCH=x86_64

The objtool build fails in a cross-compiled environment on a non-x86
host with "ARCH=x86_64":

  tools/objtool/objtool-in.o: In function `decode_instructions':
  tools/objtool/builtin-check.c:276: undefined reference to `arch_decode_instruction'

We could override the ARCH environment variable and change it back to
x86, similar to what the objtool Makefile was doing before; but it's
tricky to override environment variables consistently.

Instead, take a similar approach used by the Linux top-level Makefile
and introduce a SRCARCH Makefile variable which evaluates to "x86" when
ARCH is either "x86_64" or "x86".

Reported-by: Stephen Rothwell <[email-masked]>
Signed-off-by: Josh Poimboeuf <[email-masked]>
---
 tools/objtool/Build         |  2 +-
 tools/objtool/Makefile      |  2 +-
 tools/scripts/Makefile.arch | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/Build b/tools/objtool/Build
index 2457916..d6cdece 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -1,4 +1,4 @@
-objtool-y += arch/$(ARCH)/
+objtool-y += arch/$(SRCARCH)/
 objtool-y += builtin-check.o
 objtool-y += elf.o
 objtool-y += special.o
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index c9ad80a..577f2d4 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -29,7 +29,7 @@ elfshdr := $(shell echo '\#include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | gre
 CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
 
 AWK = awk
-export srctree OUTPUT CFLAGS ARCH AWK
+export srctree OUTPUT CFLAGS SRCARCH AWK
 include $(srctree)/tools/build/Makefile.include
 
 $(OBJTOOL_IN): fixdep FORCE
diff --git a/tools/scripts/Makefile.arch b/tools/scripts/Makefile.arch
index 887321c..ad85b92 100644
--- a/tools/scripts/Makefile.arch
+++ b/tools/scripts/Makefile.arch
@@ -5,10 +5,42 @@ HOSTARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
                                   -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
                                   -e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ \
                                   -e s/tile.*/tile/ )
+
 ifndef ARCH
 ARCH := $(HOSTARCH)
 endif
 
+SRCARCH := $(ARCH)
+
+# Additional ARCH settings for x86
+ifeq ($(ARCH),i386)
+        SRCARCH := x86
+endif
+ifeq ($(ARCH),x86_64)
+        SRCARCH := x86
+endif
+
+# Additional ARCH settings for sparc
+ifeq ($(ARCH),sparc32)
+       SRCARCH := sparc
+endif
+ifeq ($(ARCH),sparc64)
+       SRCARCH := sparc
+endif
+
+# Additional ARCH settings for sh
+ifeq ($(ARCH),sh64)
+       SRCARCH := sh
+endif
+
+# Additional ARCH settings for tile
+ifeq ($(ARCH),tilepro)
+       SRCARCH := tile
+endif
+ifeq ($(ARCH),tilegx)
+       SRCARCH := tile
+endif
+
 LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1)
 ifeq ($(LP64), 1)
   IS_64_BIT := 1