Re: [GIT PULL 00/66] perf/core improvements and fixes

[Arnaldo Carvalho de Melo]

Em Wed, Jul 13, 2016 at 10:54:49PM +0200, Peter Zijlstra escreveu:
> On Wed, Jul 13, 2016 at 03:49:14PM -0500, Josh Poimboeuf wrote:
> > That '#define BITS_PER_LONG 32' comes from the following code in
> > tools/include/asm-generic/bitsperlong.h:
> > 
> >   #ifdef CONFIG_64BIT
> >   #define BITS_PER_LONG 64
> >   #else
> >   #define BITS_PER_LONG 32
> >   #endif /* CONFIG_64BIT */
> > 
> > Because objtool doesn't have CONFIG_64BIT defined, it falls through to
> > the '#else' condition.  I think tools code shouldn't be relying on
> > kernel config options.
> 
> Right.. __LP64__ would work in general I think, or __SIZEOF_LONG__ *
> __CHAR_BIT__.

Ok, to keep it close to the kernel counterpart, I ended up with the
patch below, that builds for all the distros I have in my container set.

commit 2a00f026a15d161b47ba3d3417d0fec5193468c3
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Date:   Wed Jul 13 15:04:04 2016 -0300

    tools: Fix up BITS_PER_LONG setting
    
    It was set based on CONFIG_64BIT, that is available only when using
    Kconfig, which we're working towards but not to the point of having this
    CONFIG variable set, so synthesize it from available compiler defined
    defines, __SIZEOF_LONG__ or, lacking that, __WORDSIZE.
    
    Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
    Cc: David Ahern <dsahern@xxxxxxxxx>
    Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
    Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
    Cc: Wang Nan <wangnan0@xxxxxxxxxx>
    Link: http://lkml.kernel.org/n/tip-og5fmkr17856lhupacihwxvb@xxxxxxxxxxxxxx
    Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

diff --git a/tools/include/asm-generic/bitsperlong.h b/tools/include/asm-generic/bitsperlong.h
index d1d70aa19021..cfd661c6fc17 100644
--- a/tools/include/asm-generic/bitsperlong.h
+++ b/tools/include/asm-generic/bitsperlong.h
@@ -3,6 +3,24 @@
 
 #include <uapi/asm-generic/bitsperlong.h>
 
+/*
+ * In the kernel, where this file comes from, we can rely on CONFIG_64BIT,
+ * here we have to make amends with what the various compilers provides us
+ * to figure out if we're on a 64-bit machine...
+ */
+#ifdef __SIZEOF_LONG__
+# if __SIZEOF_LONG__ == 8
+#  define CONFIG_64BIT
+# endif
+#else
+# ifdef __WORDSIZE
+#  if __WORDSIZE == 64
+#   define CONFIG_64BIT
+#  endif
+# else
+#  error Failed to determine BITS_PER_LONG value
+# endif
+#endif
 
 #ifdef CONFIG_64BIT
 #define BITS_PER_LONG 64
@@ -10,11 +28,7 @@
 #define BITS_PER_LONG 32
 #endif /* CONFIG_64BIT */
 
-/*
- * FIXME: The check currently breaks x86-64 build, so it's
- * temporarily disabled. Please fix x86-64 and reenable
- */
-#if 0 && BITS_PER_LONG != __BITS_PER_LONG
+#if BITS_PER_LONG != __BITS_PER_LONG
 #error Inconsistent word size. Check asm/bitsperlong.h
 #endif