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

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Message-ID: <20160713232926.GB6961@kernel.org>
Date:	Wed, 13 Jul 2016 20:29:26 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Alexander Yarygin <yarygin@...ux.vnet.ibm.com>,
	Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
	Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Chris Phlipot <cphlipot0@...il.com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	David Ahern <dsahern@...il.com>,
	Davidlohr Bueso <dbueso@...e.de>,
	David Tolnay <dtolnay@...il.com>,
	Eric Auger <eric.auger@...aro.org>,
	Hemant Kumar <hemant@...ux.vnet.ibm.com>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Jiri Olsa <jolsa@...nel.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	"Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vineet Gupta <vgupta@...opsys.com>,
	Wang Nan <wangnan0@...wei.com>,
	Yunlong Song <yunlong.song@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL 00/66] perf/core improvements and fixes

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@...hat.com>
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@...el.com>
    Cc: David Ahern <dsahern@...il.com>
    Cc: Jiri Olsa <jolsa@...nel.org>
    Cc: Namhyung Kim <namhyung@...nel.org>
    Cc: Wang Nan <wangnan0@...wei.com>
    Link: http://lkml.kernel.org/n/tip-og5fmkr17856lhupacihwxvb@git.kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

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