Re: [PATCH 06/12] tools: sync small_const_nbits() macro with the kernel

From: Yury Norov <yury.norov@gmail.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
	linux-arch@vger.kernel.org, linux-sh@vger.kernel.org,
	Alexey Klimov <aklimov@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Arnd Bergmann <arnd@arndb.de>, David Sterba <dsterba@suse.com>,
	Dennis Zhou <dennis@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Jianpeng Ma <jianpeng.ma@intel.com>,
	Joe Perches <joe@perches.com>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Rich Felker <dalias@libc.org>,
	Stefano Brivio <sbrivio@redhat.com>,
	Wei Yang <richard.weiyang@linux.alibaba.com>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>
Subject: Re: [PATCH 06/12] tools: sync small_const_nbits() macro with the kernel
Date: Wed, 24 Mar 2021 12:49:11 -0700	[thread overview]
Message-ID: <20210324194911.GA18844@yury-ThinkPad> (raw)
In-Reply-To: <ef470d38-073d-2c6c-f9f8-909689a52212@rasmusvillemoes.dk>

On Mon, Mar 22, 2021 at 09:34:47AM +0100, Rasmus Villemoes wrote:
> On 21/03/2021 22.54, Yury Norov wrote:
> > Move the macro from tools/include/asm-generic/bitsperlong.h
> > to tools/include/linux/bitmap.h
> 
> The patch does it the other way around :)
> 
> > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > ---
> >  tools/include/asm-generic/bitsperlong.h | 3 +++
> >  tools/include/linux/bitmap.h            | 3 ---
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/include/asm-generic/bitsperlong.h b/tools/include/asm-generic/bitsperlong.h
> > index 8f2283052333..f530da2506cc 100644
> > --- a/tools/include/asm-generic/bitsperlong.h
> > +++ b/tools/include/asm-generic/bitsperlong.h
> > @@ -18,4 +18,7 @@
> >  #define BITS_PER_LONG_LONG 64
> >  #endif
> >  
> > +#define small_const_nbits(nbits) \
> > +	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
> > +
> 
> Well, the movement is consistent with the kernel, but shouldn't the
> definition also be updated to exclude constant-zero-size? It's not that
> they exist or ever have, in tools/ or kernel proper, but just if some
> day some oddball CONFIG_ combination ends up creating such a beast, I'd
> rather not have code like
> 
> +	if (small_const_nbits(size)) {
> +		unsigned long val = *addr & GENMASK(size - 1, 0);
> 
> blow up at run-time.
> 
> Other than that (and the above commit log typo), consider the series
> 
> Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Thanks for spotting out this. The proper version of the patch is
below.

Andrew, it seems everything else looks good. If so, should I resubmit
the series, or you can pull it as is, including this patch?

Thanks,
Yury

From 7558697d4448f01a8ef73cd31def5d3e68b44b61 Mon Sep 17 00:00:00 2001
From: Yury Norov <yury.norov@gmail.com>
Date: Wed, 17 Feb 2021 20:05:05 -0800
Subject: [PATCH] tools: sync small_const_nbits() macro with the kernel

Sync implementation with the kernel and move the macro from
tools/include/linux/bitmap.h to tools/include/asm-generic/bitsperlong.h

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 tools/include/asm-generic/bitsperlong.h | 3 +++
 tools/include/linux/bitmap.h            | 3 ---
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/include/asm-generic/bitsperlong.h b/tools/include/asm-generic/bitsperlong.h
index 8f2283052333..2093d56ddd11 100644
--- a/tools/include/asm-generic/bitsperlong.h
+++ b/tools/include/asm-generic/bitsperlong.h
@@ -18,4 +18,7 @@
 #define BITS_PER_LONG_LONG 64
 #endif
 
+#define small_const_nbits(nbits) \
+	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0)
+
 #endif /* __ASM_GENERIC_BITS_PER_LONG */
diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
index 4aabc23ec747..330dbf7509cc 100644
--- a/tools/include/linux/bitmap.h
+++ b/tools/include/linux/bitmap.h
@@ -22,9 +22,6 @@ void bitmap_clear(unsigned long *map, unsigned int start, int len);
 #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
 #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
 
-#define small_const_nbits(nbits) \
-	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
-
 static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
 {
 	if (small_const_nbits(nbits))
-- 
2.25.1

