All of lore.kernel.org
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, andy.shevchenko@gmail.com,
	ardb@kernel.org, arnd@arndb.de, linux-mm@kvack.org,
	mm-commits@vger.kernel.org, penguin-kernel@I-love.SAKURA.ne.jp,
	peterz@infradead.org, rikard.falkeborn@gmail.com,
	torvalds@linux-foundation.org, yury.norov@gmail.com
Subject: [patch 07/10] linux/bits.h: fix compilation error with GENMASK
Date: Sat, 22 May 2021 17:42:02 -0700	[thread overview]
Message-ID: <20210523004202.MOjiaAIxA%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210522174113.47fd4c853c0a1470c57deefa@linux-foundation.org>

From: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Subject: linux/bits.h: fix compilation error with GENMASK

GENMASK() has an input check which uses __builtin_choose_expr() to enable
a compile time sanity check of its inputs if they are known at compile
time.  However, it turns out that __builtin_constant_p() does not always
return a compile time constant [0].  It was thought this problem was fixed
with gcc 4.9 [1], but apparently this is not the case [2].

Switch to use __is_constexpr() instead which always returns a compile time
constant, regardless of its inputs.

[0]: https://lore.kernel.org/lkml/42b4342b-aefc-a16a-0d43-9f9c0d63ba7a@rasmusvillemoes.dk
[1]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449
[2]: https://lore.kernel.org/lkml/1ac7bbc2-45d9-26ed-0b33-bf382b8d858b@I-love.SAKURA.ne.jp

Link: https://lkml.kernel.org/r/20210511203716.117010-1-rikard.falkeborn@gmail.com
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Yury Norov <yury.norov@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/bits.h        |    2 +-
 include/linux/const.h       |    8 ++++++++
 include/linux/minmax.h      |   10 ++--------
 tools/include/linux/bits.h  |    2 +-
 tools/include/linux/const.h |    8 ++++++++
 5 files changed, 20 insertions(+), 10 deletions(-)

--- a/include/linux/bits.h~linux-bitsh-fix-compilation-error-with-genmask
+++ a/include/linux/bits.h
@@ -22,7 +22,7 @@
 #include <linux/build_bug.h>
 #define GENMASK_INPUT_CHECK(h, l) \
 	(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
-		__builtin_constant_p((l) > (h)), (l) > (h), 0)))
+		__is_constexpr((l) > (h)), (l) > (h), 0)))
 #else
 /*
  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
--- a/include/linux/const.h~linux-bitsh-fix-compilation-error-with-genmask
+++ a/include/linux/const.h
@@ -3,4 +3,12 @@
 
 #include <vdso/const.h>
 
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
+ */
+#define __is_constexpr(x) \
+	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
 #endif /* _LINUX_CONST_H */
--- a/include/linux/minmax.h~linux-bitsh-fix-compilation-error-with-genmask
+++ a/include/linux/minmax.h
@@ -2,6 +2,8 @@
 #ifndef _LINUX_MINMAX_H
 #define _LINUX_MINMAX_H
 
+#include <linux/const.h>
+
 /*
  * min()/max()/clamp() macros must accomplish three things:
  *
@@ -17,14 +19,6 @@
 #define __typecheck(x, y) \
 	(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
 
-/*
- * This returns a constant expression while determining if an argument is
- * a constant expression, most importantly without evaluating the argument.
- * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
- */
-#define __is_constexpr(x) \
-	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
-
 #define __no_side_effects(x, y) \
 		(__is_constexpr(x) && __is_constexpr(y))
 
--- a/tools/include/linux/bits.h~linux-bitsh-fix-compilation-error-with-genmask
+++ a/tools/include/linux/bits.h
@@ -22,7 +22,7 @@
 #include <linux/build_bug.h>
 #define GENMASK_INPUT_CHECK(h, l) \
 	(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
-		__builtin_constant_p((l) > (h)), (l) > (h), 0)))
+		__is_constexpr((l) > (h)), (l) > (h), 0)))
 #else
 /*
  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
--- a/tools/include/linux/const.h~linux-bitsh-fix-compilation-error-with-genmask
+++ a/tools/include/linux/const.h
@@ -3,4 +3,12 @@
 
 #include <vdso/const.h>
 
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
+ */
+#define __is_constexpr(x) \
+	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
 #endif /* _LINUX_CONST_H */
_

  parent reply	other threads:[~2021-05-23  0:42 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-23  0:41 incoming Andrew Morton
2021-05-23  0:41 ` [patch 01/10] mm/shuffle: fix section mismatch warning Andrew Morton
2021-05-23  0:41 ` [patch 02/10] Revert "mm/gup: check page posion status for coredump." Andrew Morton
2021-05-23  0:41 ` [patch 03/10] ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry Andrew Morton
2021-05-23  0:41 ` [patch 04/10] tools/testing/selftests/exec: fix link error Andrew Morton
2021-05-23  0:41 ` [patch 05/10] kasan: slab: always reset the tag in get_freepointer_safe() Andrew Morton
2021-05-23  0:41 ` [patch 06/10] watchdog: reliable handling of timestamps Andrew Morton
2021-05-23  0:42 ` Andrew Morton [this message]
2021-05-23  0:42 ` [patch 08/10] proc: remove Alexey from MAINTAINERS Andrew Morton
2021-05-23  0:42 ` [patch 09/10] lib: kunit: suppress a compilation warning of frame size Andrew Morton
2021-05-23  0:42 ` [patch 10/10] userfaultfd: hugetlbfs: fix new flag usage in error path Andrew Morton

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210523004202.MOjiaAIxA%akpm@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=andy.shevchenko@gmail.com \
    --cc=ardb@kernel.org \
    --cc=arnd@arndb.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mm-commits@vger.kernel.org \
    --cc=penguin-kernel@I-love.SAKURA.ne.jp \
    --cc=peterz@infradead.org \
    --cc=rikard.falkeborn@gmail.com \
    --cc=torvalds@linux-foundation.org \
    --cc=yury.norov@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.