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To:     arnd@arndb.de
Cc:     linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
From:   Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
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Subject: [x86] BUG()/BUG_ON() macros cannot be disabled
Message-ID: <9516e4b3-f9f2-b150-f019-8b1ef465efb3@tu-dortmund.de>
Date:   Tue, 25 Sep 2018 13:35:29 +0200
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From: Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
To: arnd@arndb.de
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Message-ID: <9516e4b3-f9f2-b150-f019-8b1ef465efb3@tu-dortmund.de>
Subject: [x86] BUG()/BUG_ON() macros cannot be disabled

--ykzM58qJSbQVMj6jyweAtzezWrFi9csp4
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--------------5E0CA33CC47A8D6B0687C66A
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Hi Arnd,

I recently tried to disable the BUG macros on x86-32. I disabled the
config item in 'General Setup -> Configure standard kernel features
(expert users) -> BUG() support'.
However, BUG/BUG_ON is still defined. In the !CONFIG_BUG branch in
include/asm-generic/bug.h (line 181) the code checks for the existence
of architecture-specific variants of those macros.
Since x86 defines its own version of BUG(), line 182 is *not* used.
In the following, the x86 variant of BUG() is then used to define the
BUG_ON() macro.

I propose a patch that really disables both macros if the developer
wants it.
It undefines the respective x86 variants, and defines both macros as
'empty' macros.

Regards,
Alex

--=20
Technische Universit=C3=A4t Dortmund
Alexander Lochmann                PGP key: 0xBC3EF6FD
Otto-Hahn-Str. 16                 phone:  +49.231.7556141
D-44227 Dortmund                  fax:    +49.231.7556116
http://ess.cs.tu-dortmund.de/Staff/al

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Content-Type: text/x-patch;
 name="disable-bug-macro.patch"
Content-Transfer-Encoding: quoted-printable
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 filename="disable-bug-macro.patch"

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 20561a60db9c..1e7977582277 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -178,14 +178,17 @@ void __warn(const char *file, int line, void *calle=
r, unsigned taint,
 })
=20
 #else /* !CONFIG_BUG */
-#ifndef HAVE_ARCH_BUG
-#define BUG() do {} while (1)
+#ifdef HAVE_ARCH_BUG
+#undef BUG
 #endif
=20
-#ifndef HAVE_ARCH_BUG_ON
-#define BUG_ON(condition) do { if (condition) BUG(); } while (0)
+#ifdef HAVE_ARCH_BUG_ON
+#undef BUG_ON
 #endif
=20
+#define BUG_ON(condition) do { if (condition) BUG(); } while (0)
+#define BUG() do {} while (1)
+
 #ifndef HAVE_ARCH_WARN_ON
 #define WARN_ON(condition) ({						\
 	int __ret_warn_on =3D !!(condition);				\

--------------5E0CA33CC47A8D6B0687C66A--

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