From: David Laight <David.Laight@ACULAB.COM>
To: 'Matthias Kaehlcke' <mka@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Evan Green <evgreen@chromium.org>,
Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
Douglas Anderson <dianders@chromium.org>,
Stephen Boyd <swboyd@chromium.org>,
Manoj Gupta <manojgupta@chromium.org>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: RE: [PATCH] tty/sysrq: Make local variable 'killer' in sysrq_handle_crash() global
Date: Tue, 18 Sep 2018 11:46:30 +0000 [thread overview]
Message-ID: <0d8470c7fdbe4429af82b830d39215f3@AcuMS.aculab.com> (raw)
In-Reply-To: <20180917213304.44476-1-mka@chromium.org>
From: Matthias Kaehlcke
> Sent: 17 September 2018 22:33
>
> sysrq_handle_crash() dereferences a NULL pointer on purpose to force
> an exception, the local variable 'killer' is assigned to NULL and
> dereferenced later. Clang detects the NULL pointer dereference at compile
> time and emits a BRK instruction (on arm64) instead of the expected NULL
> pointer exception. Change 'killer' to a global variable (and rename it
> to 'sysrq_killer' to avoid possible clashes) to prevent Clang from
> detecting the condition. By default global variables are initialized
> with zero/NULL in C, therefore an explicit initialization is not needed.
You need an explicit initialiser in order to make it global data
rather than a common section.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2018-09-18 11:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-17 21:33 [PATCH] tty/sysrq: Make local variable 'killer' in sysrq_handle_crash() global Matthias Kaehlcke
2018-09-18 6:09 ` Sai Prakash Ranjan
2018-09-18 6:11 ` Jiri Slaby
2018-09-18 6:58 ` Sai Prakash Ranjan
2018-09-18 7:20 ` Greg Kroah-Hartman
2018-09-18 9:05 ` Sai Prakash Ranjan
2018-09-18 9:17 ` Greg Kroah-Hartman
2018-09-18 9:53 ` Sai Prakash Ranjan
[not found] ` <32bf1760-4967-a37a-6a17-3f7d5f6e071e@suse.cz>
2018-09-18 17:32 ` Matthias Kaehlcke
2018-09-18 17:24 ` Matthias Kaehlcke
2018-09-18 11:46 ` David Laight [this message]
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