From: Greg KH <gregkh@linuxfoundation.org>
To: glider@google.com
Cc: tkjos@google.com, keescook@chromium.org, arve@android.com,
mingo@redhat.com, dvyukov@google.com, jannh@google.com,
devel@driverdev.osuosl.org, peterz@infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/3] binder: do not initialize locals passed to copy_from_user()
Date: Mon, 2 Mar 2020 18:38:52 +0100 [thread overview]
Message-ID: <20200302173852.GB109022@kroah.com> (raw)
In-Reply-To: <20200302130430.201037-2-glider@google.com>
On Mon, Mar 02, 2020 at 02:04:29PM +0100, glider@google.com wrote:
> Certain copy_from_user() invocations in binder.c are known to
> unconditionally initialize locals before their first use, like e.g. in
> the following case:
>
> struct binder_transaction_data tr;
> if (copy_from_user(&tr, ptr, sizeof(tr)))
> return -EFAULT;
>
> In such cases enabling CONFIG_INIT_STACK_ALL leads to insertion of
> redundant locals initialization that the compiler fails to remove.
> To work around this problem till Clang can deal with it, we apply
> __no_initialize to local Binder structures.
I would like to see actual benchmark numbers showing this is
needed/useful otherwise it's going to just be random people adding this
marking to random places with no real reason.
thanks,
greg k-h
next prev parent reply other threads:[~2020-03-02 17:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-02 13:04 [PATCH v2 1/3] compiler.h: define __no_initialize glider
2020-03-02 13:04 ` [PATCH v2 2/3] binder: do not initialize locals passed to copy_from_user() glider
2020-03-02 13:09 ` Joe Perches
2020-03-02 13:25 ` Alexander Potapenko
2020-03-02 13:52 ` Dan Carpenter
2020-03-02 13:58 ` Joe Perches
2020-03-02 18:17 ` Alexander Potapenko
2020-03-02 18:31 ` Jann Horn
2020-03-05 9:03 ` Rasmus Villemoes
2020-03-05 12:45 ` Jann Horn
2020-03-06 2:29 ` Al Viro
2020-03-02 18:50 ` Joe Perches
2020-03-03 9:14 ` Alexander Potapenko
2020-03-03 9:38 ` Dan Carpenter
2020-03-03 13:56 ` Joe Perches
2020-03-03 14:15 ` Dan Carpenter
2020-03-04 18:13 ` Kees Cook
2020-03-05 8:07 ` Dan Carpenter
2020-03-05 8:26 ` Kees Cook
2020-03-05 8:33 ` Alexander Potapenko
2020-03-02 17:38 ` Greg KH [this message]
2020-03-02 18:28 ` Alexander Potapenko
2020-03-02 13:04 ` [PATCH v2 3/3] sched/wait: avoid double initialization in ___wait_event() glider
2020-03-02 16:56 ` Todd Kjos
2020-03-02 18:03 ` Alexander Potapenko
2020-03-02 18:39 ` Greg Kroah-Hartman
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