From: Michael Ellerman <mpe@ellerman.id.au>
To: Peter Zijlstra <peterz@infradead.org>, Vlastimil Babka <vbabka@suse.cz>
Cc: Stafford Horne <shorne@gmail.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Kees Cook <keescook@chromium.org>, Jessica Yu <jeyu@redhat.com>,
Petr Mladek <pmladek@suse.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Yang Shi <yang.shi@linaro.org>, Tejun Heo <tj@kernel.org>,
Prarit Bhargava <prarit@redhat.com>,
Yaowei Bai <baiyaowei@cmss.chinamobile.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>
Subject: Re: [PATCH -next] init/main: Init jump_labels before they are used to build zonelists
Date: Mon, 23 Jan 2017 16:54:00 +1100 [thread overview]
Message-ID: <87mveimidj.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20170117134454.GB6515@twins.programming.kicks-ass.net>
Peter Zijlstra <peterz@infradead.org> writes:
> On Tue, Jan 17, 2017 at 02:07:36PM +0100, Vlastimil Babka wrote:
>
>> Anyway I'm not sure if this patch is safe. Hopefully Peter can judge
>> this better...
>>
>> > Cc: Vlastimil Babka <vbabka@suse.cz>
>> > Signed-off-by: Stafford Horne <shorne@gmail.com>
>> > ---
>> > init/main.c | 3 +--
>> > 1 file changed, 1 insertion(+), 2 deletions(-)
>> >
>> > diff --git a/init/main.c b/init/main.c
>> > index 8b1adb6e..d1ca7cb 100644
>> > --- a/init/main.c
>> > +++ b/init/main.c
>> > @@ -513,6 +513,7 @@ asmlinkage __visible void __init start_kernel(void)
>> > boot_cpu_state_init();
>> > smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
>> >
>> > + jump_label_init();
>> > build_all_zonelists(NULL, NULL);
>> > page_alloc_init();
>> >
>> > @@ -526,8 +527,6 @@ asmlinkage __visible void __init start_kernel(void)
>> > parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
>> > NULL, set_init_arg);
>> >
>> > - jump_label_init();
>> > -
>
> Urgh, that means auditing all archs that implement this. The thing
> you're looking for is if the self-modifying code cruft can be done that
> early.
You could do what we do on powerpc, which is to call jump_label_init()
early in arch code.
The second call from generic code will just return without doing
anything, see the start of jump_label_init():
void __init jump_label_init(void)
{
struct jump_entry *iter_start = __start___jump_table;
struct jump_entry *iter_stop = __stop___jump_table;
struct static_key *key = NULL;
struct jump_entry *iter;
/*
* Since we are initializing the static_key.enabled field with
* with the 'raw' int values (to avoid pulling in atomic.h) in
* jump_label.h, let's make sure that is safe. There are only two
* cases to check since we initialize to 0 or 1.
*/
BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);
if (static_key_initialized)
return;
cheers
prev parent reply other threads:[~2017-01-23 5:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-17 12:56 [PATCH -next] init/main: Init jump_labels before they are used to build zonelists Stafford Horne
2017-01-17 13:07 ` Vlastimil Babka
2017-01-17 13:44 ` Peter Zijlstra
2017-01-17 14:30 ` Stafford Horne
2017-01-17 16:11 ` Vlastimil Babka
2017-01-17 20:34 ` Andrew Morton
2017-01-17 20:49 ` Vlastimil Babka
2017-01-19 8:28 ` Vlastimil Babka
2017-01-19 9:56 ` Mel Gorman
2017-01-23 5:54 ` Michael Ellerman [this message]
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