Peter Zijlstra <pet...@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 <vba...@suse.cz>
>> > Signed-off-by: Stafford Horne <sho...@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
