On Tue, May 17, 2022 at 11:22:04AM +0800, Chen Zhongjin wrote:
> On 2022/5/10 17:46, Chen Zhongjin wrote:
> > csdlock_debug uses early_param and static_branch_enable() to enable
> > csd_lock_wait feature, which triggers a panic on arm64 with config:
> > CONFIG_SPARSEMEM=y
> > CONFIG_SPARSEMEM_VMEMMAP=n
> >
> > With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in
> > static_key_enable() and returns NULL which makes NULL dereference
> > because mem_section is initialized in sparse_init() which is later
> > than parse_early_param() stage.
> >
> > For powerpc this is also broken, because early_param stage is
> > earlier than jump_label_init() so static_key_enable won't work.
> > powerpc throws an warning: "static key 'xxx' used before call
> > to jump_label_init()".
> >
> > Thus, early_param is too early for csd_lock_wait to run
> > static_branch_enable(), so changes it to __setup to fix these.
> >
> > Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reported-by: Chen jingwen <chenjingwen6@xxxxxxxxxx>
> > Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
> > ---
> > Change v3 -> v4:
> > Fix title and description because this fix is also applied
> > to powerpc.
> > For more detailed arm64 bug report see:
> > https://lore.kernel.org/linux-arm-kernel/e8715911-f835-059d-27f8-cc5f5ad30a07@xxxxxxxxxx/t/
> >
> > Change v2 -> v3:
> > Add module name in title
> >
> > Change v1 -> v2:
> > Fix return 1 for __setup
> > ---
> > kernel/smp.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/smp.c b/kernel/smp.c
> > index 65a630f62363..381eb15cd28f 100644
> > --- a/kernel/smp.c
> > +++ b/kernel/smp.c
> > @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
> > if (val)
> > static_branch_enable(&csdlock_debug_enabled);
> >
> > - return 0;
> > + return 1;
> > }
> > -early_param("csdlock_debug", csdlock_debug);
> > +__setup("csdlock_debug=", csdlock_debug);
> >
> > static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
> > static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
>
> Ping for review. Thanks！
I have pulled it into -rcu for testing and further review. It might
well need to go through some other path, though.
Thanx, Paul
