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！
