On Mon, Jan 24, 2022 at 10:54 AM Kenny Yu <kennyyu@xxxxxx> wrote:
>
> This patch allows bpf iterator programs to use sleepable helpers by
> changing `bpf_iter_run_prog` to use the appropriate synchronization.
> With sleepable bpf iterator programs, we can no longer use
> `rcu_read_lock()` and must use `rcu_read_lock_trace()` instead
> to protect the bpf program.
>
> Signed-off-by: Kenny Yu <kennyyu@xxxxxx>
> ---
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> kernel/bpf/bpf_iter.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
> index b7aef5b3416d..110029ede71e 100644
> --- a/kernel/bpf/bpf_iter.c
> +++ b/kernel/bpf/bpf_iter.c
> @@ -5,6 +5,7 @@
> #include <linux/anon_inodes.h>
> #include <linux/filter.h>
> #include <linux/bpf.h>
> +#include <linux/rcupdate_trace.h>
>
> struct bpf_iter_target_info {
> struct list_head list;
> @@ -684,11 +685,20 @@ int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
> {
> int ret;
>
> - rcu_read_lock();
> - migrate_disable();
> - ret = bpf_prog_run(prog, ctx);
> - migrate_enable();
> - rcu_read_unlock();
> + if (prog->aux->sleepable) {
> + rcu_read_lock_trace();
> + migrate_disable();
> + might_fault();
> + ret = bpf_prog_run(prog, ctx);
> + migrate_enable();
> + rcu_read_unlock_trace();
> + } else {
> + rcu_read_lock();
> + migrate_disable();
> + ret = bpf_prog_run(prog, ctx);
> + migrate_enable();
> + rcu_read_unlock();
> + }
>
> /* bpf program can only return 0 or 1:
> * 0 : okay
> --
> 2.30.2
>
