On 11/3/22 7:28 AM, KP Singh wrote:
On Thu, Nov 3, 2022 at 8:21 AM Yonghong Song <yhs@xxxxxx> wrote:Add bpf_rcu_read_lock() and bpf_rcu_read_unlock() helpers. Both helpers are available to all program types with CAP_BPF capability. Signed-off-by: Yonghong Song <yhs@xxxxxx> --- include/linux/bpf.h | 2 ++ include/uapi/linux/bpf.h | 14 ++++++++++++++ kernel/bpf/core.c | 2 ++ kernel/bpf/helpers.c | 26 ++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 14 ++++++++++++++ 5 files changed, 58 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 8d948bfcb984..a9bda4c91fc7 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2554,6 +2554,8 @@ extern const struct bpf_func_proto bpf_get_retval_proto; extern const struct bpf_func_proto bpf_user_ringbuf_drain_proto; extern const struct bpf_func_proto bpf_cgrp_storage_get_proto; extern const struct bpf_func_proto bpf_cgrp_storage_delete_proto; +extern const struct bpf_func_proto bpf_rcu_read_lock_proto; +extern const struct bpf_func_proto bpf_rcu_read_unlock_proto; const struct bpf_func_proto *tracing_prog_func_proto( enum bpf_func_id func_id, const struct bpf_prog *prog); diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 94659f6b3395..e86389cd6133 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5481,6 +5481,18 @@ union bpf_attr { * 0 on success. * * **-ENOENT** if the bpf_local_storage cannot be found. + * + * void bpf_rcu_read_lock(void) + * Description + * Call kernel rcu_read_lock().Simple wrapper around rcu_read_lock() and maybe explain where and how it is supposed to be used. e.g. the verifier will check if __rcu pointers are being accessed with bpf_rcu_read_lock in sleepable programs.
Okay, I can add more descriptions.
Calling the helper from a non-sleepable program is inconsequential, but maybe we can even avoid exposing it to non-sleepable programs?
I actually debated myself whether to make bpf_rcu_read_lock()/unlock() to be sleepable only. Although it won't hurt for non-sleepable program, I guess I can make it as sleepable only so users don't make mistake to use them in non-sleepable programs.
+ * Return + * None. + * + * void bpf_rcu_read_unlock(void) + * Description + * Call kernel rcu_read_unlock(). + * Return + * None. */ #define ___BPF_FUNC_MAPPER(FN, ctx...) \ FN(unspec, 0, ##ctx) \ @@ -5695,6 +5707,8 @@ union bpf_attr { FN(user_ringbuf_drain, 209, ##ctx) \ FN(cgrp_storage_get, 210, ##ctx) \ FN(cgrp_storage_delete, 211, ##ctx) \ + FN(rcu_read_lock, 212, ##ctx) \ + FN(rcu_read_unlock, 213, ##ctx) \ /* */
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