ebpf: add helper for obtaining current processor id

This patch adds the possibility to obtain raw_smp_processor_id() in
eBPF. Currently, this is only possible in classic BPF where commit
da2033c28226 ("filter: add SKF_AD_RXHASH and SKF_AD_CPU") has added
facilities for this.

Perhaps most importantly, this would also allow us to track per CPU
statistics with eBPF maps, or to implement a poor-man's per CPU data
structure through eBPF maps.

Example function proto-type looks like:

  u32 (*smp_processor_id)(void) = (void *)BPF_FUNC_get_smp_processor_id;

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1c2ca2b477c8..de1f63668daf 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -166,6 +166,7 @@ enum bpf_func_id {
         BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */
         BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
         BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */
+        BPF_FUNC_get_smp_processor_id, /* u32 raw_smp_processor_id(void) */
         __BPF_FUNC_MAX_ID,
 };