Re: [PATCH bpf-next 4/8] bpf: add initial poke descriptor table for jit images

Add initial poke table data structures and management to the BPF
prog that can later be used by JITs. Also add an instance of poke
specific data for tail call maps; plan for later work is to extend
this also for BPF static keys.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <redacted>
---
 include/linux/bpf.h    | 20 ++++++++++++++++++++
 include/linux/filter.h | 10 ++++++++++
 kernel/bpf/core.c      | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 836e49855bf9..cad4382c1265 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h

@@ -488,6 +488,24 @@ struct bpf_func_info_aux {
        bool unreliable;
 };

+enum bpf_jit_poke_reason {
+       BPF_POKE_REASON_TAIL_CALL,
+};
+
+/* Descriptor of pokes pointing /into/ the JITed image. */
+struct bpf_jit_poke_descriptor {
+       void *ip;
+       union {
+               struct {
+                       struct bpf_map *map;
+                       u32 key;
+               } tail_call;
+       };
+       u8 ip_stable;