On 2024-05-14 13:54:43 [+0200], Toke Høiland-Jørgensen wrote:

quoted

--- a/include/linux/sched.h
+++ b/include/linux/sched.h

@@ -1504,6 +1505,8 @@ struct task_struct {
 	/* Used for BPF run context */
 	struct bpf_run_ctx		*bpf_ctx;
 #endif
+	/* Used by BPF for per-TASK xdp storage */
+	struct bpf_net_context		*bpf_net_context;

Okay, so if we are going the route of always putting this in 'current',
why not just embed the whole struct bpf_net_context inside task_struct,
instead of mucking about with the stack-allocated structures and
setting/clearing of pointers?

The whole struct bpf_net_context has 112 bytes. task_struct has 12352
bytes in my debug-config or 7296 bytes with defconfig on x86-64. Adding
it unconditionally would grow task_struct by ~1% but it would make
things way easier: The NULL case goes away, the assignment and cleanup
goes away, the INIT_LIST_HEAD can be moved to fork(). If the size
increase is not an issue then why not. Let me prepare…

-Toke

Sebastian