Commit 93f0d096 authored by Puranjay Mohan's avatar Puranjay Mohan Committed by Alexei Starovoitov
Browse files

bpf: move recursion detection logic to helpers 



BPF programs detect recursion by doing atomic inc/dec on a per-cpu
active counter from the trampoline. Create two helpers for operations on
this active counter, this makes it easy to changes the recursion
detection logic in future.

This commit makes no functional changes.

Acked-by: default avatarYonghong Song <yonghong.song@linux.dev>
Signed-off-by: default avatarPuranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20251219184422.2899902-2-puranjay@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 3d60306b

include/linux/bpf.h

+10 −0
Original line number Diff line number Diff line
@@ -2004,6 +2004,16 @@ struct bpf_struct_ops_common_value { 
	enum bpf_struct_ops_state state;

};



static inline bool bpf_prog_get_recursion_context(struct bpf_prog *prog)

{

	return this_cpu_inc_return(*(prog->active)) == 1;

}



static inline void bpf_prog_put_recursion_context(struct bpf_prog *prog)

{

	this_cpu_dec(*(prog->active));

}



#if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)

/* This macro helps developer to register a struct_ops type and generate

 * type information correctly. Developers should use this macro to register

kernel/bpf/trampoline.c

+4 −4
Original line number Diff line number Diff line
@@ -949,7 +949,7 @@ static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tram 


	run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);



	if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {

	if (unlikely(!bpf_prog_get_recursion_context(prog))) {

		bpf_prog_inc_misses_counter(prog);

		if (prog->aux->recursion_detected)

			prog->aux->recursion_detected(prog);
@@ -993,7 +993,7 @@ static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start, 
	bpf_reset_run_ctx(run_ctx->saved_run_ctx);



	update_prog_stats(prog, start);

	this_cpu_dec(*(prog->active));

	bpf_prog_put_recursion_context(prog);

	rcu_read_unlock_migrate();

}
@@ -1029,7 +1029,7 @@ u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog, 


	run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);



	if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {

	if (unlikely(!bpf_prog_get_recursion_context(prog))) {

		bpf_prog_inc_misses_counter(prog);

		if (prog->aux->recursion_detected)

			prog->aux->recursion_detected(prog);
@@ -1044,7 +1044,7 @@ void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start, 
	bpf_reset_run_ctx(run_ctx->saved_run_ctx);



	update_prog_stats(prog, start);

	this_cpu_dec(*(prog->active));

	bpf_prog_put_recursion_context(prog);

	migrate_enable();

	rcu_read_unlock_trace();

}

kernel/trace/bpf_trace.c

+2 −2
Original line number Diff line number Diff line
@@ -2063,7 +2063,7 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args) 
	struct bpf_trace_run_ctx run_ctx;



	cant_sleep();

	if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {

	if (unlikely(!bpf_prog_get_recursion_context(prog))) {

		bpf_prog_inc_misses_counter(prog);

		goto out;

	}
@@ -2077,7 +2077,7 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args) 


	bpf_reset_run_ctx(old_run_ctx);

out:

	this_cpu_dec(*(prog->active));

	bpf_prog_put_recursion_context(prog);

}



#define UNPACK(...)			__VA_ARGS__