Commit 7f628741 authored by Matteo Croce's avatar Matteo Croce Committed by Andrii Nakryiko
Browse files

bpf: Allow bpf_current_task_under_cgroup() with BPF_CGROUP_* 

The helper bpf_current_task_under_cgroup() currently is only allowed for
tracing programs, allow its usage also in the BPF_CGROUP_* program types.

Move the code from kernel/trace/bpf_trace.c to kernel/bpf/helpers.c,
so it compiles also without CONFIG_BPF_EVENTS.

This will be used in systemd-networkd to monitor the sysctl writes,
and filter it's own writes from others:
https://github.com/systemd/systemd/pull/32212



Signed-off-by: default avatarMatteo Croce <teknoraver@meta.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240819162805.78235-3-technoboy85@gmail.com
parent 67666479

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -3206,6 +3206,7 @@ extern const struct bpf_func_proto bpf_sock_hash_update_proto; 
extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;

extern const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto;

extern const struct bpf_func_proto bpf_get_cgroup_classid_curr_proto;

extern const struct bpf_func_proto bpf_current_task_under_cgroup_proto;

extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;

extern const struct bpf_func_proto bpf_msg_redirect_map_proto;

extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;

kernel/bpf/cgroup.c

+2 −0
Original line number Diff line number Diff line
@@ -2581,6 +2581,8 @@ cgroup_current_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
	case BPF_FUNC_get_cgroup_classid:

		return &bpf_get_cgroup_classid_curr_proto;

#endif

	case BPF_FUNC_current_task_under_cgroup:

		return &bpf_current_task_under_cgroup_proto;

	default:

		return NULL;

	}

kernel/bpf/helpers.c

+23 −0
Original line number Diff line number Diff line
@@ -2458,6 +2458,29 @@ __bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task, 
	return ret;

}



BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)

{

	struct bpf_array *array = container_of(map, struct bpf_array, map);

	struct cgroup *cgrp;



	if (unlikely(idx >= array->map.max_entries))

		return -E2BIG;



	cgrp = READ_ONCE(array->ptrs[idx]);

	if (unlikely(!cgrp))

		return -EAGAIN;



	return task_under_cgroup_hierarchy(current, cgrp);

}



const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {

	.func           = bpf_current_task_under_cgroup,

	.gpl_only       = false,

	.ret_type       = RET_INTEGER,

	.arg1_type      = ARG_CONST_MAP_PTR,

	.arg2_type      = ARG_ANYTHING,

};



/**

 * bpf_task_get_cgroup1 - Acquires the associated cgroup of a task within a

 * specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its

kernel/trace/bpf_trace.c

+2 −25
Original line number Diff line number Diff line
@@ -797,29 +797,6 @@ const struct bpf_func_proto bpf_task_pt_regs_proto = { 
	.ret_btf_id	= &bpf_task_pt_regs_ids[0],

};



BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)

{

	struct bpf_array *array = container_of(map, struct bpf_array, map);

	struct cgroup *cgrp;



	if (unlikely(idx >= array->map.max_entries))

		return -E2BIG;



	cgrp = READ_ONCE(array->ptrs[idx]);

	if (unlikely(!cgrp))

		return -EAGAIN;



	return task_under_cgroup_hierarchy(current, cgrp);

}



static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {

	.func           = bpf_current_task_under_cgroup,

	.gpl_only       = false,

	.ret_type       = RET_INTEGER,

	.arg1_type      = ARG_CONST_MAP_PTR,

	.arg2_type      = ARG_ANYTHING,

};



struct send_signal_irq_work {

	struct irq_work irq_work;

	struct task_struct *task;
@@ -1480,8 +1457,6 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
		return &bpf_get_numa_node_id_proto;

	case BPF_FUNC_perf_event_read:

		return &bpf_perf_event_read_proto;

	case BPF_FUNC_current_task_under_cgroup:

		return &bpf_current_task_under_cgroup_proto;

	case BPF_FUNC_get_prandom_u32:

		return &bpf_get_prandom_u32_proto;

	case BPF_FUNC_probe_write_user:
@@ -1510,6 +1485,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
		return &bpf_cgrp_storage_get_proto;

	case BPF_FUNC_cgrp_storage_delete:

		return &bpf_cgrp_storage_delete_proto;

	case BPF_FUNC_current_task_under_cgroup:

		return &bpf_current_task_under_cgroup_proto;

#endif

	case BPF_FUNC_send_signal:

		return &bpf_send_signal_proto;