Commit 15d83c4d authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Allow loading of a bpf_iter program 



A bpf_iter program is a tracing program with attach type
BPF_TRACE_ITER. The load attribute
  attach_btf_id
is used by the verifier against a particular kernel function,
which represents a target, e.g., __bpf_iter__bpf_map
for target bpf_map which is implemented later.

The program return value must be 0 or 1 for now.
  0 : successful, except potential seq_file buffer overflow
      which is handled by seq_file reader.
  1 : request to restart the same object

In the future, other return values may be used for filtering or
teminating the iterator.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175900.2474947-1-yhs@fb.com
parent ae24345d

include/linux/bpf.h

+3 −0
Original line number Diff line number Diff line
@@ -1127,6 +1127,8 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd); 
int bpf_obj_pin_user(u32 ufd, const char __user *pathname);

int bpf_obj_get_user(const char __user *pathname, int flags);



#define BPF_ITER_FUNC_PREFIX "__bpf_iter__"



typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);

typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
@@ -1140,6 +1142,7 @@ struct bpf_iter_reg { 


int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);

void bpf_iter_unreg_target(const char *target);

bool bpf_iter_prog_supported(struct bpf_prog *prog);



int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);

int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -218,6 +218,7 @@ enum bpf_attach_type { 
	BPF_TRACE_FEXIT,

	BPF_MODIFY_RETURN,

	BPF_LSM_MAC,

	BPF_TRACE_ITER,

	__MAX_BPF_ATTACH_TYPE

};

kernel/bpf/bpf_iter.c

+36 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ struct bpf_iter_target_info { 
	bpf_iter_init_seq_priv_t init_seq_private;

	bpf_iter_fini_seq_priv_t fini_seq_private;

	u32 seq_priv_size;

	u32 btf_id;	/* cached value */

};



static struct list_head targets = LIST_HEAD_INIT(targets);
@@ -57,3 +58,38 @@ void bpf_iter_unreg_target(const char *target) 


	WARN_ON(found == false);

}



static void cache_btf_id(struct bpf_iter_target_info *tinfo,

			 struct bpf_prog *prog)

{

	tinfo->btf_id = prog->aux->attach_btf_id;

}



bool bpf_iter_prog_supported(struct bpf_prog *prog)

{

	const char *attach_fname = prog->aux->attach_func_name;

	u32 prog_btf_id = prog->aux->attach_btf_id;

	const char *prefix = BPF_ITER_FUNC_PREFIX;

	struct bpf_iter_target_info *tinfo;

	int prefix_len = strlen(prefix);

	bool supported = false;



	if (strncmp(attach_fname, prefix, prefix_len))

		return false;



	mutex_lock(&targets_mutex);

	list_for_each_entry(tinfo, &targets, list) {

		if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {

			supported = true;

			break;

		}

		if (!strcmp(attach_fname + prefix_len, tinfo->target)) {

			cache_btf_id(tinfo, prog);

			supported = true;

			break;

		}

	}

	mutex_unlock(&targets_mutex);



	return supported;

}

kernel/bpf/verifier.c

+21 −0
Original line number Diff line number Diff line
@@ -7101,6 +7101,10 @@ static int check_return_code(struct bpf_verifier_env *env) 
			return 0;

		range = tnum_const(0);

		break;

	case BPF_PROG_TYPE_TRACING:

		if (env->prog->expected_attach_type != BPF_TRACE_ITER)

			return 0;

		break;

	default:

		return 0;

	}
@@ -10481,6 +10485,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) 
	struct bpf_prog *tgt_prog = prog->aux->linked_prog;

	u32 btf_id = prog->aux->attach_btf_id;

	const char prefix[] = "btf_trace_";

	struct btf_func_model fmodel;

	int ret = 0, subprog = -1, i;

	struct bpf_trampoline *tr;

	const struct btf_type *t;
@@ -10622,6 +10627,22 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) 
		prog->aux->attach_func_proto = t;

		prog->aux->attach_btf_trace = true;

		return 0;

	case BPF_TRACE_ITER:

		if (!btf_type_is_func(t)) {

			verbose(env, "attach_btf_id %u is not a function\n",

				btf_id);

			return -EINVAL;

		}

		t = btf_type_by_id(btf, t->type);

		if (!btf_type_is_func_proto(t))

			return -EINVAL;

		prog->aux->attach_func_name = tname;

		prog->aux->attach_func_proto = t;

		if (!bpf_iter_prog_supported(prog))

			return -EINVAL;

		ret = btf_distill_func_proto(&env->log, btf, t,

					     tname, &fmodel);

		return ret;

	default:

		if (!prog_extension)

			return -EINVAL;

tools/include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -218,6 +218,7 @@ enum bpf_attach_type { 
	BPF_TRACE_FEXIT,

	BPF_MODIFY_RETURN,

	BPF_LSM_MAC,

	BPF_TRACE_ITER,

	__MAX_BPF_ATTACH_TYPE

};

CRA Git | Maintained and supported by SUSTech CRA and CCSE