Commit c4c6c3b7 authored by Kui-Feng Lee's avatar Kui-Feng Lee Committed by Alexei Starovoitov
Browse files

selftests/bpf: Test kptr arrays and kptrs in nested struct fields. 



Make sure that BPF programs can declare global kptr arrays and kptr fields
in struct types that is the type of a global variable or the type of a
nested descendant field in a global variable.

An array with only one element is special case, that it treats the element
like a non-array kptr field. Nested arrays are also tested to ensure they
are handled properly.

Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarKui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240523174202.461236-8-thinker.li@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent f19caf57

tools/testing/selftests/bpf/prog_tests/cpumask.c

+5 −0
Original line number Diff line number Diff line
@@ -18,6 +18,11 @@ static const char * const cpumask_success_testcases[] = { 
	"test_insert_leave",

	"test_insert_remove_release",

	"test_global_mask_rcu",

	"test_global_mask_array_one_rcu",

	"test_global_mask_array_rcu",

	"test_global_mask_array_l2_rcu",

	"test_global_mask_nested_rcu",

	"test_global_mask_nested_deep_rcu",

	"test_cpumask_weight",

};

tools/testing/selftests/bpf/progs/cpumask_success.c

+171 −0
Original line number Diff line number Diff line
@@ -12,6 +12,31 @@ char _license[] SEC("license") = "GPL"; 


int pid, nr_cpus;



struct kptr_nested {

	struct bpf_cpumask __kptr * mask;

};



struct kptr_nested_pair {

	struct bpf_cpumask __kptr * mask_1;

	struct bpf_cpumask __kptr * mask_2;

};



struct kptr_nested_mid {

	int dummy;

	struct kptr_nested m;

};



struct kptr_nested_deep {

	struct kptr_nested_mid ptrs[2];

	struct kptr_nested_pair ptr_pairs[3];

};



private(MASK) static struct bpf_cpumask __kptr * global_mask_array[2];

private(MASK) static struct bpf_cpumask __kptr * global_mask_array_l2[2][1];

private(MASK) static struct bpf_cpumask __kptr * global_mask_array_one[1];

private(MASK) static struct kptr_nested global_mask_nested[2];

private(MASK_DEEP) static struct kptr_nested_deep global_mask_nested_deep;



static bool is_test_task(void)

{

	int cur_pid = bpf_get_current_pid_tgid() >> 32;
@@ -460,6 +485,152 @@ int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags) 
	return 0;

}



SEC("tp_btf/task_newtask")

int BPF_PROG(test_global_mask_array_one_rcu, struct task_struct *task, u64 clone_flags)

{

	struct bpf_cpumask *local, *prev;



	if (!is_test_task())

		return 0;



	/* Kptr arrays with one element are special cased, being treated

	 * just like a single pointer.

	 */



	local = create_cpumask();

	if (!local)

		return 0;



	prev = bpf_kptr_xchg(&global_mask_array_one[0], local);

	if (prev) {

		bpf_cpumask_release(prev);

		err = 3;

		return 0;

	}



	bpf_rcu_read_lock();

	local = global_mask_array_one[0];

	if (!local) {

		err = 4;

		bpf_rcu_read_unlock();

		return 0;

	}



	bpf_rcu_read_unlock();



	return 0;

}



static int _global_mask_array_rcu(struct bpf_cpumask **mask0,

				  struct bpf_cpumask **mask1)

{

	struct bpf_cpumask *local;



	if (!is_test_task())

		return 0;



	/* Check if two kptrs in the array work and independently */



	local = create_cpumask();

	if (!local)

		return 0;



	bpf_rcu_read_lock();



	local = bpf_kptr_xchg(mask0, local);

	if (local) {

		err = 1;

		goto err_exit;

	}



	/* [<mask 0>, NULL] */

	if (!*mask0 || *mask1) {

		err = 2;

		goto err_exit;

	}



	local = create_cpumask();

	if (!local) {

		err = 9;

		goto err_exit;

	}



	local = bpf_kptr_xchg(mask1, local);

	if (local) {

		err = 10;

		goto err_exit;

	}



	/* [<mask 0>, <mask 1>] */

	if (!*mask0 || !*mask1 || *mask0 == *mask1) {

		err = 11;

		goto err_exit;

	}



err_exit:

	if (local)

		bpf_cpumask_release(local);

	bpf_rcu_read_unlock();

	return 0;

}



SEC("tp_btf/task_newtask")

int BPF_PROG(test_global_mask_array_rcu, struct task_struct *task, u64 clone_flags)

{

	return _global_mask_array_rcu(&global_mask_array[0], &global_mask_array[1]);

}



SEC("tp_btf/task_newtask")

int BPF_PROG(test_global_mask_array_l2_rcu, struct task_struct *task, u64 clone_flags)

{

	return _global_mask_array_rcu(&global_mask_array_l2[0][0], &global_mask_array_l2[1][0]);

}



SEC("tp_btf/task_newtask")

int BPF_PROG(test_global_mask_nested_rcu, struct task_struct *task, u64 clone_flags)

{

	return _global_mask_array_rcu(&global_mask_nested[0].mask, &global_mask_nested[1].mask);

}



/* Ensure that the field->offset has been correctly advanced from one

 * nested struct or array sub-tree to another. In the case of

 * kptr_nested_deep, it comprises two sub-trees: ktpr_1 and kptr_2.  By

 * calling bpf_kptr_xchg() on every single kptr in both nested sub-trees,

 * the verifier should reject the program if the field->offset of any kptr

 * is incorrect.

 *

 * For instance, if we have 10 kptrs in a nested struct and a program that

 * accesses each kptr individually with bpf_kptr_xchg(), the compiler

 * should emit instructions to access 10 different offsets if it works

 * correctly. If the field->offset values of any pair of them are

 * incorrectly the same, the number of unique offsets in btf_record for

 * this nested struct should be less than 10. The verifier should fail to

 * discover some of the offsets emitted by the compiler.

 *

 * Even if the field->offset values of kptrs are not duplicated, the

 * verifier should fail to find a btf_field for the instruction accessing a

 * kptr if the corresponding field->offset is pointing to a random

 * incorrect offset.

 */

SEC("tp_btf/task_newtask")

int BPF_PROG(test_global_mask_nested_deep_rcu, struct task_struct *task, u64 clone_flags)

{

	int r, i;



	r = _global_mask_array_rcu(&global_mask_nested_deep.ptrs[0].m.mask,

				   &global_mask_nested_deep.ptrs[1].m.mask);

	if (r)

		return r;



	for (i = 0; i < 3; i++) {

		r = _global_mask_array_rcu(&global_mask_nested_deep.ptr_pairs[i].mask_1,

					   &global_mask_nested_deep.ptr_pairs[i].mask_2);

		if (r)

			return r;

	}

	return 0;

}



SEC("tp_btf/task_newtask")

int BPF_PROG(test_cpumask_weight, struct task_struct *task, u64 clone_flags)

{