Commit d923021c authored by Yonghong Song's avatar Yonghong Song Committed by Daniel Borkmann
Browse files

bpf: Add tests for PTR_TO_BTF_ID vs. null comparison 



Add two tests for PTR_TO_BTF_ID vs. null ptr comparison,
one for PTR_TO_BTF_ID in the ctx structure and the
other for PTR_TO_BTF_ID after one level pointer chasing.
In both cases, the test ensures condition is not
removed.

For example, for this test
 struct bpf_fentry_test_t {
     struct bpf_fentry_test_t *a;
 };
 int BPF_PROG(test7, struct bpf_fentry_test_t *arg)
 {
     if (arg == 0)
         test7_result = 1;
     return 0;
 }
Before the previous verifier change, we have xlated codes:
  int test7(long long unsigned int * ctx):
  ; int BPF_PROG(test7, struct bpf_fentry_test_t *arg)
     0: (79) r1 = *(u64 *)(r1 +0)
  ; int BPF_PROG(test7, struct bpf_fentry_test_t *arg)
     1: (b4) w0 = 0
     2: (95) exit
After the previous verifier change, we have:
  int test7(long long unsigned int * ctx):
  ; int BPF_PROG(test7, struct bpf_fentry_test_t *arg)
     0: (79) r1 = *(u64 *)(r1 +0)
  ; if (arg == 0)
     1: (55) if r1 != 0x0 goto pc+4
  ; test7_result = 1;
     2: (18) r1 = map[id:6][0]+48
     4: (b7) r2 = 1
     5: (7b) *(u64 *)(r1 +0) = r2
  ; int BPF_PROG(test7, struct bpf_fentry_test_t *arg)
     6: (b4) w0 = 0
     7: (95) exit

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200630171241.2523875-1-yhs@fb.com
parent 01c66c48

net/bpf/test_run.c

+18 −1
Original line number Diff line number Diff line
@@ -147,6 +147,20 @@ int noinline bpf_fentry_test6(u64 a, void *b, short c, int d, void *e, u64 f) 
	return a + (long)b + c + d + (long)e + f;

}



struct bpf_fentry_test_t {

	struct bpf_fentry_test_t *a;

};



int noinline bpf_fentry_test7(struct bpf_fentry_test_t *arg)

{

	return (long)arg;

}



int noinline bpf_fentry_test8(struct bpf_fentry_test_t *arg)

{

	return (long)arg->a;

}



int noinline bpf_modify_return_test(int a, int *b)

{

	*b += 1;
@@ -185,6 +199,7 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog, 
			      const union bpf_attr *kattr,

			      union bpf_attr __user *uattr)

{

	struct bpf_fentry_test_t arg = {};

	u16 side_effect = 0, ret = 0;

	int b = 2, err = -EFAULT;

	u32 retval = 0;
@@ -197,7 +212,9 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog, 
		    bpf_fentry_test3(4, 5, 6) != 15 ||

		    bpf_fentry_test4((void *)7, 8, 9, 10) != 34 ||

		    bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 ||

		    bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111)

		    bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111 ||

		    bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 ||

		    bpf_fentry_test8(&arg) != 0)

			goto out;

		break;

	case BPF_MODIFY_RETURN:

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

+1 −1
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ void test_fentry_fexit(void) 
	fentry_res = (__u64 *)fentry_skel->bss;

	fexit_res = (__u64 *)fexit_skel->bss;

	printf("%lld\n", fentry_skel->bss->test1_result);

	for (i = 0; i < 6; i++) {

	for (i = 0; i < 8; i++) {

		CHECK(fentry_res[i] != 1, "result",

		      "fentry_test%d failed err %lld\n", i + 1, fentry_res[i]);

		CHECK(fexit_res[i] != 1, "result",

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

+22 −0
Original line number Diff line number Diff line
@@ -55,3 +55,25 @@ int BPF_PROG(test6, __u64 a, void *b, short c, int d, void * e, __u64 f) 
		e == (void *)20 && f == 21;

	return 0;

}



struct bpf_fentry_test_t {

	struct bpf_fentry_test_t *a;

};



__u64 test7_result = 0;

SEC("fentry/bpf_fentry_test7")

int BPF_PROG(test7, struct bpf_fentry_test_t *arg)

{

	if (arg == 0)

		test7_result = 1;

	return 0;

}



__u64 test8_result = 0;

SEC("fentry/bpf_fentry_test8")

int BPF_PROG(test8, struct bpf_fentry_test_t *arg)

{

	if (arg->a == 0)

		test8_result = 1;

	return 0;

}

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

+22 −0
Original line number Diff line number Diff line
@@ -56,3 +56,25 @@ int BPF_PROG(test6, __u64 a, void *b, short c, int d, void *e, __u64 f, int ret) 
		e == (void *)20 && f == 21 && ret == 111;

	return 0;

}



struct bpf_fentry_test_t {

	struct bpf_fentry_test *a;

};



__u64 test7_result = 0;

SEC("fexit/bpf_fentry_test7")

int BPF_PROG(test7, struct bpf_fentry_test_t *arg)

{

	if (arg == 0)

		test7_result = 1;

	return 0;

}



__u64 test8_result = 0;

SEC("fexit/bpf_fentry_test8")

int BPF_PROG(test8, struct bpf_fentry_test_t *arg)

{

	if (arg->a == 0)

		test8_result = 1;

	return 0;

}

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