Commit 58d84bee authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Add type cast unit tests 

Three tests are added. One is from John Fastabend ({1]) which tests
tracing style access for xdp program from the kernel ctx.
Another is a tc test to test both kernel ctx tracing style access
and explicit non-ctx type cast. The third one is for negative tests
including two tests, a tp_bpf test where the bpf_rdonly_cast()
returns a untrusted ptr which cannot be used as helper argument,
and a tracepoint test where the kernel ctx is a u64.

Also added the test to DENYLIST.s390x since s390 does not currently
support calling kernel functions in JIT mode.

  [1] https://lore.kernel.org/bpf/20221109215242.1279993-1-john.fastabend@gmail.com/



Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195442.3114844-1-yhs@fb.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent a35b9af4

tools/testing/selftests/bpf/DENYLIST.s390x

+1 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ trace_printk # trace_printk__load unexpected error: 
trace_vprintk                            # trace_vprintk__open_and_load unexpected error: -9                           (?)

tracing_struct                           # failed to auto-attach: -524                                                 (trampoline)

trampoline_count                         # prog 'prog1': failed to attach: ERROR: strerror_r(-524)=22                  (trampoline)

type_cast                                # JIT does not support calling kernel function

unpriv_bpf_disabled                      # fentry

user_ringbuf                             # failed to find kernel BTF type ID of '__s390x_sys_prctl': -3                (?)

verif_stats                              # trace_vprintk__open_and_load unexpected error: -9                           (?)

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

0 → 100644
+114 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */

#include <test_progs.h>

#include <network_helpers.h>

#include "type_cast.skel.h"



static void test_xdp(void)

{

	struct type_cast *skel;

	int err, prog_fd;

	char buf[128];



	LIBBPF_OPTS(bpf_test_run_opts, topts,

		.data_in = &pkt_v4,

		.data_size_in = sizeof(pkt_v4),

		.data_out = buf,

		.data_size_out = sizeof(buf),

		.repeat = 1,

	);



	skel = type_cast__open();

	if (!ASSERT_OK_PTR(skel, "skel_open"))

		return;



	bpf_program__set_autoload(skel->progs.md_xdp, true);

	err = type_cast__load(skel);

	if (!ASSERT_OK(err, "skel_load"))

		goto out;



	prog_fd = bpf_program__fd(skel->progs.md_xdp);

	err = bpf_prog_test_run_opts(prog_fd, &topts);

	ASSERT_OK(err, "test_run");

	ASSERT_EQ(topts.retval, XDP_PASS, "xdp test_run retval");



	ASSERT_EQ(skel->bss->ifindex, 1, "xdp_md ifindex");

	ASSERT_EQ(skel->bss->ifindex, skel->bss->ingress_ifindex, "xdp_md ingress_ifindex");

	ASSERT_STREQ(skel->bss->name, "lo", "xdp_md name");

	ASSERT_NEQ(skel->bss->inum, 0, "xdp_md inum");



out:

	type_cast__destroy(skel);

}



static void test_tc(void)

{

	struct type_cast *skel;

	int err, prog_fd;



	LIBBPF_OPTS(bpf_test_run_opts, topts,

		.data_in = &pkt_v4,

		.data_size_in = sizeof(pkt_v4),

		.repeat = 1,

	);



	skel = type_cast__open();

	if (!ASSERT_OK_PTR(skel, "skel_open"))

		return;



	bpf_program__set_autoload(skel->progs.md_skb, true);

	err = type_cast__load(skel);

	if (!ASSERT_OK(err, "skel_load"))

		goto out;



	prog_fd = bpf_program__fd(skel->progs.md_skb);

	err = bpf_prog_test_run_opts(prog_fd, &topts);

	ASSERT_OK(err, "test_run");

	ASSERT_EQ(topts.retval, 0, "tc test_run retval");



	ASSERT_EQ(skel->bss->meta_len, 0, "skb meta_len");

	ASSERT_EQ(skel->bss->frag0_len, 0, "skb frag0_len");

	ASSERT_NEQ(skel->bss->kskb_len, 0, "skb len");

	ASSERT_NEQ(skel->bss->kskb2_len, 0, "skb2 len");

	ASSERT_EQ(skel->bss->kskb_len, skel->bss->kskb2_len, "skb len compare");



out:

	type_cast__destroy(skel);

}



static const char * const negative_tests[] = {

	"untrusted_ptr",

	"kctx_u64",

};



static void test_negative(void)

{

	struct bpf_program *prog;

	struct type_cast *skel;

	int i, err;



	for (i = 0; i < ARRAY_SIZE(negative_tests); i++) {

		skel = type_cast__open();

		if (!ASSERT_OK_PTR(skel, "skel_open"))

			return;



		prog = bpf_object__find_program_by_name(skel->obj, negative_tests[i]);

		if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))

			goto out;

		bpf_program__set_autoload(prog, true);

		err = type_cast__load(skel);

		ASSERT_ERR(err, "skel_load");

out:

		type_cast__destroy(skel);

	}

}



void test_type_cast(void)

{

	if (test__start_subtest("xdp"))

		test_xdp();

	if (test__start_subtest("tc"))

		test_tc();

	if (test__start_subtest("negative"))

		test_negative();

}

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

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+83 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#include <bpf/bpf_core_read.h>



struct {

	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);

	__uint(map_flags, BPF_F_NO_PREALLOC);

	__type(key, int);

	__type(value, long);

} enter_id SEC(".maps");



#define	IFNAMSIZ 16



int ifindex, ingress_ifindex;

char name[IFNAMSIZ];

unsigned int inum;

unsigned int meta_len, frag0_len, kskb_len, kskb2_len;



void *bpf_cast_to_kern_ctx(void *) __ksym;

void *bpf_rdonly_cast(void *, __u32) __ksym;



SEC("?xdp")

int md_xdp(struct xdp_md *ctx)

{

	struct xdp_buff *kctx = bpf_cast_to_kern_ctx(ctx);

	struct net_device *dev;



	dev = kctx->rxq->dev;

	ifindex = dev->ifindex;

	inum = dev->nd_net.net->ns.inum;

	__builtin_memcpy(name, dev->name, IFNAMSIZ);

	ingress_ifindex = ctx->ingress_ifindex;

	return XDP_PASS;

}



SEC("?tc")

int md_skb(struct __sk_buff *skb)

{

	struct sk_buff *kskb = bpf_cast_to_kern_ctx(skb);

	struct skb_shared_info *shared_info;

	struct sk_buff *kskb2;



	kskb_len = kskb->len;



	/* Simulate the following kernel macro:

	 *   #define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))

	 */

	shared_info = bpf_rdonly_cast(kskb->head + kskb->end,

		bpf_core_type_id_kernel(struct skb_shared_info));

	meta_len = shared_info->meta_len;

	frag0_len = shared_info->frag_list->len;



	/* kskb2 should be equal to kskb */

	kskb2 = bpf_rdonly_cast(kskb, bpf_core_type_id_kernel(struct sk_buff));

	kskb2_len = kskb2->len;

	return 0;

}



SEC("?tp_btf/sys_enter")

int BPF_PROG(untrusted_ptr, struct pt_regs *regs, long id)

{

	struct task_struct *task, *task_dup;

	long *ptr;



	task = bpf_get_current_task_btf();

	task_dup = bpf_rdonly_cast(task, bpf_core_type_id_kernel(struct task_struct));

	(void)bpf_task_storage_get(&enter_id, task_dup, 0, 0);

	return 0;

}



SEC("?tracepoint/syscalls/sys_enter_nanosleep")

int kctx_u64(void *ctx)

{

	u64 *kctx = bpf_rdonly_cast(ctx, bpf_core_type_id_kernel(u64));



	(void)kctx;

	return 0;

}



char _license[] SEC("license") = "GPL";