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: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195442.3114844-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index f70a677..12cf215 100644 (file)
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -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                           (?)

diff --git a/tools/testing/selftests/bpf/prog_tests/type_cast.c b/tools/testing/selftests/bpf/prog_tests/type_cast.c
new file mode 100644 (file)
index 0000000..9317d5f
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/type_cast.c
@@ -0,0 +1,114 @@
+// 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();
+}

diff --git a/tools/testing/selftests/bpf/progs/type_cast.c b/tools/testing/selftests/bpf/progs/type_cast.c
new file mode 100644 (file)
index 0000000..eb78e6f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/type_cast.c
@@ -0,0 +1,83 @@
+// 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";