selftests/bpf: Expand skb dynptr selftests for tp_btf

Add 3 test cases for skb dynptr used in tp_btf:
- test_dynptr_skb_tp_btf: use skb dynptr in tp_btf and make sure it is
  read-only.
- skb_invalid_ctx_fentry/skb_invalid_ctx_fexit: bpf_dynptr_from_skb
  should fail in fentry/fexit.

In test_dynptr_skb_tp_btf, to trigger the tracepoint in kfree_skb,
test_pkt_access is used for its test_run, as in kfree_skb.c. Because the
test process is different from others, a new setup type is defined,
i.e., SETUP_SKB_PROG_TP.

The result is like:
$ ./test_progs -t 'dynptr/test_dynptr_skb_tp_btf'
  #84/14   dynptr/test_dynptr_skb_tp_btf:OK
  #84      dynptr:OK
  #127     kfunc_dynptr_param:OK
  Summary: 2/1 PASSED, 0 SKIPPED, 0 FAILED

$ ./test_progs -t 'dynptr/skb_invalid_ctx_f'
  #84/85   dynptr/skb_invalid_ctx_fentry:OK
  #84/86   dynptr/skb_invalid_ctx_fexit:OK
  #84      dynptr:OK
  #127     kfunc_dynptr_param:OK
  Summary: 2/2 PASSED, 0 SKIPPED, 0 FAILED

Also fix two coding style nits (change spaces to tabs).

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240911033719.91468-6-lulie@linux.alibaba.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

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

@@ -9,6 +9,7 @@
 enum test_setup_type {
 	SETUP_SYSCALL_SLEEP,
 	SETUP_SKB_PROG,
+	SETUP_SKB_PROG_TP,
 };
 
 static struct {
@@ -28,6 +29,7 @@ static struct {
 	{"test_dynptr_clone", SETUP_SKB_PROG},
 	{"test_dynptr_skb_no_buff", SETUP_SKB_PROG},
 	{"test_dynptr_skb_strcmp", SETUP_SKB_PROG},
+	{"test_dynptr_skb_tp_btf", SETUP_SKB_PROG_TP},
 };
 
 static void verify_success(const char *prog_name, enum test_setup_type setup_type)
@@ -35,7 +37,7 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
 	struct dynptr_success *skel;
 	struct bpf_program *prog;
 	struct bpf_link *link;
-       int err;
+	int err;
 
 	skel = dynptr_success__open();
 	if (!ASSERT_OK_PTR(skel, "dynptr_success__open"))
@@ -47,7 +49,7 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
 	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
 		goto cleanup;
 
-       bpf_program__set_autoload(prog, true);
+	bpf_program__set_autoload(prog, true);
 
 	err = dynptr_success__load(skel);
 	if (!ASSERT_OK(err, "dynptr_success__load"))
@@ -87,6 +89,37 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
 
 		break;
 	}
+	case SETUP_SKB_PROG_TP:
+	{
+		struct __sk_buff skb = {};
+		struct bpf_object *obj;
+		int aux_prog_fd;
+
+		/* Just use its test_run to trigger kfree_skb tracepoint */
+		err = bpf_prog_test_load("./test_pkt_access.bpf.o", BPF_PROG_TYPE_SCHED_CLS,
+					 &obj, &aux_prog_fd);
+		if (!ASSERT_OK(err, "prog_load sched cls"))
+			goto cleanup;
+
+		LIBBPF_OPTS(bpf_test_run_opts, topts,
+			    .data_in = &pkt_v4,
+			    .data_size_in = sizeof(pkt_v4),
+			    .ctx_in = &skb,
+			    .ctx_size_in = sizeof(skb),
+		);
+
+		link = bpf_program__attach(prog);
+		if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
+			goto cleanup;
+
+		err = bpf_prog_test_run_opts(aux_prog_fd, &topts);
+		bpf_link__destroy(link);
+
+		if (!ASSERT_OK(err, "test_run"))
+			goto cleanup;
+
+		break;
+	}
 	}
 
 	ASSERT_EQ(skel->bss->err, 0, "err");

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

@@ -6,6 +6,7 @@
 #include <stdbool.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
 #include <linux/if_ether.h>
 #include "bpf_misc.h"
 #include "bpf_kfuncs.h"
@@ -1254,6 +1255,30 @@ int skb_invalid_ctx(void *ctx)
 	return 0;
 }
 
+SEC("fentry/skb_tx_error")
+__failure __msg("must be referenced or trusted")
+int BPF_PROG(skb_invalid_ctx_fentry, void *skb)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	return 0;
+}
+
+SEC("fexit/skb_tx_error")
+__failure __msg("must be referenced or trusted")
+int BPF_PROG(skb_invalid_ctx_fexit, void *skb)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	return 0;
+}
+
 /* Reject writes to dynptr slot for uninit arg */
 SEC("?raw_tp")
 __failure __msg("potential write to dynptr at off=-16")

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

@@ -5,6 +5,7 @@
 #include <stdbool.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
 #include "bpf_misc.h"
 #include "bpf_kfuncs.h"
 #include "errno.h"
@@ -544,3 +545,25 @@ int test_dynptr_skb_strcmp(struct __sk_buff *skb)
 
 	return 1;
 }
+
+SEC("tp_btf/kfree_skb")
+int BPF_PROG(test_dynptr_skb_tp_btf, void *skb, void *location)
+{
+	__u8 write_data[2] = {1, 2};
+	struct bpf_dynptr ptr;
+	int ret;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 1;
+	}
+
+	/* since tp_btf skbs are read only, writes should fail */
+	ret = bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0);
+	if (ret != -EINVAL) {
+		err = 2;
+		return 1;
+	}
+
+	return 1;
+}