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>

2 files changed, 48 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index e35bc1eac52a..c3bc186af21e 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/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")
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index 5985920d162e..bfcc85686cf0 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/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;
+}