selftests/bpf: Add tests for extending sleepable global subprogs

Add tests for freplace behavior with the combination of sleepable
and non-sleepable global subprogs. The changes_pkt_data selftest
did all the hardwork, so simply rename it and include new support
for more summarization tests for might_sleep bit.

Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: kkdwivedi

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

@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "bpf/libbpf.h"
+#include "summarization_freplace.skel.h"
+#include "summarization.skel.h"
+#include <test_progs.h>
+
+static void print_verifier_log(const char *log)
+{
+	if (env.verbosity >= VERBOSE_VERY)
+		fprintf(stdout, "VERIFIER LOG:\n=============\n%s=============\n", log);
+}
+
+static void test_aux(const char *main_prog_name,
+		     const char *to_be_replaced,
+		     const char *replacement,
+		     bool expect_load,
+		     const char *err_msg)
+{
+	struct summarization_freplace *freplace = NULL;
+	struct bpf_program *freplace_prog = NULL;
+	struct bpf_program *main_prog = NULL;
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	struct summarization *main = NULL;
+	char log[16*1024];
+	int err;
+
+	opts.kernel_log_buf = log;
+	opts.kernel_log_size = sizeof(log);
+	if (env.verbosity >= VERBOSE_SUPER)
+		opts.kernel_log_level = 1 | 2 | 4;
+	main = summarization__open_opts(&opts);
+	if (!ASSERT_OK_PTR(main, "summarization__open"))
+		goto out;
+	main_prog = bpf_object__find_program_by_name(main->obj, main_prog_name);
+	if (!ASSERT_OK_PTR(main_prog, "main_prog"))
+		goto out;
+	bpf_program__set_autoload(main_prog, true);
+	err = summarization__load(main);
+	print_verifier_log(log);
+	if (!ASSERT_OK(err, "summarization__load"))
+		goto out;
+	freplace = summarization_freplace__open_opts(&opts);
+	if (!ASSERT_OK_PTR(freplace, "summarization_freplace__open"))
+		goto out;
+	freplace_prog = bpf_object__find_program_by_name(freplace->obj, replacement);
+	if (!ASSERT_OK_PTR(freplace_prog, "freplace_prog"))
+		goto out;
+	bpf_program__set_autoload(freplace_prog, true);
+	bpf_program__set_autoattach(freplace_prog, true);
+	bpf_program__set_attach_target(freplace_prog,
+				       bpf_program__fd(main_prog),
+				       to_be_replaced);
+	err = summarization_freplace__load(freplace);
+	print_verifier_log(log);
+
+	/* The might_sleep extension doesn't work yet as sleepable calls are not
+	 * allowed, but preserve the check in case it's supported later and then
+	 * this particular combination can be enabled.
+	 */
+	if (!strcmp("might_sleep", replacement) && err) {
+		ASSERT_HAS_SUBSTR(log, "helper call might sleep in a non-sleepable prog", "error log");
+		ASSERT_EQ(err, -EINVAL, "err");
+		test__skip();
+		goto out;
+	}
+
+	if (expect_load) {
+		ASSERT_OK(err, "summarization_freplace__load");
+	} else {
+		ASSERT_ERR(err, "summarization_freplace__load");
+		ASSERT_HAS_SUBSTR(log, err_msg, "error log");
+	}
+
+out:
+	summarization_freplace__destroy(freplace);
+	summarization__destroy(main);
+}
+
+/* There are two global subprograms in both summarization.skel.h:
+ * - one changes packet data;
+ * - another does not.
+ * It is ok to freplace subprograms that change packet data with those
+ * that either do or do not. It is only ok to freplace subprograms
+ * that do not change packet data with those that do not as well.
+ * The below tests check outcomes for each combination of such freplace.
+ * Also test a case when main subprogram itself is replaced and is a single
+ * subprogram in a program.
+ *
+ * This holds for might_sleep programs. It is ok to replace might_sleep with
+ * might_sleep and with does_not_sleep, but does_not_sleep cannot be replaced
+ * with might_sleep.
+ */
+void test_summarization_freplace(void)
+{
+	struct {
+		const char *main;
+		const char *to_be_replaced;
+		bool has_side_effect;
+	} mains[2][4] = {
+		{
+			{ "main_changes_with_subprogs",		"changes_pkt_data",	    true },
+			{ "main_changes_with_subprogs",		"does_not_change_pkt_data", false },
+			{ "main_changes",			"main_changes",             true },
+			{ "main_does_not_change",		"main_does_not_change",     false },
+		},
+		{
+			{ "main_might_sleep_with_subprogs",	"might_sleep",		    true },
+			{ "main_might_sleep_with_subprogs",	"does_not_sleep",	    false },
+			{ "main_might_sleep",			"main_might_sleep",	    true },
+			{ "main_does_not_sleep",		"main_does_not_sleep",	    false },
+		},
+	};
+	const char *pkt_err = "Extension program changes packet data";
+	const char *slp_err = "Extension program may sleep";
+	struct {
+		const char *func;
+		bool has_side_effect;
+		const char *err_msg;
+	} replacements[2][2] = {
+		{
+			{ "changes_pkt_data",	      true,	pkt_err },
+			{ "does_not_change_pkt_data", false,	pkt_err },
+		},
+		{
+			{ "might_sleep",	      true,	slp_err },
+			{ "does_not_sleep",	      false,	slp_err },
+		},
+	};
+	char buf[64];
+
+	for (int t = 0; t < 2; t++) {
+		for (int i = 0; i < ARRAY_SIZE(mains); ++i) {
+			for (int j = 0; j < ARRAY_SIZE(replacements); ++j) {
+				snprintf(buf, sizeof(buf), "%s_with_%s",
+					 mains[t][i].to_be_replaced, replacements[t][j].func);
+				if (!test__start_subtest(buf))
+					continue;
+				test_aux(mains[t][i].main, mains[t][i].to_be_replaced, replacements[t][j].func,
+					 mains[t][i].has_side_effect || !replacements[t][j].has_side_effect,
+					 replacements[t][j].err_msg);
+			}
+		}
+	}
+}

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

@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+__noinline
+long changes_pkt_data(struct __sk_buff *sk)
+{
+	return bpf_skb_pull_data(sk, 0);
+}
+
+__noinline __weak
+long does_not_change_pkt_data(struct __sk_buff *sk)
+{
+	return 0;
+}
+
+SEC("?tc")
+int main_changes_with_subprogs(struct __sk_buff *sk)
+{
+	changes_pkt_data(sk);
+	does_not_change_pkt_data(sk);
+	return 0;
+}
+
+SEC("?tc")
+int main_changes(struct __sk_buff *sk)
+{
+	bpf_skb_pull_data(sk, 0);
+	return 0;
+}
+
+SEC("?tc")
+int main_does_not_change(struct __sk_buff *sk)
+{
+	return 0;
+}
+
+__noinline
+long might_sleep(struct pt_regs *ctx __arg_ctx)
+{
+	int i;
+
+	bpf_copy_from_user(&i, sizeof(i), NULL);
+	return i;
+}
+
+__noinline __weak
+long does_not_sleep(struct pt_regs *ctx __arg_ctx)
+{
+	return 0;
+}
+
+SEC("?uprobe.s")
+int main_might_sleep_with_subprogs(struct pt_regs *ctx)
+{
+	might_sleep(ctx);
+	does_not_sleep(ctx);
+	return 0;
+}
+
+SEC("?uprobe.s")
+int main_might_sleep(struct pt_regs *ctx)
+{
+	int i;
+
+	bpf_copy_from_user(&i, sizeof(i), NULL);
+	return i;
+}
+
+SEC("?uprobe.s")
+int main_does_not_sleep(struct pt_regs *ctx)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

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

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 
-#include <linux/bpf.h>
+#include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 
 SEC("?freplace")
@@ -15,4 +15,19 @@ long does_not_change_pkt_data(struct __sk_buff *sk)
 	return 0;
 }
 
+SEC("?freplace")
+long might_sleep(struct pt_regs *ctx)
+{
+	int i;
+
+	bpf_copy_from_user(&i, sizeof(i), NULL);
+	return i;
+}
+
+SEC("?freplace")
+long does_not_sleep(struct pt_regs *ctx)
+{
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";