selftests/bpf: Split test_attach_probe into multi subtests

In order to adapt to the older kernel, now we split the "attach_probe"
testing into multi subtests:

manual // manual attach tests for kprobe/uprobe
auto // auto-attach tests for kprobe and uprobe
kprobe-sleepable // kprobe sleepable test
uprobe-lib // uprobe tests for library function by name
uprobe-sleepable // uprobe sleepable test
uprobe-ref_ctr // uprobe ref_ctr test

As sleepable kprobe needs to set BPF_F_SLEEPABLE flag before loading,
we need to move it to a stand alone skel file, in case of it is not
supported by kernel and make the whole loading fail.

Therefore, we can only enable part of the subtests for older kernel.

Signed-off-by: Menglong Dong <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Reviewed-by: Biao Jiang <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
+#include "test_attach_kprobe_sleepable.skel.h"
 #include "test_attach_probe.skel.h"
 
 /* this is how USDT semaphore is actually defined, except volatile modifier */
···
 	asm volatile ("");
 }
 
+/* attach point for ref_ctr */
+static noinline void trigger_func4(void)
+{
+	asm volatile ("");
+}
+
 static char test_data[] = "test_data";
 
-void test_attach_probe(void)
+/* manual attach kprobe/kretprobe/uprobe/uretprobe testings */
+static void test_attach_probe_manual(struct test_attach_probe *skel)
 {
 	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts);
 	struct bpf_link *kprobe_link, *kretprobe_link;
 	struct bpf_link *uprobe_link, *uretprobe_link;
-	struct test_attach_probe* skel;
-	ssize_t uprobe_offset, ref_ctr_offset;
-	struct bpf_link *uprobe_err_link;
-	FILE *devnull;
-	bool legacy;
-
-	/* Check if new-style kprobe/uprobe API is supported.
-	 * Kernels that support new FD-based kprobe and uprobe BPF attachment
-	 * through perf_event_open() syscall expose
-	 * /sys/bus/event_source/devices/kprobe/type and
-	 * /sys/bus/event_source/devices/uprobe/type files, respectively. They
-	 * contain magic numbers that are passed as "type" field of
-	 * perf_event_attr. Lack of such file in the system indicates legacy
-	 * kernel with old-style kprobe/uprobe attach interface through
-	 * creating per-probe event through tracefs. For such cases
-	 * ref_ctr_offset feature is not supported, so we don't test it.
-	 */
-	legacy = access("/sys/bus/event_source/devices/kprobe/type", F_OK) != 0;
+	ssize_t uprobe_offset;
 
 	uprobe_offset = get_uprobe_offset(&trigger_func);
 	if (!ASSERT_GE(uprobe_offset, 0, "uprobe_offset"))
-		return;
-
-	ref_ctr_offset = get_rel_offset((uintptr_t)&uprobe_ref_ctr);
-	if (!ASSERT_GE(ref_ctr_offset, 0, "ref_ctr_offset"))
-		return;
-
-	skel = test_attach_probe__open();
-	if (!ASSERT_OK_PTR(skel, "skel_open"))
-		return;
-
-	/* sleepable kprobe test case needs flags set before loading */
-	if (!ASSERT_OK(bpf_program__set_flags(skel->progs.handle_kprobe_sleepable,
-		BPF_F_SLEEPABLE), "kprobe_sleepable_flags"))
-		goto cleanup;
-
-	if (!ASSERT_OK(test_attach_probe__load(skel), "skel_load"))
-		goto cleanup;
-	if (!ASSERT_OK_PTR(skel->bss, "check_bss"))
 		goto cleanup;
 
 	/* manual-attach kprobe/kretprobe */
···
 		goto cleanup;
 	skel->links.handle_kretprobe = kretprobe_link;
 
-	/* auto-attachable kprobe and kretprobe */
-	skel->links.handle_kprobe_auto = bpf_program__attach(skel->progs.handle_kprobe_auto);
-	ASSERT_OK_PTR(skel->links.handle_kprobe_auto, "attach_kprobe_auto");
-
-	skel->links.handle_kretprobe_auto = bpf_program__attach(skel->progs.handle_kretprobe_auto);
-	ASSERT_OK_PTR(skel->links.handle_kretprobe_auto, "attach_kretprobe_auto");
-
-	if (!legacy)
-		ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_before");
-
+	/* manual-attach uprobe/uretprobe */
+	uprobe_opts.ref_ctr_offset = 0;
 	uprobe_opts.retprobe = false;
-	uprobe_opts.ref_ctr_offset = legacy ? 0 : ref_ctr_offset;
 	uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe,
 						      0 /* self pid */,
 						      "/proc/self/exe",
···
 		goto cleanup;
 	skel->links.handle_uprobe = uprobe_link;
 
-	if (!legacy)
-		ASSERT_GT(uprobe_ref_ctr, 0, "uprobe_ref_ctr_after");
-
-	/* if uprobe uses ref_ctr, uretprobe has to use ref_ctr as well */
 	uprobe_opts.retprobe = true;
-	uprobe_opts.ref_ctr_offset = legacy ? 0 : ref_ctr_offset;
 	uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe,
 							 -1 /* any pid */,
 							 "/proc/self/exe",
···
 		goto cleanup;
 	skel->links.handle_uretprobe = uretprobe_link;
 
-	/* verify auto-attach fails for old-style uprobe definition */
-	uprobe_err_link = bpf_program__attach(skel->progs.handle_uprobe_byname);
-	if (!ASSERT_EQ(libbpf_get_error(uprobe_err_link), -EOPNOTSUPP,
-		       "auto-attach should fail for old-style name"))
-		goto cleanup;
-
+	/* attach uprobe by function name manually */
 	uprobe_opts.func_name = "trigger_func2";
 	uprobe_opts.retprobe = false;
 	uprobe_opts.ref_ctr_offset = 0;
···
 	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname, "attach_uprobe_byname"))
 		goto cleanup;
 
+	/* trigger & validate kprobe && kretprobe */
+	usleep(1);
+
+	/* trigger & validate uprobe & uretprobe */
+	trigger_func();
+
+	/* trigger & validate uprobe attached by name */
+	trigger_func2();
+
+	ASSERT_EQ(skel->bss->kprobe_res, 1, "check_kprobe_res");
+	ASSERT_EQ(skel->bss->kretprobe_res, 2, "check_kretprobe_res");
+	ASSERT_EQ(skel->bss->uprobe_res, 3, "check_uprobe_res");
+	ASSERT_EQ(skel->bss->uretprobe_res, 4, "check_uretprobe_res");
+	ASSERT_EQ(skel->bss->uprobe_byname_res, 5, "check_uprobe_byname_res");
+
+cleanup:
+}
+
+static void test_attach_probe_auto(struct test_attach_probe *skel)
+{
+	struct bpf_link *uprobe_err_link;
+
+	/* auto-attachable kprobe and kretprobe */
+	skel->links.handle_kprobe_auto = bpf_program__attach(skel->progs.handle_kprobe_auto);
+	ASSERT_OK_PTR(skel->links.handle_kprobe_auto, "attach_kprobe_auto");
+
+	skel->links.handle_kretprobe_auto = bpf_program__attach(skel->progs.handle_kretprobe_auto);
+	ASSERT_OK_PTR(skel->links.handle_kretprobe_auto, "attach_kretprobe_auto");
+
+	/* verify auto-attach fails for old-style uprobe definition */
+	uprobe_err_link = bpf_program__attach(skel->progs.handle_uprobe_byname);
+	if (!ASSERT_EQ(libbpf_get_error(uprobe_err_link), -EOPNOTSUPP,
+		       "auto-attach should fail for old-style name"))
+		return;
+
 	/* verify auto-attach works */
 	skel->links.handle_uretprobe_byname =
 			bpf_program__attach(skel->progs.handle_uretprobe_byname);
 	if (!ASSERT_OK_PTR(skel->links.handle_uretprobe_byname, "attach_uretprobe_byname"))
-		goto cleanup;
+		return;
+
+	/* trigger & validate kprobe && kretprobe */
+	usleep(1);
+
+	/* trigger & validate uprobe attached by name */
+	trigger_func2();
+
+	ASSERT_EQ(skel->bss->kprobe2_res, 11, "check_kprobe_auto_res");
+	ASSERT_EQ(skel->bss->kretprobe2_res, 22, "check_kretprobe_auto_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname_res, 6, "check_uretprobe_byname_res");
+}
+
+static void test_uprobe_lib(struct test_attach_probe *skel)
+{
+	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts);
+	FILE *devnull;
 
 	/* test attach by name for a library function, using the library
 	 * as the binary argument. libc.so.6 will be resolved via dlopen()/dlinfo().
···
 							"libc.so.6",
 							0, &uprobe_opts);
 	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname2, "attach_uprobe_byname2"))
-		goto cleanup;
+		return;
 
 	uprobe_opts.func_name = "fclose";
 	uprobe_opts.retprobe = true;
···
 							"libc.so.6",
 							0, &uprobe_opts);
 	if (!ASSERT_OK_PTR(skel->links.handle_uretprobe_byname2, "attach_uretprobe_byname2"))
-		goto cleanup;
-
-	/* sleepable kprobes should not attach successfully */
-	skel->links.handle_kprobe_sleepable = bpf_program__attach(skel->progs.handle_kprobe_sleepable);
-	if (!ASSERT_ERR_PTR(skel->links.handle_kprobe_sleepable, "attach_kprobe_sleepable"))
-		goto cleanup;
-
-	/* test sleepable uprobe and uretprobe variants */
-	skel->links.handle_uprobe_byname3_sleepable = bpf_program__attach(skel->progs.handle_uprobe_byname3_sleepable);
-	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname3_sleepable, "attach_uprobe_byname3_sleepable"))
-		goto cleanup;
-
-	skel->links.handle_uprobe_byname3 = bpf_program__attach(skel->progs.handle_uprobe_byname3);
-	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname3, "attach_uprobe_byname3"))
-		goto cleanup;
-
-	skel->links.handle_uretprobe_byname3_sleepable = bpf_program__attach(skel->progs.handle_uretprobe_byname3_sleepable);
-	if (!ASSERT_OK_PTR(skel->links.handle_uretprobe_byname3_sleepable, "attach_uretprobe_byname3_sleepable"))
-		goto cleanup;
-
-	skel->links.handle_uretprobe_byname3 = bpf_program__attach(skel->progs.handle_uretprobe_byname3);
-	if (!ASSERT_OK_PTR(skel->links.handle_uretprobe_byname3, "attach_uretprobe_byname3"))
-		goto cleanup;
-
-	skel->bss->user_ptr = test_data;
-
-	/* trigger & validate kprobe && kretprobe */
-	usleep(1);
+		return;
 
 	/* trigger & validate shared library u[ret]probes attached by name */
 	devnull = fopen("/dev/null", "r");
 	fclose(devnull);
 
-	/* trigger & validate uprobe & uretprobe */
-	trigger_func();
+	ASSERT_EQ(skel->bss->uprobe_byname2_res, 7, "check_uprobe_byname2_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname2_res, 8, "check_uretprobe_byname2_res");
+}
 
-	/* trigger & validate uprobe attached by name */
-	trigger_func2();
+static void test_uprobe_ref_ctr(struct test_attach_probe *skel)
+{
+	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts);
+	struct bpf_link *uprobe_link, *uretprobe_link;
+	ssize_t uprobe_offset, ref_ctr_offset;
+
+	uprobe_offset = get_uprobe_offset(&trigger_func4);
+	if (!ASSERT_GE(uprobe_offset, 0, "uprobe_offset_ref_ctr"))
+		return;
+
+	ref_ctr_offset = get_rel_offset((uintptr_t)&uprobe_ref_ctr);
+	if (!ASSERT_GE(ref_ctr_offset, 0, "ref_ctr_offset"))
+		return;
+
+	ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_before");
+
+	uprobe_opts.retprobe = false;
+	uprobe_opts.ref_ctr_offset = ref_ctr_offset;
+	uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe_ref_ctr,
+						      0 /* self pid */,
+						      "/proc/self/exe",
+						      uprobe_offset,
+						      &uprobe_opts);
+	if (!ASSERT_OK_PTR(uprobe_link, "attach_uprobe_ref_ctr"))
+		return;
+	skel->links.handle_uprobe_ref_ctr = uprobe_link;
+
+	ASSERT_GT(uprobe_ref_ctr, 0, "uprobe_ref_ctr_after");
+
+	/* if uprobe uses ref_ctr, uretprobe has to use ref_ctr as well */
+	uprobe_opts.retprobe = true;
+	uprobe_opts.ref_ctr_offset = ref_ctr_offset;
+	uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe_ref_ctr,
+							 -1 /* any pid */,
+							 "/proc/self/exe",
+							 uprobe_offset, &uprobe_opts);
+	if (!ASSERT_OK_PTR(uretprobe_link, "attach_uretprobe_ref_ctr"))
+		return;
+	skel->links.handle_uretprobe_ref_ctr = uretprobe_link;
+}
+
+static void test_kprobe_sleepable(void)
+{
+	struct test_attach_kprobe_sleepable *skel;
+
+	skel = test_attach_kprobe_sleepable__open();
+	if (!ASSERT_OK_PTR(skel, "skel_kprobe_sleepable_open"))
+		return;
+
+	/* sleepable kprobe test case needs flags set before loading */
+	if (!ASSERT_OK(bpf_program__set_flags(skel->progs.handle_kprobe_sleepable,
+		BPF_F_SLEEPABLE), "kprobe_sleepable_flags"))
+		goto cleanup;
+
+	if (!ASSERT_OK(test_attach_kprobe_sleepable__load(skel),
+		       "skel_kprobe_sleepable_load"))
+		goto cleanup;
+
+	/* sleepable kprobes should not attach successfully */
+	skel->links.handle_kprobe_sleepable = bpf_program__attach(skel->progs.handle_kprobe_sleepable);
+	ASSERT_ERR_PTR(skel->links.handle_kprobe_sleepable, "attach_kprobe_sleepable");
+
+cleanup:
+	test_attach_kprobe_sleepable__destroy(skel);
+}
+
+static void test_uprobe_sleepable(struct test_attach_probe *skel)
+{
+	/* test sleepable uprobe and uretprobe variants */
+	skel->links.handle_uprobe_byname3_sleepable = bpf_program__attach(skel->progs.handle_uprobe_byname3_sleepable);
+	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname3_sleepable, "attach_uprobe_byname3_sleepable"))
+		return;
+
+	skel->links.handle_uprobe_byname3 = bpf_program__attach(skel->progs.handle_uprobe_byname3);
+	if (!ASSERT_OK_PTR(skel->links.handle_uprobe_byname3, "attach_uprobe_byname3"))
+		return;
+
+	skel->links.handle_uretprobe_byname3_sleepable = bpf_program__attach(skel->progs.handle_uretprobe_byname3_sleepable);
+	if (!ASSERT_OK_PTR(skel->links.handle_uretprobe_byname3_sleepable, "attach_uretprobe_byname3_sleepable"))
+		return;
+
+	skel->links.handle_uretprobe_byname3 = bpf_program__attach(skel->progs.handle_uretprobe_byname3);
+	if (!ASSERT_OK_PTR(skel->links.handle_uretprobe_byname3, "attach_uretprobe_byname3"))
+		return;
+
+	skel->bss->user_ptr = test_data;
 
 	/* trigger & validate sleepable uprobe attached by name */
 	trigger_func3();
 
-	ASSERT_EQ(skel->bss->kprobe_res, 1, "check_kprobe_res");
-	ASSERT_EQ(skel->bss->kprobe2_res, 11, "check_kprobe_auto_res");
-	ASSERT_EQ(skel->bss->kretprobe_res, 2, "check_kretprobe_res");
-	ASSERT_EQ(skel->bss->kretprobe2_res, 22, "check_kretprobe_auto_res");
-	ASSERT_EQ(skel->bss->uprobe_res, 3, "check_uprobe_res");
-	ASSERT_EQ(skel->bss->uretprobe_res, 4, "check_uretprobe_res");
-	ASSERT_EQ(skel->bss->uprobe_byname_res, 5, "check_uprobe_byname_res");
-	ASSERT_EQ(skel->bss->uretprobe_byname_res, 6, "check_uretprobe_byname_res");
-	ASSERT_EQ(skel->bss->uprobe_byname2_res, 7, "check_uprobe_byname2_res");
-	ASSERT_EQ(skel->bss->uretprobe_byname2_res, 8, "check_uretprobe_byname2_res");
 	ASSERT_EQ(skel->bss->uprobe_byname3_sleepable_res, 9, "check_uprobe_byname3_sleepable_res");
 	ASSERT_EQ(skel->bss->uprobe_byname3_res, 10, "check_uprobe_byname3_res");
 	ASSERT_EQ(skel->bss->uretprobe_byname3_sleepable_res, 11, "check_uretprobe_byname3_sleepable_res");
 	ASSERT_EQ(skel->bss->uretprobe_byname3_res, 12, "check_uretprobe_byname3_res");
+}
+
+void test_attach_probe(void)
+{
+	struct test_attach_probe *skel;
+
+	skel = test_attach_probe__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	if (!ASSERT_OK(test_attach_probe__load(skel), "skel_load"))
+		goto cleanup;
+	if (!ASSERT_OK_PTR(skel->bss, "check_bss"))
+		goto cleanup;
+
+	if (test__start_subtest("manual"))
+		test_attach_probe_manual(skel);
+	if (test__start_subtest("auto"))
+		test_attach_probe_auto(skel);
+	if (test__start_subtest("kprobe-sleepable"))
+		test_kprobe_sleepable();
+	if (test__start_subtest("uprobe-lib"))
+		test_uprobe_lib(skel);
+	if (test__start_subtest("uprobe-sleepable"))
+		test_uprobe_sleepable(skel);
+	if (test__start_subtest("uprobe-ref_ctr"))
+		test_uprobe_ref_ctr(skel);
 
 cleanup:
 	test_attach_probe__destroy(skel);

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

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_misc.h"
+
+int kprobe_res = 0;
+
+/**
+ * This program will be manually made sleepable on the userspace side
+ * and should thus be unattachable.
+ */
+SEC("kprobe/" SYS_PREFIX "sys_nanosleep")
+int handle_kprobe_sleepable(struct pt_regs *ctx)
+{
+	kprobe_res = 1;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

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

···
 	return 0;
 }
 
-/**
- * This program will be manually made sleepable on the userspace side
- * and should thus be unattachable.
- */
-SEC("kprobe/" SYS_PREFIX "sys_nanosleep")
-int handle_kprobe_sleepable(struct pt_regs *ctx)
-{
-	kprobe_res = 2;
-	return 0;
-}
-
 SEC("kretprobe")
 int handle_kretprobe(struct pt_regs *ctx)
 {
···
 int handle_uretprobe(struct pt_regs *ctx)
 {
 	uretprobe_res = 4;
+	return 0;
+}
+
+SEC("uprobe")
+int handle_uprobe_ref_ctr(struct pt_regs *ctx)
+{
+	return 0;
+}
+
+SEC("uretprobe")
+int handle_uretprobe_ref_ctr(struct pt_regs *ctx)
+{
 	return 0;
 }