selftests/bpf: Add tests for uprobe auto-attach via skeleton

tests that verify auto-attach works for function entry/return for
local functions in program and library functions in a library.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1648654000-21758-6-git-send-email-alan.maguire@oracle.com

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022, Oracle and/or its affiliates. */
+
+#include <test_progs.h>
+#include "test_uprobe_autoattach.skel.h"
+
+/* uprobe attach point */
+static void autoattach_trigger_func(void)
+{
+	asm volatile ("");
+}
+
+void test_uprobe_autoattach(void)
+{
+	struct test_uprobe_autoattach *skel;
+	char *mem;
+
+	skel = test_uprobe_autoattach__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	if (!ASSERT_OK(test_uprobe_autoattach__attach(skel), "skel_attach"))
+		goto cleanup;
+
+	/* trigger & validate uprobe & uretprobe */
+	autoattach_trigger_func();
+
+	/* trigger & validate shared library u[ret]probes attached by name */
+	mem = malloc(1);
+	free(mem);
+
+	ASSERT_EQ(skel->bss->uprobe_byname_res, 1, "check_uprobe_byname_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname_res, 2, "check_uretprobe_byname_res");
+	ASSERT_EQ(skel->bss->uprobe_byname2_res, 3, "check_uprobe_byname2_res");
+	ASSERT_EQ(skel->bss->uretprobe_byname2_res, 4, "check_uretprobe_byname2_res");
+cleanup:
+	test_uprobe_autoattach__destroy(skel);
+}

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022, Oracle and/or its affiliates. */
+
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+int uprobe_byname_res = 0;
+int uretprobe_byname_res = 0;
+int uprobe_byname2_res = 0;
+int uretprobe_byname2_res = 0;
+
+/* This program cannot auto-attach, but that should not stop other
+ * programs from attaching.
+ */
+SEC("uprobe")
+int handle_uprobe_noautoattach(struct pt_regs *ctx)
+{
+	return 0;
+}
+
+SEC("uprobe//proc/self/exe:autoattach_trigger_func")
+int handle_uprobe_byname(struct pt_regs *ctx)
+{
+	uprobe_byname_res = 1;
+	return 0;
+}
+
+SEC("uretprobe//proc/self/exe:autoattach_trigger_func")
+int handle_uretprobe_byname(struct pt_regs *ctx)
+{
+	uretprobe_byname_res = 2;
+	return 0;
+}
+
+
+SEC("uprobe/libc.so.6:malloc")
+int handle_uprobe_byname2(struct pt_regs *ctx)
+{
+	uprobe_byname2_res = 3;
+	return 0;
+}
+
+SEC("uretprobe/libc.so.6:free")
+int handle_uretprobe_byname2(struct pt_regs *ctx)
+{
+	uretprobe_byname2_res = 4;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";