1 files changed, 73 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/test_legacy_printk.c b/tools/testing/selftests/bpf/progs/test_legacy_printk.c
new file mode 100644
index 000000000000..64c2d9ced529
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_legacy_printk.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <linux/bpf.h>
+#define BPF_NO_GLOBAL_DATA
+#include <bpf/bpf_helpers.h>
+
+char LICENSE[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 1);
+} my_pid_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 1);
+} res_map SEC(".maps");
+
+volatile int my_pid_var = 0;
+volatile int res_var = 0;
+
+SEC("tp/raw_syscalls/sys_enter")
+int handle_legacy(void *ctx)
+{
+	int zero = 0, *my_pid, cur_pid, *my_res;
+
+	my_pid = bpf_map_lookup_elem(&my_pid_map, &zero);
+	if (!my_pid)
+		return 1;
+
+	cur_pid = bpf_get_current_pid_tgid() >> 32;
+	if (cur_pid != *my_pid)
+		return 1;
+
+	my_res = bpf_map_lookup_elem(&res_map, &zero);
+	if (!my_res)
+		return 1;
+
+	if (*my_res == 0)
+		/* use bpf_printk() in combination with BPF_NO_GLOBAL_DATA to
+		 * force .rodata.str1.1 section that previously caused
+		 * problems on old kernels due to libbpf always tried to
+		 * create a global data map for it
+		 */
+		bpf_printk("Legacy-case bpf_printk test, pid %d\n", cur_pid);
+	*my_res = 1;
+
+	return *my_res;
+}
+
+SEC("tp/raw_syscalls/sys_enter")
+int handle_modern(void *ctx)
+{
+	int zero = 0, cur_pid;
+
+	cur_pid = bpf_get_current_pid_tgid() >> 32;
+	if (cur_pid != my_pid_var)
+		return 1;
+
+	if (res_var == 0)
+		/* we need bpf_printk() to validate libbpf logic around unused
+		 * global maps and legacy kernels; see comment in handle_legacy()
+		 */
+		bpf_printk("Modern-case bpf_printk test, pid %d\n", cur_pid);
+	res_var = 1;
+
+	return res_var;
+}