From f11ff90d616bfdbe4de3bf0670890d86cf84b694 Mon Sep 17 00:00:00 2001
From: Jesper Dangaard Brouer <brouer@redhat.com>
Date: Mon, 31 May 2021 18:57:50 +0200
Subject: [PATCH] ktrace-CO-RE: Add trivial BPF-prog

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 ktrace-CO-RE/ktrace01.c      | 80 ++++++++++++++++++++++++++++++++++++
 ktrace-CO-RE/ktrace01_kern.c | 24 +++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 ktrace-CO-RE/ktrace01.c
 create mode 100644 ktrace-CO-RE/ktrace01_kern.c

diff --git a/ktrace-CO-RE/ktrace01.c b/ktrace-CO-RE/ktrace01.c
new file mode 100644
index 0000000..ad455e9
--- /dev/null
+++ b/ktrace-CO-RE/ktrace01.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0+
+// static const char *__doc__ = " Trivial ktrace example";
+
+#include <bpf/libbpf.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include <stdio.h>
+
+#define pr_err(fmt, ...) \
+	fprintf(stderr, "%s:%d - " fmt, __FILE__, __LINE__, ##__VA_ARGS__)
+
+int main(int argc, char **argv)
+{
+	struct bpf_object *obj = NULL;
+	struct bpf_link *link = NULL;
+	struct bpf_program *prog;
+	char filename[256];
+	//char pin_file[256];
+	// char *pin_file;
+	char buf[100];
+	int err;
+	int c;
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+        obj = bpf_object__open_file(filename, NULL);
+	err = libbpf_get_error(obj);
+	if (err) {
+		libbpf_strerror(err, buf, sizeof(buf));
+		pr_err("Error(%d) opening file: %s\n", err, buf);
+		goto out;
+	}
+
+	err = bpf_object__load(obj);
+	if (err) {
+		libbpf_strerror(err, buf, sizeof(buf));
+		pr_err("Error(%d) loading: %s\n", err, buf);
+		goto out;
+	}
+
+	prog = bpf_program__next(NULL, obj);
+	if (!prog) {
+		pr_err("No program!\n");
+		err = -ENOENT;
+		goto out;
+	}
+
+	link = bpf_program__attach(prog);
+	err = libbpf_get_error(link);
+	if (err) {
+		libbpf_strerror(err, buf, sizeof(buf));
+		pr_err("Error(%d) attaching: %s\n", err, buf);
+		goto out;
+	}
+
+	printf("Loaded BPF file %s\n", filename);
+	printf( "Press any key + enter to unload program again [Y/y]:");
+	c = getchar();
+	putchar(c);
+
+	// snprintf(pin_file, sizeof(pin_file), "/sys/fs/bpf/%s", argv[0]);
+	/*
+	pin_file = "/sys/fs/bpf/ktrace01";
+	err = bpf_link__pin(link, pin_file);
+	printf("pin_file %s\n", pin_file);
+	if (err) {
+		libbpf_strerror(err, buf, sizeof(buf));
+		pr_err("Error(%d) pinning: %s\n", err, buf);
+		goto out;
+	}
+	printf("Loaded BPF file %s (pinned at %s)\n", filename, pin_file);
+	*/
+out:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
+	if (err)
+		return EXIT_FAILURE;
+	return EXIT_SUCCESS;
+}
diff --git a/ktrace-CO-RE/ktrace01_kern.c b/ktrace-CO-RE/ktrace01_kern.c
new file mode 100644
index 0000000..4ddaf70
--- /dev/null
+++ b/ktrace-CO-RE/ktrace01_kern.c
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct my_struct {
+	int v;
+	__u64 m2;
+};
+
+SEC("kprobe/open_ctree")
+int bpf_prog1(struct pt_regs *ctx)
+{
+	unsigned long rc = 0;
+	struct my_struct a;
+
+        //a.v = 42;
+
+	// bpf_override_return(ctx, rc);
+        if (a.v == 43)
+                return 0;
+	return a.v;
+}