feat: tailcall test

Author: yimingx

core/bpftests/stackmem.c

@@ -0,0 +1,17 @@
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+char LICENSE[] SEC("license") = "GPL";
+
+SEC("tracepoint/syscalls/sys_enter_mount")
+int prog(void *ctx)
+{
+
+    volatile int a;
+	bpf_printk("r10 - 8: %p: %d\n", &a, a);
+    long* r10 = (long*)((int*)(&a) + 1);
+	bpf_printk("r10: %p: %d\n", r10, *r10); // Invalid
+
+	bpf_printk("entry_prog: tail call failed\n");
+	return XDP_PASS;
+}

core/bpftests/tailcall.c

@@ -0,0 +1,40 @@
+// tailcall_kern.c
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+char LICENSE[] SEC("license") = "GPL";
+
+// Program array map
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 4);
+	__type(key, __u32);
+	__type(value, __u32);
+} jmp_table SEC(".maps");
+
+// Entry program
+SEC("tracepoint/syscalls/sys_enter_mount")
+int entry_prog(void *ctx)
+{
+	__u32 index = 1;
+
+	// int a[5] = { 1, 2, 3, 4, 5 };
+    volatile int a = 100;
+	bpf_printk("p1 %p\n", &a);
+
+	// Tail call to index 1
+	bpf_tail_call(ctx, &jmp_table, index);
+
+	bpf_printk("entry_prog: tail call failed\n");
+	return XDP_PASS;
+}
+
+// Program that is tail-called
+SEC("tracepoint/syscalls/sys_enter_mount")
+int next_prog(void *ctx)
+{
+    volatile int a;
+	bpf_printk("p2 %p\n", &a);
+	bpf_printk("p2 %d\n", a);
+	return XDP_PASS;
+}

core/bpftests/tailcall_us.c

@@ -0,0 +1,49 @@
+// tailcall_user.c
+#include <stdio.h>
+#include <bpf/libbpf.h>
+#include <bpf/bpf.h>
+#include <unistd.h>
+int main()
+{
+	struct bpf_object *obj;
+	struct bpf_program *p_entry, *p_next;
+	int prog_fd_entry, prog_fd_next;
+	int map_fd;
+
+	obj = bpf_object__open_file("output/tailcall.o", NULL);
+	if (!obj) {
+		printf("open failed\n");
+		return 1;
+	}
+
+	if (bpf_object__load(obj)) {
+		printf("load failed\n");
+		return 1;
+	}
+
+	p_entry = bpf_object__find_program_by_name(obj, "entry_prog");
+	p_next = bpf_object__find_program_by_name(obj, "next_prog");
+
+	prog_fd_entry = bpf_program__fd(p_entry);
+	prog_fd_next = bpf_program__fd(p_next);
+
+	map_fd = bpf_object__find_map_fd_by_name(obj, "jmp_table");
+
+	__u32 index = 1;
+	if (bpf_map_update_elem(map_fd, &index, &prog_fd_next, 0)) {
+		printf("update_elem failed\n");
+		return 1;
+	}
+
+	struct bpf_link *link1 = NULL, *link2 = NULL, *link3 = NULL;
+
+	link1 = bpf_program__attach_tracepoint(p_entry, "syscalls",
+					       "sys_enter_mount");
+	if (libbpf_get_error(link1)) {
+		fprintf(stderr, "Failed to attach\n");
+		return 1;
+	}
+	sleep(30);
+	bpf_link__destroy(link1);
+	return 0;
+}