selftests/bpf: Add testcases for tailcall hierarchy fixing

Add some test cases to confirm the tailcall hierarchy issue has been fixed.

On x64, the selftests result is:

cd tools/testing/selftests/bpf && ./test_progs -t tailcalls
327/18  tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
327/19  tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
327/20  tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
327/21  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
327/22  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
327/23  tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
327/24  tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
327     tailcalls:OK
Summary: 1/24 PASSED, 0 SKIPPED, 0 FAILED

On arm64, the selftests result is:

cd tools/testing/selftests/bpf && ./test_progs -t tailcalls
327/18  tailcalls/tailcall_bpf2bpf_hierarchy_1:OK
327/19  tailcalls/tailcall_bpf2bpf_hierarchy_fentry:OK
327/20  tailcalls/tailcall_bpf2bpf_hierarchy_fexit:OK
327/21  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_fexit:OK
327/22  tailcalls/tailcall_bpf2bpf_hierarchy_fentry_entry:OK
327/23  tailcalls/tailcall_bpf2bpf_hierarchy_2:OK
327/24  tailcalls/tailcall_bpf2bpf_hierarchy_3:OK
327     tailcalls:OK
Summary: 1/24 PASSED, 0 SKIPPED, 0 FAILED
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240714123902.32305-4-hffilwlqm@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy1.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count = 0;
+
+static __noinline
+int subprog_tail(struct __sk_buff *skb)
+{
+	bpf_tail_call_static(skb, &jmp_table, 0);
+	return 0;
+}
+
+SEC("tc")
+int entry(struct __sk_buff *skb)
+{
+	int ret = 1;
+
+	count++;
+	subprog_tail(skb);
+	subprog_tail(skb);
+
+	return ret;
+}
+
+char __license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy2.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+int classifier_0(struct __sk_buff *skb);
+int classifier_1(struct __sk_buff *skb);
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 2);
+	__uint(key_size, sizeof(__u32));
+	__array(values, void (void));
+} jmp_table SEC(".maps") = {
+	.values = {
+		[0] = (void *) &classifier_0,
+		[1] = (void *) &classifier_1,
+	},
+};
+
+int count0 = 0;
+int count1 = 0;
+
+static __noinline
+int subprog_tail0(struct __sk_buff *skb)
+{
+	bpf_tail_call_static(skb, &jmp_table, 0);
+	return 0;
+}
+
+__auxiliary
+SEC("tc")
+int classifier_0(struct __sk_buff *skb)
+{
+	count0++;
+	subprog_tail0(skb);
+	return 0;
+}
+
+static __noinline
+int subprog_tail1(struct __sk_buff *skb)
+{
+	bpf_tail_call_static(skb, &jmp_table, 1);
+	return 0;
+}
+
+__auxiliary
+SEC("tc")
+int classifier_1(struct __sk_buff *skb)
+{
+	count1++;
+	subprog_tail1(skb);
+	return 0;
+}
+
+__success
+__retval(33)
+SEC("tc")
+int tailcall_bpf2bpf_hierarchy_2(struct __sk_buff *skb)
+{
+	volatile int ret = 0;
+
+	subprog_tail0(skb);
+	subprog_tail1(skb);
+
+	asm volatile (""::"r+"(ret));
+	return (count1 << 16) | count0;
+}
+
+char __license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy3.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+int classifier_0(struct __sk_buff *skb);
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__array(values, void (void));
+} jmp_table0 SEC(".maps") = {
+	.values = {
+		[0] = (void *) &classifier_0,
+	},
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__array(values, void (void));
+} jmp_table1 SEC(".maps") = {
+	.values = {
+		[0] = (void *) &classifier_0,
+	},
+};
+
+int count = 0;
+
+static __noinline
+int subprog_tail(struct __sk_buff *skb, void *jmp_table)
+{
+	bpf_tail_call_static(skb, jmp_table, 0);
+	return 0;
+}
+
+__auxiliary
+SEC("tc")
+int classifier_0(struct __sk_buff *skb)
+{
+	count++;
+	subprog_tail(skb, &jmp_table0);
+	subprog_tail(skb, &jmp_table1);
+	return count;
+}
+
+__success
+__retval(33)
+SEC("tc")
+int tailcall_bpf2bpf_hierarchy_3(struct __sk_buff *skb)
+{
+	volatile int ret = 0;
+
+	bpf_tail_call_static(skb, &jmp_table0, 0);
+
+	asm volatile (""::"r+"(ret));
+	return ret;
+}
+
+char __license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_fentry.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count = 0;
+
+static __noinline
+int subprog_tail(void *ctx)
+{
+	bpf_tail_call_static(ctx, &jmp_table, 0);
+	return 0;
+}
+
+SEC("fentry/dummy")
+int BPF_PROG(fentry, struct sk_buff *skb)
+{
+	count++;
+	subprog_tail(ctx);
+	subprog_tail(ctx);
+
+	return 0;
+}
+
+
+char _license[] SEC("license") = "GPL";

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

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_legacy.h"
+
+SEC("tc")
+int entry(struct __sk_buff *skb)
+{
+	return 1;
+}
+
+char __license[] SEC("license") = "GPL";