tools/testing/selftests/bpf/progs/tailcall_bpf2bpf1.c

File Facts

System

Linux kernel

Corpus path

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf1.c

Extension

.c

Size

692 bytes

Lines

38

Domain

Support Tooling And Documentation

Bucket

tools

Inferred role

Support Tooling And Documentation: implementation source

Status

source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

• Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/bpf.h
• bpf/bpf_helpers.h

Detected Declarations

• function subprog_tail
• function entry

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>

struct {
	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
	__uint(max_entries, 2);
	__uint(key_size, sizeof(__u32));
	__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");

#define TAIL_FUNC(x) 				\
	SEC("tc")				\
	int classifier_##x(struct __sk_buff *skb)	\
	{					\
		return x;			\
	}
TAIL_FUNC(0)
TAIL_FUNC(1)

static __noinline
int subprog_tail(struct __sk_buff *skb)
{
	bpf_tail_call_static(skb, &jmp_table, 0);

	return skb->len * 2;
}

SEC("tc")
int entry(struct __sk_buff *skb)
{
	bpf_tail_call_static(skb, &jmp_table, 1);

	return subprog_tail(skb);
}

char __license[] SEC("license") = "GPL";

Annotation

• Immediate include surface: `linux/bpf.h`, `bpf/bpf_helpers.h`.
• Detected declarations: `function subprog_tail`, `function entry`.
• Atlas domain: Support Tooling And Documentation / tools.
• Implementation status: source implementation candidate.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.