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

Source file repositories/reference/linux-study-clean/tools/testing/selftests/bpf/progs/test_pkt_access.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/bpf/progs/test_pkt_access.c
Extension
.c
Size
3791 bytes
Lines
153
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.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2017 Facebook
 */
#include <stddef.h>
#include <string.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <linux/pkt_cls.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include "bpf_misc.h"

/* llvm will optimize both subprograms into exactly the same BPF assembly
 *
 * Disassembly of section .text:
 *
 * 0000000000000000 test_pkt_access_subprog1:
 * ; 	return skb->len * 2;
 *        0:	61 10 00 00 00 00 00 00	r0 = *(u32 *)(r1 + 0)
 *        1:	64 00 00 00 01 00 00 00	w0 <<= 1
 *        2:	95 00 00 00 00 00 00 00	exit
 *
 * 0000000000000018 test_pkt_access_subprog2:
 * ; 	return skb->len * val;
 *        3:	61 10 00 00 00 00 00 00	r0 = *(u32 *)(r1 + 0)
 *        4:	64 00 00 00 01 00 00 00	w0 <<= 1
 *        5:	95 00 00 00 00 00 00 00	exit
 *
 * Which makes it an interesting test for BTF-enabled verifier.
 */
static __attribute__ ((noinline))
int test_pkt_access_subprog1(volatile struct __sk_buff *skb)
{
	return skb->len * 2;
}

static __attribute__ ((noinline))
int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
{
	return skb->len * val;
}

#define MAX_STACK (512 - 2 * 32)

__attribute__ ((noinline))
int get_skb_len(struct __sk_buff *skb)
{
	volatile char buf[MAX_STACK] = {};

	__sink(buf[MAX_STACK - 1]);

	return skb->len;
}

__attribute__ ((noinline))
int get_constant(long val)
{
	return val - 122;
}

int get_skb_ifindex(int, struct __sk_buff *skb, int);

__attribute__ ((noinline))
int test_pkt_access_subprog3(int val, struct __sk_buff *skb)
{
	return get_skb_len(skb) * get_skb_ifindex(val, skb, get_constant(123));
}

__attribute__ ((noinline))
int get_skb_ifindex(int val, struct __sk_buff *skb, int var)
{
	volatile char buf[MAX_STACK] = {};

	__sink(buf[MAX_STACK - 1]);

	return skb->ifindex * val * var;
}

__attribute__ ((noinline))
int test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off)
{
	void *data = (void *)(long)skb->data;
	void *data_end = (void *)(long)skb->data_end;
	struct tcphdr *tcp = NULL;

Annotation

Implementation Notes