LXR linux/tools/testing/selftests/bpf/progs/kfree

   1// SPDX-License-Identifier: GPL-2.0
   2// Copyright (c) 2019 Facebook
   3#include <linux/bpf.h>
   4#include <stdbool.h>
   5#include <bpf/bpf_helpers.h>
   6#include <bpf/bpf_endian.h>
   7#include <bpf/bpf_tracing.h>
   8
   9char _license[] SEC("license") = "GPL";
  10struct {
  11        __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
  12        __uint(key_size, sizeof(int));
  13        __uint(value_size, sizeof(int));
  14} perf_buf_map SEC(".maps");
  15
  16#define _(P) (__builtin_preserve_access_index(P))
  17
  18/* define few struct-s that bpf program needs to access */
  19struct callback_head {
  20        struct callback_head *next;
  21        void (*func)(struct callback_head *head);
  22};
  23struct dev_ifalias {
  24        struct callback_head rcuhead;
  25};
  26
  27struct net_device /* same as kernel's struct net_device */ {
  28        int ifindex;
  29        struct dev_ifalias *ifalias;
  30};
  31
  32typedef struct {
  33        int counter;
  34} atomic_t;
  35typedef struct refcount_struct {
  36        atomic_t refs;
  37} refcount_t;
  38
  39struct sk_buff {
  40        /* field names and sizes should match to those in the kernel */
  41        unsigned int len, data_len;
  42        __u16 mac_len, hdr_len, queue_mapping;
  43        struct net_device *dev;
  44        /* order of the fields doesn't matter */
  45        refcount_t users;
  46        unsigned char *data;
  47        char __pkt_type_offset[0];
  48        char cb[48];
  49};
  50
  51struct meta {
  52        int ifindex;
  53        __u32 cb32_0;
  54        __u8 cb8_0;
  55};
  56
  57/* TRACE_EVENT(kfree_skb,
  58 *         TP_PROTO(struct sk_buff *skb, void *location),
  59 */
  60SEC("tp_btf/kfree_skb")
  61int BPF_PROG(trace_kfree_skb, struct sk_buff *skb, void *location)
  62{
  63        struct net_device *dev;
  64        struct callback_head *ptr;
  65        void *func;
  66        int users;
  67        unsigned char *data;
  68        unsigned short pkt_data;
  69        struct meta meta = {};
  70        char pkt_type;
  71        __u32 *cb32;
  72        __u8 *cb8;
  73
  74        __builtin_preserve_access_index(({
  75                users = skb->users.refs.counter;
  76                data = skb->data;
  77                dev = skb->dev;
  78                ptr = dev->ifalias->rcuhead.next;
  79                func = ptr->func;
  80                cb8 = (__u8 *)&skb->cb;
  81                cb32 = (__u32 *)&skb->cb;
  82        }));
  83
  84        meta.ifindex = _(dev->ifindex);
  85        meta.cb8_0 = cb8[8];
  86        meta.cb32_0 = cb32[2];
  87
  88        bpf_probe_read_kernel(&pkt_type, sizeof(pkt_type), _(&skb->__pkt_type_offset));
  89        pkt_type &= 7;
  90
  91        /* read eth proto */
  92        bpf_probe_read_kernel(&pkt_data, sizeof(pkt_data), data + 12);
  93
  94        bpf_printk("rcuhead.next %llx func %llx\n", ptr, func);
  95        bpf_printk("skb->len %d users %d pkt_type %x\n",
  96                   _(skb->len), users, pkt_type);
  97        bpf_printk("skb->queue_mapping %d\n", _(skb->queue_mapping));
  98        bpf_printk("dev->ifindex %d data %llx pkt_data %x\n",
  99                   meta.ifindex, data, pkt_data);
 100        bpf_printk("cb8_0:%x cb32_0:%x\n", meta.cb8_0, meta.cb32_0);
 101
 102        if (users != 1 || pkt_data != bpf_htons(0x86dd) || meta.ifindex != 1)
 103                /* raw tp ignores return value */
 104                return 0;
 105
 106        /* send first 72 byte of the packet to user space */
 107        bpf_skb_output(skb, &perf_buf_map, (72ull << 32) | BPF_F_CURRENT_CPU,
 108                       &meta, sizeof(meta));
 109        return 0;
 110}
 111
 112struct {
 113        bool fentry_test_ok;
 114        bool fexit_test_ok;
 115} result = {};
 116
 117SEC("fentry/eth_type_trans")
 118int BPF_PROG(fentry_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
 119             unsigned short protocol)
 120{
 121        int len, ifindex;
 122
 123        __builtin_preserve_access_index(({
 124                len = skb->len;
 125                ifindex = dev->ifindex;
 126        }));
 127
 128        /* fentry sees full packet including L2 header */
 129        if (len != 74 || ifindex != 1)
 130                return 0;
 131        result.fentry_test_ok = true;
 132        return 0;
 133}
 134
 135SEC("fexit/eth_type_trans")
 136int BPF_PROG(fexit_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
 137             unsigned short protocol)
 138{
 139        int len, ifindex;
 140
 141        __builtin_preserve_access_index(({
 142                len = skb->len;
 143                ifindex = dev->ifindex;
 144        }));
 145
 146        /* fexit sees packet without L2 header that eth_type_trans should have
 147         * consumed.
 148         */
 149        if (len != 60 || protocol != bpf_htons(0x86dd) || ifindex != 1)
 150                return 0;
 151        result.fexit_test_ok = true;
 152        return 0;
 153}
 154