cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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test_pkt_access.c (3709B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* Copyright (c) 2017 Facebook
      3 */
      4#include <stddef.h>
      5#include <string.h>
      6#include <linux/bpf.h>
      7#include <linux/if_ether.h>
      8#include <linux/if_packet.h>
      9#include <linux/ip.h>
     10#include <linux/ipv6.h>
     11#include <linux/in.h>
     12#include <linux/tcp.h>
     13#include <linux/pkt_cls.h>
     14#include <bpf/bpf_helpers.h>
     15#include <bpf/bpf_endian.h>
     16
     17/* llvm will optimize both subprograms into exactly the same BPF assembly
     18 *
     19 * Disassembly of section .text:
     20 *
     21 * 0000000000000000 test_pkt_access_subprog1:
     22 * ; 	return skb->len * 2;
     23 *        0:	61 10 00 00 00 00 00 00	r0 = *(u32 *)(r1 + 0)
     24 *        1:	64 00 00 00 01 00 00 00	w0 <<= 1
     25 *        2:	95 00 00 00 00 00 00 00	exit
     26 *
     27 * 0000000000000018 test_pkt_access_subprog2:
     28 * ; 	return skb->len * val;
     29 *        3:	61 10 00 00 00 00 00 00	r0 = *(u32 *)(r1 + 0)
     30 *        4:	64 00 00 00 01 00 00 00	w0 <<= 1
     31 *        5:	95 00 00 00 00 00 00 00	exit
     32 *
     33 * Which makes it an interesting test for BTF-enabled verifier.
     34 */
     35static __attribute__ ((noinline))
     36int test_pkt_access_subprog1(volatile struct __sk_buff *skb)
     37{
     38	return skb->len * 2;
     39}
     40
     41static __attribute__ ((noinline))
     42int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
     43{
     44	return skb->len * val;
     45}
     46
     47#define MAX_STACK (512 - 2 * 32)
     48
     49__attribute__ ((noinline))
     50int get_skb_len(struct __sk_buff *skb)
     51{
     52	volatile char buf[MAX_STACK] = {};
     53
     54	return skb->len;
     55}
     56
     57__attribute__ ((noinline))
     58int get_constant(long val)
     59{
     60	return val - 122;
     61}
     62
     63int get_skb_ifindex(int, struct __sk_buff *skb, int);
     64
     65__attribute__ ((noinline))
     66int test_pkt_access_subprog3(int val, struct __sk_buff *skb)
     67{
     68	return get_skb_len(skb) * get_skb_ifindex(val, skb, get_constant(123));
     69}
     70
     71__attribute__ ((noinline))
     72int get_skb_ifindex(int val, struct __sk_buff *skb, int var)
     73{
     74	volatile char buf[MAX_STACK] = {};
     75
     76	return skb->ifindex * val * var;
     77}
     78
     79__attribute__ ((noinline))
     80int test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off)
     81{
     82	void *data = (void *)(long)skb->data;
     83	void *data_end = (void *)(long)skb->data_end;
     84	struct tcphdr *tcp = NULL;
     85
     86	if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr))
     87		return -1;
     88
     89	tcp = data + off;
     90	if (tcp + 1 > data_end)
     91		return -1;
     92	/* make modification to the packet data */
     93	tcp->check++;
     94	return 0;
     95}
     96
     97SEC("tc")
     98int test_pkt_access(struct __sk_buff *skb)
     99{
    100	void *data_end = (void *)(long)skb->data_end;
    101	void *data = (void *)(long)skb->data;
    102	struct ethhdr *eth = (struct ethhdr *)(data);
    103	struct tcphdr *tcp = NULL;
    104	__u8 proto = 255;
    105	__u64 ihl_len;
    106
    107	if (eth + 1 > data_end)
    108		return TC_ACT_SHOT;
    109
    110	if (eth->h_proto == bpf_htons(ETH_P_IP)) {
    111		struct iphdr *iph = (struct iphdr *)(eth + 1);
    112
    113		if (iph + 1 > data_end)
    114			return TC_ACT_SHOT;
    115		ihl_len = iph->ihl * 4;
    116		proto = iph->protocol;
    117		tcp = (struct tcphdr *)((void *)(iph) + ihl_len);
    118	} else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
    119		struct ipv6hdr *ip6h = (struct ipv6hdr *)(eth + 1);
    120
    121		if (ip6h + 1 > data_end)
    122			return TC_ACT_SHOT;
    123		ihl_len = sizeof(*ip6h);
    124		proto = ip6h->nexthdr;
    125		tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len);
    126	}
    127
    128	if (test_pkt_access_subprog1(skb) != skb->len * 2)
    129		return TC_ACT_SHOT;
    130	if (test_pkt_access_subprog2(2, skb) != skb->len * 2)
    131		return TC_ACT_SHOT;
    132	if (test_pkt_access_subprog3(3, skb) != skb->len * 3 * skb->ifindex)
    133		return TC_ACT_SHOT;
    134	if (tcp) {
    135		if (test_pkt_write_access_subprog(skb, (void *)tcp - data))
    136			return TC_ACT_SHOT;
    137		if (((void *)(tcp) + 20) > data_end || proto != 6)
    138			return TC_ACT_SHOT;
    139		barrier(); /* to force ordering of checks */
    140		if (((void *)(tcp) + 18) > data_end)
    141			return TC_ACT_SHOT;
    142		if (tcp->urg_ptr == 123)
    143			return TC_ACT_OK;
    144	}
    145
    146	return TC_ACT_UNSPEC;
    147}