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Date: Wed, 7 Oct 2020 08:26:28 +0800
From: kernel test robot <lkp@...el.com>
To: Jesper Dangaard Brouer <brouer@...hat.com>, bpf@...r.kernel.org
Cc: kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com,
Jesper Dangaard Brouer <brouer@...hat.com>,
netdev@...r.kernel.org, Daniel Borkmann <borkmann@...earbox.net>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
maze@...gle.com, lmb@...udflare.com, shaun@...era.io,
Lorenzo Bianconi <lorenzo@...nel.org>, marek@...udflare.com
Subject: Re: [PATCH bpf-next V1 5/6] bpf: Add MTU check for TC-BPF packets
after egress hook
Hi Jesper,
I love your patch! Perhaps something to improve:
[auto build test WARNING on bpf-next/master]
url: https://github.com/0day-ci/linux/commits/Jesper-Dangaard-Brouer/bpf-New-approach-for-BPF-MTU-handling-and-enforcement/20201007-000903
base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: mips-randconfig-r024-20201005 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 1127662c6dc2a276839c75a42238b11a3ad00f32)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install mips cross compiling tool for clang build
# apt-get install binutils-mips-linux-gnu
# https://github.com/0day-ci/linux/commit/2065cee7d6b74c8f1dabae4e4e15999a841e3349
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Jesper-Dangaard-Brouer/bpf-New-approach-for-BPF-MTU-handling-and-enforcement/20201007-000903
git checkout 2065cee7d6b74c8f1dabae4e4e15999a841e3349
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
net/core/dev.c:4176:1: warning: unused label 'drop'
drop:
^~~~~
>> net/core/dev.c:4068:7: warning: unused variable 'mtu_check'
bool mtu_check = false;
^
net/core/dev.c:4949:1: warning: unused function 'sch_handle_ingress'
sch_handle_ingress(struct sk_buff struct packet_type int
^
net/core/dev.c:5094:19: warning: unused function 'nf_ingress'
static inline int nf_ingress(struct sk_buff struct packet_type
^
fatal error: error in backend: Nested variants found in inline asm string: ' .set push
.set noat
.set push
.set arch=r4000
.if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/cmpxchg.h", .line = 163, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif
1: ll $0, $2 # __cmpxchg_asm
bne $0, ${3:z}, 2f
.set pop
move $$1, ${4:z}
.set arch=r4000
sc $$1, $1
beqz $$1, 1b
.set pop
2: .if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/cmpxchg.h", .line = 163, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif
'
clang-12: error: clang frontend command failed with exit code 70 (use -v to see invocation)
clang version 12.0.0 (git://gitmirror/llvm_project 1127662c6dc2a276839c75a42238b11a3ad00f32)
Target: mipsel-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/cross/clang-1127662c6d/bin
clang-12: note: diagnostic msg:
Makefile arch drivers include kernel net scripts source usr
--
>> net/core/dev.c:4068:7: warning: unused variable 'mtu_check'
bool mtu_check = false;
^
net/core/dev.c:4176:1: warning: unused label 'drop'
drop:
^~~~~
net/core/dev.c:4949:1: warning: unused function 'sch_handle_ingress'
sch_handle_ingress(struct sk_buff struct packet_type int
^
net/core/dev.c:5094:19: warning: unused function 'nf_ingress'
static inline int nf_ingress(struct sk_buff struct packet_type
^
fatal error: error in backend: Nested variants found in inline asm string: ' .set push
.set noat
.set push
.set arch=r4000
.if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/cmpxchg.h", .line = 163, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif
1: ll $0, $2 # __cmpxchg_asm
bne $0, ${3:z}, 2f
.set pop
move $$1, ${4:z}
.set arch=r4000
sc $$1, $1
beqz $$1, 1b
.set pop
2: .if ( 0x00 ) != -1)) 0x00 ) != -1)) : ($( static struct ftrace_branch_data __attribute__((__aligned__(4))) __attribute__((__section__("_ftrace_branch"))) __if_trace = $( .func = __func__, .file = "arch/mips/include/asm/cmpxchg.h", .line = 163, $); 0x00 ) != -1)) : $))) ) && ( 0 ); .set push; .set mips64r2; .rept 1; sync 0x00; .endr; .set pop; .else; ; .endif
'
clang-12: error: clang frontend command failed with exit code 70 (use -v to see invocation)
clang version 12.0.0 (git://gitmirror/llvm_project 1127662c6dc2a276839c75a42238b11a3ad00f32)
Target: mipsel-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/cross/clang-1127662c6d/bin
clang-12: note: diagnostic msg:
Makefile arch drivers include kernel net scripts source usr
vim +/mtu_check +4068 net/core/dev.c
4037
4038 /**
4039 * __dev_queue_xmit - transmit a buffer
4040 * @skb: buffer to transmit
4041 * @sb_dev: suboordinate device used for L2 forwarding offload
4042 *
4043 * Queue a buffer for transmission to a network device. The caller must
4044 * have set the device and priority and built the buffer before calling
4045 * this function. The function can be called from an interrupt.
4046 *
4047 * A negative errno code is returned on a failure. A success does not
4048 * guarantee the frame will be transmitted as it may be dropped due
4049 * to congestion or traffic shaping.
4050 *
4051 * -----------------------------------------------------------------------------------
4052 * I notice this method can also return errors from the queue disciplines,
4053 * including NET_XMIT_DROP, which is a positive value. So, errors can also
4054 * be positive.
4055 *
4056 * Regardless of the return value, the skb is consumed, so it is currently
4057 * difficult to retry a send to this method. (You can bump the ref count
4058 * before sending to hold a reference for retry if you are careful.)
4059 *
4060 * When calling this method, interrupts MUST be enabled. This is because
4061 * the BH enable code must have IRQs enabled so that it will not deadlock.
4062 * --BLG
4063 */
4064 static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
4065 {
4066 struct net_device *dev = skb->dev;
4067 struct netdev_queue *txq;
> 4068 bool mtu_check = false;
4069 bool again = false;
4070 struct Qdisc *q;
4071 int rc = -ENOMEM;
4072
4073 skb_reset_mac_header(skb);
4074
4075 if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
4076 __skb_tstamp_tx(skb, NULL, skb->sk, SCM_TSTAMP_SCHED);
4077
4078 /* Disable soft irqs for various locks below. Also
4079 * stops preemption for RCU.
4080 */
4081 rcu_read_lock_bh();
4082
4083 skb_update_prio(skb);
4084
4085 qdisc_pkt_len_init(skb);
4086 #ifdef CONFIG_NET_CLS_ACT
4087 mtu_check = skb_is_redirected(skb);
4088 skb->tc_at_ingress = 0;
4089 # ifdef CONFIG_NET_EGRESS
4090 if (static_branch_unlikely(&egress_needed_key)) {
4091 unsigned int len_orig = skb->len;
4092
4093 skb = sch_handle_egress(skb, &rc, dev);
4094 if (!skb)
4095 goto out;
4096 /* BPF-prog ran and could have changed packet size beyond MTU */
4097 if (rc == NET_XMIT_SUCCESS && skb->len > len_orig)
4098 mtu_check = true;
4099 }
4100 # endif
4101 /* MTU-check only happens on "last" net_device in a redirect sequence
4102 * (e.g. above sch_handle_egress can steal SKB and skb_do_redirect it
4103 * either ingress or egress to another device).
4104 */
4105 if (mtu_check && !is_skb_forwardable(dev, skb)) {
4106 rc = -EMSGSIZE;
4107 goto drop;
4108 }
4109 #endif
4110 /* If device/qdisc don't need skb->dst, release it right now while
4111 * its hot in this cpu cache.
4112 */
4113 if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
4114 skb_dst_drop(skb);
4115 else
4116 skb_dst_force(skb);
4117
4118 txq = netdev_core_pick_tx(dev, skb, sb_dev);
4119 q = rcu_dereference_bh(txq->qdisc);
4120
4121 trace_net_dev_queue(skb);
4122 if (q->enqueue) {
4123 rc = __dev_xmit_skb(skb, q, dev, txq);
4124 goto out;
4125 }
4126
4127 /* The device has no queue. Common case for software devices:
4128 * loopback, all the sorts of tunnels...
4129
4130 * Really, it is unlikely that netif_tx_lock protection is necessary
4131 * here. (f.e. loopback and IP tunnels are clean ignoring statistics
4132 * counters.)
4133 * However, it is possible, that they rely on protection
4134 * made by us here.
4135
4136 * Check this and shot the lock. It is not prone from deadlocks.
4137 *Either shot noqueue qdisc, it is even simpler 8)
4138 */
4139 if (dev->flags & IFF_UP) {
4140 int cpu = smp_processor_id(); /* ok because BHs are off */
4141
4142 if (txq->xmit_lock_owner != cpu) {
4143 if (dev_xmit_recursion())
4144 goto recursion_alert;
4145
4146 skb = validate_xmit_skb(skb, dev, &again);
4147 if (!skb)
4148 goto out;
4149
4150 HARD_TX_LOCK(dev, txq, cpu);
4151
4152 if (!netif_xmit_stopped(txq)) {
4153 dev_xmit_recursion_inc();
4154 skb = dev_hard_start_xmit(skb, dev, txq, &rc);
4155 dev_xmit_recursion_dec();
4156 if (dev_xmit_complete(rc)) {
4157 HARD_TX_UNLOCK(dev, txq);
4158 goto out;
4159 }
4160 }
4161 HARD_TX_UNLOCK(dev, txq);
4162 net_crit_ratelimited("Virtual device %s asks to queue packet!\n",
4163 dev->name);
4164 } else {
4165 /* Recursion is detected! It is possible,
4166 * unfortunately
4167 */
4168 recursion_alert:
4169 net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n",
4170 dev->name);
4171 }
4172 }
4173
4174 rc = -ENETDOWN;
4175 rcu_read_unlock_bh();
4176 drop:
4177 atomic_long_inc(&dev->tx_dropped);
4178 kfree_skb_list(skb);
4179 return rc;
4180 out:
4181 rcu_read_unlock_bh();
4182 return rc;
4183 }
4184
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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