我使用buildroot为rpi2构建一个小系统。使用uboot引导rpi，使用tftp加载内核和设备树文件，通过nfs加载rootfs，但它挂起。输出如下。
[ 0.000000] Booting Linux on physical CPU 0xf00
[ 0.000000] Initializing cgroup subsys cpuset
[ 0.000000] Initializing cgroup subsys cpu
[ 0.000000] Initializing cgroup subsys cpuacct
[ 0.000000] Linux version 3.18.16-v7 (max@debian) (gcc version 4.8.3 20140106 (prerelease) (crosstool-NG linaro-1.13.1-4.8-2014.01 - Linaro GCC 2013.11) ) #1 SMP PREEMPT Sun Jul 24 21:11:38 CST 2016
[ 0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=10c5387d
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[ 0.000000] Machine model: Raspberry Pi 2 Model B
[ 0.000000] cma: Reserved 8 MiB at 0x07800000
[ 0.000000] Memory policy: Data cache writealloc
[ 0.000000] [bcm2709_smp_init_cpus] enter (8620->f3003010)
[ 0.000000] [bcm2709_smp_init_cpus] ncores=4
[ 0.000000] PERCPU: Embedded 10 pages/cpu @876c4000 s11456 r8192 d21312 u40960
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 32512
[ 0.000000] Kernel command line: earlyprintk console=ttyAMA0 console=tty1 root=/dev/nfs ip=192.168.0.101 nfsroot=192.168.0.1:/home/max/Project/rpi2_lab/nfsroot rw
[ 0.000000] PID hash table entries: 512 (order: -1, 2048 bytes)
[ 0.000000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Memory: 112436K/131072K available (5756K kernel code, 400K rwdata, 1756K rodata, 388K init, 763K bss, 18636K reserved)
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] vector : 0xffff0000 - 0xffff1000 ( 4 kB)
[ 0.000000] fixmap : 0xffc00000 - 0xffe00000 (2048 kB)
[ 0.000000] vmalloc : 0x88800000 - 0xff000000 (1896 MB)
[ 0.000000] lowmem : 0x80000000 - 0x88000000 ( 128 MB)
[ 0.000000] modules : 0x7f000000 - 0x80000000 ( 16 MB)
[ 0.000000] .text : 0x80008000 - 0x8075e434 (7514 kB)
[ 0.000000] .init : 0x8075f000 - 0x807c0000 ( 388 kB)
[ 0.000000] .data : 0x807c0000 - 0x8082404c ( 401 kB)
[ 0.000000] .bss : 0x8082404c - 0x808e2f94 ( 764 kB)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[ 0.000000] Preemptible hierarchical RCU implementation.
[ 0.000000] NR_IRQS:608
[ 0.000000] Architected cp15 timer(s) running at 19.20MHz (phys).
[ 0.000013] sched_clock: 56 bits at 19MHz, resolution 52ns, wraps every 3579139424256ns
[ 0.000039] Switching to timer-based delay loop, resolution 52ns
[ 0.000341] Console: colour dummy device 80x30
[ 0.001659] console [tty1] enabled
[ 0.001708] Calibrating delay loop (skipped), value calculated using timer frequency.. 38.40 BogoMIPS (lpj=192000)
[ 0.001790] pid_max: default: 32768 minimum: 301
[ 0.002186] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.002246] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.003505] Initializing cgroup subsys memory
[ 0.003594] Initializing cgroup subsys devices
[ 0.003648] Initializing cgroup subsys freezer
[ 0.003712] Initializing cgroup subsys net_cls
[ 0.003762] Initializing cgroup subsys blkio
[ 0.003873] CPU: Testing write buffer coherency: ok
[ 0.003987] ftrace: allocating 19735 entries in 58 pages
[ 0.052741] CPU0: update cpu_capacity 1024
[ 0.052822] CPU0: thread -1, cpu 0, socket 15, mpidr 80000f00
[ 0.052863] [bcm2709_smp_prepare_cpus] enter
[ 0.053014] Setting up static identity map for 0x530cf8 - 0x530d2c
[ 0.112668] [bcm2709_boot_secondary] cpu:1 started (0) 18
[ 0.112970] CPU1: Booted secondary processor
[ 0.112978] [bcm2709_secondary_init] enter cpu:1
[ 0.113034] CPU1: update cpu_capacity 1024
[ 0.113043] CPU1: thread -1, cpu 1, socket 15, mpidr 80000f01
[ 0.132647] [bcm2709_boot_secondary] cpu:2 started (0) 18
[ 0.132893] CPU2: Booted secondary processor
[ 0.132900] [bcm2709_secondary_init] enter cpu:2
[ 0.132933] CPU2: update cpu_capacity 1024
[ 0.132942] CPU2: thread -1, cpu 2, socket 15, mpidr 80000f02
[ 0.152685] [bcm2709_boot_secondary] cpu:3 started (0) 16
[ 0.152915] CPU3: Booted secondary processor
[ 0.152924] [bcm2709_secondary_init] enter cpu:3
[ 0.152955] CPU3: update cpu_capacity 1024
[ 0.152964] CPU3: thread -1, cpu 3, socket 15, mpidr 80000f03
[ 0.153053] Brought up 4 CPUs
[ 0.153174] SMP: Total of 4 processors activated (153.60 BogoMIPS).
[ 0.153207] CPU: All CPU(s) started in HYP mode.
[ 0.153234] CPU: Virtualization extensions available.
[ 0.154219] devtmpfs: initialized
[ 0.179040] VFP support v0.3: implementor 41 architecture 2 part 30 variant 7 rev 5
[ 0.181030] pinctrl core: initialized pinctrl subsystem
[ 0.184080] NET: Registered protocol family 16
[ 0.189530] DMA: preallocated 4096 KiB pool for atomic coherent allocations
[ 0.190536] bcm2709.uart_clock = 3000000
[ 0.193684] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers.
[ 0.193740] hw-breakpoint: maximum watchpoint size is 8 bytes.
[ 0.193800] mailbox: Broadcom VideoCore Mailbox driver
[ 0.193935] bcm2708_vcio: mailbox at f300b880
[ 0.194298] bcm_power: Broadcom power driver
[ 0.194337] bcm_power_open() -> 0
[ 0.194364] bcm_power_request(0, 8)
[ 0.219620] bcm_mailbox_read -> 00000080, 0
[ 0.219653] bcm_power_request -> 0
[ 0.219794] Serial: AMBA PL011 UART driver
[ 0.219938] dev:f1: ttyAMA0 at MMIO 0x3f201000 (irq = 83, base_baud = 0) is a PL011 rev3
[ 0.709149] console [ttyAMA0] enabled
[ 0.785724] SCSI subsystem initialized
[ 0.789741] usbcore: registered new interface driver usbfs
[ 0.795415] usbcore: registered new interface driver hub
[ 0.800872] usbcore: registered new device driver usb
[ 0.807688] Switched to clocksource arch_sys_counter
[ 0.843378] FS-Cache: Loaded
[ 0.846630] CacheFiles: Loaded
[ 0.861272] NET: Registered protocol family 2
[ 0.866979] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.874035] TCP bind hash table entries: 1024 (order: 1, 8192 bytes)
[ 0.880480] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.886930] TCP: reno registered
[ 0.890209] UDP hash table entries: 256 (order: 1, 8192 bytes)
[ 0.896085] UDP-Lite hash table entries: 256 (order: 1, 8192 bytes)
[ 0.902696] NET: Registered protocol family 1
[ 0.907769] RPC: Registered named UNIX socket transport module.
[ 0.913711] RPC: Registered udp transport module.
[ 0.918473] RPC: Registered tcp transport module.
[ 0.923191] RPC: Registered tcp NFSv4.1 backchannel transport module.
[ 0.930490] hw perfevents: enabled with armv7_cortex_a7 PMU driver, 5 counters available
[ 0.938913] bcm2708_dma: DMA manager at f3007000
[ 0.943701] vc-mem: phys_addr:0x00000000 mem_base=0x00000000 mem_size:0x00000000(0 MiB)
[ 0.953309] futex hash table entries: 1024 (order: 4, 65536 bytes)
[ 0.959778] audit: initializing netlink subsys (disabled)
[ 0.965250] audit: type=2000 audit(0.779:1): initialized
[ 0.987025] VFS: Disk quotas dquot_6.5.2
[ 0.991388] Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
[ 1.000929] FS-Cache: Netfs 'nfs' registered for caching
[ 1.007325] NFS: Registering the id_resolver key type
[ 1.012519] Key type id_resolver registered
[ 1.016716] Key type id_legacy registered
[ 1.021994] msgmni has been set to 235
[ 1.027570] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
[ 1.035233] io scheduler noop registered
[ 1.039216] io scheduler deadline registered
[ 1.043842] io scheduler cfq registered (default)
[ 1.051214] BCM2708FB: allocated DMA memory c7c00000
[ 1.056239] BCM2708FB: allocated DMA channel 4 @ f3007400
[ 1.069026] Console: switching to colour frame buffer device 100x30
[ 1.081941] bcm2708-dmaengine bcm2708-dmaengine: Load BCM2835 DMA engine driver
[ 1.091651] uart-pl011 dev:f1: no DMA platform data
[ 1.099124] vc-cma: Videocore CMA driver
[ 1.105018] vc-cma: vc_cma_base = 0x00000000
[ 1.111701] vc-cma: vc_cma_size = 0x00000000 (0 MiB)
[ 1.119017] vc-cma: vc_cma_initial = 0x00000000 (0 MiB)
[ 1.138305] brd: module loaded
[ 1.149082] loop: module loaded
[ 1.154796] vchiq: vchiq_init_state: slot_zero = 0x87c80000, is_master = 0
[ 1.164334] Loading iSCSI transport class v2.0-870.
[ 1.172046] usbcore: registered new interface driver smsc95xx
[ 1.179712] dwc_otg: version 3.00a 10-AUG-2012 (platform bus)
[ 1.387571] Core Release: 2.80a
[ 1.392504] Setting default values for core params
[ 1.399110] Finished setting default values for core params
[ 1.606883] Using Buffer DMA mode
[ 1.612020] Periodic Transfer Interrupt Enhancement - disabled
[ 1.619688] Multiprocessor Interrupt Enhancement - disabled
[ 1.627035] OTG VER PARAM: 0, OTG VER FLAG: 0
[ 1.633183] Dedicated Tx FIFOs mode
[ 1.638758] WARN::dwc_otg_hcd_init:1047: FIQ DMA bounce buffers: virt = 0x87c14000 dma = 0xc7c14000 len=9024
[ 1.652457] FIQ FSM acceleration enabled for :
[ 1.652457] Non-periodic Split Transactions
[ 1.652457] Periodic Split Transactions
[ 1.652457] High-Speed Isochronous Endpoints
[ 1.676889] WARN::hcd_init_fiq:412: FIQ on core 1 at 0x803dea3c
[ 1.684697] WARN::hcd_init_fiq:413: FIQ ASM at 0x803ded98 length 36
[ 1.692845] WARN::hcd_init_fiq:438: MPHI regs_base at 0x8880a000
[ 1.700765] dwc_otg bcm2708_usb: DWC OTG Controller
[ 1.707632] dwc_otg bcm2708_usb: new USB bus registered, assigned bus number 1
[ 1.716898] dwc_otg bcm2708_usb: irq 32, io mem 0x00000000
[ 1.724444] Init: Port Power? op_state=1
[ 1.730332] Init: Power Port (0)
[ 1.735715] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
[ 1.744488] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1.753683] usb usb1: Product: DWC OTG Controller
[ 1.760328] usb usb1: Manufacturer: Linux 3.18.16-v7 dwc_otg_hcd
[ 1.768298] usb usb1: SerialNumber: bcm2708_usb
[ 1.775638] hub 1-0:1.0: USB hub found
[ 1.781420] hub 1-0:1.0: 1 port detected
[ 1.788176] usbcore: registered new interface driver usb-storage
[ 1.796373] mousedev: PS/2 mouse device common for all mice
[ 1.804525] bcm2835-cpufreq: min=600000 max=900000
[ 1.811614] sdhci: Secure Digital Host Controller Interface driver
[ 1.819718] sdhci: Copyright(c) Pierre Ossman
[ 1.826245] mmc-bcm2835 3f300000.mmc: mmc-bcm2835: Unable to initialise DMA channels. Falling back to PIO
[ 1.878023] sdhci-pltfm: SDHCI platform and OF driver helper
[ 1.890701] ledtrig-cpu: registered to indicate activity on CPUs
[ 1.899019] hidraw: raw HID events driver (C) Jiri Kosina
[ 1.908891] usbcore: registered new interface driver usbhid
[ 1.917562] usbhid: USB HID core driver
[ 1.923880] TCP: cubic registered
[ 1.930377] Initializing XFRM netlink socket
[ 1.937859] NET: Registered protocol family 17
[ 1.944435] Key type dns_resolver registered
[ 1.950940] Registering SWP/SWPB emulation handler
[ 1.958605] registered taskstats version 1
[ 1.964890] vc-sm: Videocore shared memory driver
[ 1.965360] mmc0: host does not support reading read-only switch, assuming write-enable
[ 1.967514] mmc0: new high speed SDHC card at address 0001
[ 1.968238] mmcblk0: mmc0:0001 SD8GB 7.27 GiB
[ 1.972935] mmcblk0: p1 p2
[ 2.000382] [vc_sm_connected_init]: start
[ 2.006472] Indeed it is in host mode hprt0 = 00021501
[ 2.014172] [vc_sm_connected_init]: end - returning 0
[ 2.187774] usb 1-1: new high-speed USB device number 2 using dwc_otg
[ 2.196438] Indeed it is in host mode hprt0 = 00001101
[ 2.398072] usb 1-1: New USB device found, idVendor=0424, idProduct=9514
[ 2.406856] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 2.416864] hub 1-1:1.0: USB hub found
[ 2.422683] hub 1-1:1.0: 5 ports detected
[ 2.707816] usb 1-1.1: new high-speed USB device number 3 using dwc_otg
[ 2.828046] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00
[ 2.836842] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 2.848859] smsc95xx v1.0.4
[ 2.911753] smsc95xx 1-1.1:1.0 eth0: register 'smsc95xx' at usb-bcm2708_usb-1.1, smsc95xx USB 2.0 Ethernet, 12:3a:57:23:f2:2e
[ 3.090398] smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup
[ 4.566372] smsc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1
[ 4.597728] IP-Config: Guessing netmask 255.255.255.0
[ 4.605127] IP-Config: Complete:
[ 4.610583] device=eth0, hwaddr=12:3a:57:23:f2:2e, ipaddr=192.168.0.101, mask=255.255.255.0, gw=255.255.255.255
[ 4.625541] host=192.168.0.101, domain=, nis-domain=(none)
[ 4.633711] bootserver=255.255.255.255, rootserver=192.168.0.1, rootpath=
[ 4.650420] VFS: Mounted root (nfs filesystem) on device 0:13.
[ 4.659302] devtmpfs: mounted
[ 4.665275] Freeing unused kernel memory: 388K (8075f000 - 807c0000)
[ 5.111631] random: dd urandom read with 112 bits of entropy available
[ 5.610645] random: nonblocking pool is initialized
[ 5.736051] NET: Registered protocol family 10
在NET之后我已经等了很长时间没有输出：已注册的协议族10＆＃39;。