Linux kernel debug技巧----开启DEBUG选项
作者：wowo 发布于：2016-11-1 19:39
分类：Linux应用技巧
kernel的source code中有很多使用pr_debug/dev_dbg输出的日志信息(例如device tree解析的代码，drivers/of/fdt.c)。默认情况下，kernel不会将这些日志输出到控制台上，除非：
1)开启了DEBUG宏，并且
2)kernel printk的默认日志级别大于7
看似简单，不过我相信每个人都问过这样的问题(不管是问自己还是问别人，特别是在调试kernel启动过程的时候，例如device tree的匹配、device probe等)：怎么开启DEBUG选项？
之所以有这篇短文，是因为我也问过(不止一次)，于是就记录如下：
1)开启了DEBUG宏
其实开启DEBUG宏的方法很简单，在需要pr_debug/dev_dbg输出的模块开头，直接#define DEBUG即可，kernel中有一个例子：
#define DEBUG
不过这种方法有个缺点：我们必须准确的知道需要debug那个C文件，如果想大网撒鱼(例如，想debug为什么新修改的DTS文件没有起作用，而又对kernel fdt的代码不是很熟悉)，就麻烦了。这里我给一个大杀器：在编译kernel的时候，通过KCFLAGS直接传递，这样可以全局生效，如下(以本站的“X Project”为例)：
diff --git a/Makefile b/Makefile
index 0835b1c..59625f4 100644
--- a/Makefile
+++ b/Makefile
@@ -83,7 +83,7 @@ kernel-config:
kernel:
mkdir -p $(KERNEL_OUT_DIR)
make -C $(KERNEL_DIR) CROSS_COMPILE=$(CROSS_COMPILE) KBUILD_OUTPUT=$(KERNEL_OUT_DIR) ARCH=$(BOARD_ARCH) $(KERNEL_D
- make -C $(KERNEL_DIR) CROSS_COMPILE=$(CROSS_COMPILE) KBUILD_OUTPUT=$(KERNEL_OUT_DIR) ARCH=$(BOARD_ARCH) $(KERNEL_T
+ make -C $(KERNEL_DIR) CROSS_COMPILE=$(CROSS_COMPILE) KBUILD_OUTPUT=$(KERNEL_OUT_DIR) KCFLAGS=-DDEBUG ARCH=$(BOARD_
2)设置kernel printk的默认日志级别为8
修改printk的默认日志级别的方法有多种，例如直接修改printk.c(新kernel为printk.h)中的CONSOLE_LOGLEVEL_DEFAULT宏定义。不过修改kernel原生代码的方式稍显粗暴，我们还有优雅一些的手段，例如通过命令行参数的loglevel变量传递，如下：
diff --git a/arch/arm64/configs/xprj_defconfig b/arch/arm64/configs/xprj_defconfig
index 5d0d591..9335d3f 100644
--- a/arch/arm64/configs/xprj_defconfig
+++ b/arch/arm64/configs/xprj_defconfig
@@ -320,7 +320,7 @@ CONFIG_FORCE_MAX_ZONEORDER=11
#
# Boot options
#
-CONFIG_CMDLINE="earlycon=owl_serial"
+CONFIG_CMDLINE="earlycon=owl_serial loglevel=8"
CONFIG_CMDLINE_FORCE=y
# CONFIG_EFI is not set
3)修改完之后，编译并启动kernel看看效果吧(是不是很爽？)
Starting kernel ...
flushing dcache successfully.
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 4.6.0-rc5+ ([email protected]) (gcc version 4.8.3 20131202 (prerelease) (crosstool-NG linaro-1.13.1-4.8-2013.12 - Linaro GCC 2013.11) ) #17 SMP Tue Nov 1 03:52:32 PDT 2016
[ 0.000000] Boot CPU: AArch64 Processor [410fd032]
[ 0.000000] earlycon: owl_serial0 at I/O port 0x0 (options '')
[ 0.000000] bootconsole [owl_serial0] enabled
[ 0.000000] On node 0 totalpages: 524288
[ 0.000000] DMA zone: 8192 pages used for memmap
[ 0.000000] DMA zone: 0 pages reserved
[ 0.000000] DMA zone: 524288 pages, LIFO batch:31
[ 0.000000] -> unflatten_device_tree()
[ 0.000000] Unflattening device tree:
[ 0.000000] magic: d00dfeed
[ 0.000000] size: 00001000
[ 0.000000] version: 00000011
[ 0.000000] size is cb0, allocating...
[ 0.000000] unflattening ffffffc07ffed1c8...
[ 0.000000] fixed up name for ->
[ 0.000000] fixed up name for memory -> memory
[ 0.000000] fixed up name for chosen -> chosen
[ 0.000000] fixed up name for [email protected] -> interrupt-controller
[ 0.000000] fixed up name for timer -> timer
[ 0.000000]
[ 0.000000] Failed to find device node for boot cpu
[ 0.000000] missing boot CPU MPIDR, not enabling secondaries
[ 0.000000] mask of set bits 0x0
[ 0.000000] MPIDR hash: aff0[0] aff1[8] aff2[16] aff3[32] mask[0x0] bits[0]
[ 0.000000] percpu: Embedded 14 pages/cpu @ffffffc07ffdd000 s28032 r0 d29312 u57344
[ 0.000000] pcpu-alloc: s28032 r0 d29312 u57344 alloc=14*4096
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Detected VIPT I-cache on CPU0
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 516096
[ 0.000000] Kernel command line: earlycon=owl_serial loglevel=8
[ 0.000000] doing Booting kernel, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 0.000000] doing Booting kernel: earlycon='owl_serial'
[ 0.000000] doing Booting kernel: loglevel='8'
[ 0.000000] PID hash table entries: 4096 (order: 3, 32768 bytes)
[ 0.000000] Dentry cache hash table entries: 262144 (order: 9, 2097152 bytes)
[ 0.000000] Inode-cache hash table entries: 131072 (order: 8, 1048576 bytes)
[ 0.000000] software IO TLB [mem 0x79cb3000-0x7dcb3000] (64MB) mapped at [ffffffc079cb3000-ffffffc07dcb2fff]
[ 0.000000] Memory: 1993604K/2097152K available (1032K kernel code, 78K rwdata, 128K rodata, 120K init, 201K bss, 103548K reserved, 0K cma-reserved)
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] modules : 0xffffff8000000000 - 0xffffff8008000000 ( 128 MB)
[ 0.000000] vmalloc : 0xffffff8008000000 - 0xffffffbdbfff0000 ( 246 GB)
[ 0.000000] .text : 0xffffff8008080000 - 0xffffff8008182000 ( 1032 KB)
[ 0.000000] .rodata : 0xffffff8008182000 - 0xffffff80081a3000 ( 132 KB)
[ 0.000000] .init : 0xffffff80081a3000 - 0xffffff80081c1000 ( 120 KB)
[ 0.000000] .data : 0xffffff80081c1000 - 0xffffff80081d4800 ( 78 KB)
[ 0.000000] fixed : 0xffffffbffe7fd000 - 0xffffffbffec00000 ( 4108 KB)
[ 0.000000] PCI I/O : 0xffffffbffee00000 - 0xffffffbfffe00000 ( 16 MB)
[ 0.000000] memory : 0xffffffc000000000 - 0xffffffc080000000 ( 2048 MB)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] Hierarchical RCU implementation.
[ 0.000000] Build-time adjustment of leaf fanout to 64.
[ 0.000000] RCU restricting CPUs from NR_CPUS=64 to nr_cpu_ids=1.
[ 0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=64, nr_cpu_ids=1
[ 0.000000] NR_IRQS:64 nr_irqs:64 0
[ 0.000000] of_irq_init: init /[email protected] (ffffffc07ffed800), parent (null)
[ 0.000000] OF: ** translation for device /[email protected] **
[ 0.000000] OF: bus is default (na=2, ns=2) on /
[ 0.000000] OF: translating address: 00000000 e00f1000
[ 0.000000] OF: reached root node
[ 0.000000] OF: ** translation for device /[email protected] **
[ 0.000000] OF: bus is default (na=2, ns=2) on /
[ 0.000000] OF: translating address: 00000000 e00f2000
[ 0.000000] OF: reached root node
[ 0.000000] OF: ** translation for device /[email protected] **
[ 0.000000] OF: bus is default (na=2, ns=2) on /
[ 0.000000] OF: translating address: 00000000 e00f2000
[ 0.000000] OF: reached root node
[ 0.000000] irq: Added domain (null)
[ 0.000000] of_irq_parse_one: dev=/timer, index=0
[ 0.000000] intspec=1 intlen=12
[ 0.000000] intsize=3 intlen=12
[ 0.000000] of_irq_parse_raw: /[email protected]:00000001,0000000d,00000f08
[ 0.000000] of_irq_parse_raw: ipar=/[email protected], size=3
[ 0.000000] -> addrsize=0
[ 0.000000] -> got it !
[ 0.000000] of_irq_parse_one: dev=/timer, index=1
[ 0.000000] intspec=1 intlen=12
[ 0.000000] intsize=3 intlen=12
[ 0.000000] of_irq_parse_raw: /[email protected]:00000001,0000000e,00000f08
[ 0.000000] of_irq_parse_raw: ipar=/[email protected], size=3
[ 0.000000] -> addrsize=0
[ 0.000000] -> got it !
[ 0.000000] of_irq_parse_one: dev=/timer, index=2
[ 0.000000] intspec=1 intlen=12
[ 0.000000] intsize=3 intlen=12
[ 0.000000] of_irq_parse_raw: /[email protected]:00000001,0000000b,00000f08
[ 0.000000] of_irq_parse_raw: ipar=/[email protected], size=3
[ 0.000000] -> addrsize=0
[ 0.000000] -> got it !
[ 0.000000] of_irq_parse_one: dev=/timer, index=3
[ 0.000000] intspec=1 intlen=12
[ 0.000000] intsize=3 intlen=12
[ 0.000000] of_irq_parse_raw: /[email protected]:00000001,0000000a,00000f08
[ 0.000000] of_irq_parse_raw: ipar=/[email protected], size=3
[ 0.000000] -> addrsize=0
[ 0.000000] -> got it !
[ 0.000000] Architected cp15 timer(s) running at 24.00MHz (phys).
[ 0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x588fe9dc0, max_idle_ns: 440795202592 ns
[ 0.000031] sched_clock: 56 bits at 24MHz, resolution 41ns, wraps every 4398046511097ns
[ 0.007999] Registered 0xffffff800816bf78 as sched_clock source
[ 0.013906] Calibrating delay loop (skipped), value calculated using timer frequency.. 48.00 BogoMIPS (lpj=96000)
[ 0.024093] pid_max: default: 4096 minimum: 301
[ 0.028687] Mount-cache hash table entries: 4096 (order: 3, 32768 bytes)
[ 0.035281] Mountpoint-cache hash table entries: 4096 (order: 3, 32768 bytes)
[ 0.042468] kobject: 'fs' (ffffffc079802c00): kobject_add_internal: parent: '', set: ''
[ 0.051687] No CPU information found in DT
[ 0.055499] CPU0: cluster 0 core 0 thread -1 mpidr 0x00000080000000
[ 0.061718] ASID allocator initialised with 65536 entries
[ 0.067687] Brought up 1 CPUs
[ 0.070031] SMP: Total of 1 processors activated.
[ 0.074718] CPU: All CPU(s) started at EL2
[ 0.079281] kobject: 'devices' (ffffffc079823a98): kobject_add_internal: parent: '', set: ''
[ 0.088249] kobject: 'devices' (ffffffc079823a98): kobject_uevent_env
[ 0.094656] kobject: 'devices' (ffffffc079823a98): kobject_uevent_env: attempted to send uevent without kset!
[ 0.104531] kobject: 'dev' (ffffffc079823b00): kobject_add_internal: parent: '', set: ''
[ 0.113624] kobject: 'block' (ffffffc079823b80): kobject_add_internal: parent: 'dev', set: ''
[ 0.122656] kobject: 'char' (ffffffc079823c00): kobject_add_internal: parent: 'dev', set: ''
[ 0.131562] kobject: 'bus' (ffffffc079823c98): kobject_add_internal: parent: '', set: ''
[ 0.140687] kobject: 'bus' (ffffffc079823c98): kobject_uevent_env
[ 0.146749] kobject: 'bus' (ffffffc079823c98): kobject_uevent_env: attempted to send uevent without kset!
[ 0.156281] kobject: 'system' (ffffffc079823d18): kobject_add_internal: parent: 'devices', set: ''
[ 0.165718] kobject: 'system' (ffffffc079823d18): kobject_uevent_env
[ 0.172062] kobject: 'system' (ffffffc079823d18): kobject_uevent_env: attempted to send uevent without kset!
[ 0.181843] kobject: 'class' (ffffffc079823d98): kobject_add_internal: parent: '', set: ''
[ 0.191124] kobject: 'class' (ffffffc079823d98): kobject_uevent_env
[ 0.197343] kobject: 'class' (ffffffc079823d98): kobject_uevent_env: attempted to send uevent without kset!
[ 0.207062] kobject: 'firmware' (ffffffc079823e00): kobject_add_internal: parent: '', set: ''
[ 0.216593] device: 'platform': device_add
[ 0.220656] kobject: 'platform' (ffffff80081d2680): kobject_add_internal: parent: 'devices', set: 'devices'
[ 0.230374] kobject: 'platform' (ffffff80081d2680): kobject_uevent_env
[ 0.236874] kobject: 'platform' (ffffff80081d2680): kobject_uevent_env: filter function caused the event to drop!
[ 0.247093] kobject: 'platform' (ffffffc079822818): kobject_add_internal: parent: 'bus', set: 'bus'
[ 0.256124] kobject: 'platform' (ffffffc079822818): kobject_uevent_env
[ 0.262624] kobject: 'platform' (ffffffc079822818): fill_kobj_path: path = '/bus/platform'
[ 0.270843] kobject: 'devices' (ffffffc079823e98): kobject_add_internal: parent: 'platform', set: ''
[ 0.280468] kobject: 'devices' (ffffffc079823e98): kobject_uevent_env
[ 0.286874] kobject: 'devices' (ffffffc079823e98): kobject_uevent_env: filter function caused the event to drop!
[ 0.297031] kobject: 'drivers' (ffffffc079823f18): kobject_add_internal: parent: 'platform', set: ''
[ 0.306656] kobject: 'drivers' (ffffffc079823f18): kobject_uevent_env
[ 0.313062] kobject: 'drivers' (ffffffc079823f18): kobject_uevent_env: filter function caused the event to drop!
[ 0.323187] bus: 'platform': registered
[ 0.326999] kobject: 'cpu' (ffffffc079822a18): kobject_add_internal: parent: 'bus', set: 'bus'
[ 0.335593] kobject: 'cpu' (ffffffc079822a18): kobject_uevent_env
[ 0.341656] kobject: 'cpu' (ffffffc079822a18): fill_kobj_path: path = '/bus/cpu'
[ 0.349031] kobject: 'devices' (ffffffc079823f98): kobject_add_internal: parent: 'cpu', set: ''
[ 0.358218] kobject: 'devices' (ffffffc079823f98): kobject_uevent_env
[ 0.364624] kobject: 'devices' (ffffffc079823f98): kobject_uevent_env: filter function caused the event to drop!
[ 0.374749] kobject: 'drivers' (ffffffc079820d18): kobject_add_internal: parent: 'cpu', set: ''
[ 0.383937] kobject: 'drivers' (ffffffc079820d18): kobject_uevent_env
[ 0.390374] kobject: 'drivers' (ffffffc079820d18): kobject_uevent_env: filter function caused the event to drop!
[ 0.400499] bus: 'cpu': registered
[ 0.403874] device: 'cpu': device_add
[ 0.407531] kobject: 'cpu' (ffffffc079822c10): kobject_add_internal: parent: 'system', set: 'devices'
[ 0.416718] kobject: 'cpu' (ffffffc079822c10): kobject_uevent_env
[ 0.422781] kobject: 'cpu' (ffffffc079822c10): kobject_uevent_env: filter function caused the event to drop!
[ 0.432562] kobject: 'container' (ffffffc079822e18): kobject_add_internal: parent: 'bus', set: 'bus'
[ 0.441656] kobject: 'container' (ffffffc079822e18): kobject_uevent_env
[ 0.448249] kobject: 'container' (ffffffc079822e18): fill_kobj_path: path = '/bus/container'
[ 0.456656] kobject: 'devices' (ffffffc079820d98): kobject_add_internal: parent: 'container', set: ''
[ 0.466374] kobject: 'devices' (ffffffc079820d98): kobject_uevent_env
[ 0.472781] kobject: 'devices' (ffffffc079820d98): kobject_uevent_env: filter function caused the event to drop!
[ 0.482937] kobject: 'drivers' (ffffffc079820e18): kobject_add_internal: parent: 'container', set: ''
[ 0.492624] kobject: 'drivers' (ffffffc079820e18): kobject_uevent_env
[ 0.499031] kobject: 'drivers' (ffffffc079820e18): kobject_uevent_env: filter function caused the event to drop!
[ 0.509187] bus: 'container': registered
[ 0.513093] device: 'container': device_add
[ 0.517249] kobject: 'container' (ffffffc079824010): kobject_add_internal: parent: 'system', set: 'devices'
[ 0.526937] kobject: 'container' (ffffffc079824010): kobject_uevent_env
[ 0.533531] kobject: 'container' (ffffffc079824010): kobject_uevent_env: filter function caused the event to drop!
[ 0.543843] kobject: 'devicetree' (ffffffc079820f98): kobject_add_internal: parent: 'firmware', set: ''
[ 0.553718] kobject: 'devicetree' (ffffffc079820f98): kobject_uevent_env
[ 0.560406] kobject: 'devicetree' (ffffffc079820f98): kobject_uevent_env: attempted to send uevent without kset!
[ 0.570531] doing early, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 0.577124] doing early: earlycon='owl_serial'
[ 0.581562] doing early: loglevel='8'
[ 0.585187] doing core, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 0.591687] doing core: earlycon='owl_serial'
[ 0.596031] doing core: loglevel='8'
[ 0.599593] kobject: 'kernel' (ffffffc079825000): kobject_add_internal: parent: '', set: ''
[ 0.608937] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[ 0.618656] doing postcore, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 0.625499] doing postcore: earlycon='owl_serial'
[ 0.630156] doing postcore: loglevel='8'
[ 0.634062] device class 'bdi': registering
[ 0.638218] kobject: 'bdi' (ffffffc079824218): kobject_add_internal: parent: 'class', set: 'class'
[ 0.647156] kobject: 'bdi' (ffffffc079824218): kobject_uevent_env
[ 0.653218] kobject: 'bdi' (ffffffc079824218): fill_kobj_path: path = '/class/bdi'
[ 0.660781] kobject: 'mm' (ffffffc079825100): kobject_add_internal: parent: 'kernel', set: ''
[ 0.669781] kobject: 'amba' (ffffffc079824418): kobject_add_internal: parent: 'bus', set: 'bus'
[ 0.678437] kobject: 'amba' (ffffffc079824418): kobject_uevent_env
[ 0.684593] kobject: 'amba' (ffffffc079824418): fill_kobj_path: path = '/bus/amba'
[ 0.692124] kobject: 'devices' (ffffffc079825198): kobject_add_internal: parent: 'amba', set: ''
[ 0.701406] kobject: 'devices' (ffffffc079825198): kobject_uevent_env
[ 0.707812] kobject: 'devices' (ffffffc079825198): kobject_uevent_env: filter function caused the event to drop!
[ 0.717968] kobject: 'drivers' (ffffffc079825218): kobject_add_internal: parent: 'amba', set: ''
[ 0.727249] kobject: 'drivers' (ffffffc079825218): kobject_uevent_env
[ 0.733656] kobject: 'drivers' (ffffffc079825218): kobject_uevent_env: filter function caused the event to drop!
[ 0.743781] bus: 'amba': registered
[ 0.747249] device class 'tty': registering
[ 0.751406] kobject: 'tty' (ffffffc079824618): kobject_add_internal: parent: 'class', set: 'class'
[ 0.760343] kobject: 'tty' (ffffffc079824618): kobject_uevent_env
[ 0.766406] kobject: 'tty' (ffffffc079824618): fill_kobj_path: path = '/class/tty'
[ 0.773937] doing arch, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 0.780437] doing arch: earlycon='owl_serial'
[ 0.784781] doing arch: loglevel='8'
[ 0.788343] vdso: 2 pages (1 code @ ffffff8008186000, 1 data @ ffffff80081c8000)
[ 0.795874] DMA: preallocated 256 KiB pool for atomic allocations
[ 0.801781] of_platform_bus_create() - skipping /memory, no compatible prop
[ 0.808687] of_platform_bus_create() - skipping /chosen, no compatible prop
[ 0.815656] OF: ** translation for device /[email protected] **
[ 0.822562] OF: bus is default (na=2, ns=2) on /
[ 0.827156] OF: translating address: 00000000 e00f1000
[ 0.832281] OF: reached root node
[ 0.835562] OF: ** translation for device /[email protected] **
[ 0.842499] OF: bus is default (na=2, ns=2) on /
[ 0.847093] OF: translating address: 00000000 e00f2000
[ 0.852218] OF: reached root node
[ 0.855499] of_irq_parse_one: dev=/[email protected], index=0
[ 0.862249] OF: ** translation for device /[email protected] **
[ 0.869187] OF: bus is default (na=2, ns=2) on /
[ 0.873781] OF: translating address: 00000000 e00f1000
[ 0.878906] OF: reached root node
[ 0.882187] OF: ** translation for device /[email protected] **
[ 0.889124] OF: bus is default (na=2, ns=2) on /
[ 0.893718] OF: translating address: 00000000 e00f2000
[ 0.898843] OF: reached root node
[ 0.902124] OF: ** translation for device /[email protected] **
[ 0.909062] OF: bus is default (na=2, ns=2) on /
[ 0.913656] OF: translating address: 00000000 e00f1000
[ 0.918781] OF: reached root node
[ 0.922062] of_dma_get_range: no dma-ranges found for node(/[email protected])
[ 0.930312] platform e00f1000.interrupt-controller: device is not dma coherent
[ 0.937499] platform e00f1000.interrupt-controller: device is not behind an iommu
[ 0.944937] device: 'e00f1000.interrupt-controller': device_add
[ 0.950843] kobject: 'e00f1000.interrupt-controller' (ffffffc079824820): kobject_add_internal: parent: 'platform', set: 'devices'
[ 0.962437] bus: 'platform': add device e00f1000.interrupt-controller
[ 0.968874] kobject: 'e00f1000.interrupt-controller' (ffffffc079824820): kobject_uevent_env
[ 0.977187] kobject: 'e00f1000.interrupt-controller' (ffffffc079824820): fill_kobj_path: path = '/devices/platform/e00f1000.interrupt-controller'
[ 0.990218] of_irq_parse_one: dev=/timer, index=0
[ 0.994874] intspec=1 intlen=12
[ 0.998062] intsize=3 intlen=12
[ 1.001281] of_irq_parse_raw: /[email protected]:00000001,0000000d,00000f08
[ 1.009343] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.016093] -> addrsize=0
[ 1.018781] -> got it !
[ 1.021281] of_irq_parse_one: dev=/timer, index=1
[ 1.025968] intspec=1 intlen=12
[ 1.029187] intsize=3 intlen=12
[ 1.032374] of_irq_parse_raw: /[email protected]:00000001,0000000e,00000f08
[ 1.040437] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.047218] -> addrsize=0
[ 1.049906] -> got it !
[ 1.052406] of_irq_parse_one: dev=/timer, index=2
[ 1.057093] intspec=1 intlen=12
[ 1.060281] intsize=3 intlen=12
[ 1.063499] of_irq_parse_raw: /[email protected]:00000001,0000000b,00000f08
[ 1.071562] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.078312] -> addrsize=0
[ 1.080999] -> got it !
[ 1.083531] of_irq_parse_one: dev=/timer, index=3
[ 1.088187] intspec=1 intlen=12
[ 1.091406] intsize=3 intlen=12
[ 1.094624] of_irq_parse_raw: /[email protected]:00000001,0000000a,00000f08
[ 1.102687] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.109437] -> addrsize=0
[ 1.112124] -> got it !
[ 1.114624] of_irq_parse_one: dev=/timer, index=4
[ 1.119312] intspec=1 intlen=12
[ 1.122531] intsize=3 intlen=12
[ 1.125718] of_irq_parse_one: dev=/timer, index=0
[ 1.130406] intspec=1 intlen=12
[ 1.133624] intsize=3 intlen=12
[ 1.136812] of_irq_parse_raw: /[email protected]:00000001,0000000d,00000f08
[ 1.144874] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.151624] -> addrsize=0
[ 1.154312] -> got it !
[ 1.156843] of_irq_parse_one: dev=/timer, index=1
[ 1.161531] intspec=1 intlen=12
[ 1.164718] intsize=3 intlen=12
[ 1.167937] of_irq_parse_raw: /[email protected]:00000001,0000000e,00000f08
[ 1.175999] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.182749] -> addrsize=0
[ 1.185437] -> got it !
[ 1.187968] of_irq_parse_one: dev=/timer, index=2
[ 1.192624] intspec=1 intlen=12
[ 1.195843] intsize=3 intlen=12
[ 1.199031] of_irq_parse_raw: /[email protected]:00000001,0000000b,00000f08
[ 1.207093] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.213874] -> addrsize=0
[ 1.216562] -> got it !
[ 1.219062] of_irq_parse_one: dev=/timer, index=3
[ 1.223749] intspec=1 intlen=12
[ 1.226968] intsize=3 intlen=12
[ 1.230156] of_irq_parse_raw: /[email protected]:00000001,0000000a,00000f08
[ 1.238218] of_irq_parse_raw: ipar=/[email protected], size=3
[ 1.244968] -> addrsize=0
[ 1.247656] -> got it !
[ 1.250187] of_dma_get_range: no dma-ranges found for node(/timer)
[ 1.256343] platform timer: device is not dma coherent
[ 1.261437] platform timer: device is not behind an iommu
[ 1.266812] device: 'timer': device_add
[ 1.270624] kobject: 'timer' (ffffffc079824a20): kobject_add_internal: parent: 'platform', set: 'devices'
[ 1.280156] bus: 'platform': add device timer
[ 1.284499] kobject: 'timer' (ffffffc079824a20): kobject_uevent_env
[ 1.290749] kobject: 'timer' (ffffffc079824a20): fill_kobj_path: path = '/devices/platform/timer'
[ 1.299593] doing subsys, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 1.306249] doing subsys: earlycon='owl_serial'
[ 1.310749] doing subsys: loglevel='8'
[ 1.314499] device: 'cpu0': device_add
[ 1.318218] kobject: 'cpu0' (ffffffc07ffe1468): kobject_add_internal: parent: 'cpu', set: 'devices'
[ 1.327218] bus: 'cpu': add device cpu0
[ 1.331031] kobject: 'cpu0' (ffffffc07ffe1468): kobject_uevent_env
[ 1.337187] kobject: 'cpu0' (ffffffc07ffe1468): fill_kobj_path: path = '/devices/system/cpu/cpu0'
[ 1.346156] device class 'misc': registering
[ 1.350281] kobject: 'misc' (ffffffc079824e18): kobject_add_internal: parent: 'class', set: 'class'
[ 1.359281] kobject: 'misc' (ffffffc079824e18): kobject_uevent_env
[ 1.365437] kobject: 'misc' (ffffffc079824e18): fill_kobj_path: path = '/class/misc'
[ 1.373156] device class 'power_supply': registering
[ 1.378093] kobject: 'power_supply' (ffffffc079803018): kobject_add_internal: parent: 'class', set: 'class'
[ 1.387812] kobject: 'power_supply' (ffffffc079803018): kobject_uevent_env
[ 1.394656] kobject: 'power_supply' (ffffffc079803018): fill_kobj_path: path = '/class/power_supply'
[ 1.403749] doing fs, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 1.410093] doing fs: earlycon='owl_serial'
[ 1.414249] doing fs: loglevel='8'
[ 1.417656] clocksource: Switched to clocksource arch_sys_counter
[ 1.423718] device class 'mem': registering
[ 1.427843] kobject: 'mem' (ffffffc079827018): kobject_add_internal: parent: 'class', set: 'class'
[ 1.436781] kobject: 'mem' (ffffffc079827018): kobject_uevent_env
[ 1.442843] kobject: 'mem' (ffffffc079827018): fill_kobj_path: path = '/class/mem'
[ 1.450374] device: 'null': device_add
[ 1.454124] kobject: 'virtual' (ffffffc079826080): kobject_add_internal: parent: 'devices', set: ''
[ 1.463656] kobject: 'mem' (ffffffc079826100): kobject_add_internal: parent: 'virtual', set: '(null)'
[ 1.472843] kobject: 'null' (ffffffc079827210): kobject_add_internal: parent: 'mem', set: 'devices'
[ 1.481843] kobject: 'null' (ffffffc079827210): kobject_uevent_env
[ 1.487999] kobject: 'null' (ffffffc079827210): fill_kobj_path: path = '/devices/virtual/mem/null'
[ 1.496937] device: 'zero': device_add
[ 1.500656] kobject: 'zero' (ffffffc079827410): kobject_add_internal: parent: 'mem', set: 'devices'
[ 1.509656] kobject: 'zero' (ffffffc079827410): kobject_uevent_env
[ 1.515812] kobject: 'zero' (ffffffc079827410): fill_kobj_path: path = '/devices/virtual/mem/zero'
[ 1.524749] device: 'full': device_add
[ 1.528468] kobject: 'full' (ffffffc079827610): kobject_add_internal: parent: 'mem', set: 'devices'
[ 1.537468] kobject: 'full' (ffffffc079827610): kobject_uevent_env
[ 1.543624] kobject: 'full' (ffffffc079827610): fill_kobj_path: path = '/devices/virtual/mem/full'
[ 1.552562] device: 'random': device_add
[ 1.556468] kobject: 'random' (ffffffc079827810): kobject_add_internal: parent: 'mem', set: 'devices'
[ 1.565656] kobject: 'random' (ffffffc079827810): kobject_uevent_env
[ 1.571968] kobject: 'random' (ffffffc079827810): fill_kobj_path: path = '/devices/virtual/mem/random'
[ 1.581249] device: 'urandom': device_add
[ 1.585249] kobject: 'urandom' (ffffffc079827a10): kobject_add_internal: parent: 'mem', set: 'devices'
[ 1.594499] kobject: 'urandom' (ffffffc079827a10): kobject_uevent_env
[ 1.600937] kobject: 'urandom' (ffffffc079827a10): fill_kobj_path: path = '/devices/virtual/mem/urandom'
[ 1.610374] device: 'kmsg': device_add
[ 1.614093] kobject: 'kmsg' (ffffffc079827c10): kobject_add_internal: parent: 'mem', set: 'devices'
[ 1.623124] kobject: 'kmsg' (ffffffc079827c10): kobject_uevent_env
[ 1.629249] kobject: 'kmsg' (ffffffc079827c10): fill_kobj_path: path = '/devices/virtual/mem/kmsg'
[ 1.638187] device: 'tty': device_add
[ 1.641843] kobject: 'tty' (ffffffc079826280): kobject_add_internal: parent: 'virtual', set: '(null)'
[ 1.651031] kobject: 'tty' (ffffffc079827e10): kobject_add_internal: parent: 'tty', set: 'devices'
[ 1.659937] kobject: 'tty' (ffffffc079827e10): kobject_uevent_env
[ 1.665999] kobject: 'tty' (ffffffc079827e10): fill_kobj_path: path = '/devices/virtual/tty/tty'
[ 1.674781] device: 'console': device_add
[ 1.678749] kobject: 'console' (ffffffc079829010): kobject_add_internal: parent: 'tty', set: 'devices'
[ 1.688031] kobject: 'console' (ffffffc079829010): kobject_uevent_env
[ 1.694437] kobject: 'console' (ffffffc079829010): fill_kobj_path: path = '/devices/virtual/tty/console'
[ 1.703937] doing device, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 1.710562] doing device: earlycon='owl_serial'
[ 1.715062] doing device: loglevel='8'
[ 1.718812] bus: 'platform': add driver alarmtimer
[ 1.723562] kobject: 'alarmtimer' (ffffffc079828600): kobject_add_internal: parent: 'drivers', set: 'drivers'
[ 1.733437] kobject: 'alarmtimer' (ffffffc079828600): kobject_uevent_env
[ 1.740124] kobject: 'alarmtimer' (ffffffc079828600): fill_kobj_path: path = '/bus/platform/drivers/alarmtimer'
[ 1.750156] Registering platform device 'alarmtimer'. Parent at platform
[ 1.756843] device: 'alarmtimer': device_add
[ 1.761093] kobject: 'alarmtimer' (ffffffc079829220): kobject_add_internal: parent: 'platform', set: 'devices'
[ 1.771062] bus: 'platform': add device alarmtimer
[ 1.775812] kobject: 'alarmtimer' (ffffffc079829220): kobject_uevent_env
[ 1.782499] kobject: 'alarmtimer' (ffffffc079829220): fill_kobj_path: path = '/devices/platform/alarmtimer'
[ 1.792218] bus: 'platform': driver_probe_device: matched device alarmtimer with driver alarmtimer
[ 1.801124] bus: 'platform': really_probe: probing driver alarmtimer with device alarmtimer
[ 1.809437] devices_kset: Moving alarmtimer to end of list
[ 1.814906] driver: 'alarmtimer': driver_bound: bound to device 'alarmtimer'
[ 1.821937] bus: 'platform': really_probe: bound device alarmtimer to driver alarmtimer
[ 1.829999] workingset: timestamp_bits=60 max_order=19 bucket_order=0
[ 1.836312] Failed to find cpu0 device node
[ 1.840468] Unable to detect cache hierarchy from DT for CPU 0
[ 1.846281] bus: 'platform': add driver gpio-clk
[ 1.850874] kobject: 'gpio-clk' (ffffffc079828900): kobject_add_internal: parent: 'drivers', set: 'drivers'
[ 1.860593] kobject: 'gpio-clk' (ffffffc079828900): kobject_uevent_env
[ 1.867093] kobject: 'gpio-clk' (ffffffc079828900): fill_kobj_path: path = '/bus/platform/drivers/gpio-clk'
[ 1.876781] doing late, parsing ARGS: 'earlycon=owl_serial loglevel=8'
[ 1.883281] doing late: earlycon='owl_serial'
[ 1.887624] doing late: loglevel='8'
[ 1.891187] device: 'cpu_dma_latency': device_add
[ 1.895843] kobject: 'misc' (ffffffc079826780): kobject_add_internal: parent: 'virtual', set: '(null)'
[ 1.905124] kobject: 'cpu_dma_latency' (ffffffc079829610): kobject_add_internal: parent: 'misc', set: 'devices'
[ 1.915187] kobject: 'cpu_dma_latency' (ffffffc079829610): kobject_uevent_env
[ 1.922281] kobject: 'cpu_dma_latency' (ffffffc079829610): fill_kobj_path: path = '/devices/virtual/misc/cpu_dma_latency'
[ 1.933218] device: 'network_latency': device_add
[ 1.937874] kobject: 'network_latency' (ffffffc079829810): kobject_add_internal: parent: 'misc', set: 'devices'
[ 1.947937] kobject: 'network_latency' (ffffffc079829810): kobject_uevent_env
[ 1.955031] kobject: 'network_latency' (ffffffc079829810): fill_kobj_path: path = '/devices/virtual/misc/network_latency'
[ 1.965968] device: 'network_throughput': device_add
[ 1.970906] kobject: 'network_throughput' (ffffffc079829a10): kobject_add_internal: parent: 'misc', set: 'devices'
[ 1.981218] kobject: 'network_throughput' (ffffffc079829a10): kobject_uevent_env
[ 1.988593] kobject: 'network_throughput' (ffffffc079829a10): fill_kobj_path: path = '/devices/virtual/misc/network_throughput'
[ 2.000031] device: 'memory_bandwidth': device_add
[ 2.004781] kobject: 'memory_bandwidth' (ffffffc079829c10): kobject_add_internal: parent: 'misc', set: 'devices'
[ 2.014937] kobject: 'memory_bandwidth' (ffffffc079829c10): kobject_uevent_env
[ 2.022124] kobject: 'memory_bandwidth' (ffffffc079829c10): fill_kobj_path: path = '/devices/virtual/misc/memory_bandwidth'
[ 2.033437] Warning: unable to open an initial console.
[ 2.038531] Freeing unused kernel memory: 120K (ffffff80081a3000 - ffffff80081c1000)
[ 2.046124] This architecture does not have kernel memory protection.
[ 2.052593] Kernel panic - not syncing: No working init found. Try passing init= option to kernel. See Linux Documentation/init.txt for guidance.
[ 2.065624] Kernel Offset: disabled
[ 2.069093] Memory Limit: none
[ 2.072124] ---[ end Kernel panic - not syncing: No working init found. Try passing init= option to kernel. See Linux Documentation/init.txt for guidance.
原创文章，转发请注明出处。蜗窝科技，www.wowotech.net。
评论：
Jere
2019-07-17 21:42
@wowo，您好，
我在在kernel/Makefile中，加入KCFLAGS += -DDEBUG，然后make编译出zImage，烧到板子里，启动会停在starting kernel就没任何打印了，不加KCFLAGS += -DDEBUG的zImage可以正常启动。您有没有遇到这种情况？
谢谢
大鱼
2019-08-07 11:28
@Jere：打印太多了？
L
2019-05-10 19:46
我在linux的顶层Makefile中
KBUILD_CFLAGS 后添加 -DDEBUG
由于linux里面的c文件有很多定义了DEBUG，编译时会报重复定义DEBUG的错误，怎么比较好的解决呢，谢谢
gongcm
2019-05-31 13:39
@L：直接在顶层makefile中 加上 KCFLAGS += -DDEBUG
uxer
2019-07-10 10:17
@gongcm：在kernel/Makefile中，加入KCFLAGS += -DDEBUG，还是会报错，重复定义DEBUG
EP
2019-09-03 17:52
@uxer：KBUILD_CFLAGS += -w
但一般打印太多，开机卡死，最好不要在顶层的Makefile中添加
肤了个浅
2017-11-08 10:38
去掉DEBUG这个宏之后，dev_dbg这个函数还会编译进去吗？
2017-11-09 18:19
@肤了个浅：不会了，你可以去看代码:-)
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