linux 内核 assert,Linux Kernel Oops异常分析

0．linux内核异常常用分析方法

异常地址是否在0附近，确认是否是空指针解引用问题异常地址是否在iomem映射区，确认是否是设备访问总线异常问题，如PCI异常导致的地址访问异常异常地址是否在stack附近，如果相邻，要考虑是否被踩比较delay reset/nmi watchdog等多种机制打印的栈信息，看看pc是否在动，确定是否是死锁用SysRq判断是真死还是假死通过反汇编获得发生异常的C代码段和函数，查找开源社区是否已有补丁修复

下面分别通过PowerPC和Mips64的2个异常例子详细讲解分析过程。

1．PowerPC小系统内核异常分析

1.1  异常打印

Unable to handle kernel paging request for data at address 0x36fef31eFaulting instruction address: 0xc0088b8cOops: Kernel access of bad area, sig: 11 [#1]PREEMPT SMP NR_CPUS=2Modules linked in: ossmod tipc ohci_hcd ehci_hcd cmm uart1655x bcm334 bootflash mtdchar bsp_flash_init boardctrl 85xx_debug utilNIP: C0088B8C LR: C0088CF8 CTR: 00000000REGS: ce283e20 TRAP: 0300 Not tainted (2.6.21.7-EMBSYS-CGEL-3.04.10.P6.F5)MSR: 00021000 CR: 22004222 XER: 00000000DAR: 36FEF31E, DSISR: 00800000TASK = cffdf180[26] 'events/1' THREAD: ce282000 CPU: 1GPR00: 00100100 CE283ED0 CFFDF180 CF528000 C09EA500 EFFEAD20 CF5188A0 00000000GPR08: CF5188BC 00200200 36FEF31E D1FD7F9E 22004222 1010DA44 00000290 00000000GPR16: 1011C858 100147F4 BF9BC9C4 10100000 00000001 C0460000 C06454CC 00000000GPR24: C0640000 CE282000 C0640000 00000005 00000000 00000000 EFFE8EC0 CFFED958NIP [C0088B8C] free_block+0xc4/0x16cLR [C0088CF8] drain_array+0xc4/0x100Pass 2: Checking directory structurePass 3: Checking directory connectivityPass 4: Checking reference countsCall Trace:[CE283ED0] [C06ABEC0] 0xc06abec0(unreliable)[CE283EF0] [C0088CF8] drain_array+0xc4/0x100[CE283F10] [C008A70C] cache_reap+0x94/0x13c[CE283F30] [C003DA2C] run_workqueue+0xc4/0x198[CE283F60] [C003E6D4] worker_thread+0x130/0x154[CE283FB0] [C0042E80] kthread+0xd4/0x110[CE283FF0] [C0011A70] original_kernel_thread+0x44/0x60

Instruction dump:5400cffe 0f000000 80c4001c 7d1cf214 3c000010 3d200020 80a8001c 6000010081660000 61290200 81460004 3906001c <916a0000> 914b0004 90060000 91260004------------[ cut here ]------------Badness at c0011e4c [verbose debug info unavailable]Call Trace:[CE283C50] [C00080BC] show_stack+0x3c/0x1a0 (unreliable)[CE283C80] [C018EA28] report_bug+0xb0/0xb8[CE283C90] [C000EC94] program_check_exception+0xcc/0x4f8[CE283CD0] [C0010BE4] ret_from_except_full+0x0/0x4c[CE283D90] [C0640000] 0xc0640000[CE283DD0] [C000E61C] die+0x1f0/0x27c[CE283E00] [C0014B18] bad_page_fault+0x98/0xe8[CE283E10] [C0010A88] handle_page_fault+0x7c/0x80[CE283ED0] [C06ABEC0] 0xc06abec0[CE283EF0] [C0088CF8] drain_array+0xc4/0x100[CE283F10] [C008A70C] cache_reap+0x94/0x13c[CE283F30] [C003DA2C] run_workqueue+0xc4/0x198[CE283F60] [C003E6D4] worker_thread+0x130/0x154[CE283FB0] [C0042E80] kthread+0xd4/0x110[CE283FF0] [C0011A70] original_kernel_thread+0x44/0x60

1.2  Oops分析

Oops: Kernel access of bad area, sig: 11 [#1]

异常分类

Oops：内核态指令异常；

BUG：内核检测到逻辑异常(类似于assert)，会影响内核的后续运行；

WARNING：类似于BUG，但是不会影响内核的后续运行；

PANIC：类似于BUG，系统不能继续运行，直接挂起或重启；

SOFTLOCK：长时间任务得不到调度；

异常信号

Signal  Code  Default Action  Description  SIGABRT  6  A  Process abort signal  SIGALRM  14  T  Alarm clock  SIGBUS  10  A  Access to an undefined portion of a memory object  SIGCHLD  18  I - Ignore the Signal  Child process terminated, stopped,  SIGCONT  25  C - Continue the process  Continue executing, if stopped.  SIGFPE  8  A  Erroneous arithmetic operation.  SIGHUP  1  T  Hangup.  SIGILL  4  A  Illegal instruction.  SIGINT  2  T  Terminal interrupt signal.  SIGKILL  9  T  Kill (cannot be caught or ignored).  SIGPIPE  13  T - Abnormal termination of the process  Write on a pipe with no one to read it.  SIGQUIT  3  A - Abnormal termination of the process  Terminal quit signal.  SIGSEGV  11  A  Invalid memory reference.  SIGSTOP  23  S - Stop the process  Stop executing (cannot be caught or ignored).  SIGTERM  15  T  Termination signal.  SIGTSTP  23  S  Terminal stop signal.  SIGTTIN  26  S  Background process attempting read.  SIGTTOU  27  S  Background process attempting write.  SIGUSR1  16  T  User-defined signal 1.  SIGUSR2  17  T  User-defined signal 2.  SIGPOLL  22  T  Pollable event.  SIGPROF  29  T  Profiling time