kdump 的亲密战友 crash（2）

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look_w发表于 2018-6-18 12:19 | 只看该作者

kdump 的亲密战友 crash（2）

crash 内置命令简介crash 命令行启动后，可以通过一些内置命令来打印系统崩溃前的信息。
bt - backtracebt 命令用于查看系统崩溃前的堆栈等信息，这是系统调试中非常常用和好用的一个命令。
清单 2. bt 命令结果

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crash> bt
PID: 2860 TASK: c0000000677e9550  CPU: 0 COMMAND: "bash"

R0:  0000000000000001 R1:  c0000000018978b0 R2:  c00000000061c460
R3:  c000000001897920 R4:  0000000000000000 R5:  0000000000000000
R6:  0000000000019e07 R7:  0000000000000000 R8:  000000000a000000
R9:  c000000072938d80 R10: c0000000006b5d58 R11: c000000000740178
R12: 0000000000000000 R13: c00000000054ea80 R14: 00000000100d0000
R15: 0000000000000000 R16: 00000000100e2ab8 R17: 00000000100b0000
R18: 00000000100d0000 R19: 00000000100d0000 R20: 0000000000000000
R21: 0000000000000000 R22: 00000000100e8a28 R23: 0000000000000000
R24: 8000000000009032 R25: 0000000000000000 R26: 0000000000000000
R27: 0000000000000063 R28: 0000000000000006 R29: 0000000000000000
R30: c00000000058bfe8 R31: c0000000005a5ed0
NIP: c00000000009d9b0 MSR: 8000000000001032 OR3: c000000001897ab0
CTR: c00000000028b6ec LR:  c00000000028b708 XER: 0000000000000005
CCR: 0000000000000006 MQ:  0000000000000000 DAR: c0000000005a5ed0
DSISR: c000000001897b10    Syscall Result: 0000000000000000
NIP [c00000000009d9b0] .crash_kexec
LR  [c00000000028b708] .sysrq_handle_crashdump

#0 [c0000000018978b0] .crash_kexec at c00000000009d9e0
#1 [c000000001897a90] .sysrq_handle_crashdump at c00000000028b708
#2 [c000000001897b10] .__handle_sysrq at c00000000028b1fc
#3 [c000000001897bc0] .write_sysrq_trigger at c00000000015eadc
#4 [c000000001897c50] .proc_reg_write at c000000000156670
#5 [c000000001897cf0] .vfs_write at c0000000000fd490
#6 [c000000001897d90] .sys_write at c0000000000fdc00
#7 [c000000001897e30] syscall_exit at c0000000000086a4
syscall  [c00] exception frame:
R0:  0000000000000004 R1:  00000000ffb6f820 R2:  00000000f7fe95c0
R3:  0000000000000001 R4:  00000000f7d70000 R5:  0000000000000002
R6:  0000000000000001 R7:  ffffffffffffffff R8:  0000000000000000
R9:  0000000000000000 R10: 0000000000000000 R11: 0000000000000000
R12: 0000000000000000 R13: 00000000100dc8e8 R14: 00000000100d0000
R15: 0000000000000000 R16: 00000000100e2ab8 R17: 00000000100b0000
R18: 00000000100d0000 R19: 00000000100d0000 R20: 0000000000000000
R21: 0000000000000000 R22: 00000000100e8a28 R23: 0000000000000000
R24: 0000000000000001 R25: 00000000100e9718 R26: 0000000000000000
R27: 0000000000000002 R28: 000000000ff703f8 R29: 00000000f7d70000
R30: 000000000ff6fff4 R31: 0000000000000002
NIP: 000000000fec0988 MSR: 000000000000d032 OR3: 0000000000000001
CTR: 000000000fe59270 LR:  000000000fe592dc XER: 0000000000000000
CCR: 0000000040242442 MQ:  00000000010b6c30 DAR: 00000000f7d70000
DSISR: 0000000042000000    Syscall Result: 0000000000000000

crash>

如上输出中，以“# 数字”开头的行为调用堆栈，即系统崩溃前内核依次调用的一系列函数，通过这个可以迅速推断内核在何处崩溃。
log - dump system message bufferlog 命令可以打印系统消息缓冲区，从而可能找到系统崩溃的线索。log 命令的截图如下（为节省篇幅，已将部分行省略）：
清单 3. log 命令结果

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crash> log
Crash kernel location must be 0x2000000
Using pSeries machine description
Page orders: linear mapping = 24, virtual = 16, io = 12
Found initrd at 0xc000000001500000:0xc000000001c90400
Partition configured for 2 cpus.
Starting Linux PPC64 #1 SMP Tue Jan 24 20:12:50 EST 2012
-----------------------------------------------------
ppc64_pft_size             = 0x19
physicalMemorySize          = 0x80000000
ppc64_caches.dcache_line_size = 0x80
ppc64_caches.icache_line_size = 0x80
htab_address                = 0x0000000000000000
htab_hash_mask             = 0x3ffff
-----------------------------------------------------
Linux version 2.6.18-307.el5 (mockbuild@ppc-001.build.bos.redhat.com)
(gcc version 4.1.2 20080704 (Red Hat 4.1.2-50)) #1 SMP Tue Jan 24 20:12:50 EST 2012
[boot]0012 Setup Arch
Node 0 Memory: 0x0-0x80000000

ps - display process status informationps 命令用于显示进程的状态，（如图）带 > 标识代表是活跃的进程。ps 命令的截图如下（省略部分行）：
清单 4. ps 命令结果

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crash> ps
  PID PPID  CPU    TASK       ST  %MEM    VSZ RSS  COMM
   0    0 0  c00000000054e190  RU 0.0    0    0  [swapper]
   0    1 1  c00000007ff15150  RU 0.0    0    0  [swapper]
   1    0 1  c00000007ff15960  IN 0.1 4672 2688  init
   2    1 0  c00000007ff14940  IN 0.0    0    0  [migration/0]
   3    1 0  c00000007ff14130  IN 0.0    0    0  [ksoftirqd/0]
   4    1 0  c00000007ff13920  IN 0.0    0    0  [watchdog/0]
   5    1 1  c00000007ff13110  IN 0.0    0    0  [migration/1]
   6    1 1  c00000007ff12900  IN 0.0    0    0  [ksoftirqd/1]
   7    1 1  c00000007ff120f0  IN 0.0    0    0  [watchdog/1]
   8    1 0  c00000007ff118e0  IN 0.0    0    0  [events/0]
   9    1 1  c00000007ff1ba20  IN 0.0    0    0  [events/1]
10    1 1  c00000007ff110d0  IN 0.0    0    0  [khelper]
139    1 0  c0000000015822f0  IN 0.0    0    0  [kthread]
143 139 0  c000000001c6eb00  IN 0.0    0    0  [kblockd/0]
144 139 1  c000000001580ac0  IN 0.0    0    0  [kblockd/1]
145 139 0  c000000001c6f310  IN 0.0    0    0  [cqueue/0]
146 139 1  c0000000015802b0  IN 0.0    0    0  [cqueue/1]
150 139 0  c00000007ff1e270  IN 0.0    0    0  [khubd]
152 139 0  c00000007ff1ea80  IN 0.0    0    0  [kseriod]
169    1 1  c000000001c62170  IN 0.0    0    0  [rtasd]
209 139 0  c00000007f4ca370  IN 0.0    0    0  [khungtaskd]
>  1771    1 1  c000000001c36a80  RU 0.1 4096 2240  syslogd

dis - disassembling instructiondis 命令用于对给定地址的内容进行反汇编。dis 命令的截图如下：
清单 5. dis 命令结果

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crash> dis -l c000000000255900
/usr/src/debug/kernel-ppc64-3.0.8/linux-3.0/fs/proc/mmu.c: 47
0xc000000000255900 <.get_vmalloc_info+112>:    ld    r10,8(r11)
5.5 struct – view data struct
struct 命令用于查看数据结构的定义原型。命令截图如下：
crash> struct -o vm_struct
struct vm_struct {
  [0] struct vm_struct *next;
  [8] void *addr;
[16] long unsigned int size;
[24] long unsigned int flags;
[32] struct page **pages;
[40] unsigned int nr_pages;
[48] phys_addr_t phys_addr;
[56] void *caller;
}
SIZE: 64

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