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sig(task signal handling)

概述

sig [[-l] | [-s sigset]] | [-g] [pid | taskp] ...

sig命令是crash工具中的一个命令，它用于显示或设置进程的信号处理信息。

信号是一种在软件层次上对硬件异常的的抽象，它可以通知进程发生了某些事件，例如除零错误，非法内存访问，键盘中断等。

进程可以对信号进行三种处理：

  • 忽略该信号。
  • 捕捉该信号并执行对应的信号处理函数 (signal handler)。
  • 执行该信号的缺省操作 (如 SIGSEGV， 其缺省操作是终止进程)。

sig命令有以下几种用法：

  • sig：显示当前进程的信号处理信息，包括信号编号，信号名字，信号处理函数地址，信号掩码等。
  • sig -s ：显示当前进程对指定信号的处理信息。
  • sig -p ：显示指定进程的信号处理信息。
  • sig -p -s ：显示指定进程对指定信号的处理信息。
  • sig -p -s -f ：设置指定进程对指定信号的处理函数为指定地址。

举例子

  • 查看当前进程的信号处理信息：
crash> sig |more
PID: 2429976  TASK: ff352c8c1e7fbc80  CPU: 53  COMMAND: "ovs-vswitchd"
SIGNAL_STRUCT: ff352c8cd0600d80  NR_THREADS: 139
 SIG    SIGACTION        HANDLER       MASK       FLAGS           
 [1] ff352c8cca438008 555fb7a4ffb0 0000000000000001 14000000 (SA_RESTORER|SA_RESTART)
 [2] ff352c8cca438028 555fb7a4ffb0 0000000000000002 14000000 (SA_RESTORER|SA_RESTART)
 [3] ff352c8cca438048    SIG_DFL 0000000000000000 0 
 [4] ff352c8cca438068    SIG_DFL 0000000000000000 0 
 [5] ff352c8cca438088    SIG_DFL 0000000000000000 0 
 [6] ff352c8cca4380a8    SIG_DFL 0000000000000000 0 
 [7] ff352c8cca4380c8    SIG_DFL 0000000000000000 4000000 (SA_RESTORER)
 [8] ff352c8cca4380e8    SIG_DFL 0000000000000000 0 
 [9] ff352c8cca438108    SIG_DFL 0000000000000000 0
  • 查看当前进程对SIGSEGV的处理信息：
crash> sig -s SIGSEGV
   PID: 2613   TASK: ffff88011e8b8000  CPU: 2   COMMAND: "bash"
    NR SIG      VALUE  ACTION       MASK    FLAGS
    11 SIGSEGV  CATCH  ffff88011e8b8000 0000000000000000
  • 查看PID为1234的进程的信号处理信息：
crash> sig -p 1234
   PID: 1234   TASK: ffff88011e8b8000  CPU: 0   COMMAND: "httpd"
    NR SIG     VALUE  ACTION       MASK    FLAGS
     1 SIGHUP  CATCH  ffff88011e8b8000 0000000000000000
     2 SIGINT  CATCH  ffff88011e8b8000 0000000000000000
     ...
  • 查看PID为1234的进程对SIGTERM的处理信息：
crash> sig -p 1234 -s SIGTERM
   PID: 1234   TASK: ffff88011e8b8000  CPU: 0   COMMAND: "httpd"
    NR SIG      VALUE  ACTION       MASK    FLAGS
    15 SIGTERM  CATCH  ffff88011e8b8000 0000000000000000
  • 设置PID为1234的进程对SIGTERM的处理函数为ffff88011e8b8000：
crash> sig -p 1234 -s SIGTERM -f ffff88011e8b8000
   PID: 1234   TASK: ffff88011e8b8000  CPU: 0   COMMAND: "httpd"
    NR SIG      VALUE      ACTION       MASK    FLAGS
    OLD:
    15 SIGTERM CATCH      ffff88011e8b8000       (none)
    NEW:
    NR SIG      VALUE      ACTION       MASK    FLAGS
    OLD:
    NEW:
    NR SIG      VALUE      ACTION       MASK    FLAGS
    OLD:
    NEW:
    NR SIG      VALUE      ACTION       MASK    FLAGS
    OLD:
    NEW:
    NR SIG      VALUE      ACTION       MASK    FLAGS
    OLD:
    NEW:
  • 列出所有信号
crash> sig -l
 [6] SIGABRT/SIGIOT
 [7] SIGBUS
 [8] SIGFPE
 [9] SIGKILL
[10] SIGUSR1
[11] SIGSEGV
[12] SIGUSR2
[13] SIGPIPE
[14] SIGALRM
[15] SIGTERM
[16] SIGSTKFLT
[17] SIGCHLD/SIGCLD
[18] SIGCONT
[19] SIGSTOP
[20] SIGTSTP
[21] SIGTTIN
[22] SIGTTOU
[23] SIGURG
[24] SIGXCPU
[25] SIGXFSZ
[26] SIGVTALRM
[27] SIGPROF
[28] SIGWINCH
[29] SIGIO/SIGPOLL
[30] SIGPWR
[31] SIGSYS/SIGUNUSED
[32] SIGRTMIN
[33] SIGRTMIN+1
[34] SIGRTMIN+2
[35] SIGRTMIN+3
[36] SIGRTMIN+4
[37] SIGRTMIN+5
[38] SIGRTMIN+6
[39] SIGRTMIN+7
[40] SIGRTMIN+8
[41] SIGRTMIN+9
[42] SIGRTMIN+10
[43] SIGRTMIN+11
[44] SIGRTMIN+12
[45] SIGRTMIN+13
[46] SIGRTMIN+14
[47] SIGRTMIN+15
[48] SIGRTMIN+16
[49] SIGRTMAX-15
[50] SIGRTMAX-14
[51] SIGRTMAX-13
[52] SIGRTMAX-12
[53] SIGRTMAX-11
[54] SIGRTMAX-10
[55] SIGRTMAX-9
[56] SIGRTMAX-8
[57] SIGRTMAX-7
[58] SIGRTMAX-6
[59] SIGRTMAX-5
[60] SIGRTMAX-4
[61] SIGRTMAX-3
[62] SIGRTMAX-2
[63] SIGRTMAX-1
[64] SIGRTMAX

帮助信息

NAME
  sig - task signal handling

SYNOPSIS
  sig [[-l] | [-s sigset]] | [-g] [pid | taskp] ...

DESCRIPTION
  This command displays signal-handling data of one or more tasks.  Multiple
  task or PID numbers may be entered; if no arguments are entered, the signal
  handling data of the current context will be displayed.  The default display
  shows:

    1.  A formatted dump of the "sig" signal_struct structure referenced by
        the task_struct.  For each defined signal, it shows the sigaction
        structure address, the signal handler, the signal sigset_t mask
        (also expressed as a 64-bit hexadecimal value), and the flags.
    2.  Whether the task has an unblocked signal pending.
    3.  The contents of the "blocked" and "signal" sigset_t structures
        from the task_struct/signal_struct, both of which are represented
        as a 64-bit hexadecimal value.
    4.  For each queued signal, private and/or shared, if any, its signal
        number and associated siginfo structure address.

  The -l option lists the signal numbers and their name(s).  The -s option
  translates a 64-bit hexadecimal value representing the contents of a
  sigset_t structure into the signal names whose bits are set.

        pid  a process PID.
      taskp  a hexadecimal task_struct pointer.
         -g  displays signal information for all threads in a task's
             thread group.
         -l  displays the defined signal numbers and names.
  -s sigset  translates a 64-bit hexadecimal value representing a sigset_t
             into a list of signal names associated with the bits set.

EXAMPLES
  Dump the signal-handling data of PID 8970:

    crash> sig 8970
    PID: 8970   TASK: f67d8560  CPU: 1   COMMAND: "procsig"
    SIGNAL_STRUCT: f6018680  COUNT: 1
     SIG SIGACTION  HANDLER       MASK       FLAGS   
     [1]  f7877684  SIG_DFL 0000000000000000 0
     [2]  f7877698  SIG_DFL 0000000000000000 0
    ...
     [8]  f7877710  SIG_DFL 0000000000000000 0
     [9]  f7877724  SIG_DFL 0000000000000000 0
    [10]  f7877738  804867a 0000000000000000 80000000 (SA_RESETHAND)
    [11]  f787774c  SIG_DFL 0000000000000000 0
    [12]  f7877760  804867f 0000000000000000 10000004 (SA_SIGINFO|SA_RESTART)
    [13]  f7877774  SIG_DFL 0000000000000000 0
    ...
    [31]  f78778dc  SIG_DFL 0000000000000000 0
    [32]  f78778f0  SIG_DFL 0000000000000000 0
    [33]  f7877904  SIG_DFL 0000000000000000 0
    [34]  f7877918  804867f 0000000000000000 10000004 (SA_SIGINFO|SA_RESTART)
    [35]  f787792c  SIG_DFL 0000000000000000 0
    [36]  f7877940  SIG_DFL 0000000000000000 0
    ...
    [58]  f7877af8  SIG_DFL 0000000000000000 0
    [59]  f7877b0c  SIG_DFL 0000000000000000 0
    [60]  f7877b20  SIG_DFL 0000000000000000 0
    [61]  f7877b34  SIG_DFL 0000000000000000 0
    [62]  f7877b48  SIG_DFL 0000000000000000 0
    [63]  f7877b5c  SIG_DFL 0000000000000000 0
    [64]  f7877b70  804867f 0000000000000000 10000004 (SA_SIGINFO|SA_RESTART)
   SIGPENDING: no
      BLOCKED: 8000000200000800
   PRIVATE_PENDING
       SIGNAL: 0000000200000800
     SIGQUEUE:  SIG  SIGINFO
                 12  f51b9c84
                 34  f51b9594
   SHARED_PENDING
       SIGNAL: 8000000000000800
     SIGQUEUE:  SIG  SIGINFO
                 12  f51b9188
                 64  f51b9d18
                 64  f51b9500

  Dump the signal-handling data for all tasks in the thread group containing
  PID 2578:

    crash> sig -g 2578
    PID: 2387   TASK: f617d020  CPU: 0   COMMAND: "slapd"
    SIGNAL_STRUCT: f7dede00  COUNT: 6
    SIG SIGACTION  HANDLER       MASK       FLAGS
    [1]  c1f60c04   a258a7 0000000000000000 10000000 (SA_RESTART)
    [2]  c1f60c18   a258a7 0000000000000000 10000000 (SA_RESTART)
    [3]  c1f60c2c  SIG_DFL 0000000000000000 0
    [4]  c1f60c40  SIG_DFL 0000000000000000 0
    [5]  c1f60c54   a258a7 0000000000000000 10000000 (SA_RESTART)
    [6]  c1f60c68  SIG_DFL 0000000000000000 0
    [7]  c1f60c7c  SIG_DFL 0000000000000000 0
    [8]  c1f60c90  SIG_DFL 0000000000000000 0
    [9]  c1f60ca4  SIG_DFL 0000000000000000 0
   [10]  c1f60cb8   a25911 0000000000000000 10000000 (SA_RESTART)
   ...
   [64]  c1f610f0  SIG_DFL 0000000000000000 0
   SHARED_PENDING
       SIGNAL: 0000000000000000
     SIGQUEUE: (empty)

     PID: 2387   TASK: f617d020  CPU: 0   COMMAND: "slapd"
     SIGPENDING: no
        BLOCKED: 0000000000000000
     PRIVATE_PENDING
         SIGNAL: 0000000000000000
       SIGQUEUE: (empty)

     PID: 2392   TASK: f6175aa0  CPU: 0   COMMAND: "slapd"
     SIGPENDING: no
        BLOCKED: 0000000000000000
     PRIVATE_PENDING
         SIGNAL: 0000000000000000
       SIGQUEUE: (empty)

     PID: 2523   TASK: f7cd4aa0  CPU: 1   COMMAND: "slapd"
     SIGPENDING: no
        BLOCKED: 0000000000000000
     PRIVATE_PENDING
         SIGNAL: 0000000000000000
       SIGQUEUE: (empty)

     ...

  Translate the sigset_t mask value, cut-and-pasted from the signal handling
  data from signals 1 and 10 above:

    crash> sig -s 800A000000000201
    SIGHUP SIGUSR1 SIGRTMAX-14 SIGRTMAX-12 SIGRTMAX

  List the signal numbers and their names:

    crash> sig -l
     [1] SIGHUP
     [2] SIGINT
     [3] SIGQUIT
     [4] SIGILL
     [5] SIGTRAP
     [6] SIGABRT/SIGIOT
     [7] SIGBUS
     [8] SIGFPE
     [9] SIGKILL
    [10] SIGUSR1
    [11] SIGSEGV
    [12] SIGUSR2
    [13] SIGPIPE
    [14] SIGALRM
    [15] SIGTERM
    [16] SIGSTKFLT
    [17] SIGCHLD/SIGCLD
    [18] SIGCONT
    [19] SIGSTOP
    [20] SIGTSTP
    [21] SIGTTIN
    [22] SIGTTOU
    [23] SIGURG
    [24] SIGXCPU
    [25] SIGXFSZ
    [26] SIGVTALRM
    [27] SIGPROF
    [28] SIGWINCH
    [29] SIGIO/SIGPOLL
    [30] SIGPWR
    [31] SIGSYS
    [32] SIGRTMIN
    [33] SIGRTMIN+1
    [34] SIGRTMIN+2
    [35] SIGRTMIN+3
    [36] SIGRTMIN+4
    [37] SIGRTMIN+5
    [38] SIGRTMIN+6
    [39] SIGRTMIN+7
    [40] SIGRTMIN+8
    [41] SIGRTMIN+9
    [42] SIGRTMIN+10
    [43] SIGRTMIN+11
    [44] SIGRTMIN+12
    [45] SIGRTMIN+13
    [46] SIGRTMIN+14
    [47] SIGRTMIN+15
    [48] SIGRTMIN+16
    [49] SIGRTMAX-15
    [50] SIGRTMAX-14
    [51] SIGRTMAX-13
    [52] SIGRTMAX-12
    [53] SIGRTMAX-11
    [54] SIGRTMAX-10
    [55] SIGRTMAX-9
    [56] SIGRTMAX-8
    [57] SIGRTMAX-7
    [58] SIGRTMAX-6
    [59] SIGRTMAX-5
    [60] SIGRTMAX-4
    [61] SIGRTMAX-3
    [62] SIGRTMAX-2
    [63] SIGRTMAX-1
    [64] SIGRTMAX