crash dis command

crash> help dis

NAME
  dis - disassemble

SYNOPSIS
  dis [-rludx][-b [num]] [address | symbol | (expression)] [count]

DESCRIPTION
  This command disassembles source code instructions starting (or ending) at
  a text address that may be expressed by value, symbol or expression:
/*-r:reverse
 *-l:displays source code line number data
 **/
            -r  (reverse) displays all instructions from the start of the
                routine up to and including the designated address.
            -l  displays source code line number data in addition to the
                disassembly output.
            -u  address is a user virtual address in the current context;
                otherwise the address is assumed to be a kernel virtual address.
                If this option is used, then -r and -l are ignored.
/*-x/d:output format
 **/
            -x  override default output format with hexadecimal format.
            -d  override default output format with decimal format.
      -b [num]  modify the pre-calculated number of encoded bytes to skip after
                a kernel BUG ("ud2a") instruction; with no argument, displays
                the current number of bytes being skipped. (x86 and x86_64 only)
/*从那个位置开始 dis-assember:
 *address, symbol and expression.
 **/
       address  starting hexadecimal text address.
        symbol  symbol of starting text address.  On ppc64, the symbol
                preceded by '.' is used.
  (expression)  expression evaluating to a starting text address.

/*count: the number of instructions to be disassembled (default is 1)*/
         count  the number of instructions to be disassembled (default is 1).
                If no count argument is entered, and the starting address
                is entered as a text symbol, then the whole routine will be
                disassembled.  The count argument is ignored when used with
                the -r option.

EXAMPLES
  Disassemble the sys_signal() routine without, and then with, line numbers:

crash> dis run_init_process
    0xc000863c <run_init_process>:  mov     r12, sp
    0xc0008640 <run_init_process+4>:        push    {r11, r12, lr, pc}
    0xc0008644 <run_init_process+8>:        sub     r11, r12, #4
    0xc0008648 <run_init_process+12>:       ldr     r1, [pc, #12]   ; 0xc000865c <run_init_process+32>
    0xc000864c <run_init_process+16>:       mov     r2, r1
    0xc0008650 <run_init_process+20>:       str     r0, [r2], #136  ; 0x88
    0xc0008654 <run_init_process+24>:       bl      0xc0011a40 <kernel_execve>
    0xc0008658 <run_init_process+28>:       ldm     sp, {r11, sp, pc}

 

crash> dis -l run_init_process

    /home/wenshuai/code/3.4kernel/linux_kernel/init/main.c: 793
    0xc000863c <run_init_process>:  mov     r12, sp
    0xc0008640 <run_init_process+4>:        push    {r11, r12, lr, pc}
    0xc0008644 <run_init_process+8>:        sub     r11, r12, #4
    /home/wenshuai/code/3.4kernel/linux_kernel/init/main.c: 794
    0xc0008648 <run_init_process+12>:       ldr     r1, [pc, #12]   ; 0xc000865c <run_init_process+32>
    0xc000864c <run_init_process+16>:       mov     r2, r1
    0xc0008650 <run_init_process+20>:       str     r0, [r2], #136  ; 0x88
    /home/wenshuai/code/3.4kernel/linux_kernel/init/main.c: 795
    0xc0008654 <run_init_process+24>:       bl      0xc0011a40 <kernel_execve>
    /home/wenshuai/code/3.4kernel/linux_kernel/init/main.c: 796
    0xc0008658 <run_init_process+28>:       ldm     sp, {r11, sp, pc}
 
  Given a return address expression of "run_init_process+16", find out the
  function that run_init_process calls by using the reverse flag:

crash> dis -r (run_init_process+16)

0xc000863c <run_init_process>:  mov     r12, sp
0xc0008640 <run_init_process+4>:        push    {r11, r12, lr, pc}
0xc0008644 <run_init_process+8>:        sub     r11, r12, #4
0xc0008648 <run_init_process+12>:       ldr     r1, [pc, #12]   ; 0xc000865c <run_init_process+32>
0xc000864c <run_init_process+16>:       mov     r2, r1

    
  Disassemble 10 instructions starting at user virtual address 0x81ec624:

    crash> dis -u 81ec624 10
    0x81ec624:      push   %ebp
    0x81ec625:      mov    %esp,%ebp
    0x81ec627:      sub    $0x18,%esp
    0x81ec62a:      movl   $0x1,0x8(%ebp)
    0x81ec631:      mov    0x82f9040,%eax
    0x81ec636:      mov    0x10(%eax),%edx
    0x81ec639:      and    $0x100,%edx
    0x81ec63f:      mov    0x14(%eax),%ecx
    0x81ec642:      and    $0x0,%ecx
    0x81ec645:      mov    %ecx,%eax
 
  Override the current decimal output radix format:

    crash> dis sys_read 10 -x
    0xffffffff8001178f <sys_read>:  push   %r13
    0xffffffff80011791 <sys_read+0x2>:      mov    %rsi,%r13
    0xffffffff80011794 <sys_read+0x5>:      push   %r12
    0xffffffff80011796 <sys_read+0x7>:      mov    $0xfffffffffffffff7,%r12
    0xffffffff8001179d <sys_read+0xe>:      push   %rbp
    0xffffffff8001179e <sys_read+0xf>:      mov    %rdx,%rbp
    0xffffffff800117a1 <sys_read+0x12>:     push   %rbx
    0xffffffff800117a2 <sys_read+0x13>:     sub    $0x18,%rsp
    0xffffffff800117a6 <sys_read+0x17>:     lea    0x14(%rsp),%rsi
    0xffffffff800117ab <sys_read+0x1c>:     callq  0xffffffff8000b5b4 <fget_light>

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