在gdb中查看ASCII中的寄存器内容 [英] Seeing register contents in ASCII in gdb

问题描述

假设我现在在这个位置，我想以ascii格式查看cl，ch，cx，ecx等的内容.

Suppose, I am at this position now, and I want to see the content of cl, ch, cx, ecx, etc in ascii format.

该怎么办?

以下是layout asm命令中显示的子例程.

The following is the subroutine displayed in the layout asm command.

RemCharCodeFromAToB:
    ; standard entry sequence
    push    ebp             ; save the previous value of ebp for the benefi$
    mov     ebp, esp        ; copy esp -> ebp so that ebp can be used as a $   

    ; accessing arguments  
                            ; [ebp + 0] = old ebp stack frame
                            ; [ebp + 4] = return address
    mov     edx, [ebp + 8]  ; string address

    while_loop_rcc:
        mov cl, [edx]       ; obtain the address of the 1st character of the string
        cmp cl, 0           ; check the null value  

        je  while_loop_exit_rcc     ; exit if the null-character is reached

        mov al, cl ; save cl
        mov cl, [ebp + 16]      ; end-char
        push cx                 ; push end-char
        mov cl, [ebp + 12]      ; start-char
        push cx                 ; push start-char
        push ax;                ; push ch
        call IsBetweenAandB
        add esp, 12

        cmp eax, 0          ; if(ch is not between 'a' and 'e')

        je inner_loop_exit_rcc

        mov eax, edx    ; copy the current address

        inner_loop_rcc:
            mov cl, [eax+1]
            cmp cl, 0
            je  inner_loop_exit_rcc

            mov [eax], cl

            inc eax
            jmp inner_loop_rcc
        inner_loop_exit_rcc:

        inc edx             ; increment the address
        jmp while_loop_rcc  ; start the loop again
    while_loop_exit_rcc:

    ; standard exit sequence
    mov     esp, ebp        ; restore esp with ebp
    pop     ebp             ; remove ebp from stack
    ret                     ; return the value of temporary variable

• 完整的asm代码在这里.
• C ++代码在这里.
• Makefile 在这里.
• Full asm code is here.
• C++ code is here.
• Makefile is here.

推荐答案

这将定义一个asciiprint宏，该宏会将其参数寄存器的值打印为从最低有效字节到最高字节的字符序列.

This will define an asciiprint macro, which will print its argument register's value as a sequence of characters, from least significant byte to most.

(gdb) define asciiprint
 set $len = sizeof($arg0)
 set $val = (unsigned long long)($arg0)
 while $len-- > 0
   set $char = $val & 0xff
   if $char >= 0x20 && $char <= 0x7e
     printf "%c", $char
   else
     printf "\\x%02x", $char
   end
   set $val >>= 8
 end
 printf "\n"
end




(gdb) set $rcx=0x6b63616a70616c66
(gdb) asciiprint $rcx
flapjack
(gdb) asciiprint $ecx
flap
(gdb) asciiprint $cx
fl
(gdb) asciiprint $cl
f
(gdb) asciiprint $ch
l

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