cgdb---ubuntu14.04下安裝cgdb及gdb的使用

一. ubuntu 14.04 下安裝cgdb
1.ubuntun14.04下安裝cgdb
cong@msi:~$ sudo apt-get install cgdb

2. 使用: cgdb ./hello就可以了
a. cgdb分爲上面的vi窗口與下面的gdb窗口

ESC-->切到vi窗口
i -->切到gdb窗口
- -->減小vi窗口
= -->增大vi窗口
 shift - -->減小很多vi窗口
 shift = -->增大很多vi窗口

b.斷點
空格添加/刪除斷點
c. gdbinit腳本不能用

warning: File "/work/ffmpeg/jpeg/jpegc/.gdbinit" auto-loading
has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add   add-auto-load-safe-path /work/ffmpeg/jpeg/jpegc/.gdbinit   line to your
configuration file "/home/cong/.gdbinit".
To completely disable this security protection add    set auto-load
safe-path /  
 line to your configuration file "/home/cong/.gdbinit".
For more information about this security protection see the  "Auto-loading safe path" section in the
GDB manual. E.g., run
from the shell:
        info "(gdb)Auto-loading safe path"

臨時的方法: 在gdb的命令行裏面  source .gdbinit
永久的方法: cong@msi:~$ cat .gdbinit 
set auto-load safe-path /

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二. gdb的使用
1. 斷點
a. 在指定文件中指定函數處設斷點

b <filename>: <func_name>
b <filename>: <line_num> 
 --> 例: break mm/slab.c:673

2. 打印
2.1 
p {i,j,k,l}            -->打印多個變量
display {i,j,k,l}   --> 每執行一次都打印這幾個變量
undisplay           --> 去掉display

3.2 打印某個地址處的數據

(gdb) help x
Examine memory: x/FMT ADDRESS.
ADDRESS is an expression for the memory address to examine.
FMT is a repeat count followed by a format letter and a size letter. -->顯示格式用兩部分表示
Format letters are:                     -->格式類型
    o(octal),
    x(hex),
    d(decimal),
    u(unsigned decimal),
    t(binary),
    f(float),
    a(address),
    i(instruction),
    c(char),
    s(string)
    z(hex, zero padded on the left).
Size letters are:                        -->長度類型
    b(byte),
    h(halfword),
    w(word),
    g(giant, 8 bytes).
The specified number of objects of the specified size are printed
according to the format.

例如要按16進制顯示類型爲short的inode->i_zone
(gdb) x /20xh  inode->i_zone
0x2cb92 : 0xbbc7 0xbbc8 0xbbc9 0xbbca 0xbbcb 0xbbcc 0xbbcd 0xbbce
0x2cba2 : 0x0000 0x0000 0x0000 0x0000 0x0000 0x0b6b 0x9bdc 0x0000
0x2cbb2 : 0x0000 0x0301 0x0931 0x0001

注: 要用display自動顯示--> display /40wx 0xc0101f80

2.3 gdb彙編級調試

(gdb) display /5i
$pc                  -->pc是gdb的一個內部變量,打印當前的5條彙編指令
1: x/5i $pc
=> 0x1111dc <system_call>:    push %eax
   0x1111dd <system_call+1>:    cld
   0x1111de <system_call+2>:    push %gs
   0x1111e0 <system_call+4>:    push %fs
   0x1111e2 <system_call+6>:    push %es
(gdb) ni                              -->
ni(nexti) 或si(stepi)進行彙編指令級調試
0x001111dd in system_call ()