用gdb获得寄存器的值This GDB was configured as i686-linux-gnu.For bug reporting instructions, plea
用gdb获得寄存器的值
This GDB was configured as "i686-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/ubuntu/gdb_debug...done.
(gdb) b main
Breakpoint 1 at 0x804840a: file gdb_debug.c, line 11.
(gdb) r
Starting program: /home/ubuntu/gdb_debug
Breakpoint 1, main () at gdb_debug.c:11
11f1();
(gdb) list
6double x = -5.5625;
7printf("%d\n",x);
8}
9main()
10{
11f1();
12}
(gdb) x/i $pc
=> 0x804840a <main+6>:call 0x80483c4 <f1>
(gdb) si
f1 () at gdb_debug.c:3
3{
(gdb) si
0x080483c53{
(gdb) si
0x080483c73{
(gdb) disass main
Dump of assembler code for function main:
0x08048404 <+0>:push %ebp
0x08048405 <+1>:mov %esp,%ebp
0x08048407 <+3>:and $0xfffffff0,%esp
0x0804840a <+6>:call 0x80483c4 <f1>
0x0804840f <+11>:mov %ebp,%esp
0x08048411 <+13>:pop %ebp
0x08048412 <+14>:ret
End of assembler dump.
(gdb) disass f1
Dump of assembler code for function f1:
0x080483c4 <+0>:push %ebp
0x080483c5 <+1>:mov %esp,%ebp
=> 0x080483c7 <+3>:push %ebx
0x080483c8 <+4>:sub $0x24,%esp
0x080483cb <+7>:mov $0x3039,%ebx
0x080483d0 <+12>:mov $0x80484e0,%eax
0x080483d5 <+17>:mov %ebx,0x4(%esp)
0x080483d9 <+21>:mov %eax,(%esp)
0x080483dc <+24>:call 0x80482f4 <printf@plt>
0x080483e1 <+29>:fldl 0x80484e8
0x080483e7 <+35>:fstpl -0x10(%ebp)
0x080483ea <+38>:mov $0x80484e0,%eax
0x080483ef <+43>:fldl -0x10(%ebp)
0x080483f2 <+46>:fstpl 0x4(%esp)
0x080483f6 <+50>:mov %eax,(%esp)
0x080483f9 <+53>:call 0x80482f4 <printf@plt>
0x080483fe <+58>:add $0x24,%esp
0x08048401 <+61>:pop %ebx
0x08048402 <+62>:pop %ebp
0x08048403 <+63>:ret
---Type <return> to continue, or q <return> to quit---
End of assembler dump.
(gdb)
IP是指令寄存器，存放当前指令的下一条指令的地址。CPU该执行哪条指令就是通过IP来指示的。
EIP是32位机的指令寄存器。
IP：instruction pointer
PC: progtam counter
两者都是一个寄存器，指向当前执行指令的下一条指令。
(gdb) info all-registers //显示所有寄存器的内容
eip 0x80483c50x80483c5 <f1+1>
(gdb) disass f1 //反汇编函数f1
Dump of assembler code for function f1:
0x080483c4 <+0>:push %ebp
=> 0x080483c5 <+1>:mov %esp,%ebp
0x080483c7 <+3>:push %ebx
EBP: 栈底指针
ESP: 栈顶指针
通用寄存器：
(gdb) info all-registers
eax 0xbffff1d4-1073745452
ecx 0xf877f12f-126357201
edx 0x11
ebx 0x303912345 //寄存器变量存在此
st0~7是80位的浮点数寄存器，用于存放浮点数：
st0 0(raw 0x00000000000000000000)
st1 0(raw 0x00000000000000000000)
st2 0(raw 0x00000000000000000000)
st3 0(raw 0x00000000000000000000)
st4 0(raw 0x00000000000000000000)
---Type <return> to continue, or q <return> to quit---
st5 0(raw 0x00000000000000000000)
st6 0(raw 0x00000000000000000000)
st7 -5.5625(raw 0xc001b200000000000000)
