写操作系统----8.调试堆栈

1.1 用bochs对堆栈调试
a. bochs打印栈 print-stack,结合r 打印出的esp看
b. call === push IP    ;即把下一条的指令压栈
   ret ===  pop IP      ;即把栈顶赋到IP中
1.2 代码如下

[bits 32]
section .text
global put_test
put_test:
    mov ecx, 'A'
    push ecx
    call put_char
    ;pop ecx              -->正确的代码是要把pop ecx打开
    ret

1.3 调试过程

Next at t=0
(0) [0x0000fffffff0] f000:fff0 (unk. ctxt): jmpf 0xf000:e05b ; ea5be000f0
<bochs:1> b 0x1500                          -->kernel.bin的运行地址,由0x70000挪到了0x1500处
<bochs:2> c
(0) Breakpoint 1, 0xc0001500 in ?? ()
Next at t=157030835
(0) [0x000000001500] 0008:c0001500 (unk. ctxt): push ebp ; 55
<bochs:3> n
Next at t=157030836
(0) [0x000000001501] 0008:c0001501 (unk. ctxt): mov ebp, esp ; 89e5
<bochs:4> n
Next at t=157030837
(0) [0x000000001503] 0008:c0001503 (unk. ctxt): and esp, 0xfffffff0 ; 83e4f0
<bochs:5>
Next at t=157030838
(0) [0x000000001506] 0008:c0001506 (unk. ctxt): sub esp, 0x00000020 ; 83ec20
<bochs:6>
Next at t=157030839
(0) [0x000000001509] 0008:c0001509 (unk. ctxt): mov dword ptr ss:[esp+28], 0x00000003 ; c744241c03000000
<bochs:7>
Next at t=157030840
(0) [0x000000001511] 0008:c0001511 (unk. ctxt): mov dword ptr ss:[esp], 0x0000006b ; c704246b000000
<bochs:8>
Next at t=157030841
(0) [0x000000001518] 0008:c0001518 (unk. ctxt): call .+47 (0xc000154c) ; e82f000000   -->0xc000154C是函数put_char的地址
<bochs:9> n
Next at t=157030887
(0) [0x00000000151d] 0008:c000151d (unk. ctxt): call .+30 (0xc0001540) ; e81e000000  -->0xc0001540是函数put_test的地址
<bochs:10> s                           -->step in跟进call的函数，即进入put_test
Next at t=157030888
(0) [0x000000001540] 0008:c0001540 (unk. ctxt): mov ecx, 0x00000041 ; b941000000
<bochs:11> print-stack      -->查看栈
Stack address size 4
 | STACK 0xc009efcc [0xc0001522]      -->call之后的栈信息是正确的 esp=0xc009efcc,它的内容是0xc0001522,call后要执行的指令地址
 | STACK 0xc009efd0 [0x0000006b]
 | STACK 0xc009efd4 [0x00000000]
 | STACK 0xc009efd8 [0x00000000]
 | STACK 0xc009efdc [0x00000000]
 | STACK 0xc009efe0 [0x00000000]
 | STACK 0xc009efe4 [0x00000000]
 | STACK 0xc009efe8 [0x00000000]
 | STACK 0xc009efec [0x00000003]
 | STACK 0xc009eff0 [0x00000000]
 | STACK 0xc009eff4 [0x00000000]
 | STACK 0xc009eff8 [0x00000000]
 | STACK 0xc009effc [0x00000000]
 | STACK 0xc009f000 [0x8ec031fa]
 | STACK 0xc009f004 [0x10bb66d8]
 | STACK 0xc009f008 [0x67000005]
<bochs:12> r
eax: 0x00070000 458752
ecx: 0x00000000 0
edx: 0x00000020 32
ebx: 0x00070094 458900
esp: 0xc009efcc -1073090612        -->esp=0xc009efcc
ebp: 0xc009effc -1073090564
esi: 0x00070000 458752
edi: 0x00000000 0
eip: 0xc0001540
eflags 0x00000087: id vip vif ac vm rf nt IOPL=0 of df if tf SF zf af PF CF
<bochs:13> n
Next at t=157030889
(0) [0x000000001545] 0008:c0001545 (unk. ctxt): push ecx ; 51
<bochs:14>
Next at t=157030890
(0) [0x000000001546] 0008:c0001546 (unk. ctxt): call .+1 (0xc000154c) ; e801000000
<bochs:15> print-stack
Stack address size 4
 | STACK 0xc009efc8 [0x00000041]       -->push之后破坏了stack的栈顶
 | STACK 0xc009efcc [0xc0001522]
 | STACK 0xc009efd0 [0x0000006b]
 | STACK 0xc009efd4 [0x00000000]
 | STACK 0xc009efd8 [0x00000000]
 | STACK 0xc009efdc [0x00000000]
 | STACK 0xc009efe0 [0x00000000]
 | STACK 0xc009efe4 [0x00000000]
 | STACK 0xc009efe8 [0x00000000]
 | STACK 0xc009efec [0x00000003]
 | STACK 0xc009eff0 [0x00000000]
 | STACK 0xc009eff4 [0x00000000]
 | STACK 0xc009eff8 [0x00000000]
 | STACK 0xc009effc [0x00000000]
 | STACK 0xc009f000 [0x8ec031fa]
 | STACK 0xc009f004 [0x10bb66d8]
<bochs:16> n
Next at t=157030936
(0) [0x00000000154b] 0008:c000154b (unk. ctxt): ret ; c3
<bochs:17> n
Next at t=157030937
(0) [0x000000000041] 0008:00000041 (unk. ctxt): add dword ptr ds:[eax], eax ; 0100  -->这儿ret是要把栈顶当成下一条要执行的地址

1.4 代码打包
6_1print.rar(下载后改名为6_1print.tar.gz)