我想调试引导扇区并读取软盘。我在bochs中调试它，并想检查它是否成功读取或失败。我知道AH寄存器可以返回代码，但我也想查看它读取的内容，所以我想检查物理内存中的es：bx堆栈，但它都扩展了0x00。为什么呢？
此代码由as86编写，由ld86链接。
我使用bochs磁盘映像创建工具创建了软盘映像，并使用命令dd bs=32 if=boot of=/dev/fd0 skip=1创建了这个可启动软盘映像。
我注意到该标志重新传输了0x00000046，因此CF为0表示操作没有错误。但是ax寄存器是0x0201。啊寄存器是0x02是errcode。我不知道为什么？
以下是我的bochs文件：
megs: 16
romimage: file=$BXSHARE/BIOS-bochs-latest
vgaromimage: file=$BXSHARE/VGABIOS-lgpl-latest
floppya: 1_44="floppya.img", status=inserted
ata0-master: type=disk, path="hd.img", cylinders=365, heads=16, spt=63
boot: a
log: bochsout.txt
panic: action=ask
error: action=report
info: action=report
debug: action=ignore
cpu: ips=15000000
clock: sync=both
vga: extension=vbe, update_freq=15
mouse: enabled=0
这是代码：
BOOTSEG = 0x07c0
SYSSEG = 0x1000
entry start
start:
jmpi go, #BOOTSEG
go: mov ax, cs
mov ds, ax
mov ss, ax
mov sp, #400
mov dx, #0x0000
mov cx, #0x0002
mov ax, #SYSSEG
mov es, ax
xor bx, bx
mov ax, #0x201
int 0x13
.org 510
.word 0xAA55
.word 0xFFFF
由as86编写的代码，我在第二个扇区的开头添加一个单词。
我将调试信息粘贴在bochs中。
========================================================================
00000000000i[ ] reading configuration from bochsrc
00000000000i[ ] installing win32 module as the Bochs GUI
00000000000i[ ] using log file bochsout.txt
Next at t=0
(0) [0x0000fffffff0] f000:fff0 (unk. ctxt): jmpf 0xf000:e05b ; ea5be000
f0
<bochs:1> b 0x7c00
<bochs:2> c
(0) Breakpoint 1, 0x0000000000007c00 in ?? ()
Next at t=61419250
(0) [0x000000007c00] 0000:7c00 (unk. ctxt): jmpf 0x07c0:0005 ; ea0500c0
07
<bochs:3> s
Next at t=61419251
(0) [0x000000007c05] 07c0:0005 (unk. ctxt): mov ax, cs ; 8cc8
<bochs:4> s
Next at t=61419252
(0) [0x000000007c07] 07c0:0007 (unk. ctxt): mov ds, ax ; 8ed8
<bochs:5> s
Next at t=61419253
(0) [0x000000007c09] 07c0:0009 (unk. ctxt): mov ss, ax ; 8ed0
<bochs:6> s
Next at t=61419254
(0) [0x000000007c0b] 07c0:000b (unk. ctxt): mov sp, 0x0400 ; bc0004
<bochs:7> s
Next at t=61419255
(0) [0x000000007c0e] 07c0:000e (unk. ctxt): mov dx, 0x0000 ; ba0000
<bochs:8> s
Next at t=61419256
(0) [0x000000007c11] 07c0:0011 (unk. ctxt): mov cx, 0x0002 ; b90200
<bochs:9> s
Next at t=61419257
(0) [0x000000007c14] 07c0:0014 (unk. ctxt): mov ax, 0x1000 ; b80010
<bochs:10> s
Next at t=61419258
(0) [0x000000007c17] 07c0:0017 (unk. ctxt): mov es, ax ; 8ec0
<bochs:11> s
Next at t=61419259
(0) [0x000000007c19] 07c0:0019 (unk. ctxt): xor bx, bx ; 31db
<bochs:12> s
Next at t=61419260
(0) [0x000000007c1b] 07c0:001b (unk. ctxt): mov ax, 0x0201 ; b80102
<bochs:13> s
Next at t=61419261
(0) [0x000000007c1e] 07c0:001e (unk. ctxt): int 0x13 ; cd13
<bochs:14> s
Next at t=61419262
(0) [0x0000000fe3fe] f000:e3fe (unk. ctxt): jmp .-19908 (0x000f963d) ; e93cb2
<bochs:15> r
rax: 00000000_00000201 rcx: 00000000_00090002
rdx: 00000000_00000000 rbx: 00000000_00000000
rsp: 00000000_000003fa rbp: 00000000_00000000
rsi: 00000000_000e0000 rdi: 00000000_0000ffac
r8 : 00000000_00000000 r9 : 00000000_00000000
r10: 00000000_00000000 r11: 00000000_00000000
r12: 00000000_00000000 r13: 00000000_00000000
r14: 00000000_00000000 r15: 00000000_00000000
rip: 00000000_0000e3fe
eflags 0x00000046: id vip vif ac vm rf nt IOPL=0 of df if tf sf ZF af PF cf
<bochs:16> sreg
es:0x1000, dh=0x00009301, dl=0x0000ffff, valid=1
Data segment, base=0x00010000, limit=0x0000ffff, Read/Write, Accessed
cs:0xf000, dh=0x0000930f, dl=0x0000ffff, valid=1
Data segment, base=0x000f0000, limit=0x0000ffff, Read/Write, Accessed
ss:0x07c0, dh=0x00009300, dl=0x7c00ffff, valid=7
Data segment, base=0x00007c00, limit=0x0000ffff, Read/Write, Accessed
ds:0x07c0, dh=0x00009300, dl=0x7c00ffff, valid=1
Data segment, base=0x00007c00, limit=0x0000ffff, Read/Write, Accessed
fs:0x0000, dh=0x00009300, dl=0x0000ffff, valid=1
Data segment, base=0x00000000, limit=0x0000ffff, Read/Write, Accessed
gs:0x0000, dh=0x00009300, dl=0x0000ffff, valid=1
Data segment, base=0x00000000, limit=0x0000ffff, Read/Write, Accessed
ldtr:0x0000, dh=0x00008200, dl=0x0000ffff, valid=1
tr:0x0000, dh=0x00008b00, dl=0x0000ffff, valid=1
gdtr:base=0x00000000000fa1f7, limit=0x30
idtr:base=0x0000000000000000, limit=0x3ff
<bochs:17> xp /40bx 0x10000
[bochs]:
0x0000000000010000 <bogus+ 0>: 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00
0x0000000000010008 <bogus+ 8>: 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00
0x0000000000010010 <bogus+ 16>: 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00
0x0000000000010018 <bogus+ 24>: 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00
0x0000000000010020 <bogus+ 32>: 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00
答案 0 :(得分：0)
你忘了显示你尝试过的命令（也许你正在查看错误的地址），以及你加载的扇区中你的软盘映像是否还有零字节;）你也没有说你是什么汇编程序使用以及如何创建图像。
我使用nasm
mov dx, 0x0000
mov cx, 0x0002
mov ax, 0x1000
mov es, ax
xor bx, bx
mov ax, 0x201
int 0x13
jmp $
times 510 - ($-$$) db 0
dw 0xAA55 ; signature
times 512 db 0xaa ; fill 2nd sector with 0xaa
times 1474560 - ($-$$) db 0 ; fill rest of image with 00
在bochs中引导创建的图像：
(0) [0x0000000000007c10] 0000:7c10 (unk. ctxt): int 0x13 ; cd13
<bochs:9>
Next at t=13210529
(0) [0x0000000000007c12] 0000:7c12 (unk. ctxt): jmp .-2 (0x00007c12) ; ebfe
<bochs:10> r
rax: 0x00000000_00000001 rcx: 0x00000000_00000002
rdx: 0x00000000_00000000 rbx: 0x00000000_00000000
rsp: 0x00000000_0000ffd6 rbp: 0x00000000_00000000
rsi: 0x00000000_000e91b9 rdi: 0x00000000_0000ffac
r8 : 0x00000000_00000000 r9 : 0x00000000_00000000
r10: 0x00000000_00000000 r11: 0x00000000_00000000
r12: 0x00000000_00000000 r13: 0x00000000_00000000
r14: 0x00000000_00000000 r15: 0x00000000_00000000
rip: 0x00000000_00007c12
eflags 0x00000046: id vip vif ac vm rf nt IOPL=0 of df if tf sf ZF af PF cf
<bochs:11> xp/32bx 0x10000
[bochs]:
0x0000000000010000 <bogus+ 0>: 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa
0x0000000000010008 <bogus+ 8>: 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa
0x0000000000010010 <bogus+ 16>: 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa
0x0000000000010018 <bogus+ 24>: 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa 0xaa
您可以看到AH=0（表示没有错误），AL=1（表示已加载1个扇区），实际上数据存在于内存中。
答案 1 :(得分：0)
你进入中断处理程序的最后s步骤（注意地址f000:e3fe - 这是在BIOS内部）。它还没有做任何事情，所以ax保留你传递给中断的值。您需要先步骤直到返回代码，或在中断后放置断点并继续。只有这样你才能检查CF和其他寄存器。