bochs 调试
bochs 基本调试
基本操作
Bochs 调试指令
行为 指令 举例
在某物理地址设置断点 b addr b 0x7c00
显示当前所有断点信息 info break info break
继续执行，直至遇到断点 c c
单步执行 s s
单步执行（遇到函数跳过） n n
查看寄存器信息 info cpu
r
fp
sreg
creg info cpu
r
fp
sreg
cre
查看堆栈 print-stack print-stack
查看内存物理地址内容 xp /nuf addr xp /40bx 0x9013e
查看线性地址内容 x /nuf addr x /40bx 0x13e
反汇编一段内存 u start end u 0x30400 0x3040d
反汇编执行的每一条指令 trace-on trace-on
每执行一条指令就打印 CPU 信息 trace-reg trace-reg
b 0x7c00
c
(0) Breakpoint 1, 0x00007c00 in ?? ()
Next at t=12943099
(0) [0x00007c00] 0000:7c00 (unk. ctxt): mov ax, cx ; 89c8
sreg
es:0x0000, dh=0x00009300, dl=0x0000ffff, valid=1
Data segment, base=0x00000000, limit=0x0000ffff, Read/Write, Accessed
cs:0x0000, dh=0x00009300, dl=0x0000ffff, valid=1
Data segment, base=0x00000000, limit=0x0000ffff, Read/Write, Accessed
ss:0x0000, dh=0x00009300, dl=0x0000ffff, valid=7
Data segment, base=0x00000000, limit=0x0000ffff, Read/Write, Accessed
ds:0x0000, dh=0x00009300, dl=0x0000ffff, valid=1
Data segment, base=0x00000000, 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=0x000fb997, limit=0x30
idtr:base=0x00000000, limit=0x3ff
r
eax: 0x0000aa55 43605
ecx: 0x00000000 0
edx: 0x00000000 0
ebx: 0x00000000 0
esp: 0x0000ffd6 65494
ebp: 0x00000000 0
esi: 0x000e32f8 930552
edi: 0x0000ffac 65452
eip: 0x00007c00
eflags 0x00000082: id vip vif ac vm rf nt IOPL=0 of df if tf SF zf af pf cf
blist
Num Type Disp Enb Address
1 pbreakpoint keep y 0x00007c00
# A bootsect, which print a string by BIOS interrupt video services(int 0x10)
.section .text
.global _start
.code16
_start:
movw %cx, %ax
movw %ax, %ds
movw %ax, %es
movw $msgstr,%bp
movw len, %cx
movb $0x05, %dh
movb $0x08, %dl
movb $0x01, %al
movb $0x13, %ah
movb $0x01, %bl
movb $0x00, %bh
int $0x10
1:
jmp 1b
msgstr:
.asciz "Hello babyos(print by BIOS int 0x10:0x13, mode 0x01)!"
len:
.int . - msgstr
.org 0x1fe, 0x90
.word 0xaa55
makefile:
all: boot.img
boot.o: boot.s
as -o $@ $<
boot: boot.o
ld --oformat binary -N -Ttext 0x7c00 -o $@ $<
boot.img: boot
dd if=boot of=boot.img bs=512 count=1
clean:
rm ./boot ./boot.img ./boot.o
u 0x7c00
00007c00: ( ): mov ax, cx ; 89c8
u 0x7c00 0x7c00+512
00007c00: ( ): mov ax, cx ; 89c8
00007c02: ( ): mov ds, ax ; 8ed8
00007c04: ( ): mov es, ax ; 8ec0
00007c06: ( ): mov bp, 0x7c1d ; bd1d7c 0x7c1d 是msg地址
00007c09: ( ): mov cx, word ptr ds:0x7c53 ; 8b0e537c
00007c0d: ( ): mov dh, 0x05 ; b605
00007c0f: ( ): mov dl, 0x08 ; b208
00007c11: ( ): mov al, 0x01 ; b001
00007c13: ( ): mov ah, 0x13 ; b413
00007c15: ( ): mov bl, 0x01 ; b301
00007c17: ( ): mov bh, 0x00 ; b700
00007c19: ( ): int 0x10 ; cd10
00007c1b: ( ): jmp .-2 ; ebfe
00007c1d: ( ): dec ax ; 48 要输出的字符从这里开始
00007c1e: ( ): insb byte ptr es:[di], dx ; 656c
00007c20: ( ): insb byte ptr es:[di], dx ; 6c
00007c21: ( ): outsw dx, word ptr ds:[si] ; 6f
00007c22: ( ): and byte ptr ss:[bp+si+97], ah ; 206261
00007c25: ( ): bound di, ds:[bx+di+111] ; 62796f
00007c28: ( ): jnb .+40 ; 7328
00007c2a: ( ): jo .+114 ; 7072
00007c2c: ( ): imul bp, word ptr ss:[bp+116], 0x6220 ; 696e742062
00007c31: ( ): jns .+32 ; 7920
00007c33: ( ): inc dx ; 42
00007c34: ( ): dec cx ; 49
00007c35: ( ): dec di ; 4f
00007c36: ( ): push bx ; 53
00007c37: ( ): and byte ptr ds:[bx+di+110], ch ; 20696e
00007c3a: ( ): jz .+32 ; 7420
00007c3c: ( ): xor byte ptr ds:[bx+si+49], bh ; 307831
00007c3f: ( ): xor byte ptr ss:[bp+si], bh ; 303a
00007c41: ( ): xor byte ptr ds:[bx+si+49], bh ; 307831
00007c44: ( ): xor bp, word ptr ds:[si] ; 332c
00007c46: ( ): and byte ptr ds:[di+111], ch ; 206d6f
00007c49: ( ): and byte ptr gs:[bx+si], dh ; 64652030
00007c4d: ( ): js .+48 ; 7830
00007c4f: ( ): xor word ptr ds:[bx+di], bp ; 3129
00007c51: ( ): and word ptr ds:[bx+si], ax ; 2100
00007c53: ( ): add byte ptr ss:[bx+si], al ; 360000 这里这个 36 是字符长度
00007c56: ( ): add byte ptr ds:[bx+si-28528], dl ; 00909090
00007c5a: ( ): nop ; 90
00007c5b: ( ): nop ; 90
页映射相关
查看一个地址所属的物理页，查看相应的页表项，以及看该地址所具备的属性。
格式 page addr
page 0x90000
PML4: 0x0000000000102027 ps A pcd pwt U W P
PDPE: 0x0000000000103023 ps A pcd pwt S W P
PDE: 0x00000000000000e3 PS g pat D A pcd pwt S W P
linear page 0x0000000000090000 maps to physical page 0x000000090000
page 0xffff800000105b60
PML4: 0x0000000000102027 ps A pcd pwt U W P
PDPE: 0x0000000000103023 ps A pcd pwt S W P
PDE: 0x00000000000000e3 PS g pat D A pcd pwt S W P
linear page 0xffff800000105000 maps to physical page 0x000000105000
page 0xffff800000a00000
PML4: 0x0000000000102027 ps A pcd pwt U W P
PDPE: 0x0000000000103023 ps A pcd pwt S W P
PDE: 0x00000000e0000083 PS g pat d a pcd pwt S W P
linear page 0xffff800000a00000 maps to physical page 0x0000e0000000
查看断点
blist
Num Type Disp Enb Address
1 pbreakpoint keep y 0x000000010000
2 pbreakpoint keep y 0x000000100000
3 pbreakpoint keep y 0x000000100048
4 pbreakpoint keep y 0xffff8000001000bb
5 pbreakpoint keep y 0x0000001000c2
6 pbreakpoint keep y 0xffff8000001000c2
特殊寄存器查看
creg
CR0=0xe0000011: PG CD NW ac wp ne ET ts em mp PE
CR2=page fault laddr=0x0000000000000000
CR3=0x000000101000
PCD=page-level cache disable=0
PWT=page-level write-through=0
CR4=0x00000020: pke smap smep osxsave pcid fsgsbase smx vmx osxmmexcpt umip osfxsr pce pge mce PAE pse de tsd pvi vme
CR8: 0x0
EFER=0x00000500: ffxsr nxe LMA LME sce
XCR0=0x00000001: pkru hi_zmm zmm_hi256 opmask bndcfg bndregs ymm sse FPU
sreg
es:0x0010, dh=0x00009300, dl=0x00000000, valid=1
Data segment, base=0x00000000, limit=0x00000000, Read/Write, Accessed
cs:0x0008, dh=0x00209900, dl=0x00000000, valid=1
Code segment, base=0x00000000, limit=0x00000000, Execute-Only, Non-Conforming, Accessed, 64-bit
ss:0x0010, dh=0x00009300, dl=0x00000000, valid=1
Data segment, base=0x00000000, limit=0x00000000, Read/Write, Accessed
ds:0x0010, dh=0x00009300, dl=0x00000000, valid=1
Data segment, base=0x00000000, limit=0x00000000, Read/Write, Accessed
fs:0x0010, dh=0x00009300, dl=0x00000000, valid=1
Data segment, base=0x00000000, limit=0x00000000, Read/Write, Accessed
gs:0x0010, dh=0x00009300, dl=0x00000000, valid=1
Data segment, base=0x00000000, limit=0x00000000, Read/Write, Accessed
ldtr:0x0000, dh=0x00008200, dl=0x0000ffff, valid=1
tr:0x0000, dh=0x00008b00, dl=0x0000ffff, valid=1
gdtr:base=0xffff800000105b60, limit=0x87
idtr:base=0xffff800000105bf2, limit=0xfff