下列能够改变CS:IP所指位置并能通过编译的指令是______。
1、 jmp short [bx]
2、 jne [bx]
3、 loop byte ptr [bx]
4、 jmp [bx]
为什么是3，怎么分析的？
根据书本我只得出五种：
jmp为无条件转移指令,可以只改IP,也可以同时改cs:ip
jmp short s
jmp near ptr s
jmp far ptr s
jmp word ptr [...] ;段内转移
jmp dword ptr [...] ;段间转移,高地址是CS,低地址是IP
好像没有jmp [...]这样的形式
后来网上还看到了jmp s这样的形式
很糊涂了，书上不够全面呀，初学者这么分析呢？难道排除法？书上jne指令也没介绍，汗死人。
网上还发现：
JMP - Unconditional Jump
Usage: JMP target
Modifies flags: None
Unconditionally transfers control to "label". Jumps by default
are within -32768 to 32767 bytes from the instruction following
the jump. NEAR and SHORT jumps cause the IP to be updated while FAR
jumps cause CS and IP to be updated.
Clocks
Operands 808x 286 386 486
rel8 (relative) 15 7+m 7+m 3
rel16 (relative) 15 7+m 7+m 3
rel32 (relative) - - 7+m 3
reg16 (near, register indirect) 11 7+m 7+m 5
reg32 (near, register indirect) - - 7+m 5
mem16 (near, mem indirect) 18+EA 11+m 10+m 5
mem32 (near, mem indirect) 24+EA 15+m 10+m 5
ptr16:16 (far, dword immed) - - 12+m 17
ptr16:16 (far, PM dword immed) - - 27+m 19
ptr16:16 (call gate, same priv.) - 38+m 45+m 32
ptr16:16 (via TSS) - 175+m TS 42+TS
ptr16:16 (via task gate) - 180+m TS 43+TS
mem16:16 (far, indirect) - - 43+m 13
mem16:16 (far, PM indirect) - - 31+m 18
mem16:16 (call gate, same priv.) - 41+m 49+m 31
mem16:16 (via TSS) - 178+m 5+TS 41+TS
mem16:16 (via task gate) - 183+m 5+TS 42+TS
ptr16:32 (far, 6 byte immed) - - 12+m 13
ptr16:32 (far, PM 6 byte immed) - - 27+m 18
ptr16:32 (call gate, same priv.) - - 45+m 31
ptr16:32 (via TSS) - - TS 42+TS
ptr16:32 (via task state) - - TS 43+TS
m16:32 (far, address at dword) - - 43+m 13
m16:32 (far, address at dword) - - 31+m 18
m16:32 (call gate, same priv.) - - 49+m 31
m16:32 (via TSS) - - 5+TS 41+TS
m16:32 (via task state) - - 5+TS 42+TS
有这么多，但是看不太懂，有高手分析下吗？ |
