ret/retf/iret

ret/retf/iret

 (2011-03-10 23:10:27)

http://blog.sina.com.cn/s/blog_67146a750100ra3l.html

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杂谈

分类： OS学习

• RET: and its exact synonym RETN, pop IP or EIP from the stack and transfer control to the new address. Optionally, if a numeric second operand is provided, they increment the stack pointer by a further imm16 bytes after popping the return address.

• RETF: executes a far return: after popping IP/EIP, it then pops CS, and then increments the stack pointer by the optional argument if present.

• IRET: returns from an interrupt (hardware or software) by means of popping IP (or EIP), CS and the flags off the stack and then continuing execution from the new CS:IP.

• IRETW: pops IP, CS and the flags as 2 bytes each, taking 6 bytes off the stack in total.

• IRETD: pops EIP as 4 bytes, pops a further 4 bytes of which the top two are discarded and the bottom two go into CS, and pops the flags as 4 bytes as well, taking 12 bytes off the stack.
• IRET: is a shorthand for either IRETW or IRETD, depending on the default BITS setting at the time.