段寄存器吧。

选择子
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补充一下。
这个是intel指令的限制。
jmp far 必须是
jmp far xxx：xxxxxxx的格式
其中
：之前的是赋给CS的
：之后的给EIP
其中忽略了权限比较等操作。

Opcode \ Instruction  \64-Bit Mode  \Compat/Leg Mode     \Description
EB cb     \JMP rel8     \Valid     \Valid             \ Jump short, RIP = RIP + 8-bit displacement sign extended to 64-bits
E9 cw     \JMP rel16     \N.S.    \ Valid           \   Jump near, relative, displacement relative to next instruction. Not supported in 64-bit mode.
E9 cd     \JMP rel32     \Valid    \ Valid          \   Jump near, relative, RIP = RIP + 32-bit displacement sign extended to 64-bits
FF /4     \JMP r/m16   \  N.S.  \   Valid           \   Jump near, absolute indirect, address = sign-extended r/m16. Not supported in 64-bit mode.
FF /4     \JMP r/m32    \ N.S.   \  Valid        \     Jump near, absolute indirect, address = sign-extended r/m32. Not supported in 64-bit mode.
FF /4     \JMP r/m64   \  Valid  \   N.E.          \   Jump near, absolute indirect, RIP = 64-Bitoffset from register or memory
EA cd     \JMP ptr16:16 \    Inv.  \   Valid     \     Jump far, absolute, address given in operand
EA cp     \JMP ptr16:32   \  Inv.   \  Valid      \    Jump far, absolute, address given in operand
FF /5     \JMP m16:16     \Valid    \ Valid        \   Jump far, absolute indirect, address given in m16:16
FF /5     \JMP m16:32   \  Valid   \  Valid       \    Jump far, absolute indirect, address given in m16:32.REX.W +
FF /5     \JMP m16:64    \ Valid     \N.E.        \    Jump far, absolute indirect, address given in m16:64.

非常感谢您的讲解！