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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Opcode ARPL</TITLE></HEAD><BODY><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="AND.htm"> AND Logical AND</A><BR><B>next:</B><A HREF="BOUND.htm"> BOUND Check Array Index Against Bounds</A><P><HR><P><H1>ARPL -- Adjust RPL Field of Selector</H1><PRE>Opcode Instruction Clocks Description63 /r ARPL r/m16,r16 pm=20/21 Adjust RPL of r/m16 to not less than RPL of r16</PRE><H2>Operation</H2><PRE>IF RPL bits(0,1) of DEST < RPL bits(0,1) of SRCTHEN ZF := 1; RPL bits(0,1) of DEST := RPL bits(0,1) of SRC;ELSE ZF := 0;FI;</PRE><H2>Description</H2>The ARPL instruction has two operands. The first operand is a 16-bitmemory variable or word register that contains the value of a selector. Thesecond operand is a word register. If the RPL field ("requested privilegelevel"--bottom two bits) of the first operand is less than the RPL field ofthe second operand, the zero flag is set to 1 and the RPL field of thefirst operand is increased to match the second operand. Otherwise, the zeroflag is set to 0 and no change is made to the first operand.<P>ARPL appears in operating system software, not in application programs. Itis used to guarantee that a selector parameter to a subroutine does notrequest more privilege than the caller is allowed. The second operand ofARPL is normally a register that contains the CS selector value of thecaller.<H2>Flags Affected</H2>ZF as described above<H2>Protected Mode Exceptions</H2>#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegalmemory operand effective address in the CS, DS, ES, FS, or GS segments;#SS(0) for an illegal address in the SS segment; #PF(fault-code) for a pagefault<H2>Real Address Mode Exceptions</H2>Interrupt 6; ARPL is not recognized in Real Address Mode<H2>Virtual 8086 Mode Exceptions</H2>Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault<P><HR><P><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="AND.htm"> AND Logical AND</A><BR><B>next:</B><A HREF="BOUND.htm"> BOUND Check Array Index Against Bounds</A></BODY>⌨️ 快捷键说明
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