74 lines
3.6 KiB
HTML
74 lines
3.6 KiB
HTML
<html><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<html>
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<head>
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<title>80386 Programmer's Reference Manual -- Opcode LSL</title>
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</head>
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<body>
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<b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="LOOP.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/LOOP.HTM"> LOOP/LOOPcond Loop Control with CX Counter</a><br>
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<b>next:</b><a href="LTR.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/LTR.HTM"> LTR Load Task Register</a>
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<p>
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<hr>
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<p>
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<h1>LSL -- Load Segment Limit</h1>
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<pre>
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Opcode Instruction Clocks Description
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0F 03 /r LSL r16,r/m16 pm=20/21 Load: r16 := segment limit,
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selector r/m16 (byte granular)
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0F 03 /r LSL r32,r/m32 pm=20/21 Load: r32 := segment limit,
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selector r/m32 (byte granular)
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0F 03 /r LSL r16,r/m16 pm=25/26 Load: r16 := segment limit,
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selector r/m16 (page granular)
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0F 03 /r LSL r32,r/m32 pm=25/26 Load: r32 := segment limit,
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selector r/m32 (page granular)
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</pre>
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<h2>Description</h2>
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The LSL instruction loads a register with an unscrambled segment limit, and sets ZF to 1, provided that the source selector is visible at the CPL weakened by RPL, and that the descriptor is a type accepted by LSL. Otherwise, ZF is cleared to 0, and the destination register is unchanged. The segment limit is loaded as a byte granular value. If the descriptor has a page granular segment limit, LSL will translate it to a byte limit before loading it in the destination register (shift left 12 the 20-bit "raw" limit from descriptor, then OR with 00000FFFH).
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<p>The 32-bit forms of this instruction store the 32-bit byte granular limit in the 16-bit destination register.
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<p>Code and data segment descriptors are valid for LSL.
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<p>The valid special segment and gate descriptor types for LSL are given in the following table:
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<pre>
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Type Name Valid/Invalid
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0 Invalid Invalid
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1 Available 80286 TSS Valid
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2 LDT Valid
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3 Busy 80286 TSS Valid
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4 80286 call gate Invalid
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5 80286/80386 task gate Invalid
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6 80286 trap gate Invalid
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7 80286 interrupt gate Invalid
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8 Invalid Valid
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9 Available 80386 TSS Valid
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A Invalid Invalid
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B Busy 80386 TSS Valid
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C 80386 call gate Invalid
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D Invalid Invalid
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E 80386 trap gate Invalid
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F 80386 interrupt gate Invalid
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</pre>
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<h2>Flags Affected</h2>
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ZF as described above
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<h2>Protected Mode Exceptions</h2>
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#GP(0) for an illegal memory 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 page fault
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<h2>Real Address Mode Exceptions</h2>
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Interrupt 6; LSL is not recognized in Real Address Mode
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<h2>Virtual 8086 Mode Exceptions</h2>
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Same exceptions as in Real Address Mode
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<p>
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<hr>
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<p><b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="LOOP.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/LOOP.HTM"> LOOP/LOOPcond Loop Control with CX Counter</a><br>
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<b>next:</b><a href="LTR.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/LTR.HTM"> LTR Load Task Register</a>
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</body>
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