hw/i386.reference/LLDT.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode LLDT</TITLE>
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   8 Chapter 17 -- 80386 Instruction Set</A><BR>
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  14 <H1>LLDT -- Load Local Descriptor Table Register</H1>
  15
  16 <PRE>
  17 Opcode      Instruction      Clocks   Description
  18
  19 0F  00 /2   LLDT r/m16       20       Load selector r/m16 into LDTR
  20 </PRE>
  21
  22 <H2>Operation</H2>
  23
  24 <PRE>
  25 LDTR := SRC;
  26 </PRE>
  27
  28 <H2>Description</H2>
  29
  30 LLDT loads the Local Descriptor Table register (LDTR). The word
  31 operand (memory or register) to LLDT should contain a selector to the
  32 Global Descriptor Table (GDT). The GDT entry should be a Local Descriptor
  33 Table. If so, then the LDTR is loaded from the entry. The descriptor
  34 registers DS, ES, SS, FS, GS, and CS are not affected. The LDT field in the
  35 task state segment does not change.
  36 <P>
  37 The selector operand can be 0; if so, the LDTR is marked invalid. All
  38 descriptor references (except by the LAR, VERR, VERW or LSL
  39 instructions) cause a #GP fault.
  40 <P>
  41 LLDT is used in operating system software; it is not used in application
  42 programs.
  43
  44 <H2>Flags Affected</H2>
  45
  46 None
  47
  48 <H2>Protected Mode Exceptions</H2>
  49
  50 #GP(0) if the current privilege level is not 0; #GP(selector) if the
  51 selector operand does not point into the Global Descriptor Table, or if the
  52 entry in the GDT is not a Local Descriptor Table; #NP(selector) if the
  53 LDT descriptor is not present; #GP(0) for an illegal memory operand
  54 effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an
  55 illegal address in the SS segment; #PF(fault-code) for a page fault
  56
  57 <H2>Real Address Mode Exceptions</H2>
  58
  59 Interrupt 6; LLDT is not recognized in Real Address Mode
  60
  61 <H2>Virtual 8086 Mode Exceptions</H2>
  62
  63 Same exceptions as in Real Address Mode (because the instruction is
  64 not recognized, it will not execute or perform a memory reference)
  65
  66 <EM>
  67 <H3>Note</H3>
  68
  69 The operand-size attribute has no effect on this instruction.
  70 </EM>
  71
  72
  73 <P>
  74 <HR>
  75 <P>
  76 <B>up:</B> <A HREF="c17.htm">
  77 Chapter 17 -- 80386 Instruction Set</A><BR>
  78 <B>prev:</B><A HREF="LGS.htm"> LGS/LSS/LDS/LES/LFS Load Full Pointer</A><BR>
  79 <B>next:</B><A HREF="LMSW.htm"> LMSW Load Machine Status Word</A>
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