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X86-lgdt

Signature
(x86-lgdt proc-mode start-rip temp-rip prefixes rex-byte opcode modr/m sib x86) → x86
Returns: x86 — Type (x86p x86), given (x86p x86).

Op/En = M: [OP m16&m32]

Op/En = M: [OP m16&m64]

In 64-bit mode, the instruction's operand size is fixed at 8+2 bytes (an 8-byte base and a 2-byte limit).

[OP M]
0F 01/2: LGDT m16&32
0F 01/2: LGDT m16&64

TO-DO: If a memory address referencing the SS segment is in a non-canonical form, raise the SS exception.

Definitions and Theorems

Function: x86-lgdt

(defun x86-lgdt (proc-mode start-rip temp-rip
                           prefixes rex-byte opcode modr/m sib x86)
 (declare (xargs :stobjs (x86)))
 (declare (type (integer 0 4) proc-mode)
          (type (signed-byte 48) start-rip)
          (type (signed-byte 48) temp-rip)
          (type (unsigned-byte 52) prefixes)
          (type (unsigned-byte 8) rex-byte)
          (type (unsigned-byte 8) opcode)
          (type (unsigned-byte 8) modr/m)
          (type (unsigned-byte 8) sib))
 (declare (ignorable proc-mode start-rip temp-rip
                     prefixes rex-byte opcode modr/m sib))
 (declare (xargs :guard (and (prefixes-p prefixes)
                             (modr/m-p modr/m)
                             (sib-p sib)
                             (rip-guard-okp proc-mode temp-rip)
                             (not (equal (modr/m->mod modr/m) 3)))))
 (let ((__function__ 'x86-lgdt))
  (declare (ignorable __function__))
  (b* ((?ctx 'x86-lgdt)
       (?r/m (the (unsigned-byte 3)
                  (modr/m->r/m modr/m)))
       (?mod (the (unsigned-byte 2)
                  (modr/m->mod modr/m)))
       (?reg (the (unsigned-byte 3)
                  (modr/m->reg modr/m))))
   (b*
    (((when (app-view x86))
      (!!ms-fresh :lgdt-unimplemented-in-app-view))
     (p2 (prefixes->seg prefixes))
     (p4? (equal 103 (prefixes->adr prefixes)))
     (seg-reg
         (select-segment-register proc-mode p2 p4? mod r/m sib x86))
     ((the (integer 4 8) base-size)
      (if (64-bit-modep x86) 8 4))
     ((the (integer 6 10) base-size+2)
      (+ 2 base-size))
     (inst-ac? nil)
     ((mv flg0 mem
          (the (unsigned-byte 3) increment-rip-by)
          (the (signed-byte 64) addr)
          x86)
      (x86-operand-from-modr/m-and-sib-bytes
           proc-mode
           0 base-size+2 inst-ac? t seg-reg p4?
           temp-rip rex-byte r/m mod sib 0 x86))
     ((when flg0)
      (!!ms-fresh :x86-operand-from-modr/m-and-sib-bytes flg0))
     ((mv flg (the (signed-byte 48) temp-rip))
      (add-to-*ip proc-mode
                  temp-rip increment-rip-by x86))
     ((when flg)
      (!!ms-fresh :rip-increment-error temp-rip))
     (badlength? (check-instruction-length start-rip temp-rip 0))
     ((when badlength?)
      (!!fault-fresh :gp 0
                     :instruction-length badlength?))
     (p3? (eql 102 (prefixes->opr prefixes)))
     (operand-size
      (if (eql base-size 8)
          8
       (b*
        (((the (unsigned-byte 16) cs-attr)
          (seg-hidden-attri 1 x86))
         (cs.d (code-segment-descriptor-attributesbits->d cs-attr)))
        (if (= cs.d 1)
            (if p3? 2 4)
          (if p3? 4 2)))))
     (base-bits (case operand-size
                  (8 64)
                  (4 32)
                  (t 24)))
     (gdtr-limit
          (!gdtr/idtrbits->limit (part-select mem :low 0 :width 16)
                                 0))
     (gdtr (!gdtr/idtrbits->base-addr (part-select mem
                                                   :low 16
                                                   :width base-bits)
                                      gdtr-limit))
     (x86 (!stri *gdtr* gdtr x86))
     (x86 (write-*ip proc-mode temp-rip x86)))
    x86))))

Theorem: x86p-of-x86-lgdt

(defthm x86p-of-x86-lgdt
  (implies (x86p x86)
           (b* ((x86 (x86-lgdt proc-mode start-rip temp-rip prefixes
                               rex-byte opcode modr/m sib x86)))
             (x86p x86)))
  :rule-classes :rewrite)