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• Top-level-memory

Rme16

Read an unsigned 16-bit value from memory via an effective address.

Signature

(rme16 proc-mode eff-addr seg-reg r-x check-alignment? x86) 
  → 
(mv flg value x86-new)

Arguments

check-alignment? — Guard (booleanp check-alignment?).

Returns

value — Type (unsigned-byte-p 16 value), given (x86p x86).

x86-new — Type (x86p x86-new), given (x86p x86).

The effective address eff-addr is translated to a canonical linear address using ea-to-la. If this translation is successful and no other errors (like alignment errors) occur, then rml16 is called.

Prior to the effective address translation, we check whether read access is allowed. The only case in which it is not allowed is when a read access is attempted on an execute-only code segment, in 32-bit mode. In 64-bit mode, the R bit of the code segment descriptor is ignored (see Atmel manual, Dec'17, Volume 2, Section 4.8.1).

Definitions and Theorems

Function: rme16$inline

(defun rme16$inline (proc-mode eff-addr
                               seg-reg r-x check-alignment? x86)
 (declare (xargs :stobjs (x86)))
 (declare (type (integer 0 4) proc-mode)
          (type (signed-byte 64) eff-addr)
          (type (integer 0 5) seg-reg)
          (type (member :r :x) r-x))
 (declare (xargs :guard (booleanp check-alignment?)))
 (b*
  (((when
     (and (/= proc-mode 0)
          (= seg-reg 1)
          (eq r-x :r)
          (b* ((attr (loghead 16 (seg-hidden-attri seg-reg x86)))
               (r (code-segment-descriptor-attributesbits->r attr)))
            (= r 0))))
    (mv (list :execute-only-code-segment eff-addr)
        0 x86))
   ((mv flg lin-addr)
    (ea-to-la proc-mode eff-addr seg-reg 2 x86))
   ((when flg) (mv flg 0 x86))
   ((unless (or (not check-alignment?)
                (address-aligned-p lin-addr 2 nil)))
    (mv (list :unaligned-linear-address lin-addr)
        0 x86)))
  (rml16 lin-addr r-x x86)))

Theorem: return-type-of-rme16.value

(defthm return-type-of-rme16.value
  (implies (x86p x86)
           (b* (((mv ?flg acl2::?value ?x86-new)
                 (rme16$inline proc-mode eff-addr
                               seg-reg r-x check-alignment? x86)))
             (unsigned-byte-p 16 value)))
  :rule-classes :rewrite)

Theorem: x86p-of-rme16.x86-new

(defthm x86p-of-rme16.x86-new
  (implies (x86p x86)
           (b* (((mv ?flg acl2::?value ?x86-new)
                 (rme16$inline proc-mode eff-addr
                               seg-reg r-x check-alignment? x86)))
             (x86p x86-new)))
  :rule-classes :rewrite)

Theorem: n16p-of-mv-nth-1-rme16

(defthm n16p-of-mv-nth-1-rme16
 (unsigned-byte-p 16
                  (mv-nth 1
                          (rme16 proc-mode eff-addr
                                 seg-reg r-x check-alignment? x86)))
 :rule-classes
 (:rewrite
  (:type-prescription
      :corollary
      (natp (mv-nth 1
                    (rme16 proc-mode eff-addr
                           seg-reg r-x check-alignment? x86)))
      :hints
      (("Goal" :in-theory '(unsigned-byte-p integer-range-p natp))))
  (:linear
   :corollary
   (and (<= 0
            (mv-nth 1
                    (rme16 proc-mode eff-addr
                           seg-reg r-x check-alignment? x86)))
        (< (mv-nth 1
                   (rme16 proc-mode eff-addr
                          seg-reg r-x check-alignment? x86))
           65536))
   :hints
   (("Goal"
        :in-theory '(unsigned-byte-p integer-range-p (:e expt)))))))

Theorem: rme16-value-when-error

(defthm rme16-value-when-error
  (implies (mv-nth 0
                   (rme16 proc-mode eff-addr
                          seg-reg r-x check-alignment? x86))
           (equal (mv-nth 1
                          (rme16 proc-mode eff-addr
                                 seg-reg r-x check-alignment? x86))
                  0)))

Theorem: rme16-does-not-affect-state-in-app-view

(defthm rme16-does-not-affect-state-in-app-view
  (implies (app-view x86)
           (equal (mv-nth 2
                          (rme16 proc-mode eff-addr
                                 seg-reg r-x check-alignment? x86))
                  x86)))

Theorem: xr-rme16-state-app-view

(defthm xr-rme16-state-app-view
  (implies
       (app-view x86)
       (equal (xr fld index
                  (mv-nth 2
                          (rme16 proc-mode eff-addr
                                 seg-reg r-x check-alignment? x86)))
              (xr fld index x86))))

Theorem: xr-rme16-state-sys-view

(defthm xr-rme16-state-sys-view
  (implies
       (and (not (equal fld :mem))
            (not (equal fld :fault))
            (not (equal fld :tlb)))
       (equal (xr fld index
                  (mv-nth 2
                          (rme16 proc-mode eff-addr
                                 seg-reg r-x check-alignment? x86)))
              (xr fld index x86))))

Theorem: rme16-xw-app-view

(defthm rme16-xw-app-view
 (implies
   (and (app-view x86)
        (not (equal fld :mem))
        (not (equal fld :app-view))
        (not (equal fld :seg-hidden-base))
        (not (equal fld :seg-hidden-limit))
        (not (equal fld :seg-hidden-attr))
        (not (equal fld :seg-visible))
        (not (equal fld :msr)))
   (and (equal (mv-nth 0
                       (rme16 proc-mode
                              eff-addr seg-reg r-x check-alignment?
                              (xw fld index value x86)))
               (mv-nth 0
                       (rme16 proc-mode eff-addr
                              seg-reg r-x check-alignment? x86)))
        (equal (mv-nth 1
                       (rme16 proc-mode
                              eff-addr seg-reg r-x check-alignment?
                              (xw fld index value x86)))
               (mv-nth 1
                       (rme16 proc-mode eff-addr
                              seg-reg r-x check-alignment? x86))))))

Theorem: rme16-xw-sys-view

(defthm rme16-xw-sys-view
 (implies
  (and (not (app-view x86))
       (not (equal fld :fault))
       (not (equal fld :seg-visible))
       (not (equal fld :seg-hidden-base))
       (not (equal fld :seg-hidden-limit))
       (not (equal fld :seg-hidden-attr))
       (not (equal fld :mem))
       (not (equal fld :ctr))
       (not (equal fld :msr))
       (not (equal fld :rflags))
       (not (equal fld :app-view))
       (not (equal fld :tlb))
       (not (equal fld :marking-view))
       (not (equal fld :implicit-supervisor-access))
       (member-equal fld *x86-field-names-as-keywords*))
  (and
   (equal (mv-nth 0
                  (rme16 proc-mode
                         eff-addr seg-reg r-x check-alignment?
                         (xw fld index value x86)))
          (mv-nth 0
                  (rme16 proc-mode eff-addr
                         seg-reg r-x check-alignment? x86)))
   (equal (mv-nth 1
                  (rme16 proc-mode
                         eff-addr seg-reg r-x check-alignment?
                         (xw fld index value x86)))
          (mv-nth 1
                  (rme16 proc-mode eff-addr
                         seg-reg r-x check-alignment? x86)))
   (equal (mv-nth 2
                  (rme16 proc-mode
                         eff-addr seg-reg r-x check-alignment?
                         (xw fld index value x86)))
          (xw fld index value
              (mv-nth 2
                      (rme16 proc-mode eff-addr
                             seg-reg r-x check-alignment? x86)))))))

Theorem: rme16-xw-sys-view-rflags-not-ac

(defthm rme16-xw-sys-view-rflags-not-ac
 (implies
  (and (not (app-view x86))
       (equal (rflagsbits->ac value)
              (rflagsbits->ac (rflags x86))))
  (and
   (equal (mv-nth 0
                  (rme16 proc-mode
                         eff-addr seg-reg r-x check-alignment?
                         (xw :rflags nil value x86)))
          (mv-nth 0
                  (rme16 proc-mode eff-addr
                         seg-reg r-x check-alignment? x86)))
   (equal (mv-nth 1
                  (rme16 proc-mode
                         eff-addr seg-reg r-x check-alignment?
                         (xw :rflags nil value x86)))
          (mv-nth 1
                  (rme16 proc-mode eff-addr
                         seg-reg r-x check-alignment? x86)))
   (equal (mv-nth 2
                  (rme16 proc-mode
                         eff-addr seg-reg r-x check-alignment?
                         (xw :rflags nil value x86)))
          (xw :rflags nil value
              (mv-nth 2
                      (rme16 proc-mode eff-addr
                             seg-reg r-x check-alignment? x86)))))))

Theorem: rme16-when-64-bit-modep-and-not-fs/gs

(defthm rme16-when-64-bit-modep-and-not-fs/gs
  (implies (and (not (equal seg-reg 4))
                (not (equal seg-reg 5))
                (canonical-address-p eff-addr)
                (or (not check-alignment?)
                    (address-aligned-p eff-addr 2 nil)))
           (equal (rme16 0 eff-addr
                         seg-reg r-x check-alignment? x86)
                  (rml16 eff-addr r-x x86))))

Theorem: rme16-unaligned-when-64-bit-modep-and-not-fs/gs

(defthm rme16-unaligned-when-64-bit-modep-and-not-fs/gs
  (implies (and (not (equal seg-reg 4))
                (not (equal seg-reg 5))
                (not (or (not check-alignment?)
                         (address-aligned-p eff-addr 2 nil)))
                (canonical-address-p eff-addr))
           (equal (rme16 0 eff-addr
                         seg-reg r-x check-alignment? x86)
                  (list (list :unaligned-linear-address eff-addr)
                        0 x86))))

Theorem: rme16-when-64-bit-modep-and-fs/gs

(defthm rme16-when-64-bit-modep-and-fs/gs
  (implies
       (or (equal seg-reg 4) (equal seg-reg 5))
       (equal (rme16 0 eff-addr
                     seg-reg r-x check-alignment? x86)
              (b* (((mv flg lin-addr)
                    (b* (((mv base & &)
                          (segment-base-and-bounds 0 seg-reg x86))
                         (lin-addr (i64 (+ base (n64 eff-addr)))))
                      (if (canonical-address-p lin-addr)
                          (mv nil lin-addr)
                        (mv (list :non-canonical-address lin-addr)
                            0))))
                   ((when flg) (mv flg 0 x86))
                   ((unless (or (not check-alignment?)
                                (address-aligned-p lin-addr 2 nil)))
                    (mv (list :unaligned-linear-address lin-addr)
                        0 x86)))
                (rml16 lin-addr r-x x86)))))