duskos

commit 34d5f6375a2a57d6cb5d55fff6fedf235122830c
parent df2a6f97cd432cbd79a6936abfd3c45691bf6c64
Author: Virgil Dupras <hsoft@hardcoded.net>
Date:   Fri, 22 Jul 2022 07:57:30 -0400

asm/i386: add ability to MOV to/from special (CR*, DR*, TR*) registers

Diffstat:
M
fs/asm/i386.fs
 | 
29
+++++++++++++++++++----------

1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/fs/asm/i386.fs b/fs/asm/i386.fs
@@ -12,7 +12,7 @@
 4 const SIB \ mod 0/1/2 + r/m 4 == SIB
 
 0 value op8b    \ is current op in 8bit mode?
-0 value opsreg  \ is current op an Sreg?
+0 value opsreg  \ if we have a "special" reg, this contains the override opcode.
 1 value opdirec \ 1: reg=tgt r/m=src  0: reg=src r/m=tgt
 3 value opmod   \ by default, we're in "direct reg" mode
 -1 value opreg  \ -1 = unset
@@ -33,6 +33,7 @@
 : is16bit? realmode ;
 \ in 16bit, abs mem = mod0 + rm 6, in 32-bit, it's rm 5
 : memoprm 5 is16bit? + ;
+: maybe8b ( opcode -- opcode ) op8b not or ;
 : dw, is16bit? if w, else , then ;
 : dwc, op8b if c, else dw, then ;
 
@@ -53,7 +54,7 @@
 
 \ "opcode" needs to habe bits 1 and 0 *unset*
 : op, ( opcode -- ) \ write "opcode", mixing it with opdirec and op8b
-  opdirec << or op8b not or dup $ff > if w, else c, then ;
+  opdirec << or dup 8 rshift $ff and ?dup if c, then c, ;
 
 : modrm, ( -- ) \ write down modrm, errors out if not all parts are there.
   opmod 3 lshift opreg or 3 lshift oprm or dup $100 < _assert c, ;
@@ -78,7 +79,7 @@
 
 : opimm, ( opcode opreg -- ) \ write the operation in "immediate" mode
   0 to opdirec \ TODO: allow sign-extend by making this logic variable
-  opreg! op, msd, imm, asm$ ;
+  opreg! maybe8b op, msd, imm, asm$ ;
 
 \ Setting arguments
 
@@ -111,9 +112,18 @@ AX _ ax   BX _ bx   CX _ cx   DX _ dx   SP _ sp   BP _ bp   SI _ si   DI _ di
 : _ doer ( reg -- ) c, does> c@ ( reg ) r! 1 to op8b ;
 AL _ al   BL _ bl   CL _ cl   DL _ dl   AH _ ah   BH _ bh   CH _ ch   DH _ dh
 
-: _ doer ( reg -- ) c, does> c@ ( reg ) opreg! 1 to opsreg ;
+: _ doer ( reg -- ) c, does> c@ ( reg ) opreg! $8c to opsreg ;
 ES _ es   SS _ ss   DS _ ds   FS _ fs   GS _ gs
 
+: _ doer ( reg -- ) c, does> c@ ( reg ) opreg! $0f20 to opsreg ;
+0 _ cr0   2 _ cr2   3 _ cr3
+
+: _ doer ( reg -- ) c, does> c@ ( reg ) opreg! $0f21 to opsreg ;
+0 _ dr0   1 _ dr1   2 _ dr2   3 _ dr3   6 _ dr6   7 _ dr7
+
+: _ doer ( reg -- ) c, does> c@ ( reg ) opreg! $0f24 to opsreg ;
+6 _ tr6   7 _ tr7
+
 : i) ( imm -- ) 1 to imm? to imm ;
 
 : 16breg>[oprm] ( reg ) case
@@ -163,7 +173,7 @@ $c3 op ret,        $fa op cli,         $fc op cld,
 
 \ Conditional jumps
 : op ( opcode -- ) doer , does> ( rel32-or-16 a -- ) @ op, rel, ;
-$840f op jz,        $850f op jnz,
+$0f84 op jz,        $0f85 op jnz,
 
 \ JMP and CALL
 \ These are special. They can either be called with a modrm tgt, or with *no
@@ -186,8 +196,8 @@ $04e9 op jmp,      $02e8 op call,
   dup 16 rshift opreg! $ffff and opmodrm, ;
 $0400f7 op mul,    $0300f7 op neg,     $0200f7 op not,
 $0100ff op dec,    $0000ff op inc,
-$009f0f op setg,   $009c0f op setl,    $00940f op setz,    $00950f op setnz,
-$02010f op lgdt,   $03010f op lidt,
+$000f9f op setg,   $000f9c op setl,    $000f94 op setz,    $000f95 op setnz,
+$020f01 op lgdt,   $030f01 op lidt,
 
 \ Two operands
 \ opcode format 00000000 ssssssss iiiiirrr mmmmmm00
@@ -198,7 +208,7 @@ $02010f op lgdt,   $03010f op lidt,
 : op ( opcode -- ) doer , does> @ ( opcode )
   imm? if
     8 rshift dup >> $fc and $80 or swap 7 and ( opcode opreg ) opimm,
-  else $ff and opmodrm, then ;
+  else $ff and maybe8b opmodrm, then ;
 $040000 op add,    $3c0738 op cmp,     $2c0528 op sub,     $a8f084 op _test,
 $240420 op and,    $0c0108 op or,      $340630 op xor,
 
@@ -231,8 +241,7 @@ $58 op pop,        $50 op _push,
       $b0 op8b not 3 lshift or ( b0 or b8 ) opreg or c, imm, asm$
     else $c7 c, 0 opreg! msd, imm, asm$ then
   else
-    opsreg if $8c opdirec << or c, msd, asm$ else
-    $88 opmodrm, then then ;
+    opsreg if opsreg else $88 maybe8b then opmodrm, then ;
 
 \ INT is special
 : int, ( n -- ) $cd c, c, ;