Commit 5c73b757 authored by Matthew Ogilvie's avatar Matthew Ogilvie Committed by malc
Browse files

target-i386/translate.c: mov to/from crN/drN: ignore mod bits



> This instruction is always treated as a register-to-register (MOD = 11)
> instruction, regardless of the encoding of the MOD field in the MODR/M
> byte.

Also, Microport UNIX System V/386 v 2.1 (ca 1987) runs fine on
real Intel 386 and 486 CPU's (at least), but does not run in qemu without
this patch.
Signed-off-by: default avatarMatthew Ogilvie <mmogilvi_qemu@miniinfo.net>
Signed-off-by: default avatarmalc <av1474@comtv.ru>
parent 145c7c88
......@@ -7551,8 +7551,11 @@ static target_ulong disas_insn(DisasContext *s, target_ulong pc_start)
gen_exception(s, EXCP0D_GPF, pc_start - s->cs_base);
} else {
modrm = cpu_ldub_code(cpu_single_env, s->pc++);
if ((modrm & 0xc0) != 0xc0)
goto illegal_op;
/* Ignore the mod bits (assume (modrm&0xc0)==0xc0).
* AMD documentation (24594.pdf) and testing of
* intel 386 and 486 processors all show that the mod bits
* are assumed to be 1's, regardless of actual values.
*/
rm = (modrm & 7) | REX_B(s);
reg = ((modrm >> 3) & 7) | rex_r;
if (CODE64(s))
......@@ -7594,8 +7597,11 @@ static target_ulong disas_insn(DisasContext *s, target_ulong pc_start)
gen_exception(s, EXCP0D_GPF, pc_start - s->cs_base);
} else {
modrm = cpu_ldub_code(cpu_single_env, s->pc++);
if ((modrm & 0xc0) != 0xc0)
goto illegal_op;
/* Ignore the mod bits (assume (modrm&0xc0)==0xc0).
* AMD documentation (24594.pdf) and testing of
* intel 386 and 486 processors all show that the mod bits
* are assumed to be 1's, regardless of actual values.
*/
rm = (modrm & 7) | REX_B(s);
reg = ((modrm >> 3) & 7) | rex_r;
if (CODE64(s))
......
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