diff options
| author | Matthew Ogilvie <mmogilvi_qemu@miniinfo.net> | 2012-08-23 00:24:39 -0600 |
|---|---|---|
| committer | malc <av1474@comtv.ru> | 2012-08-24 07:44:37 +0400 |
| commit | 5c73b757e3aa80dc84352b2ede0d8bdea5419f6d (patch) | |
| tree | 2e539f550a62f8be5bdbe578662296f167ae2292 /target-i386/translate.c | |
| parent | 145c7c880ff520a9348cc2401ba291330b9606fe (diff) | |
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: Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>
Signed-off-by: malc <av1474@comtv.ru>
Diffstat (limited to 'target-i386/translate.c')
| -rw-r--r-- | target-i386/translate.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/target-i386/translate.c b/target-i386/translate.c index 7ab2ccb190..eb0cabcf19 100644 --- a/target-i386/translate.c +++ b/target-i386/translate.c @@ -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)) |