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KVM: x86 emulator: simplify rip relative decoding 

rip relative decoding is relative to the instruction pointer of the next
instruction; by moving address adjustment until after decoding is complete,
we remove the need to determine the instruction size.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity 2008-06-15 22:09:11 -07:00
parent 84411d85da
commit f5b4edcd52
2 changed files with 6 additions and 18 deletions
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23
arch/x86/kvm/x86_emulate.c
View File

@ -664,7 +664,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
{
struct decode_cache *c = &ctxt->decode;
u8 sib;
int index_reg = 0, base_reg = 0, scale, rip_relative = 0;
int index_reg = 0, base_reg = 0, scale;
int rc = 0;
if (c->rex_prefix) {
@ -754,7 +754,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
c->modrm_ea += c->regs[index_reg] << scale;
} else if ((c->modrm_rm & 7) == 5 && c->modrm_mod == 0) {
if (ctxt->mode == X86EMUL_MODE_PROT64)
rip_relative = 1;
c->rip_relative = 1;
} else
c->modrm_ea += c->regs[c->modrm_rm];
switch (c->modrm_mod) {
@ -770,22 +770,6 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
break;
}
}
if (rip_relative) {
c->modrm_ea += c->eip;
switch (c->d & SrcMask) {
case SrcImmByte:
c->modrm_ea += 1;
break;
case SrcImm:
if (c->d & ByteOp)
c->modrm_ea += 1;
else
if (c->op_bytes == 8)
c->modrm_ea += 4;
else
c->modrm_ea += c->op_bytes;
}
}
done:
return rc;
}
@ -1044,6 +1028,9 @@ done_prefixes:
break;
}
if (c->rip_relative)
c->modrm_ea += c->eip;
done:
return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
}

1
include/asm-x86/kvm_x86_emulate.h
View File

@ -134,6 +134,7 @@ struct decode_cache {
u8 modrm_reg;
u8 modrm_rm;
u8 use_modrm_ea;
bool rip_relative;
unsigned long modrm_ea;
void *modrm_ptr;
unsigned long modrm_val;