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>

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index c3a8231..20b6044 100644 (file)
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -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;
 }

diff --git a/include/asm-x86/kvm_x86_emulate.h b/include/asm-x86/kvm_x86_emulate.h
index b877bbd..9fda4b3 100644 (file)
--- a/include/asm-x86/kvm_x86_emulate.h
+++ b/include/asm-x86/kvm_x86_emulate.h
@@ -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;