KVM: emulator: Use linearize() when fetching instructions

Since segments need to be handled slightly differently when fetching
instructions, we add a __linearize helper that accepts a new 'fetch' boolean.

[avi: fix oops caused by wrong segmented_address initialization order]

Signed-off-by: Nelson Elhage <nelhage@ksplice.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 18 insertions, 9 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 081844860a3d..9b760c8f2576 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -265,7 +265,6 @@ struct x86_emulate_ctxt {
         unsigned long eip; /* eip before instruction emulation */
         /* Emulated execution mode, represented by an X86EMUL_MODE value. */
         int mode;
-        u32 cs_base;
 
         /* interruptibility state, as a result of execution of STI or MOV SS */
         int interruptibility;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 4c5ff22d101a..e1f77de95404 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -540,9 +540,9 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt)
         return emulate_exception(ctxt, NM_VECTOR, 0, false);
 }
 
-static int linearize(struct x86_emulate_ctxt *ctxt,
+static int __linearize(struct x86_emulate_ctxt *ctxt,
                      struct segmented_address addr,
-                     unsigned size, bool write,
+                     unsigned size, bool write, bool fetch,
                      ulong *linear)
 {
         struct decode_cache *c = &ctxt->decode;
@@ -569,7 +569,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
                 if (((desc.type & 8) || !(desc.type & 2)) && write)
                         goto bad;
                 /* unreadable code segment */
-                if ((desc.type & 8) && !(desc.type & 2))
+                if (!fetch && (desc.type & 8) && !(desc.type & 2))
                         goto bad;
                 lim = desc_limit_scaled(&desc);
                 if ((desc.type & 8) || !(desc.type & 4)) {
@@ -602,7 +602,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
                 }
                 break;
         }
-        if (c->ad_bytes != 8)
+        if (fetch ? ctxt->mode != X86EMUL_MODE_PROT64 : c->ad_bytes != 8)
                 la &= (u32)-1;
         *linear = la;
         return X86EMUL_CONTINUE;
@@ -613,6 +613,15 @@ bad:
                 return emulate_gp(ctxt, addr.seg);
 }
 
+static int linearize(struct x86_emulate_ctxt *ctxt,
+                     struct segmented_address addr,
+                     unsigned size, bool write,
+                     ulong *linear)
+{
+        return __linearize(ctxt, addr, size, write, false, linear);
+}
+
+
 static int segmented_read_std(struct x86_emulate_ctxt *ctxt,
                               struct segmented_address addr,
                               void *data,
@@ -637,11 +646,13 @@ static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt,
         int size, cur_size;
 
         if (eip == fc->end) {
-                unsigned long linear = eip + ctxt->cs_base;
-                if (ctxt->mode != X86EMUL_MODE_PROT64)
-                        linear &= (u32)-1;
+                unsigned long linear;
+                struct segmented_address addr = { .seg=VCPU_SREG_CS, .ea=eip};
                 cur_size = fc->end - fc->start;
                 size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip));
+                rc = __linearize(ctxt, addr, size, false, true, &linear);
+                if (rc != X86EMUL_CONTINUE)
+                        return rc;
                 rc = ops->fetch(linear, fc->data + cur_size,
                                 size, ctxt->vcpu, &ctxt->exception);
                 if (rc != X86EMUL_CONTINUE)
@@ -3127,7 +3138,6 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
         c->fetch.end = c->fetch.start + insn_len;
         if (insn_len > 0)
                 memcpy(c->fetch.data, insn, insn_len);
-        ctxt->cs_base = seg_base(ctxt, ops, VCPU_SREG_CS);
 
         switch (mode) {
         case X86EMUL_MODE_REAL: