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Subject[PATCH v2] KVM: emulator: Use linearize() when fetching instructions.
Date
Since segments need to be handled slightly differently when fetching
instructions, we add a __linearize helper that accepts a new 'fetch' boolean.

Signed-off-by: Nelson Elhage <nelhage@ksplice.com>
---
arch/x86/include/asm/kvm_emulate.h | 1 -
arch/x86/kvm/emulate.c | 26 ++++++++++++++++++--------
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 0818448..9b760c8 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 a5f63d4..427d78a 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 = {VCPU_SREG_CS, 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)
@@ -3154,7 +3165,6 @@ 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:
--
1.7.4.44.gf9e72


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