x86_emulate_insn() is too long and has many confusing goto statements.
This patch is the first part of a work which tries to split it into
a few meaningful functions: just encapsulates the switch statement for
the one byte instruction emulation as emulate_onebyte_insn().
Note that goto done with rc set to X86EMUL_UNHANDLEABLE will result in
returning EMULATION_FAILED which is defined as -1.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 179 +++++++++++++++++++++++++++---------------------
1 files changed, 100 insertions(+), 79 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index ad46239..18d7c07 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2945,88 +2945,14 @@ static bool string_insn_completed(struct x86_emulate_ctxt *ctxt)
return false;
}
-int
-x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
+static int emulate_onebyte_insn(struct x86_emulate_ctxt *ctxt,
+ struct x86_emulate_ops *ops,
+ struct decode_cache *c,
+ bool *need_writeback)
{
- struct x86_emulate_ops *ops = ctxt->ops;
- u64 msr_data;
- struct decode_cache *c = &ctxt->decode;
int rc = X86EMUL_CONTINUE;
- int saved_dst_type = c->dst.type;
int irq; /* Used for int 3, int, and into */
- ctxt->decode.mem_read.pos = 0;
-
- if (ctxt->mode == X86EMUL_MODE_PROT64 && (c->d & No64)) {
- rc = emulate_ud(ctxt);
- goto done;
- }
-
- /* LOCK prefix is allowed only with some instructions */
- if (c->lock_prefix && (!(c->d & Lock) || c->dst.type != OP_MEM)) {
- rc = emulate_ud(ctxt);
- goto done;
- }
-
- if ((c->d & SrcMask) == SrcMemFAddr && c->src.type != OP_MEM) {
- rc = emulate_ud(ctxt);
- goto done;
- }
-
- /* Privileged instruction can be executed only in CPL=0 */
- if ((c->d & Priv) && ops->cpl(ctxt->vcpu)) {
- rc = emulate_gp(ctxt, 0);
- goto done;
- }
-
- if (c->rep_prefix && (c->d & String)) {
- /* All REP prefixes have the same first termination condition */
- if (address_mask(c, c->regs[VCPU_REGS_RCX]) == 0) {
- ctxt->eip = c->eip;
- goto done;
- }
- }
-
- if ((c->src.type == OP_MEM) && !(c->d & NoAccess)) {
- rc = read_emulated(ctxt, ops, linear(ctxt, c->src.addr.mem),
- c->src.valptr, c->src.bytes);
- if (rc != X86EMUL_CONTINUE)
- goto done;
- c->src.orig_val64 = c->src.val64;
- }
-
- if (c->src2.type == OP_MEM) {
- rc = read_emulated(ctxt, ops, linear(ctxt, c->src2.addr.mem),
- &c->src2.val, c->src2.bytes);
- if (rc != X86EMUL_CONTINUE)
- goto done;
- }
-
- if ((c->d & DstMask) == ImplicitOps)
- goto special_insn;
-
-
- if ((c->dst.type == OP_MEM) && !(c->d & Mov)) {
- /* optimisation - avoid slow emulated read if Mov */
- rc = read_emulated(ctxt, ops, linear(ctxt, c->dst.addr.mem),
- &c->dst.val, c->dst.bytes);
- if (rc != X86EMUL_CONTINUE)
- goto done;
- }
- c->dst.orig_val = c->dst.val;
-
-special_insn:
-
- if (c->execute) {
- rc = c->execute(ctxt);
- if (rc != X86EMUL_CONTINUE)
- goto done;
- goto writeback;
- }
-
- if (c->twobyte)
- goto twobyte_insn;
-
switch (c->b) {
case 0x00 ... 0x05:
add: /* add */
@@ -3371,7 +3297,102 @@ special_insn:
goto cannot_emulate;
}
- if (rc != X86EMUL_CONTINUE)
+ *need_writeback = (rc == X86EMUL_CONTINUE);
+ return rc;
+
+done:
+ *need_writeback = false;
+ return rc;
+
+cannot_emulate:
+ *need_writeback = false;
+ return X86EMUL_UNHANDLEABLE;
+}
+
+int
+x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
+{
+ struct x86_emulate_ops *ops = ctxt->ops;
+ u64 msr_data;
+ struct decode_cache *c = &ctxt->decode;
+ int rc = X86EMUL_CONTINUE;
+ int saved_dst_type = c->dst.type;
+ bool need_writeback;
+
+ ctxt->decode.mem_read.pos = 0;
+
+ if (ctxt->mode == X86EMUL_MODE_PROT64 && (c->d & No64)) {
+ rc = emulate_ud(ctxt);
+ goto done;
+ }
+
+ /* LOCK prefix is allowed only with some instructions */
+ if (c->lock_prefix && (!(c->d & Lock) || c->dst.type != OP_MEM)) {
+ rc = emulate_ud(ctxt);
+ goto done;
+ }
+
+ if ((c->d & SrcMask) == SrcMemFAddr && c->src.type != OP_MEM) {
+ rc = emulate_ud(ctxt);
+ goto done;
+ }
+
+ /* Privileged instruction can be executed only in CPL=0 */
+ if ((c->d & Priv) && ops->cpl(ctxt->vcpu)) {
+ rc = emulate_gp(ctxt, 0);
+ goto done;
+ }
+
+ if (c->rep_prefix && (c->d & String)) {
+ /* All REP prefixes have the same first termination condition */
+ if (address_mask(c, c->regs[VCPU_REGS_RCX]) == 0) {
+ ctxt->eip = c->eip;
+ goto done;
+ }
+ }
+
+ if ((c->src.type == OP_MEM) && !(c->d & NoAccess)) {
+ rc = read_emulated(ctxt, ops, linear(ctxt, c->src.addr.mem),
+ c->src.valptr, c->src.bytes);
+ if (rc != X86EMUL_CONTINUE)
+ goto done;
+ c->src.orig_val64 = c->src.val64;
+ }
+
+ if (c->src2.type == OP_MEM) {
+ rc = read_emulated(ctxt, ops, linear(ctxt, c->src2.addr.mem),
+ &c->src2.val, c->src2.bytes);
+ if (rc != X86EMUL_CONTINUE)
+ goto done;
+ }
+
+ if ((c->d & DstMask) == ImplicitOps)
+ goto special_insn;
+
+
+ if ((c->dst.type == OP_MEM) && !(c->d & Mov)) {
+ /* optimisation - avoid slow emulated read if Mov */
+ rc = read_emulated(ctxt, ops, linear(ctxt, c->dst.addr.mem),
+ &c->dst.val, c->dst.bytes);
+ if (rc != X86EMUL_CONTINUE)
+ goto done;
+ }
+ c->dst.orig_val = c->dst.val;
+
+special_insn:
+
+ if (c->execute) {
+ rc = c->execute(ctxt);
+ if (rc != X86EMUL_CONTINUE)
+ goto done;
+ goto writeback;
+ }
+
+ if (c->twobyte)
+ goto twobyte_insn;
+
+ rc = emulate_onebyte_insn(ctxt, ops, c, &need_writeback);
+ if (!need_writeback)
goto done;
writeback:
--
1.7.1
--
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