From 64f3dae485bf96dee436b93300a49209fa8fef3e Mon Sep 17 00:00:00 2001
From: Achilleas Anagnostopoulos <achilleas.imap.mbox@gmail.com>
Date: Wed, 11 Oct 2017 19:58:00 +0100
Subject: [PATCH] acpi: define VM type and structs to maintain execution state

---
 src/gopheros/device/acpi/aml/vm.go      | 119 ++++++++++++++++++++++++
 src/gopheros/device/acpi/aml/vm_test.go |  33 +++++++
 2 files changed, 152 insertions(+)
 create mode 100644 src/gopheros/device/acpi/aml/vm.go
 create mode 100644 src/gopheros/device/acpi/aml/vm_test.go

diff --git a/src/gopheros/device/acpi/aml/vm.go b/src/gopheros/device/acpi/aml/vm.go
new file mode 100644
index 0000000..3d482d4
--- /dev/null
+++ b/src/gopheros/device/acpi/aml/vm.go
@@ -0,0 +1,119 @@
+package aml
+
+import (
+	"gopheros/device/acpi/table"
+	"io"
+)
+
+const (
+	// According to the ACPI spec, methods can use up to 8 local args and
+	// can receive up to 7 method args.
+	maxLocalArgs  = 8
+	maxMethodArgs = 7
+)
+
+// ctrlFlowType describes the different ways that the control flow can be altered
+// while executing a set of AML opcodes.
+type ctrlFlowType uint8
+
+// The list of supported control flows.
+const (
+	ctrlFlowTypeNextOpcode ctrlFlowType = iota
+	ctrlFlowTypeBreak
+	ctrlFlowTypeContinue
+	ctrlFlowTypeFnReturn
+)
+
+// execContext encapsulates
+type execContext struct {
+	localArg  [maxLocalArgs]interface{}
+	methodArg [maxMethodArgs]interface{}
+
+	// ctrlFlow specifies how the VM should select the next instruction to
+	// execute.
+	ctrlFlow ctrlFlowType
+
+	// retVal holds the return value from a method if ctrlFlow is set to
+	// the value ctrlFlowTypeFnReturn.
+	retVal interface{}
+
+	vm *VM
+}
+
+// Error describes errors that occur while executing AML code.
+type Error struct {
+	message string
+}
+
+// Error implements the error interface.
+func (e *Error) Error() string {
+	return e.message
+}
+
+// VM is a structure that stores the output of the AML bytecode parser and
+// provides methods for interpreting any executable opcode.
+type VM struct {
+	errWriter io.Writer
+
+	tableResolver table.Resolver
+	tableParser   *Parser
+
+	// rootNS holds a pointer to the root of the ACPI tree.
+	rootNS ScopeEntity
+
+	// According to the ACPI spec, the Revision field in the DSDT specifies
+	// whether integers are treated as 32 or 64-bits. The VM memoizes this
+	// value so that it can be used by the data conversion helpers.
+	sizeOfIntInBits int
+}
+
+// NewVM creates a new AML VM and initializes it with the default scope
+// hierarchy and pre-defined objects contained in the ACPI specification.
+func NewVM(errWriter io.Writer, resolver table.Resolver) *VM {
+	root := defaultACPIScopes()
+
+	return &VM{
+		rootNS:        root,
+		errWriter:     errWriter,
+		tableResolver: resolver,
+		tableParser:   NewParser(errWriter, root),
+	}
+}
+
+// Init attempts to locate and parse the AML byte-code contained in the
+// system's DSDT and SSDT tables.
+func (vm *VM) Init() *Error {
+	for tableHandle, tableName := range []string{"DSDT", "SSDT"} {
+		header := vm.tableResolver.LookupTable(tableName)
+		if header == nil {
+			continue
+		}
+
+		if err := vm.tableParser.ParseAML(uint8(tableHandle+1), tableName, header); err != nil {
+			return &Error{message: err.Module + ": " + err.Error()}
+		}
+
+		if tableName == "DSDT" {
+			vm.sizeOfIntInBits = 32
+			if header.Revision >= 2 {
+				vm.sizeOfIntInBits = 64
+			}
+		}
+	}
+
+	return nil
+}
+
+// defaultACPIScopes constructs a tree of scoped entities that correspond to
+// the predefined scopes contained in the ACPI specification and returns back
+// its root node.
+func defaultACPIScopes() ScopeEntity {
+	rootNS := &scopeEntity{op: opScope, name: `\`}
+	rootNS.Append(&scopeEntity{op: opScope, name: `_GPE`}) // General events in GPE register block
+	rootNS.Append(&scopeEntity{op: opScope, name: `_PR_`}) // ACPI 1.0 processor namespace
+	rootNS.Append(&scopeEntity{op: opScope, name: `_SB_`}) // System bus with all device objects
+	rootNS.Append(&scopeEntity{op: opScope, name: `_SI_`}) // System indicators
+	rootNS.Append(&scopeEntity{op: opScope, name: `_TZ_`}) // ACPI 1.0 thermal zone namespace
+
+	return rootNS
+}
diff --git a/src/gopheros/device/acpi/aml/vm_test.go b/src/gopheros/device/acpi/aml/vm_test.go
new file mode 100644
index 0000000..d71db1b
--- /dev/null
+++ b/src/gopheros/device/acpi/aml/vm_test.go
@@ -0,0 +1,33 @@
+package aml
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestVMInit(t *testing.T) {
+	t.Run("success", func(t *testing.T) {
+		resolver := &mockResolver{
+			tableFiles: []string{"DSDT.aml"},
+		}
+
+		vm := NewVM(os.Stderr, resolver)
+		if err := vm.Init(); err != nil {
+			t.Fatal(err)
+		}
+	})
+
+	t.Run("parse error", func(t *testing.T) {
+		resolver := &fixedPayloadResolver{
+			// invalid payload (incomplete opcode)
+			payload: []byte{extOpPrefix},
+		}
+
+		expErr := &Error{message: errParsingAML.Module + ": " + errParsingAML.Error()}
+		vm := NewVM(os.Stderr, resolver)
+		if err := vm.Init(); !reflect.DeepEqual(err, expErr) {
+			t.Fatalf("expected Init() to return errParsingAML; got %v", err)
+		}
+	})
+}