symbol API implementation for interacting with static/global vars [test missing]

Signed-off-by: Simone Magnani <[email protected]>

Author: smagnani96

cmd/bpf2go/gen/output.go

@@ -49,6 +49,10 @@ func (n templateName) MapSpecs() string {
 	return string(n) + "MapSpecs"
 }
 
+func (n templateName) VariableSpecs() string {
+	return string(n) + "VariableSpecs"
+}
+
 func (n templateName) Load() string {
 	return n.maybeExport("load" + toUpperFirst(string(n)))
 }
@@ -65,6 +69,10 @@ func (n templateName) Maps() string {
 	return string(n) + "Maps"
 }
 
+func (n templateName) Variables() string {
+	return string(n) + "Variables"
+}
+
 func (n templateName) Programs() string {
 	return string(n) + "Programs"
 }
@@ -82,6 +90,8 @@ type GenerateArgs struct {
 	Constraints constraint.Expr
 	// Maps to be emitted.
 	Maps []string
+	// Variables to be emitted.
+	Variables []string
 	// Programs to be emitted.
 	Programs []string
 	// Types to be emitted.
@@ -116,6 +126,11 @@ func Generate(args GenerateArgs) error {
 		maps[name] = internal.Identifier(name)
 	}
 
+	vars := make(map[string]string)
+	for _, name := range args.Variables {
+		vars[name] = internal.Identifier(name)
+	}
+
 	programs := make(map[string]string)
 	for _, name := range args.Programs {
 		programs[name] = internal.Identifier(name)
@@ -146,6 +161,7 @@ func Generate(args GenerateArgs) error {
 		Constraints constraint.Expr
 		Name        templateName
 		Maps        map[string]string
+		Variables   map[string]string
 		Programs    map[string]string
 		Types       []btf.Type
 		TypeNames   map[btf.Type]string
@@ -157,6 +173,7 @@ func Generate(args GenerateArgs) error {
 		args.Constraints,
 		templateName(args.Stem),
 		maps,
+		vars,
 		programs,
 		types,
 		typeNames,

cmd/bpf2go/gen/output.tpl

@@ -54,6 +54,7 @@ func {{ .Name.LoadObjects }}(obj interface{}, opts *ebpf.CollectionOptions) (err
 type {{ .Name.Specs }} struct {
 	{{ .Name.ProgramSpecs }}
 	{{ .Name.MapSpecs }}
+	{{ .Name.VariableSpecs }}
 }
 
 // {{ .Name.Specs }} contains programs before they are loaded into the kernel.
@@ -80,12 +81,14 @@ type {{ .Name.MapSpecs }} struct {
 type {{ .Name.Objects }} struct {
 	{{ .Name.Programs }}
 	{{ .Name.Maps }}
+	{{ .Name.Variables }}
 }
 
 func (o *{{ .Name.Objects }}) Close() error {
 	return {{ .Name.CloseHelper }}(
 		&o.{{ .Name.Programs }},
 		&o.{{ .Name.Maps }},
+		&o.{{ .Name.Variables }},
 	)
 }
 
@@ -106,6 +109,32 @@ func (m *{{ .Name.Maps }}) Close() error {
 	)
 }
 
+// {{ .Name.VariableSpecs }} contains variables before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type {{ .Name.VariableSpecs }} struct {
+{{- range $name, $id := .Variables }}
+	{{ $id }} *ebpf.VariableSpec `ebpf:"{{ $name }}"`
+{{- end }}
+}
+
+// {{ .Name.Variables }} contains all variables after they have been loaded into the kernel.
+//
+// It can be passed to {{ .Name.LoadObjects }} or ebpf.CollectionSpec.LoadAndAssign.
+type {{ .Name.Variables }} struct {
+{{- range $name, $id := .Variables }}
+	{{ $id }} *ebpf.Variable `ebpf:"{{ $name }}"`
+{{- end }}
+}
+
+func (m *{{ .Name.Variables }}) Close() error {
+	return {{ .Name.CloseHelper }}(
+{{- range $id := .Variables }}
+		m.{{ $id }},
+{{- end }}
+	)
+}
+
 // {{ .Name.Programs }} contains all programs after they have been loaded into the kernel.
 //
 // It can be passed to {{ .Name.LoadObjects }} or ebpf.CollectionSpec.LoadAndAssign.

cmd/bpf2go/main.go

@@ -370,6 +370,11 @@ func (b2g *bpf2go) convert(tgt gen.Target, goarches gen.GoArches) (err error) {
 		}
 	}
 
+	var vars []string
+	for name := range spec.Variables {
+		vars = append(vars, name)
+	}
+
 	var programs []string
 	for name := range spec.Programs {
 		programs = append(programs, name)
@@ -397,6 +402,7 @@ func (b2g *bpf2go) convert(tgt gen.Target, goarches gen.GoArches) (err error) {
 		Stem:        b2g.identStem,
 		Constraints: constraints,
 		Maps:        maps,
+		Variables:   vars,
 		Programs:    programs,
 		Types:       types,
 		ObjectFile:  filepath.Base(objFileName),

collection.go

@@ -18,8 +18,9 @@ import (
 //
 // Maps and Programs are passed to NewMapWithOptions and NewProgramsWithOptions.
 type CollectionOptions struct {
-	Maps     MapOptions
-	Programs ProgramOptions
+	Maps      MapOptions
+	Variables VariableOptions
+	Programs  ProgramOptions
 
 	// MapReplacements takes a set of Maps that will be used instead of
 	// creating new ones when loading the CollectionSpec.
@@ -35,8 +36,9 @@ type CollectionOptions struct {
 
 // CollectionSpec describes a collection.
 type CollectionSpec struct {
-	Maps     map[string]*MapSpec
-	Programs map[string]*ProgramSpec
+	Maps      map[string]*MapSpec
+	Variables map[string]*VariableSpec
+	Programs  map[string]*ProgramSpec
 
 	// Types holds type information about Maps and Programs.
 	// Modifications to Types are currently undefined behaviour.
@@ -55,6 +57,7 @@ func (cs *CollectionSpec) Copy() *CollectionSpec {
 
 	cpy := CollectionSpec{
 		Maps:      make(map[string]*MapSpec, len(cs.Maps)),
+		Variables: make(map[string]*VariableSpec, len(cs.Variables)),
 		Programs:  make(map[string]*ProgramSpec, len(cs.Programs)),
 		ByteOrder: cs.ByteOrder,
 		Types:     cs.Types.Copy(),
@@ -64,6 +67,10 @@ func (cs *CollectionSpec) Copy() *CollectionSpec {
 		cpy.Maps[name] = spec.Copy()
 	}
 
+	for name, spec := range cs.Variables {
+		cpy.Variables[name] = spec.Copy()
+	}
+
 	for name, spec := range cs.Programs {
 		cpy.Programs[name] = spec.Copy()
 	}
@@ -285,6 +292,7 @@ func (cs *CollectionSpec) LoadAndAssign(to interface{}, opts *CollectionOptions)
 
 	// Support assigning Programs and Maps, lazy-loading the required objects.
 	assignedMaps := make(map[string]bool)
+	assignedVars := make(map[string]bool)
 	assignedProgs := make(map[string]bool)
 
 	getValue := func(typ reflect.Type, name string) (interface{}, error) {
@@ -298,6 +306,10 @@ func (cs *CollectionSpec) LoadAndAssign(to interface{}, opts *CollectionOptions)
 			assignedMaps[name] = true
 			return loader.loadMap(name)
 
+		case reflect.TypeOf((*Variable)(nil)):
+			assignedVars[name] = true
+			return loader.loadVariable(name)
+
 		default:
 			return nil, fmt.Errorf("unsupported type %s", typ)
 		}
@@ -335,18 +347,21 @@ func (cs *CollectionSpec) LoadAndAssign(to interface{}, opts *CollectionOptions)
 	for m := range assignedMaps {
 		delete(loader.maps, m)
 	}
+	for v := range assignedVars {
+		delete(loader.vars, v)
+	}
 	for p := range assignedProgs {
 		delete(loader.programs, p)
 	}
 
 	return nil
 }
 
-// Collection is a collection of Programs and Maps associated
-// with their symbols
+// Collection is a collection of Programs and Maps associated with their varaibles
 type Collection struct {
-	Programs map[string]*Program
-	Maps     map[string]*Map
+	Programs  map[string]*Program
+	Maps      map[string]*Map
+	Variables map[string]*Variable
 }
 
 // NewCollection creates a Collection from the given spec, creating and
@@ -376,6 +391,11 @@ func NewCollectionWithOptions(spec *CollectionSpec, opts CollectionOptions) (*Co
 			return nil, err
 		}
 	}
+	for varName := range spec.Variables {
+		if _, err := loader.loadVariable(varName); err != nil {
+			return nil, err
+		}
+	}
 
 	for progName, prog := range spec.Programs {
 		if prog.Type == UnspecifiedProgram {
@@ -393,20 +413,22 @@ func NewCollectionWithOptions(spec *CollectionSpec, opts CollectionOptions) (*Co
 		return nil, err
 	}
 
-	// Prevent loader.cleanup from closing maps and programs.
-	maps, progs := loader.maps, loader.programs
-	loader.maps, loader.programs = nil, nil
+	// Prevent loader.cleanup from closing maps, vars and programs.
+	maps, vars, progs := loader.maps, loader.vars, loader.programs
+	loader.maps, loader.vars, loader.programs = nil, nil, nil
 
 	return &Collection{
 		progs,
 		maps,
+		vars,
 	}, nil
 }
 
 type collectionLoader struct {
 	coll     *CollectionSpec
 	opts     *CollectionOptions
 	maps     map[string]*Map
+	vars     map[string]*Variable
 	programs map[string]*Program
 }
 
@@ -431,6 +453,7 @@ func newCollectionLoader(coll *CollectionSpec, opts *CollectionOptions) (*collec
 		coll,
 		opts,
 		make(map[string]*Map),
+		make(map[string]*Variable),
 		make(map[string]*Program),
 	}, nil
 }
@@ -445,6 +468,35 @@ func (cl *collectionLoader) close() {
 	}
 }
 
+func (cl *collectionLoader) loadVariable(varName string) (*Variable, error) {
+	if s := cl.vars[varName]; s != nil {
+		return s, nil
+	}
+
+	varSpec := cl.coll.Variables[varName]
+	if varSpec == nil {
+		return nil, fmt.Errorf("missing variable %s", varName)
+	}
+
+	m := cl.maps[varSpec.MapName]
+	if m == nil {
+		return nil, fmt.Errorf("map %s for variable %s not found", varSpec.MapName, varName)
+	}
+
+	mc, err := m.Clone()
+	if err != nil {
+		return nil, err
+	}
+
+	v, err := newVariableWithOptions(varSpec, mc, cl.opts.Variables)
+	if err != nil {
+		return nil, fmt.Errorf("variable %v: %w", varName, err)
+	}
+
+	cl.vars[varName] = v
+	return v, nil
+}
+
 func (cl *collectionLoader) loadMap(mapName string) (*Map, error) {
 	if m := cl.maps[mapName]; m != nil {
 		return m, nil
@@ -722,6 +774,7 @@ func LoadCollection(file string) (*Collection, error) {
 // for any successful assigns. On error `to` is left in an undefined state.
 func (coll *Collection) Assign(to interface{}) error {
 	assignedMaps := make(map[string]bool)
+	assignedVars := make(map[string]bool)
 	assignedProgs := make(map[string]bool)
 
 	// Assign() only transfers already-loaded Maps and Programs. No extra
@@ -743,6 +796,13 @@ func (coll *Collection) Assign(to interface{}) error {
 			}
 			return nil, fmt.Errorf("missing map %q", name)
 
+		case reflect.TypeOf((*Variable)(nil)):
+			if v := coll.Variables[name]; v != nil {
+				assignedVars[name] = true
+				return v, nil
+			}
+			return nil, fmt.Errorf("missing variable %q", name)
+
 		default:
 			return nil, fmt.Errorf("unsupported type %s", typ)
 		}
@@ -756,6 +816,9 @@ func (coll *Collection) Assign(to interface{}) error {
 	for p := range assignedProgs {
 		delete(coll.Programs, p)
 	}
+	for s := range assignedVars {
+		delete(coll.Variables, s)
+	}
 	for m := range assignedMaps {
 		delete(coll.Maps, m)
 	}

collection_test.go

@@ -66,6 +66,14 @@ func TestCollectionSpecCopy(t *testing.T) {
 				MaxEntries: 1,
 			},
 		},
+		map[string]*VariableSpec{
+			"test": {
+				Name:    "test",
+				MapName: ".rodata",
+				Offset:  0,
+				Size:    4,
+			},
+		},
 		map[string]*ProgramSpec{
 			"test": {
 				Type: SocketFilter,