Add iterator for bpf programs/maps in a bpf object (#166)

* Helper for getting section name

Signed-off-by: grantseltzer <grantseltzer@gmail.com>

* Add ProgramIterator for iterating over programs in a BPF object, and a
selftest

Signed-off-by: grantseltzer <grantseltzer@gmail.com>

* Add map iteration

Signed-off-by: grantseltzer <grantseltzer@gmail.com>

libbpfgo.go

@@ -897,6 +897,66 @@ func (b *BPFMap) Update(key, value unsafe.Pointer) error {
 	return nil
 }
 
+// BPFObjectProgramIterator iterates over maps in a BPF object
+type BPFObjectIterator struct {
+	m        *Module
+	prevProg *BPFProg
+	prevMap  *BPFMap
+}
+
+func (m *Module) Iterator() *BPFObjectIterator {
+	return &BPFObjectIterator{
+		m:        m,
+		prevProg: nil,
+		prevMap:  nil,
+	}
+}
+
+func (it *BPFObjectIterator) NextMap() *BPFMap {
+	var startMap *C.struct_bpf_map
+	if it.prevMap != nil && it.prevMap.bpfMap != nil {
+		startMap = it.prevMap.bpfMap
+	}
+
+	m := C.bpf_object__next_map(it.m.obj, startMap)
+	if m == nil {
+		return nil
+	}
+	cName := C.bpf_map__name(m)
+
+	bpfMap := &BPFMap{
+		name:   C.GoString(cName),
+		bpfMap: m,
+		module: it.m,
+	}
+
+	it.prevMap = bpfMap
+	return bpfMap
+}
+
+func (it *BPFObjectIterator) NextProgram() *BPFProg {
+
+	var startProg *C.struct_bpf_program
+	if it.prevProg != nil && it.prevProg.prog != nil {
+		startProg = it.prevProg.prog
+	}
+
+	p := C.bpf_object__next_program(it.m.obj, startProg)
+	if p == nil {
+		return nil
+	}
+	cName := C.bpf_program__name(p)
+
+	prog := &BPFProg{
+		name:   C.GoString(cName),
+		prog:   p,
+		module: it.m,
+	}
+	it.prevProg = prog
+	return prog
+}
+
+// BPFMapIterator iterates over keys in a BPF map
 type BPFMapIterator struct {
 	b    *BPFMap
 	err  error

selftest/object-iterator/Makefile

@@ -0,0 +1 @@
+../common/Makefile

selftest/object-iterator/go.mod

@@ -0,0 +1,7 @@
+module github.com/aquasecurity/libbpfgo/selftest/perfbuffers
+
+go 1.16
+
+require github.com/aquasecurity/libbpfgo v0.2.1-libbpf-0.4.0
+
+replace github.com/aquasecurity/libbpfgo => ../../

selftest/object-iterator/go.sum

@@ -0,0 +1,11 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/sys v0.0.0-20210514084401-e8d321eab015/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

selftest/object-iterator/main.bpf.c

@@ -0,0 +1,43 @@
+//+build ignore
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#ifdef asm_inline
+#undef asm_inline
+#define asm_inline asm
+#endif
+
+struct {
+    __uint(type, BPF_MAP_TYPE_HASH);
+    __type(key, u32);
+    __type(value, u32);
+    __uint(max_entries, 1);
+} one SEC(".maps");
+
+struct {
+    __uint(type, BPF_MAP_TYPE_ARRAY);
+    __uint(key_size, sizeof(u32));
+    __uint(value_size, sizeof(u32));
+    __uint(max_entries, 1);
+} two SEC(".maps");
+
+SEC("fentry/__x64_sys_mmap")
+int mmap_fentry(struct pt_regs *ctx)
+{
+    return 0;
+}
+
+SEC("fentry/__x64_sys_execve")
+int execve_fentry(struct pt_regs *ctx)
+{
+    return 0;
+}
+
+SEC("fentry/__x64_sys_execveat")
+int execveat_fentry(struct pt_regs *ctx)
+{
+    return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";

selftest/object-iterator/main.go

@@ -0,0 +1,76 @@
+package main
+
+import "C"
+
+import (
+	"os"
+
+	"fmt"
+
+	bpf "github.com/aquasecurity/libbpfgo"
+)
+
+func main() {
+
+	bpfModule, err := bpf.NewModuleFromFile("main.bpf.o")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(-1)
+	}
+	defer bpfModule.Close()
+
+	err = bpfModule.BPFLoadObject()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(-1)
+	}
+
+	iterator := bpfModule.Iterator()
+
+	// Iterate over programs
+	expectedProgramNames := map[string]bool{
+		"mmap_fentry":     false,
+		"execve_fentry":   false,
+		"execveat_fentry": false,
+	}
+
+	currentProg := iterator.NextProgram()
+	for currentProg != nil {
+		expectedProgramNames[currentProg.GetName()] = true
+		currentProg = iterator.NextProgram()
+	}
+
+	if len(expectedProgramNames) != 3 {
+		fmt.Fprintln(os.Stderr, "did not iterate over expected programs")
+		os.Exit(-1)
+	}
+	for k, v := range expectedProgramNames {
+		if v == false {
+			fmt.Fprintf(os.Stderr, "did not iterate over expected program: %s", k)
+			os.Exit(-1)
+		}
+	}
+
+	// Iterate over maps
+	expectedMapNames := map[string]bool{
+		"one": false,
+		"two": false,
+	}
+
+	currentMap := iterator.NextMap()
+	for currentMap != nil {
+		expectedMapNames[currentMap.GetName()] = true
+		currentMap = iterator.NextMap()
+	}
+
+	if len(expectedMapNames) != 2 {
+		fmt.Fprintln(os.Stderr, "did not iterate over expected maps")
+		os.Exit(-1)
+	}
+	for k, v := range expectedMapNames {
+		if v == false {
+			fmt.Fprintf(os.Stderr, "did not iterate over expected map: %s", k)
+			os.Exit(-1)
+		}
+	}
+}

selftest/object-iterator/run.sh

@@ -0,0 +1 @@
+../common/run-5.8.sh