selftest: add selftest for AttachKprobeOffset

selftest/tracing-by-offset/Makefile

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

selftest/tracing-by-offset/go.mod

@@ -0,0 +1,14 @@
+module github.com/aquasecurity/libbpfgo/selftest/tracing-by-offset
+
+go 1.18
+
+require (
+	github.com/aquasecurity/libbpfgo v0.4.7-libbpf-1.2.0-b2e29a1
+	github.com/aquasecurity/libbpfgo/helpers v0.4.5
+)
+
+require golang.org/x/sys v0.7.0 // indirect
+
+replace github.com/aquasecurity/libbpfgo => ../../
+
+replace github.com/aquasecurity/libbpfgo/helpers => ../../helpers

selftest/tracing-by-offset/go.sum

@@ -0,0 +1,6 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
+golang.org/x/sys v0.7.0 h1:3jlCCIQZPdOYu1h8BkNvLz8Kgwtae2cagcG/VamtZRU=
+golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

selftest/tracing-by-offset/main.bpf.c

@@ -0,0 +1,14 @@
+//+build ignore
+
+#include <vmlinux.h>
+
+#include <bpf/bpf_helpers.h>
+
+SEC("kprobe/sys_mmap")
+int kprobe__sys_mmap(struct pt_regs *ctx)
+{
+    bpf_printk("Hello, World!\n");
+    return 0;
+}
+
+char LICENSE[] SEC("license") = "Dual BSD/GPL";

selftest/tracing-by-offset/main.go

@@ -0,0 +1,70 @@
+package main
+
+import "C"
+
+import (
+	"os"
+	"runtime"
+	"time"
+
+	"fmt"
+	"syscall"
+
+	bpf "github.com/aquasecurity/libbpfgo"
+	"github.com/aquasecurity/libbpfgo/helpers"
+)
+
+func main() {
+	funcName := fmt.Sprintf("__%s_sys_mmap", ksymArch())
+
+	kst, err := helpers.NewKernelSymbolTable()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "NewKernelSymbolTable() failed: %v", err)
+		os.Exit(-1)
+	}
+
+	funcSymbol, err := kst.GetSymbolByName(funcName)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Expected to find symbol %s, but it was not found", funcSymbol)
+		os.Exit(-1)
+	}
+
+	bpfModule, err := bpf.NewModuleFromFile("main.bpf.o")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(-1)
+	}
+	defer bpfModule.Close()
+
+	bpfModule.BPFLoadObject()
+	prog, err := bpfModule.GetProgram("kprobe__sys_mmap")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(-1)
+	}
+
+	_, err = prog.AttachKprobeOffset(funcSymbol[0].Address)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(-1)
+	}
+
+	go func() {
+		time.Sleep(time.Second)
+		syscall.Mmap(999, 999, 999, 1, 1)
+		syscall.Mmap(999, 999, 999, 1, 1)
+	}()
+
+	time.Sleep(time.Second * 2)
+}
+
+func ksymArch() string {
+	switch runtime.GOARCH {
+	case "amd64":
+		return "x64"
+	case "arm64":
+		return "arm64"
+	default:
+		panic("unsupported architecture")
+	}
+}

selftest/tracing-by-offset/run.sh

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

selftest/tracing/main.go

@@ -42,7 +42,7 @@ func main() {
 		os.Exit(-1)
 	}
 
-	if sym[0].Address == 0 || sym[0].Name == "" {
+	if sym[0].Address == 0 && sym[0].Name == "" {
 		fmt.Fprintln(os.Stderr, "could not find symbol to attach to")
 		os.Exit(-1)
 	}