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aquasecurity / libbpfgo

eBPF library for Go. Powered by libbpf.

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BPFMap.GetValue(): panic: runtime error: cgo argument has Go pointer to Go pointer

Songrui625 opened this issue · comments

commented 
...
connStatsMap, err := bpfModule.GetMap("conn_stats")
if err != nil {
    log.Fatal(err)
}

iter := connStatsMap.Iterator()
for iter.Next() {
    keyBytes := iter.Key()
    valBytes, err := connStatsMap.GetValue(unsafe.Pointer(&keyBytes))
    if err != nil {
        log.Fatal(err)
    }
    ...
}

After go build and I got results:

panic: runtime error: cgo argument has Go pointer to Go pointer

goroutine 1 [running]:
github.com/aquasecurity/libbpfgo.(*BPFMap).GetValue.func1(0x10000c000108030, 0x7f974c5e8328, 0x8)
	/home/songrui.771/go/pkg/mod/github.com/aquasecurity/libbpfgo@v0.4.0-libbpf-1.0.0/libbpfgo.go:717 +0x39
github.com/aquasecurity/libbpfgo.(*BPFMap).GetValue(0xc000090000, 0xc00000e048)
	/home/songrui.771/go/pkg/mod/github.com/aquasecurity/libbpfgo@v0.4.0-libbpf-1.0.0/libbpfgo.go:717 +0x70
main.main()
	/home/songrui.771/codespace/demo/go/libbpfgo-demo/main.go:87 +0x630
commented

Hi @Songrui625. It would be nice to know what you are trying to achieve. Could you also provide the whole code generating such an error?

In the meantime, you can take a look at these Iterator() examples:

commented

Hi @Songrui625 . It would be nice to know what you are trying to achieve. Could you also provide the whole code generating such an error?

In the meantime, you can take a look at these Iterator() examples:

Hi @geyslan , I am trying to iterate all elements of the bpf hash map conn_stats which key and value is an object of struct in c. The bpf program will be hooked to kprobe and update the bpf hash map conn_stats dynamically. So I deserialize the bytes to the struct I want and print it.

commented

Hi @Songrui625 . It would be nice to know what you are trying to achieve. Could you also provide the whole code generating such an error?
In the meantime, you can take a look at these Iterator() examples:

Hi @geyslan , I am trying to iterate all elements of the bpf hash map conn_stats which key and value is an object of struct in c. The bpf program will be hooked to kprobe and update the bpf hash map conn_stats dynamically. So I deserialize the bytes to the struct I want and print it.

I didn't look at the comment of GetValue() closely. I solved it by changing &keyBytes to &keyBytes[0].
Thanks @geyslan