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Merge pull request #7 from umanwizard/customlabels
Support native custom labels
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,130 @@ | ||
| package customlabels | ||
|
|
||
| // #include <stdlib.h> | ||
| // #include "../../support/ebpf/types.h" | ||
| import "C" | ||
| import ( | ||
| "debug/elf" | ||
| "errors" | ||
| "fmt" | ||
| "regexp" | ||
| "unsafe" | ||
|
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| "github.com/open-telemetry/opentelemetry-ebpf-profiler/interpreter" | ||
| "github.com/open-telemetry/opentelemetry-ebpf-profiler/libpf" | ||
| "github.com/open-telemetry/opentelemetry-ebpf-profiler/libpf/pfelf" | ||
| "github.com/open-telemetry/opentelemetry-ebpf-profiler/remotememory" | ||
| ) | ||
|
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| const ( | ||
| abiVersionExport = "custom_labels_abi_version" | ||
| tlsExport = "custom_labels_thread_local_data" | ||
| ) | ||
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| var dsoRegex = regexp.MustCompile(`.*/libcustomlabels.*\.so`) | ||
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| type data struct { | ||
| abiVersionElfVA libpf.Address | ||
| tlsAddr libpf.Address | ||
| isSharedLibrary bool | ||
| } | ||
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| var _ interpreter.Data = &data{} | ||
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| func Loader(_ interpreter.EbpfHandler, info *interpreter.LoaderInfo) (interpreter.Data, error) { | ||
| ef, err := info.GetELF() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| abiVersionSym, err := ef.LookupSymbol(abiVersionExport) | ||
| if err != nil { | ||
| if errors.Is(err, pfelf.ErrSymbolNotFound) { | ||
| return nil, nil | ||
| } | ||
|
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| return nil, err | ||
| } | ||
|
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| if abiVersionSym.Size != 4 { | ||
| return nil, fmt.Errorf("abi version export has wrong size %d", abiVersionSym.Size) | ||
| } | ||
|
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| // If this is the libcustomlabels.so library, we are using | ||
| // global-dynamic TLS model and have to look up the TLS descriptor. | ||
| // Otherwise, assume we're the main binary and just look up the | ||
| // symbol. | ||
| isSharedLibrary := dsoRegex.MatchString(info.FileName()) | ||
| var tlsAddr libpf.Address | ||
| if isSharedLibrary { | ||
| // Resolve thread info TLS export. | ||
| tlsDescs, err := ef.TLSDescriptors() | ||
| if err != nil { | ||
| return nil, errors.New("failed to extract TLS descriptors") | ||
| } | ||
| var ok bool | ||
| tlsAddr, ok = tlsDescs[tlsExport] | ||
| if !ok { | ||
| return nil, errors.New("failed to locate TLS descriptor for custom labels") | ||
| } | ||
| } else { | ||
| tlsSym, err := ef.LookupSymbol(tlsExport) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if ef.Machine == elf.EM_AARCH64 { | ||
| tlsAddr = libpf.Address(tlsSym.Address + 16) | ||
| } else if ef.Machine == elf.EM_X86_64 { | ||
| tbss, err := ef.Tbss() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| tlsAddr = libpf.Address(int64(tlsSym.Address) - int64(tbss.Size)) | ||
| } else { | ||
| return nil, fmt.Errorf("unrecognized machine: %s", ef.Machine.String()) | ||
| } | ||
| } | ||
|
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| d := data{ | ||
| abiVersionElfVA: libpf.Address(abiVersionSym.Address), | ||
| tlsAddr: tlsAddr, | ||
| isSharedLibrary: isSharedLibrary, | ||
| } | ||
| return &d, nil | ||
| } | ||
|
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| type instance struct { | ||
| interpreter.InstanceStubs | ||
| } | ||
|
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| func (d data) Attach(ebpf interpreter.EbpfHandler, pid libpf.PID, | ||
| bias libpf.Address, rm remotememory.RemoteMemory) (interpreter.Instance, error) { | ||
|
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| abiVersionPtr := rm.Ptr(bias + d.abiVersionElfVA) | ||
| abiVersion := rm.Uint32(abiVersionPtr) | ||
|
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| if abiVersion != 0 { | ||
| return nil, fmt.Errorf("unsupported custom labels ABI version: %d"+ | ||
| " (only 0 is supported)", abiVersion) | ||
| } | ||
|
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| var tlsOffset uint64 | ||
| if d.isSharedLibrary { | ||
| // Read TLS offset from the TLS descriptor | ||
| tlsOffset = rm.Uint64(bias + d.tlsAddr + 8) | ||
| } else { | ||
| // We're in the main executable: TLS offset is known statically. | ||
| tlsOffset = uint64(d.tlsAddr) | ||
| } | ||
|
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| procInfo := C.NativeCustomLabelsProcInfo{tls_offset: C.u64(tlsOffset)} | ||
| if err := ebpf.UpdateProcData(libpf.CustomLabels, pid, unsafe.Pointer(&procInfo)); err != nil { | ||
| return nil, err | ||
| } | ||
|
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| return &instance{}, nil | ||
| } | ||
|
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| func (i *instance) Detach(ebpf interpreter.EbpfHandler, pid libpf.PID) error { | ||
| return ebpf.DeleteProcData(libpf.CustomLabels, pid) | ||
| } |
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