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SynchronizeMappings like v8 does, or using JITDump
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| // Copyright The OpenTelemetry Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
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| package beam // import "go.opentelemetry.io/ebpf-profiler/interpreter/beam" | ||
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| // Minimal JITDUMP file reader for BEAM | ||
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| // This has the minimal code we need to read the JITDUMP files that the BEAM | ||
| // writes to `/tmp/jit-<pid>.dump`. It isn't BEAM-specific, so it could probably | ||
| // be used more generally. The spec for this file format is at: | ||
| // https://raw.githubusercontent.com/torvalds/linux/refs/heads/master/tools/perf/Documentation/jitdump-specification.txt | ||
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| import ( | ||
| "encoding/binary" | ||
| "fmt" | ||
| "io" | ||
| ) | ||
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| type JITDumpHeader struct { | ||
| Magic uint32 // the ASCII string "JiTD", written is as 0x4A695444. The reader will detect an endian mismatch when it reads 0x4454694a | ||
| Version uint32 // a 4-byte value representing the format version. It is currently set to 1 | ||
| TotalSize uint32 // size in bytes of file header | ||
| ELFMach uint32 // ELF architecture encoding (ELF e_machine value as specified in /usr/include/elf.h) | ||
| Pad1 uint32 // padding. Reserved for future use | ||
| Pid uint32 // JIT runtime process identification (OS specific) | ||
| Timestamp uint64 // timestamp of when the file was created | ||
| Flags uint64 // a bitmask of flags | ||
| } | ||
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| type JITDumpRecordHeader struct { | ||
| ID uint32 // a value identifying the record type (e.g. beam.JITCodeLoad) | ||
| TotalSize uint32 // the size in bytes of the record including this header | ||
| Timestamp uint64 // a timestamp of when the record was created | ||
| } | ||
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| const ( | ||
| JITCodeLoad = 0 // record describing a jitted function | ||
| JITCodeMove = 1 // record describing an already jitted function which is moved | ||
| JITCodeDebugInfo = 2 // record describing the debug information for a jitted function | ||
| JITCodeClose = 3 // record marking the end of the jit runtime (optional) | ||
| JITCodeUnwindingInfo = 4 // record describing a function unwinding information | ||
| ) | ||
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| type JITDumpRecordCodeLoad struct { | ||
| PID uint32 // OS process id of the runtime generating the jitted code | ||
| TID uint32 // OS thread identification of the runtime thread generating the jitted code | ||
| VMA uint64 // virtual address of jitted code start | ||
| CodeAddr uint64 // code start address for the jitted code. By default vma = code_addr | ||
| CodeSize uint64 // size in bytes of the generated jitted code | ||
| CodeIndex uint64 // unique identifier for the jitted code | ||
| } | ||
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| func ReadJITDumpHeader(file io.ReadSeeker) (*JITDumpHeader, error) { | ||
| header := JITDumpHeader{} | ||
| err := binary.Read(file, binary.LittleEndian, &header) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
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| if header.Magic != 0x4A695444 { | ||
| return nil, fmt.Errorf("File malformed, or maybe wrong endianness. Found magic number: %x", header.Magic) | ||
| } | ||
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| return &header, nil | ||
| } | ||
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| func ReadJITDumpRecordHeader(file io.ReadSeeker) (*JITDumpRecordHeader, error) { | ||
| header := JITDumpRecordHeader{} | ||
| err := binary.Read(file, binary.LittleEndian, &header) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &header, nil | ||
| } | ||
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| func ReadJITDumpRecordCodeLoad(file io.ReadSeeker, header *JITDumpRecordHeader) (*JITDumpRecordCodeLoad, string, error) { | ||
| record := JITDumpRecordCodeLoad{} | ||
| err := binary.Read(file, binary.LittleEndian, &record) | ||
| if err != nil { | ||
| return nil, "", err | ||
| } | ||
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| recordHeaderSize := uint32(16) | ||
| codeLoadRecordHeaderSize := uint32(40) | ||
| nameSize := header.TotalSize - uint32(record.CodeSize) - recordHeaderSize - codeLoadRecordHeaderSize | ||
| name := make([]byte, nameSize) | ||
| err = binary.Read(file, binary.LittleEndian, &name) | ||
| if err != nil { | ||
| return nil, "", err | ||
| } | ||
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| if name[nameSize-1] != '\x00' { | ||
| return nil, "", fmt.Errorf("Expected null terminated string, found %c", name[nameSize-1]) | ||
| } | ||
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| // Skip over the actual native code because we don't need it but we | ||
| // probably do want to read the next record. | ||
| _, err = file.Seek(int64(record.CodeSize), io.SeekCurrent) | ||
| if err != nil { | ||
| return nil, "", err | ||
| } | ||
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| return &record, string(name), nil | ||
| } | ||
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| func SkipJITDumpRecord(file io.ReadSeeker, header *JITDumpRecordHeader) error { | ||
| recordHeaderSize := uint64(16) | ||
| _, err := file.Seek(int64(header.TotalSize)-int64(recordHeaderSize), io.SeekCurrent) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| return nil | ||
| } | ||