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| 1 | +// SPDX-FileCopyrightText: Copyright The Lima Authors |
| 2 | +// SPDX-License-Identifier: Apache-2.0 |
| 3 | + |
| 4 | +package ticker |
| 5 | + |
| 6 | +import ( |
| 7 | + "strings" |
| 8 | + "time" |
| 9 | + |
| 10 | + "github.com/cilium/ebpf" |
| 11 | + "github.com/cilium/ebpf/asm" |
| 12 | + "github.com/cilium/ebpf/link" |
| 13 | + "github.com/cilium/ebpf/ringbuf" |
| 14 | + "github.com/sirupsen/logrus" |
| 15 | +) |
| 16 | + |
| 17 | +func NewEbpfTicker(tracepoints []string) (Ticker, error) { |
| 18 | + var ( |
| 19 | + ticker ebpfTicker |
| 20 | + err error |
| 21 | + ) |
| 22 | + ticker.events, err = ebpf.NewMap(&ebpf.MapSpec{ |
| 23 | + Name: "lima_ticker_events", |
| 24 | + Type: ebpf.RingBuf, |
| 25 | + MaxEntries: 1 << 20, |
| 26 | + }) |
| 27 | + if err != nil { |
| 28 | + ticker.Stop() |
| 29 | + return nil, err |
| 30 | + } |
| 31 | + |
| 32 | + ticker.prog, err = buildEbpfProg(ticker.events) |
| 33 | + if err != nil { |
| 34 | + ticker.Stop() |
| 35 | + return nil, err |
| 36 | + } |
| 37 | + |
| 38 | + for _, tp := range tracepoints { |
| 39 | + tpPair := strings.SplitN(tp, ":", 2) |
| 40 | + tpLink, err := link.Tracepoint(tpPair[0], tpPair[1], ticker.prog, nil) |
| 41 | + if err != nil { |
| 42 | + ticker.Stop() |
| 43 | + return nil, err |
| 44 | + } |
| 45 | + ticker.links = append(ticker.links, tpLink) |
| 46 | + } |
| 47 | + |
| 48 | + ticker.reader, err = ringbuf.NewReader(ticker.events) |
| 49 | + if err != nil { |
| 50 | + ticker.Stop() |
| 51 | + return nil, err |
| 52 | + } |
| 53 | + |
| 54 | + ticker.ch = make(chan time.Time) |
| 55 | + go func() { |
| 56 | + for { |
| 57 | + _, rdErr := ticker.reader.Read() |
| 58 | + if rdErr != nil { |
| 59 | + logrus.WithError(rdErr).Warn("ebpfTicker: failed to read ringbuf") |
| 60 | + ticker.Stop() |
| 61 | + return |
| 62 | + } |
| 63 | + ticker.ch <- time.Now() |
| 64 | + } |
| 65 | + }() |
| 66 | + |
| 67 | + return &ticker, nil |
| 68 | +} |
| 69 | + |
| 70 | +type ebpfTicker struct { |
| 71 | + events *ebpf.Map |
| 72 | + prog *ebpf.Program |
| 73 | + links []link.Link |
| 74 | + reader *ringbuf.Reader |
| 75 | + ch chan time.Time |
| 76 | +} |
| 77 | + |
| 78 | +func (ticker *ebpfTicker) Chan() <-chan time.Time { |
| 79 | + return ticker.ch |
| 80 | +} |
| 81 | + |
| 82 | +func (ticker *ebpfTicker) Stop() { |
| 83 | + if ticker.events != nil { |
| 84 | + _ = ticker.events.Close() |
| 85 | + } |
| 86 | + if ticker.prog != nil { |
| 87 | + _ = ticker.prog.Close() |
| 88 | + } |
| 89 | + for _, l := range ticker.links { |
| 90 | + _ = l.Close() |
| 91 | + } |
| 92 | + if ticker.reader != nil { |
| 93 | + _ = ticker.reader.Close() |
| 94 | + } |
| 95 | + if ticker.ch != nil { |
| 96 | + close(ticker.ch) |
| 97 | + } |
| 98 | +} |
| 99 | + |
| 100 | +func buildEbpfProg(events *ebpf.Map) (*ebpf.Program, error) { |
| 101 | + inst := asm.Instructions{ |
| 102 | + // ringbuf = &map |
| 103 | + asm.LoadMapPtr(asm.R1, events.FD()), |
| 104 | + |
| 105 | + // data = FP - 8 |
| 106 | + asm.Mov.Reg(asm.R2, asm.R10), |
| 107 | + asm.Add.Imm(asm.R2, -8), |
| 108 | + |
| 109 | + // *data = 1 |
| 110 | + asm.StoreImm(asm.R2, 0, 1, asm.Word), |
| 111 | + |
| 112 | + // size = 1 |
| 113 | + asm.Mov.Imm(asm.R3, 1), |
| 114 | + |
| 115 | + // flags = 0 |
| 116 | + asm.Mov.Imm(asm.R4, 0), |
| 117 | + |
| 118 | + // long bpf_ringbuf_output(void *ringbuf, void *data, u64 size, u64 flags) |
| 119 | + // https://man7.org/linux/man-pages/man7/bpf-helpers.7.html |
| 120 | + asm.FnRingbufOutput.Call(), |
| 121 | + |
| 122 | + // return 0 |
| 123 | + asm.Mov.Imm(asm.R0, 0), |
| 124 | + asm.Return(), |
| 125 | + } |
| 126 | + |
| 127 | + spec := &ebpf.ProgramSpec{ |
| 128 | + Name: "lima_ticker", |
| 129 | + Type: ebpf.TracePoint, |
| 130 | + License: "Apache-2.0", // No need to be GPL? |
| 131 | + Instructions: inst, |
| 132 | + } |
| 133 | + |
| 134 | + return ebpf.NewProgram(spec) |
| 135 | +} |
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