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package link
import (
"fmt"
"github.com/cilium/ebpf"
"github.com/cilium/ebpf/internal/tracefs"
)
// TracepointOptions defines additional parameters that will be used
// when loading Tracepoints.
type TracepointOptions struct {
// Arbitrary value that can be fetched from an eBPF program
// via `bpf_get_attach_cookie()`.
//
// Needs kernel 5.15+.
Cookie uint64
}
// Tracepoint attaches the given eBPF program to the tracepoint with the given
// group and name. See /sys/kernel/tracing/events to find available
// tracepoints. The top-level directory is the group, the event's subdirectory
// is the name. Example:
//
// tp, err := Tracepoint("syscalls", "sys_enter_fork", prog, nil)
//
// Losing the reference to the resulting Link (tp) will close the Tracepoint
// and prevent further execution of prog. The Link must be Closed during
// program shutdown to avoid leaking system resources.
//
// Note that attaching eBPF programs to syscalls (sys_enter_*/sys_exit_*) is
// only possible as of kernel 4.14 (commit cf5f5ce).
//
// The returned Link may implement [PerfEvent].
func Tracepoint(group, name string, prog *ebpf.Program, opts *TracepointOptions) (Link, error) {
if group == "" || name == "" {
return nil, fmt.Errorf("group and name cannot be empty: %w", errInvalidInput)
}
if prog == nil {
return nil, fmt.Errorf("prog cannot be nil: %w", errInvalidInput)
}
if prog.Type() != ebpf.TracePoint {
return nil, fmt.Errorf("eBPF program type %s is not a Tracepoint: %w", prog.Type(), errInvalidInput)
}
tid, err := tracefs.EventID(group, name)
if err != nil {
return nil, err
}
fd, err := openTracepointPerfEvent(tid, perfAllThreads)
if err != nil {
return nil, err
}
var cookie uint64
if opts != nil {
cookie = opts.Cookie
}
pe := newPerfEvent(fd, nil)
lnk, err := attachPerfEvent(pe, prog, cookie)
if err != nil {
pe.Close()
return nil, err
}
return lnk, nil
}
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