71 lines
1.7 KiB
Go
71 lines
1.7 KiB
Go
package ebpf
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import (
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"github.com/cilium/ebpf/asm"
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"github.com/cilium/ebpf/internal/btf"
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"github.com/pkg/errors"
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)
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// link resolves bpf-to-bpf calls.
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//
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// Each library may contain multiple functions / labels, and is only linked
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// if the program being edited references one of these functions.
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//
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// Libraries must not require linking themselves.
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func link(prog *ProgramSpec, libs []*ProgramSpec) error {
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for _, lib := range libs {
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insns, err := linkSection(prog.Instructions, lib.Instructions)
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if err != nil {
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return errors.Wrapf(err, "linking %s", lib.Name)
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}
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if len(insns) == len(prog.Instructions) {
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continue
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}
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prog.Instructions = insns
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if prog.BTF != nil && lib.BTF != nil {
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if err := btf.ProgramAppend(prog.BTF, lib.BTF); err != nil {
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return errors.Wrapf(err, "linking BTF of %s", lib.Name)
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}
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}
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}
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return nil
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}
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func linkSection(insns, section asm.Instructions) (asm.Instructions, error) {
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// A map of symbols to the libraries which contain them.
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symbols, err := section.SymbolOffsets()
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if err != nil {
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return nil, err
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}
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for _, ins := range insns {
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if ins.Reference == "" {
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continue
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}
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if ins.OpCode.JumpOp() != asm.Call || ins.Src != asm.R1 {
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continue
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}
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if ins.Constant != -1 {
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// This is already a valid call, no need to link again.
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continue
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}
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if _, ok := symbols[ins.Reference]; !ok {
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// Symbol isn't available in this section
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continue
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}
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// At this point we know that at least one function in the
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// library is called from insns. Merge the two sections.
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// The rewrite of ins.Constant happens in asm.Instruction.Marshal.
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return append(insns, section...), nil
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}
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// None of the functions in the section are called. Do nothing.
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return insns, nil
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}
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