github.com/inspektor-gadget/inspektor-gadget@v0.28.1/pkg/kallsyms/symbol-resolver.go (about)

     1  // Copyright 2024 The Inspektor Gadget authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package kallsyms
    16  
    17  import (
    18  	"fmt"
    19  	"os"
    20  
    21  	"github.com/inspektor-gadget/inspektor-gadget/pkg/kfilefields"
    22  )
    23  
    24  // symbolResolver is an interface to resolve kernel symbols.
    25  type symbolResolver interface {
    26  	resolve(symbol string) (uint64, error)
    27  }
    28  
    29  // kAllSymsResolver is a symbolResolver that resolves kernel symbols using a KAllSyms.
    30  // It isn't safe for concurrent use.
    31  type kAllSymsResolver struct {
    32  	kAllSyms *KAllSyms
    33  }
    34  
    35  // newKAllSymsResolver returns a new kAllSymsResolver.
    36  func newKAllSymsResolver() *kAllSymsResolver {
    37  	return &kAllSymsResolver{}
    38  }
    39  
    40  // Resolve resolves a kernel symbol using the KAllSyms.
    41  func (r *kAllSymsResolver) resolve(symbol string) (uint64, error) {
    42  	if r.kAllSyms == nil {
    43  		if err := r.init(); err != nil {
    44  			return 0, fmt.Errorf("initializing kallsyms: %w", err)
    45  		}
    46  	}
    47  	addr, ok := r.kAllSyms.symbolsMap[symbol]
    48  	if !ok {
    49  		return 0, fmt.Errorf("symbol %q was not found in kallsyms", symbol)
    50  	}
    51  	return addr, nil
    52  }
    53  
    54  func (r *kAllSymsResolver) init() error {
    55  	kAllSyms, err := NewKAllSyms()
    56  	if err != nil {
    57  		return err
    58  	}
    59  	r.kAllSyms = kAllSyms
    60  	return nil
    61  }
    62  
    63  // ebpfResolver is a symbolResolver that resolves kernel symbols using eBPF.
    64  type ebpfResolver struct {
    65  	symbolsBypass map[string]kfilefields.FdType
    66  }
    67  
    68  // newEbpfResolver returns a new ebpfResolver.
    69  func newEbpfResolver() *ebpfResolver {
    70  	// List of symbols that we're able to find in 'struct file *' using eBPF
    71  	return &ebpfResolver{
    72  		symbolsBypass: map[string]kfilefields.FdType{
    73  			"bpf_prog_fops":   kfilefields.FdTypeEbpfProgram,
    74  			"socket_file_ops": kfilefields.FdTypeSocket,
    75  		},
    76  	}
    77  }
    78  
    79  // Resolve resolves a kernel symbol using eBPF.
    80  func (r *ebpfResolver) resolve(symbol string) (uint64, error) {
    81  	fdT, ok := r.symbolsBypass[symbol]
    82  	if !ok {
    83  		return 0, os.ErrInvalid
    84  	}
    85  
    86  	fop, err := kfilefields.ReadFOpForFdType(fdT)
    87  	if err != nil {
    88  		return 0, err
    89  	}
    90  	return fop, nil
    91  }