github.com/inspektor-gadget/inspektor-gadget@v0.28.1/pkg/operators/ebpf/params_defaults.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 ebpfoperator
    16  
    17  import (
    18  	"errors"
    19  	"fmt"
    20  	"strings"
    21  	"unsafe"
    22  
    23  	"github.com/cilium/ebpf"
    24  	"github.com/cilium/ebpf/btf"
    25  
    26  	"github.com/inspektor-gadget/inspektor-gadget/pkg/btfhelpers"
    27  )
    28  
    29  var errMapNoBTFValue = errors.New("map spec does not contain a BTF Value")
    30  
    31  // fillParamDefaults will fill out i.Params' default values
    32  func (i *ebpfInstance) fillParamDefaults() error {
    33  	spec := i.collectionSpec
    34  	for name, spec := range spec.Maps {
    35  		if !strings.HasPrefix(name, ".rodata") {
    36  			continue
    37  		}
    38  		b, ds, err := dataSection(spec)
    39  		if errors.Is(err, errMapNoBTFValue) {
    40  			continue
    41  		}
    42  		if err != nil {
    43  			return fmt.Errorf("map %s: %w", name, err)
    44  		}
    45  
    46  		for _, v := range ds.Vars {
    47  			vname := v.Type.TypeName()
    48  
    49  			param, ok := i.params[vname]
    50  			if !ok {
    51  				continue
    52  			}
    53  
    54  			if int(v.Offset+v.Size) > len(b) {
    55  				continue
    56  			}
    57  
    58  			btfVar, ok := v.Type.(*btf.Var)
    59  			if !ok {
    60  				continue
    61  			}
    62  
    63  			btfConst, ok := btfVar.Type.(*btf.Const)
    64  			if !ok {
    65  				continue
    66  			}
    67  
    68  			btfVolatile, ok := btfConst.Type.(*btf.Volatile)
    69  			if !ok {
    70  				continue
    71  			}
    72  
    73  			vtype := btfVolatile.Type
    74  
    75  			if typedef, ok := vtype.(*btf.Typedef); ok {
    76  				vtype = btfhelpers.GetUnderlyingType(typedef)
    77  			}
    78  
    79  			bytes := b[v.Offset : v.Offset+v.Size]
    80  
    81  			var defaultValue string
    82  
    83  			switch t := vtype.(type) {
    84  			case *btf.Int:
    85  				if t.Encoding&btf.Signed != 0 {
    86  					switch t.Size {
    87  					case 1:
    88  						defaultValue = fmt.Sprintf("%d", int8(bytes[0]))
    89  					case 2:
    90  						defaultValue = fmt.Sprintf("%d", *(*int16)(unsafe.Pointer(&bytes[0])))
    91  					case 4:
    92  						defaultValue = fmt.Sprintf("%d", *(*int32)(unsafe.Pointer(&bytes[0])))
    93  					case 8:
    94  						defaultValue = fmt.Sprintf("%d", *(*int64)(unsafe.Pointer(&bytes[0])))
    95  					}
    96  				} else {
    97  					switch t.Size {
    98  					case 1:
    99  						defaultValue = fmt.Sprintf("%d", bytes[0])
   100  					case 2:
   101  						defaultValue = fmt.Sprintf("%d", *(*uint16)(unsafe.Pointer(&bytes[0])))
   102  					case 4:
   103  						defaultValue = fmt.Sprintf("%d", *(*uint32)(unsafe.Pointer(&bytes[0])))
   104  					case 8:
   105  						defaultValue = fmt.Sprintf("%d", *(*uint64)(unsafe.Pointer(&bytes[0])))
   106  					}
   107  				}
   108  				if t.Encoding&btf.Bool != 0 {
   109  					if defaultValue == "0" {
   110  						defaultValue = "false"
   111  					} else {
   112  						defaultValue = "true"
   113  					}
   114  				}
   115  			}
   116  
   117  			i.gadgetCtx.Logger().Debugf("default value for param %q set to %q (%.2X), type was %T", vname, defaultValue, bytes, vtype)
   118  
   119  			param.DefaultValue = defaultValue
   120  		}
   121  	}
   122  	return nil
   123  }
   124  
   125  // dataSection returns the contents and BTF Datasec descriptor of the spec.
   126  // borrowed from cilium/ebpf
   127  func dataSection(ms *ebpf.MapSpec) ([]byte, *btf.Datasec, error) {
   128  	if ms.Value == nil {
   129  		return nil, nil, errMapNoBTFValue
   130  	}
   131  
   132  	ds, ok := ms.Value.(*btf.Datasec)
   133  	if !ok {
   134  		return nil, nil, fmt.Errorf("map value BTF is a %T, not a *btf.Datasec", ms.Value)
   135  	}
   136  
   137  	if n := len(ms.Contents); n != 1 {
   138  		return nil, nil, fmt.Errorf("expected one key, found %d", n)
   139  	}
   140  
   141  	kv := ms.Contents[0]
   142  	value, ok := kv.Value.([]byte)
   143  	if !ok {
   144  		return nil, nil, fmt.Errorf("value at first map key is %T, not []byte", kv.Value)
   145  	}
   146  
   147  	return value, ds, nil
   148  }