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host.go
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host.go
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//go:build linux
// +build linux
// Copyright 2023 The Inspektor Gadget authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package host provides ways to access the host filesystem.
//
// Inspektor Gadget can run either in the host or in a container. When running
// in a container, the host filesystem must be available in a specific
// directory.
package host
import (
"fmt"
"os"
"path/filepath"
"strings"
"github.com/spf13/cobra"
)
var (
HostRoot string
HostProcFs string
)
func init() {
// Initialize HostRoot and HostProcFs
HostRoot = os.Getenv("HOST_ROOT")
if HostRoot == "" {
HostRoot = "/"
}
HostProcFs = filepath.Join(HostRoot, "/proc")
}
type Config struct {
// AutoMountFilesystems will automatically mount bpffs, debugfs and
// tracefs if they are not already mounted.
//
// This is useful for some environments where those filesystems are not
// mounted by default on the host, such as:
// - minikube with the Docker driver
// - Docker Desktop with WSL2
// - Talos Linux
AutoMountFilesystems bool
}
var (
autoSdUnitRestartFlag bool
autoMountFilesystemsFlag bool
autoWSLWorkaroundFlag bool
initDone bool
)
func Init(config Config) error {
var err error
// Init() is called both from the local runtime and the local manager operator.
// Different gadgets (trace-exec and top-ebpf) have different code paths, and we need both to make both work.
// TODO: understand why we need to call Init() twice and fix it.
if initDone {
return nil
}
// Apply systemd workaround first because it might start a new process and
// exit before the other workarounds.
if autoSdUnitRestartFlag {
exit, err := autoSdUnitRestart()
if exit {
if err != nil {
fmt.Fprintf(os.Stderr, "error: %v\n", err)
os.Exit(1)
}
os.Exit(0)
}
if err != nil {
return err
}
} else {
if err := suggestSdUnitRestart(); err != nil {
fmt.Fprintf(os.Stderr, "error: %v\n", err)
os.Exit(1)
}
}
// The mount workaround could either be applied unconditionally (in the
// gadget DaemonSet) or with the flag (in ig).
if config.AutoMountFilesystems || autoMountFilesystemsFlag {
_, err = autoMountFilesystems(false)
if err != nil {
return err
}
} else {
mountsSuggested, err := autoMountFilesystems(true)
if err != nil {
fmt.Fprintf(os.Stderr, "error: %v\n", err)
os.Exit(1)
}
if len(mountsSuggested) != 0 {
fmt.Fprintf(os.Stderr, "error: filesystems %s not mounted (did you try --auto-mount-filesystems?)\n", strings.Join(mountsSuggested, ", "))
os.Exit(1)
}
}
// The WSL workaround is applied with the flag (in ig).
if autoWSLWorkaroundFlag {
err = autoWSLWorkaround()
if err != nil {
return err
}
} else {
err = suggestWSLWorkaround()
if err != nil {
fmt.Fprintf(os.Stderr, "error: %v\n", err)
os.Exit(1)
}
}
initDone = true
return nil
}
// AddFlags adds CLI flags for various workarounds
func AddFlags(command *cobra.Command) {
command.PersistentFlags().BoolVarP(
&autoSdUnitRestartFlag,
"auto-sd-unit-restart",
"",
false,
"Automatically run in a privileged systemd unit if lacking enough capabilities",
)
// Enable the mount workaround by default when running inside a container.
automountFilesystemsDefault := false
if HostRoot != "" && HostRoot != "/" {
automountFilesystemsDefault = true
}
command.PersistentFlags().BoolVarP(
&autoMountFilesystemsFlag,
"auto-mount-filesystems",
"",
automountFilesystemsDefault,
"Automatically mount bpffs, debugfs and tracefs if they are not already mounted",
)
command.PersistentFlags().BoolVarP(
&autoWSLWorkaroundFlag,
"auto-wsl-workaround",
"",
false,
"Automatically find the host procfs when running in WSL2",
)
}
func GetProcComm(pid int) string {
pidStr := fmt.Sprint(pid)
commBytes, _ := os.ReadFile(filepath.Join(HostProcFs, pidStr, "comm"))
return strings.TrimRight(string(commBytes), "\n")
}
func GetProcCmdline(pid int) []string {
pidStr := fmt.Sprint(pid)
cmdlineBytes, _ := os.ReadFile(filepath.Join(HostProcFs, pidStr, "cmdline"))
return strings.Split(string(cmdlineBytes), "\x00")
}