kfuzztest: address minor nits

Author: Ethan Graham

pkg/kcov/kcov.go

@@ -10,10 +10,9 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const kcovPath string = "/sys/kernel/debug/kcov"
-
 const (
-	kcovCoverSize = 64 << 10
+	kcovPath      string = "/sys/kernel/debug/kcov"
+	kcovCoverSize        = 64 << 10
 )
 
 // Holds resources for a single traced thread.

prog/kfuzztest.go

@@ -211,7 +211,7 @@ func kFuzzTestExpandRegion(reg Arg) ([]byte, []kFuzzTestRelocation) {
 // given pointee is allocated only once.
 //
 // For a concrete example of the final binary layout, see the test cases for this
-// function in `prog/encodingexec_test.go`.
+// function in `prog/kfuzztest_test.go`.
 func MarshallKFuzztestArg(topLevel Arg) []byte {
 	regions := []kFuzzTestRegion{}
 	allRelocations := []kFuzzTestRelocation{}

syz-kfuzztest/main.go

@@ -5,6 +5,7 @@ package main
 import (
 	"context"
 	"flag"
+	"fmt"
 	"os"
 	"os/signal"
 	"syscall"
@@ -13,16 +14,28 @@ import (
 )
 
 var (
-	flagVmlinux         = flag.String("vmlinux", "", "Path to vmlinux binary")
+	flagVmlinux         = flag.String("vmlinux", "vmlinux", "Path to vmlinux binary")
 	flagTimeout         = flag.Int("timeout", 0, "Timeout in milliseconds")
-	flagThreads         = flag.Int("threads", 1, "Number of threads")
+	flagThreads         = flag.Int("threads", 2, "Number of threads")
 	flagDisplayInterval = flag.Int("display", 5, "Display interval")
-	flagDisplayProgs    = flag.Bool("display-progs", false, "Display last executed prog for each target")
+	flagDisplayProgs    = flag.Bool("display-progs", false, "If enabled, display the last executed prog for each target")
 )
 
 func main() {
-	flag.Parse()
+	usage := func() {
+		w := flag.CommandLine.Output()
+		fmt.Fprintf(w, "usage: %s [flags] [enabled targets]\n\n", os.Args[0])
+		fmt.Fprintln(w, `Args:
+  One fuzz test name per enabled fuzz test arg. If empty, defaults to
+  all discovered targets.`)
+		fmt.Fprintln(w, `Example:
+  ./syz-kfuzztest -vmlinux ~/kernel/vmlinux fuzz_target_0 fuzz_target_1`)
+		fmt.Fprintln(w, "Flags:")
+		flag.PrintDefaults()
+	}
+	flag.Usage = usage
 	enabledTargets := flag.Args()
+	flag.Parse()
 
 	cfg := config{
 		vmlinuxPath:         *flagVmlinux,