tools/syz-kconf: don't enable configs implicitly

Currenty we run oldconfig and set all missing configs to their
default values. Sometimes this enables configs implicitly/unintentionally.
Set all missing configs to "is not set" proactively to prevent
using default values.

Also replace oldconfig with olddefconfig.
I assumed oldconfig sets missing values to "is not set",
but it does not. It does the same as olddefconfig without stdin.

Update #2171

1 files changed, 24 insertions, 13 deletions

diff --git a/tools/syz-kconf/kconf.go b/tools/syz-kconf/kconf.go
index 97b28f79a..02ce0e929 100644
--- a/tools/syz-kconf/kconf.go
+++ b/tools/syz-kconf/kconf.go
@@ -58,6 +58,7 @@ func main() {
 		fail(err)
 	}
 	// In order to speed up the process we generate instances that use the same kernel revision in parallel.
+	failed := false
 	generated := make(map[string]bool)
 	for _, inst := range instances {
 		// Find the first instance that we did not generate yet.
@@ -105,10 +106,14 @@ func main() {
 		}
 		for i := 0; i < batch; i++ {
 			if err := <-results; err != nil {
-				fail(err)
+				fmt.Printf("%v\n", err)
+				failed = true
 			}
 		}
 	}
+	if failed {
+		failf("some configs failed")
+	}
 	if len(generated) == 0 {
 		failf("unknown instance name")
 	}
@@ -155,18 +160,34 @@ func (ctx *Context) generate() error {
 	}
 	ctx.applyConfigs(cf)
 	cf.ModToYes()
+	// Set all configs that are not present (actually not present, rather than "is not set") to "is not set".
+	// This avoids olddefconfig turning on random things we did not ask for.
+	for _, cfg := range ctx.Kconf.Configs {
+		if (cfg.Type == kconfig.TypeTristate || cfg.Type == kconfig.TypeBool) && cf.Map[cfg.Name] == nil {
+			cf.Set(cfg.Name, kconfig.No)
+		}
+	}
 	original := cf.Serialize()
 	if err := osutil.WriteFile(configFile, original); err != nil {
 		return fmt.Errorf("failed to write .config file: %v", err)
 	}
-	if err := ctx.Make("oldconfig"); err != nil {
+	// Save what we've got before olddefconfig for debugging purposes, it allows to see if we did not set a config,
+	// or olddefconfig removed it. Save as .tmp so that it's not checked-in accidentially.
+	outputFile := filepath.Join(ctx.ConfigDir, ctx.Inst.Name+".config")
+	outputFileTmp := outputFile + ".tmp"
+	if err := osutil.WriteFile(outputFileTmp, original); err != nil {
+		return fmt.Errorf("failed to write tmp config file: %v", err)
+	}
+	if err := ctx.Make("olddefconfig"); err != nil {
 		return err
 	}
 	cf, err = kconfig.ParseConfig(configFile)
 	if err != nil {
 		return err
 	}
-	verifyErr := ctx.verifyConfigs(cf)
+	if err := ctx.verifyConfigs(cf); err != nil {
+		return fmt.Errorf("%vsaved config before olddefconfig to %v", err, outputFileTmp)
+	}
 	cf.ModToNo()
 	config := []byte(fmt.Sprintf(`# Automatically generated by syz-kconf; DO NOT EDIT.
 # Kernel: %v %v
@@ -175,15 +196,6 @@ func (ctx *Context) generate() error {
 %s
 `,
 		ctx.Inst.Kernel.Repo, ctx.Inst.Kernel.Tag, cf.Serialize(), ctx.Inst.Verbatim))
-	outputFile := filepath.Join(ctx.ConfigDir, ctx.Inst.Name+".config")
-	if verifyErr != nil {
-		// Write bad config for debugging with .tmp suffix so that it's not checked-in accidentially.
-		outputFile += ".tmp"
-		if err := osutil.WriteFile(outputFile, original); err != nil {
-			return fmt.Errorf("failed to write output file: %v", err)
-		}
-		return fmt.Errorf("%vsaved config to %v (run oldconfig)", verifyErr, outputFile)
-	}
 	return osutil.WriteFile(outputFile, config)
 }
 
@@ -250,7 +262,6 @@ func (ctx *Context) addUSBConfigs(cf *kconfig.ConfigFile) error {
 	distroConfig := filepath.Join(ctx.ConfigDir, "distros", android+"*")
 	// Some USB drivers don't depend on any USB related symbols, but rather on a generic symbol
 	// for some input subsystem (e.g. HID), so include it as well.
-	// TODO: don't include HID, it does not seem to add anything relevant.
 	return ctx.addDependentConfigs(cf, []string{"USB_SUPPORT", "HID"}, distroConfig)
 }