pkg/build: share extractRootCause with openbsd

* pkg/build: share extractRootCause with openbsd

This should get kernel build errors reported in syz-ci console.

* Add a test

* lint

4 files changed, 67 insertions, 38 deletions

diff --git a/pkg/build/build.go b/pkg/build/build.go
index b7fdb1664..64f32f29e 100644
--- a/pkg/build/build.go
+++ b/pkg/build/build.go
@@ -5,6 +5,7 @@
 package build
 
 import (
+	"bytes"
 	"fmt"
 	"path/filepath"
 	"strings"
@@ -113,3 +114,44 @@ func CompilerIdentity(compiler string) (string, error) {
 	}
 	return "", fmt.Errorf("no output from compiler --version")
 }
+
+func extractRootCause(err error) error {
+	verr, ok := err.(*osutil.VerboseError)
+	if !ok {
+		return err
+	}
+	cause := extractCauseInner(verr.Output)
+	if cause != nil {
+		verr.Title = string(cause)
+	}
+	return KernelBuildError{verr}
+}
+
+func extractCauseInner(s []byte) []byte {
+	var cause []byte
+	for _, line := range bytes.Split(s, []byte{'\n'}) {
+		for _, pattern := range buildFailureCauses {
+			if pattern.weak && cause != nil {
+				continue
+			}
+			if bytes.Contains(line, pattern.pattern) {
+				cause = line
+				break
+			}
+		}
+	}
+	return cause
+}
+
+type buildFailureCause struct {
+	pattern []byte
+	weak    bool
+}
+
+var buildFailureCauses = [...]buildFailureCause{
+	{pattern: []byte(": error: ")},
+	{pattern: []byte(": fatal error: ")},
+	{pattern: []byte(": undefined reference to")},
+	{weak: true, pattern: []byte(": final link failed: ")},
+	{weak: true, pattern: []byte("collect2: error: ")},
+}
diff --git a/pkg/build/build_test.go b/pkg/build/build_test.go
index 1698d3bd8..830c4f39c 100644
--- a/pkg/build/build_test.go
+++ b/pkg/build/build_test.go
@@ -4,6 +4,7 @@
 package build
 
 import (
+	"bytes"
 	"os/exec"
 	"strings"
 	"testing"
@@ -34,3 +35,26 @@ func TestCompilerIdentity(t *testing.T) {
 		})
 	}
 }
+
+func TestExtractRootCause(t *testing.T) {
+	for _, s := range []struct{ e, expect string }{
+		{`
+cc -g -Werror db_break.c
+sys/dev/kcov.c:93:6: error: use of undeclared identifier 'kcov_cold123'; did you mean 'kcov_cold'?
+        if (kcov_cold123)
+            ^~~~~~~~~~~~
+            kcov_cold
+sys/dev/kcov.c:65:5: note: 'kcov_cold' declared here
+int kcov_cold = 1;
+    ^
+1 error generated.
+`,
+			"sys/dev/kcov.c:93:6: error: use of undeclared identifier 'kcov_cold123'; did you mean 'kcov_cold'?",
+		},
+	} {
+		got := extractCauseInner([]byte(s.e))
+		if !bytes.Equal([]byte(s.expect), got) {
+			t.Errorf("Expected %s, got %s", s.expect, got)
+		}
+	}
+}
diff --git a/pkg/build/linux.go b/pkg/build/linux.go
index dbe9cfbb7..f4dff538f 100644
--- a/pkg/build/linux.go
+++ b/pkg/build/linux.go
@@ -10,7 +10,6 @@
 package build
 
 import (
-	"bytes"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -124,39 +123,3 @@ func (linux) clean(kernelDir string) error {
 	_, err := osutil.Run(10*time.Minute, cmd)
 	return err
 }
-
-func extractRootCause(err error) error {
-	verr, ok := err.(*osutil.VerboseError)
-	if !ok {
-		return err
-	}
-	var cause []byte
-	for _, line := range bytes.Split(verr.Output, []byte{'\n'}) {
-		for _, pattern := range buildFailureCauses {
-			if pattern.weak && cause != nil {
-				continue
-			}
-			if bytes.Contains(line, pattern.pattern) {
-				cause = line
-				break
-			}
-		}
-	}
-	if cause != nil {
-		verr.Title = string(cause)
-	}
-	return KernelBuildError{verr}
-}
-
-type buildFailureCause struct {
-	pattern []byte
-	weak    bool
-}
-
-var buildFailureCauses = [...]buildFailureCause{
-	{pattern: []byte(": error: ")},
-	{pattern: []byte(": fatal error: ")},
-	{pattern: []byte(": undefined reference to")},
-	{weak: true, pattern: []byte(": final link failed: ")},
-	{weak: true, pattern: []byte("collect2: error: ")},
-}
diff --git a/pkg/build/openbsd.go b/pkg/build/openbsd.go
index d7fe62f36..9c4b7f119 100644
--- a/pkg/build/openbsd.go
+++ b/pkg/build/openbsd.go
@@ -35,7 +35,7 @@ func (ctx openbsd) build(targetArch, vmType, kernelDir, outputDir, compiler, use
 	}
 	for _, tgt := range []string{"clean", "obj", "config", "all"} {
 		if err := ctx.make(compileDir, tgt); err != nil {
-			return err
+			return extractRootCause(err)
 		}
 	}
 	for _, s := range []struct{ dir, src, dst string }{