sys/targets: better detection for missing/broken cross-compilers

1. Detect when compiler is present, but is not functioning
(can't build a simple program, common for Linux distros).

2. Be more strict with skipping tests due to missing/broken compilers on CI
(on CI they should work, so fail loudly if not).

3. Dedup this logic across syz-env and pkg/csource tests.

4. Add better error reporting for syz-env.

Fixes #1606

2 files changed, 1 insertions, 23 deletions

diff --git a/pkg/csource/build.go b/pkg/csource/build.go
index 56d5487a8..1269987e5 100644
--- a/pkg/csource/build.go
+++ b/pkg/csource/build.go
@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"runtime"
 
 	"github.com/google/syzkaller/pkg/osutil"
@@ -37,9 +36,6 @@ func BuildFile(target *prog.Target, src string) (string, error) {
 func build(target *prog.Target, src []byte, file string, warn bool) (string, error) {
 	sysTarget := targets.Get(target.OS, target.Arch)
 	compiler := sysTarget.CCompiler
-	if _, err := exec.LookPath(compiler); err != nil {
-		return "", fmt.Errorf("no target compiler %v", compiler)
-	}
 	// We call the binary syz-executor because it sometimes shows in bug titles,
 	// and we don't want 2 different bugs for when a crash is triggered during fuzzing and during repro.
 	bin, err := osutil.TempFile("syz-executor")
diff --git a/pkg/csource/csource_test.go b/pkg/csource/csource_test.go
index 59ca230b6..78145c8fa 100644
--- a/pkg/csource/csource_test.go
+++ b/pkg/csource/csource_test.go
@@ -8,7 +8,6 @@ import (
 	"io/ioutil"
 	"math/rand"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"regexp"
 	"runtime"
@@ -33,26 +32,9 @@ func TestGenerate(t *testing.T) {
 			continue
 		}
 		t.Run(target.OS+"/"+target.Arch, func(t *testing.T) {
-			if target.OS == "linux" && target.Arch == "arm64" {
-				// Episodically fails on travis with:
-				// collect2: error: ld terminated with signal 11 [Segmentation fault]
-				t.Skip("broken")
-			}
-			if target.OS == "test" && target.PtrSize == 4 {
-				// The same reason as linux/32.
-				t.Skip("broken")
-			}
-			if _, err := exec.LookPath(sysTarget.CCompiler); err != nil {
-				t.Skipf("no target compiler %v", sysTarget.CCompiler)
-			}
-			bin, err := Build(target, []byte(`
-#include <stdio.h>
-int main() { printf("Hello, World!\n"); }
-`))
-			if err != nil {
+			if err := sysTarget.BrokenCrossCompiler; err != "" {
 				t.Skipf("target compiler is broken: %v", err)
 			}
-			os.Remove(bin)
 			full := !checked[target.OS]
 			checked[target.OS] = true
 			t.Parallel()