cmd/go: consolidate fuzz-support checks

We had been repeating conditions for specific platforms and
architectures to gate fuzzing tests, but the more of those tests we
add the more we will have to update if the set of supported platforms
and archictures expands over time.

We also ought to provide a friendlier error message when
'go test -fuzz' is used on non-supported platforms.

This change adds predicates in cmd/internal/sys, which already
contains similar predicates for related functionality (such as the
race detector), and uses those predicates in 'go test' and TestScript.

For #48495

Change-Id: If24c3997aeb4d201258e21e5b6cf4f7c08fbadd7
Reviewed-on: https://go-review.googlesource.com/c/go/+/359481
Trust: Bryan C. Mills <bcmills@google.com>
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>

26 files changed, 88 insertions, 79 deletions

diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 339014e94e..c13d77a1af 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -43,10 +43,12 @@ func init() {
 }
 
 var (
-	canRace = false // whether we can run the race detector
-	canCgo  = false // whether we can use cgo
-	canMSan = false // whether we can run the memory sanitizer
-	canASan = false // whether we can run the address sanitizer
+	canRace          = false // whether we can run the race detector
+	canCgo           = false // whether we can use cgo
+	canMSan          = false // whether we can run the memory sanitizer
+	canASan          = false // whether we can run the address sanitizer
+	canFuzz          = false // whether we can search for new fuzz failures
+	fuzzInstrumented = false // whether fuzzing uses instrumentation
 )
 
 var exeSuffix string = func() string {
@@ -206,6 +208,8 @@ func TestMain(m *testing.M) {
 		if isAlpineLinux() || runtime.Compiler == "gccgo" {
 			canRace = false
 		}
+		canFuzz = sys.FuzzSupported(runtime.GOOS, runtime.GOARCH)
+		fuzzInstrumented = sys.FuzzInstrumented(runtime.GOOS, runtime.GOARCH)
 	}
 	// Don't let these environment variables confuse the test.
 	os.Setenv("GOENV", "off")
diff --git a/src/cmd/go/internal/test/test.go b/src/cmd/go/internal/test/test.go
index ea1d4ff20e..0806d29f21 100644
--- a/src/cmd/go/internal/test/test.go
+++ b/src/cmd/go/internal/test/test.go
@@ -31,9 +31,10 @@ import (
 	"cmd/go/internal/lockedfile"
 	"cmd/go/internal/modload"
 	"cmd/go/internal/search"
+	"cmd/go/internal/str"
 	"cmd/go/internal/trace"
 	"cmd/go/internal/work"
-	"cmd/go/internal/str"
+	"cmd/internal/sys"
 	"cmd/internal/test2json"
 )
 
@@ -651,8 +652,13 @@ func runTest(ctx context.Context, cmd *base.Command, args []string) {
 	if testO != "" && len(pkgs) != 1 {
 		base.Fatalf("cannot use -o flag with multiple packages")
 	}
-	if testFuzz != "" && len(pkgs) != 1 {
-		base.Fatalf("cannot use -fuzz flag with multiple packages")
+	if testFuzz != "" {
+		if !sys.FuzzSupported(cfg.Goos, cfg.Goarch) {
+			base.Fatalf("-fuzz flag is not supported on %s/%s", cfg.Goos, cfg.Goarch)
+		}
+		if len(pkgs) != 1 {
+			base.Fatalf("cannot use -fuzz flag with multiple packages")
+		}
 	}
 	if testProfile() != "" && len(pkgs) != 1 {
 		base.Fatalf("cannot use %s flag with multiple packages", testProfile())
diff --git a/src/cmd/go/internal/work/init.go b/src/cmd/go/internal/work/init.go
index b2ee00d53c..9111150233 100644
--- a/src/cmd/go/internal/work/init.go
+++ b/src/cmd/go/internal/work/init.go
@@ -67,20 +67,7 @@ func BuildInit() {
 // instrumentation is added. 'go test -fuzz' still works without coverage,
 // but it generates random inputs without guidance, so it's much less effective.
 func fuzzInstrumentFlags() []string {
-	// TODO: expand the set of supported platforms, with testing. Nothing about
-	// the instrumentation is OS specific, but only amd64 and arm64 are
-	// supported in the runtime. See src/runtime/libfuzzer*.
-	//
-	// Keep in sync with build constraints in
-	// internal/fuzz/counters_{un,}supported.go
-	switch cfg.Goos {
-	case "darwin", "freebsd", "linux", "windows":
-	default:
-		return nil
-	}
-	switch cfg.Goarch {
-	case "amd64", "arm64":
-	default:
+	if !sys.FuzzInstrumented(cfg.Goos, cfg.Goarch) {
 		return nil
 	}
 	return []string{"-d=libfuzzer"}
diff --git a/src/cmd/go/script_test.go b/src/cmd/go/script_test.go
index acb1f91b44..98c1b68ed9 100644
--- a/src/cmd/go/script_test.go
+++ b/src/cmd/go/script_test.go
@@ -357,6 +357,10 @@ Script:
 				ok = canASan
 			case "race":
 				ok = canRace
+			case "fuzz":
+				ok = canFuzz
+			case "fuzz-instrumented":
+				ok = fuzzInstrumented
 			case "net":
 				ok = testenv.HasExternalNetwork()
 			case "link":
diff --git a/src/cmd/go/testdata/script/README b/src/cmd/go/testdata/script/README
index 2b88e880c9..2b55fa8977 100644
--- a/src/cmd/go/testdata/script/README
+++ b/src/cmd/go/testdata/script/README
@@ -80,6 +80,8 @@ should only run when the condition is satisfied. The available conditions are:
  - Test environment details:
    - [short] for testing.Short()
    - [cgo], [msan], [asan], [race] for whether cgo, msan, asan, and the race detector can be used
+   - [fuzz] for whether 'go test -fuzz' can be used at all
+   - [fuzz-instrumented] for whether 'go test -fuzz' uses coverage-instrumented binaries
    - [net] for whether the external network can be used
    - [link] for testenv.HasLink()
    - [root] for os.Geteuid() == 0
diff --git a/src/cmd/go/testdata/script/test_fuzz.txt b/src/cmd/go/testdata/script/test_fuzz.txt
index 4665202bf0..020012d73e 100644
--- a/src/cmd/go/testdata/script/test_fuzz.txt
+++ b/src/cmd/go/testdata/script/test_fuzz.txt
@@ -1,5 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 
 # Test that running a fuzz target that returns without failing or calling
 # f.Fuzz fails and causes a non-zero exit status.
@@ -495,4 +494,4 @@ go test fuzz v1
 []byte("12345")
 -- corpustesting/testdata/fuzz/FuzzWrongType/1 --
 go test fuzz v1
-int("00000")
\ No newline at end of file
+int("00000")
diff --git a/src/cmd/go/testdata/script/test_fuzz_cache.txt b/src/cmd/go/testdata/script/test_fuzz_cache.txt
index fc1c9a1752..552966b06b 100644
--- a/src/cmd/go/testdata/script/test_fuzz_cache.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_cache.txt
@@ -1,9 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
-# Instrumentation not supported on other archs.
-# See #14565.
-[!amd64] [!arm64] skip
+[!fuzz-instrumented] skip
 
 [short] skip
 env GOCACHE=$WORK/cache
diff --git a/src/cmd/go/testdata/script/test_fuzz_chatty.txt b/src/cmd/go/testdata/script/test_fuzz_chatty.txt
index 9ebd480c90..1abcbbd389 100644
--- a/src/cmd/go/testdata/script/test_fuzz_chatty.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_chatty.txt
@@ -1,6 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 
 # Run chatty fuzz targets with an error.
diff --git a/src/cmd/go/testdata/script/test_fuzz_cleanup.txt b/src/cmd/go/testdata/script/test_fuzz_cleanup.txt
index 88625916ba..b65022bd74 100644
--- a/src/cmd/go/testdata/script/test_fuzz_cleanup.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_cleanup.txt
@@ -1,5 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 [short] skip
 
 # Cleanup should run after F.Skip.
diff --git a/src/cmd/go/testdata/script/test_fuzz_deadline.txt b/src/cmd/go/testdata/script/test_fuzz_deadline.txt
index 12f1054f61..5ba76a3d4f 100644
--- a/src/cmd/go/testdata/script/test_fuzz_deadline.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_deadline.txt
@@ -1,6 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 
 # The fuzz function should be able to detect whether -timeout
diff --git a/src/cmd/go/testdata/script/test_fuzz_fuzztime.txt b/src/cmd/go/testdata/script/test_fuzz_fuzztime.txt
index c3933bc7e2..56d94a4bcf 100644
--- a/src/cmd/go/testdata/script/test_fuzz_fuzztime.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_fuzztime.txt
@@ -1,6 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 
 # There are no seed values, so 'go test' should finish quickly.
diff --git a/src/cmd/go/testdata/script/test_fuzz_io_error.txt b/src/cmd/go/testdata/script/test_fuzz_io_error.txt
index 4c7ab4c152..1a0aa6427e 100644
--- a/src/cmd/go/testdata/script/test_fuzz_io_error.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_io_error.txt
@@ -6,7 +6,7 @@
 # This is unlikely, but possible. It's difficult to simulate interruptions
 # due to ^C and EOF errors which are more common. We don't report those.
 [short] skip
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 
 # If the I/O error occurs before F.Fuzz is called, the coordinator should
 # stop the worker and say that.
diff --git a/src/cmd/go/testdata/script/test_fuzz_match.txt b/src/cmd/go/testdata/script/test_fuzz_match.txt
index 3a2ca631ad..0c0085f2c2 100644
--- a/src/cmd/go/testdata/script/test_fuzz_match.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_match.txt
@@ -1,5 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 
 # Matches only fuzz targets to test.
 go test standalone_fuzz_test.go
diff --git a/src/cmd/go/testdata/script/test_fuzz_minimize.txt b/src/cmd/go/testdata/script/test_fuzz_minimize.txt
index 3293e878bb..462fb9a963 100644
--- a/src/cmd/go/testdata/script/test_fuzz_minimize.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_minimize.txt
@@ -1,6 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 
 # We clean the fuzz cache during this test. Don't clean the user's cache.
diff --git a/src/cmd/go/testdata/script/test_fuzz_minimize_interesting.txt b/src/cmd/go/testdata/script/test_fuzz_minimize_interesting.txt
index 8ea4cdb8a5..e017a4cad3 100644
--- a/src/cmd/go/testdata/script/test_fuzz_minimize_interesting.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_minimize_interesting.txt
@@ -1,8 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
-# Instrumentation only supported on 64-bit architectures.
-[!amd64] [!arm64] skip
+[!fuzz-instrumented] skip
 
 # Test that when an interesting value is discovered (one that expands coverage),
 # the fuzzing engine minimizes it before writing it to the cache.
diff --git a/src/cmd/go/testdata/script/test_fuzz_multiple.txt b/src/cmd/go/testdata/script/test_fuzz_multiple.txt
index 6a7732f514..d96b2b6206 100644
--- a/src/cmd/go/testdata/script/test_fuzz_multiple.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_multiple.txt
@@ -2,9 +2,7 @@
 # enabled, and multiple package or multiple fuzz targets match.
 # TODO(#46312): support fuzzing multiple targets in multiple packages.
 
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 
 # With fuzzing disabled, multiple targets can be tested.
diff --git a/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt b/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt
index 628e003f41..4c4fa8e651 100644
--- a/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt
@@ -1,5 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 
 # Tests that a crash caused by a mutator-discovered input writes the bad input
 # to testdata, and fails+reports correctly. This tests the end-to-end behavior
diff --git a/src/cmd/go/testdata/script/test_fuzz_mutate_fail.txt b/src/cmd/go/testdata/script/test_fuzz_mutate_fail.txt
index 935c22a05e..b5eab17349 100644
--- a/src/cmd/go/testdata/script/test_fuzz_mutate_fail.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_mutate_fail.txt
@@ -1,5 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 
 # Check that if a worker does not call F.Fuzz or calls F.Fail first,
 # 'go test' exits non-zero and no crasher is recorded.
diff --git a/src/cmd/go/testdata/script/test_fuzz_mutator.txt b/src/cmd/go/testdata/script/test_fuzz_mutator.txt
index 9d0738e169..76b86488ad 100644
--- a/src/cmd/go/testdata/script/test_fuzz_mutator.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_mutator.txt
@@ -1,5 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
+[!fuzz] skip
 
 # Test basic fuzzing mutator behavior.
 #
diff --git a/src/cmd/go/testdata/script/test_fuzz_non_crash_signal.txt b/src/cmd/go/testdata/script/test_fuzz_non_crash_signal.txt
index 1568757de7..f1a4c6669f 100644
--- a/src/cmd/go/testdata/script/test_fuzz_non_crash_signal.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_non_crash_signal.txt
@@ -1,7 +1,7 @@
 # NOTE: this test is skipped on Windows, since there's no concept of signals.
 # When a process terminates another process, it provides an exit code.
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!freebsd] [!linux] skip
+[windows] skip
+[!fuzz] skip
 [short] skip
 
 # FuzzNonCrash sends itself a signal that does not appear to be a crash.
diff --git a/src/cmd/go/testdata/script/test_fuzz_parallel.txt b/src/cmd/go/testdata/script/test_fuzz_parallel.txt
index a49f30a27f..1795e0b2a5 100644
--- a/src/cmd/go/testdata/script/test_fuzz_parallel.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_parallel.txt
@@ -1,6 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 
 # When running seed inputs, T.Parallel should let multiple inputs run in
diff --git a/src/cmd/go/testdata/script/test_fuzz_run.txt b/src/cmd/go/testdata/script/test_fuzz_run.txt
index e546d997cb..99a4413d32 100644
--- a/src/cmd/go/testdata/script/test_fuzz_run.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_run.txt
@@ -1,6 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
+[!fuzz] skip
 [short] skip
 env GOCACHE=$WORK/cache
 
@@ -142,4 +140,4 @@ go test fuzz v1
 string("fails")
 -- testdata/fuzz/FuzzFoo/thispasses --
 go test fuzz v1
-string("passes")
\ No newline at end of file
+string("passes")
diff --git a/src/cmd/go/testdata/script/test_fuzz_seed_corpus.txt b/src/cmd/go/testdata/script/test_fuzz_seed_corpus.txt
index 18f634a3b6..4be9a6e385 100644
--- a/src/cmd/go/testdata/script/test_fuzz_seed_corpus.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_seed_corpus.txt
@@ -1,10 +1,4 @@
-# TODO(jayconrod): support shared memory on more platforms.
-[!darwin] [!linux] [!windows] skip
-
-# Instrumentation not supported on other archs.
-# See #14565.
-[!amd64] [!arm64] skip
-
+[!fuzz-instrumented] skip
 [short] skip
 env GOCACHE=$WORK/cache
 
@@ -206,4 +200,4 @@ go test fuzz v1
 int(10)
 -- cache-file-bytes --
 go test fuzz v1
-[]byte("11111111111111111111")
\ No newline at end of file
+[]byte("11111111111111111111")
diff --git a/src/cmd/go/testdata/script/test_fuzz_setenv.txt b/src/cmd/go/testdata/script/test_fuzz_setenv.txt
index 9738697a91..2924569de1 100644
--- a/src/cmd/go/testdata/script/test_fuzz_setenv.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_setenv.txt
@@ -1,5 +1,5 @@
+[!fuzz] skip
 [short] skip
-[!darwin] [!linux] [!windows] skip
 
 go test -fuzz=FuzzA -fuzztime=100x fuzz_setenv_test.go
 
diff --git a/src/cmd/go/testdata/script/test_fuzz_unsupported.txt b/src/cmd/go/testdata/script/test_fuzz_unsupported.txt
new file mode 100644
index 0000000000..1ed0b8a6f7
--- /dev/null
+++ b/src/cmd/go/testdata/script/test_fuzz_unsupported.txt
@@ -0,0 +1,18 @@
+[fuzz] skip
+
+! go test -fuzz=. -fuzztime=1x
+! stdout .
+stderr '^-fuzz flag is not supported on '$GOOS'/'$GOARCH'$'
+
+-- go.mod --
+module example
+
+go 1.18
+-- fuzz_test.go --
+package example
+
+import "testing"
+
+func FuzzTrivial(f *testing.F) {
+	f.Fuzz(func(t *testing.T, _ []byte) {})
+}
diff --git a/src/cmd/internal/sys/supported.go b/src/cmd/internal/sys/supported.go
index 473e390587..18ca50f927 100644
--- a/src/cmd/internal/sys/supported.go
+++ b/src/cmd/internal/sys/supported.go
@@ -45,6 +45,29 @@ func ASanSupported(goos, goarch string) bool {
 	}
 }
 
+// FuzzSupported reports whether goos/goarch supports fuzzing
+// ('go test -fuzz=.').
+func FuzzSupported(goos, goarch string) bool {
+	switch goos {
+	case "darwin", "linux", "windows":
+		return true
+	default:
+		return false
+	}
+}
+
+// FuzzInstrumented reports whether fuzzing on goos/goarch uses coverage
+// instrumentation. (FuzzInstrumented implies FuzzSupported.)
+func FuzzInstrumented(goos, goarch string) bool {
+	switch goarch {
+	case "amd64", "arm64":
+		// TODO(#14565): support more architectures.
+		return FuzzSupported(goos, goarch)
+	default:
+		return false
+	}
+}
+
 // MustLinkExternal reports whether goos/goarch requires external linking.
 // (This is the opposite of internal/testenv.CanInternalLink. Keep them in sync.)
 func MustLinkExternal(goos, goarch string) bool {