Increase gofer coverage in tests

Lots of tests use /tmp for the tests. Force /tmp to be
mounted over fsgofer instead of tmpfs.

PiperOrigin-RevId: 230788985
Change-Id: Id6597ed88133232d15e808c48126bf77cb32673e

test/syscalls/BUILD

@@ -42,6 +42,7 @@ syscall_test(test = "//test/syscalls/linux:chmod_test")
 syscall_test(
     size = "medium",
     test = "//test/syscalls/linux:chown_test",
+    use_tmpfs = True,  # chwon tests require gofer to be running as root.
 )
 
 syscall_test(test = "//test/syscalls/linux:chroot_test")
@@ -137,7 +138,10 @@ syscall_test(
 
 syscall_test(test = "//test/syscalls/linux:kill_test")
 
-syscall_test(test = "//test/syscalls/linux:link_test")
+syscall_test(
+    test = "//test/syscalls/linux:link_test",
+    use_tmpfs = True,  # gofer needs CAP_DAC_READ_SEARCH to use AT_EMPTY_PATH with linkat(2)
+)
 
 syscall_test(test = "//test/syscalls/linux:lseek_test")
 
@@ -151,7 +155,10 @@ syscall_test(test = "//test/syscalls/linux:mincore_test")
 
 syscall_test(test = "//test/syscalls/linux:mkdir_test")
 
-syscall_test(test = "//test/syscalls/linux:mknod_test")
+syscall_test(
+    test = "//test/syscalls/linux:mknod_test",
+    use_tmpfs = True,  # mknod is not supported over gofer.
+)
 
 syscall_test(
     size = "medium",

test/syscalls/build_defs.bzl

@@ -2,12 +2,12 @@
 
 # syscall_test is a macro that will create targets to run the given test target
 # on the host (native) and runsc.
-def syscall_test(test, shard_count = 5, size = "small"):
-    _syscall_test(test, shard_count, size, "native")
-    _syscall_test(test, shard_count, size, "kvm")
-    _syscall_test(test, shard_count, size, "ptrace")
+def syscall_test(test, shard_count = 5, size = "small", use_tmpfs = False):
+    _syscall_test(test, shard_count, size, "native", False)
+    _syscall_test(test, shard_count, size, "kvm", use_tmpfs)
+    _syscall_test(test, shard_count, size, "ptrace", use_tmpfs)
 
-def _syscall_test(test, shard_count, size, platform):
+def _syscall_test(test, shard_count, size, platform, use_tmpfs):
     test_name = test.split(":")[1]
 
     # Prepend "runsc" to non-native platform names.
@@ -39,6 +39,7 @@ def _syscall_test(test, shard_count, size, platform):
             # Arguments are passed directly to syscall_test_runner binary.
             "--test-name=" + test_name,
             "--platform=" + platform,
+            "--use-tmpfs=" + str(use_tmpfs),
             "--debug=false",
             "--strace=false",
             "--parallel=true",

test/syscalls/linux/inotify.cc

@@ -1222,7 +1222,8 @@ TEST(Inotify, LinkGeneratesAttribAndCreateEvents) {
 
   const int rc = link(file1.path().c_str(), link1.path().c_str());
   // link(2) is only supported on tmpfs in the sandbox.
-  SKIP_IF(IsRunningOnGvisor() && rc != 0 && errno == EPERM);
+  SKIP_IF(IsRunningOnGvisor() && rc != 0 &&
+          (errno == EPERM || errno == ENOENT));
   ASSERT_THAT(rc, SyscallSucceeds());
 
   const std::vector<Event> events =
@@ -1238,7 +1239,8 @@ TEST(Inotify, HardlinksReuseSameWatch) {
   TempPath link1(root.path() + "/link1");
   const int rc = link(file1.path().c_str(), link1.path().c_str());
   // link(2) is only supported on tmpfs in the sandbox.
-  SKIP_IF(IsRunningOnGvisor() && rc != 0 && errno == EPERM);
+  SKIP_IF(IsRunningOnGvisor() && rc != 0 &&
+          (errno == EPERM || errno == ENOENT));
   ASSERT_THAT(rc, SyscallSucceeds());
 
   const FileDescriptor fd =

test/syscalls/syscall_test_runner.go

@@ -45,6 +45,7 @@ var (
 	debug     = flag.Bool("debug", false, "enable debug logs")
 	strace    = flag.Bool("strace", false, "enable strace logs")
 	platform  = flag.String("platform", "ptrace", "platform to run on")
+	useTmpfs  = flag.Bool("use-tmpfs", false, "mounts tmpfs for /tmp")
 	parallel  = flag.Bool("parallel", false, "run tests in parallel")
 	runscPath = flag.String("runsc", "", "path to runsc binary")
 )
@@ -109,10 +110,14 @@ func runTestCaseRunsc(testBin string, tc gtest.TestCase, t *testing.T) {
 	// write to the rootfs, and expect EACCES, not EROFS.
 	spec.Root.Readonly = false
 
-	// Forces '/tmp' to be mounted as tmpfs, otherwise test that rely on features
-	// available in gVisor's tmpfs and not gofers, may fail.
-	spec.Mounts = []specs.Mount{
-		{Destination: "/tmp", Type: "tmpfs"},
+	// Test spec comes with pre-defined mounts that we don't want. Reset it.
+	spec.Mounts = nil
+	if *useTmpfs {
+		// Forces '/tmp' to be mounted as tmpfs, otherwise test that rely on
+		// features available in gVisor's tmpfs and not gofers, may fail.
+		spec.Mounts = []specs.Mount{
+			{Destination: "/tmp", Type: "tmpfs"},
+		}
 	}
 
 	// Set environment variable that indicates we are