Add negative integration tests for fcntl syscalls (task 348)

Add two negative scenarios:
- fcntl-invalid-fd: calls SYS_FCNTL F_GETFL on invalid fd 99999 (EBADF)
- fcntl-dupfd-max: calls F_DUPFD with minfd=1<<30 beyond RLIMIT_NOFILE (EINVAL)

Both verify ior captures enter_fcntl tracepoints even when syscalls fail.

Amp-Thread-ID: https://ampcode.com/threads/T-019c819b-5673-75ab-8eb4-227b6cf56b38
Co-authored-by: Amp <amp@ampcode.com>

2 files changed, 59 insertions, 0 deletions

diff --git a/integrationtests/cmd/ioworkload/scenarios.go b/integrationtests/cmd/ioworkload/scenarios.go
index dd8d46e..4275fb6 100644
--- a/integrationtests/cmd/ioworkload/scenarios.go
+++ b/integrationtests/cmd/ioworkload/scenarios.go
@@ -42,6 +42,8 @@ var scenarios = map[string]func() error{
 	"fcntl-dupfd":          fcntlDupfd,
 	"fcntl-setfl":          fcntlSetfl,
 	"fcntl-dupfd-cloexec":  fcntlDupfdCloexec,
+	"fcntl-invalid-fd":     fcntlInvalidFd,
+	"fcntl-dupfd-max":      fcntlDupfdMax,
 	"rename-basic":         renameBasic,
 	"rename-renameat":      renameRenameat,
 	"rename-renameat2":     renameRenameat2,
@@ -789,6 +791,42 @@ func fcntlDupfdCloexec() error {
 	return nil
 }
 
+// fcntlInvalidFd calls fcntl F_GETFL on an invalid fd (99999).
+// The syscall fails with EBADF, but ior should capture the enter_fcntl
+// tracepoint because it is recorded on syscall entry.
+func fcntlInvalidFd() error {
+	_, _, errno := syscall.Syscall(syscall.SYS_FCNTL, 99999, syscall.F_GETFL, 0)
+	if errno == 0 {
+		return fmt.Errorf("expected fcntl on invalid fd to fail")
+	}
+	return nil
+}
+
+// fcntlDupfdMax opens a file and calls fcntl F_DUPFD with a minfd value
+// that exceeds the process RLIMIT_NOFILE. The kernel rejects this with
+// EINVAL, but ior should capture the enter_fcntl tracepoint.
+func fcntlDupfdMax() error {
+	dir, cleanup, err := makeTempDir("fcntl-dupfd-max")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "fcntldupfdmaxfile.txt")
+	fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	defer syscall.Close(fd)
+
+	// Use a minfd far beyond any realistic RLIMIT_NOFILE.
+	_, _, errno := syscall.Syscall(syscall.SYS_FCNTL, uintptr(fd), syscall.F_DUPFD, 1<<30)
+	if errno == 0 {
+		return fmt.Errorf("expected fcntl F_DUPFD with extreme minfd to fail")
+	}
+	return nil
+}
+
 // renameBasic creates a file and renames it via rename(2).
 // Uses raw SYS_RENAME because Go's syscall.Rename wraps renameat on amd64.
 func renameBasic() error {
diff --git a/integrationtests/fcntl_test.go b/integrationtests/fcntl_test.go
index f9c95bd..5062bd6 100644
--- a/integrationtests/fcntl_test.go
+++ b/integrationtests/fcntl_test.go
@@ -34,3 +34,24 @@ func TestFcntlDupfdCloexec(t *testing.T) {
 		},
 	})
 }
+
+func TestFcntlInvalidFd(t *testing.T) {
+	runScenario(t, "fcntl-invalid-fd", []ExpectedEvent{
+		{
+			Tracepoint: "enter_fcntl",
+			Comm:       "ioworkload",
+			MinCount:   1,
+		},
+	})
+}
+
+func TestFcntlDupfdMax(t *testing.T) {
+	runScenario(t, "fcntl-dupfd-max", []ExpectedEvent{
+		{
+			PathContains: "fcntldupfdmaxfile.txt",
+			Tracepoint:   "enter_fcntl",
+			Comm:         "ioworkload",
+			MinCount:     1,
+		},
+	})
+}