Add negative integration tests for dir syscalls (task 348)

Add three negative test scenarios for directory operations:
- dir-mkdir-eexist: SYS_MKDIR on existing directory (EEXIST)
- dir-chdir-enoent: SYS_CHDIR to nonexistent directory (ENOENT)
- dir-getdents-ebadf: SYS_GETDENTS64 with invalid fd (EBADF)

All use raw syscalls to hit exact tracepoints. Tests verify ior
captures events even when syscalls fail (entry-side capture).

Amp-Thread-ID: https://ampcode.com/threads/T-019c81ab-0d62-726e-b859-91b4898be6fe
Co-authored-by: Amp <amp@ampcode.com>

2 files changed, 110 insertions, 4 deletions

diff --git a/integrationtests/cmd/ioworkload/scenarios.go b/integrationtests/cmd/ioworkload/scenarios.go
index b4a153b..5eb8acb 100644
--- a/integrationtests/cmd/ioworkload/scenarios.go
+++ b/integrationtests/cmd/ioworkload/scenarios.go
@@ -62,10 +62,13 @@ var scenarios = map[string]func() error{
 	"unlink-enoent":          unlinkEnoent,
 	"unlink-rmdir-notempty":  unlinkRmdirNotempty,
 	"unlink-unlinkat-enoent": unlinkUnlinkatEnoent,
-	"dir-basic":       dirBasic,
-	"dir-mkdirat":     dirMkdirat,
-	"dir-chdir":       dirChdir,
-	"dir-getdents":    dirGetdents,
+	"dir-basic":            dirBasic,
+	"dir-mkdirat":          dirMkdirat,
+	"dir-chdir":            dirChdir,
+	"dir-getdents":         dirGetdents,
+	"dir-mkdir-eexist":     dirMkdirEexist,
+	"dir-chdir-enoent":     dirChdirEnoent,
+	"dir-getdents-ebadf":   dirGetdentsEbadf,
 	"stat-basic":      statBasic,
 	"stat-fstat":      statFstat,
 	"stat-lstat":      statLstat,
@@ -1732,6 +1735,77 @@ func dirGetdents() error {
 	return nil
 }
 
+// dirMkdirEexist attempts to create a directory that already exists via raw
+// SYS_MKDIR. The syscall fails with EEXIST, but ior captures the tracepoint
+// on entry.
+func dirMkdirEexist() error {
+	dir, cleanup, err := makeTempDir("dir-mkdir-eexist")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	subDir := filepath.Join(dir, "mkdir-eexist-subdir")
+	pathBytes, err := syscall.BytePtrFromString(subDir)
+	if err != nil {
+		return fmt.Errorf("path bytes: %w", err)
+	}
+
+	// Create the directory first so the second attempt fails.
+	_, _, errno := syscall.Syscall(syscall.SYS_MKDIR, uintptr(unsafe.Pointer(pathBytes)), 0o755, 0)
+	runtime.KeepAlive(pathBytes)
+	if errno != 0 {
+		return fmt.Errorf("first mkdir: %w", errno)
+	}
+
+	// Second mkdir on the same path should fail with EEXIST.
+	pathBytes2, err := syscall.BytePtrFromString(subDir)
+	if err != nil {
+		return fmt.Errorf("path bytes: %w", err)
+	}
+	_, _, errno = syscall.Syscall(syscall.SYS_MKDIR, uintptr(unsafe.Pointer(pathBytes2)), 0o755, 0)
+	runtime.KeepAlive(pathBytes2)
+	if errno == 0 {
+		return fmt.Errorf("expected EEXIST, but mkdir succeeded")
+	}
+	return nil
+}
+
+// dirChdirEnoent attempts to change to a nonexistent directory via raw
+// SYS_CHDIR. The syscall fails with ENOENT, but ior captures the tracepoint
+// on entry.
+func dirChdirEnoent() error {
+	dir, cleanup, err := makeTempDir("dir-chdir-enoent")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	badPath := filepath.Join(dir, "chdir-enoent-missing")
+	pathBytes, err := syscall.BytePtrFromString(badPath)
+	if err != nil {
+		return fmt.Errorf("path bytes: %w", err)
+	}
+	_, _, errno := syscall.Syscall(syscall.SYS_CHDIR, uintptr(unsafe.Pointer(pathBytes)), 0, 0)
+	runtime.KeepAlive(pathBytes)
+	if errno == 0 {
+		return fmt.Errorf("expected ENOENT, but chdir succeeded")
+	}
+	return nil
+}
+
+// dirGetdentsEbadf calls getdents64(2) with an invalid file descriptor.
+// The syscall fails with EBADF, but ior captures the tracepoint on entry.
+func dirGetdentsEbadf() error {
+	buf := make([]byte, 4096)
+	_, _, errno := syscall.Syscall(syscall.SYS_GETDENTS64, uintptr(9999), uintptr(unsafe.Pointer(&buf[0])), uintptr(len(buf)))
+	runtime.KeepAlive(buf)
+	if errno == 0 {
+		return fmt.Errorf("expected EBADF, but getdents64 succeeded")
+	}
+	return nil
+}
+
 // statBasic creates a file and stats it via raw SYS_STAT (newstat).
 // We use the raw syscall because Go's syscall.Stat wraps newfstatat on amd64.
 func statBasic() error {
diff --git a/integrationtests/dir_test.go b/integrationtests/dir_test.go
index 67bbe93..585f03f 100644
--- a/integrationtests/dir_test.go
+++ b/integrationtests/dir_test.go
@@ -45,3 +45,35 @@ func TestDirGetdents(t *testing.T) {
 		},
 	})
 }
+
+func TestDirMkdirEexist(t *testing.T) {
+	runScenario(t, "dir-mkdir-eexist", []ExpectedEvent{
+		{
+			PathContains: "mkdir-eexist-subdir",
+			Tracepoint:   "enter_mkdir",
+			Comm:         "ioworkload",
+			MinCount:     2,
+		},
+	})
+}
+
+func TestDirChdirEnoent(t *testing.T) {
+	runScenario(t, "dir-chdir-enoent", []ExpectedEvent{
+		{
+			PathContains: "chdir-enoent-missing",
+			Tracepoint:   "enter_chdir",
+			Comm:         "ioworkload",
+			MinCount:     1,
+		},
+	})
+}
+
+func TestDirGetdentsEbadf(t *testing.T) {
+	runScenario(t, "dir-getdents-ebadf", []ExpectedEvent{
+		{
+			Tracepoint: "enter_getdents64",
+			Comm:       "ioworkload",
+			MinCount:   1,
+		},
+	})
+}