Add negative integration tests for truncate syscalls (task 348)

Add two negative test scenarios:
- truncate-enoent: SYS_TRUNCATE on nonexistent file, expects ENOENT
- truncate-ftruncate-ebadf: SYS_FTRUNCATE on invalid fd 99999, expects EBADF

Both verify ior captures tracepoints even when syscalls fail.

Amp-Thread-ID: https://ampcode.com/threads/T-019c81b7-9641-763e-b99e-20a0d3552005
Co-authored-by: Amp <amp@ampcode.com>

2 files changed, 59 insertions, 2 deletions

diff --git a/integrationtests/cmd/ioworkload/scenarios.go b/integrationtests/cmd/ioworkload/scenarios.go
index 58c78e1..f25b8a4 100644
--- a/integrationtests/cmd/ioworkload/scenarios.go
+++ b/integrationtests/cmd/ioworkload/scenarios.go
@@ -86,8 +86,10 @@ var scenarios = map[string]func() error{
 	"sync-fsync-ebadf":           syncFsyncEbadf,
 	"sync-fdatasync-ebadf":       syncFdatasyncEbadf,
 	"sync-file-range-ebadf":      syncFileRangeEbadf,
-	"truncate-basic":      truncateBasic,
-	"truncate-ftruncate":  truncateFtruncate,
+	"truncate-basic":          truncateBasic,
+	"truncate-ftruncate":      truncateFtruncate,
+	"truncate-enoent":         truncateEnoent,
+	"truncate-ftruncate-ebadf": truncateFtruncateEbadf,
 	"iouring-setup":       iouringSetup,
 	"iouring-enter":       iouringEnter,
 	"iouring-register":    iouringRegister,
@@ -2225,6 +2227,40 @@ func truncateFtruncate() error {
 	return syscall.Ftruncate(fd, 5)
 }
 
+// truncateEnoent attempts to truncate a nonexistent file via raw SYS_TRUNCATE.
+// The syscall fails with ENOENT, but ior captures the enter_truncate
+// tracepoint because the path is read on entry.
+func truncateEnoent() error {
+	dir, cleanup, err := makeTempDir("truncate-enoent")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "truncate-enoent-missing.txt")
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return fmt.Errorf("path bytes: %w", err)
+	}
+	_, _, errno := syscall.Syscall(syscall.SYS_TRUNCATE, uintptr(unsafe.Pointer(pathBytes)), 0, 0)
+	runtime.KeepAlive(pathBytes)
+	if errno == 0 {
+		return fmt.Errorf("expected ENOENT, but truncate succeeded")
+	}
+	return nil
+}
+
+// truncateFtruncateEbadf calls raw SYS_FTRUNCATE on an invalid fd (99999).
+// The syscall fails with EBADF, but ior captures the enter_ftruncate
+// tracepoint because it is recorded on syscall entry.
+func truncateFtruncateEbadf() error {
+	_, _, errno := syscall.Syscall(syscall.SYS_FTRUNCATE, 99999, 0, 0)
+	if errno == 0 {
+		return fmt.Errorf("expected EBADF, but ftruncate succeeded")
+	}
+	return nil
+}
+
 // openByHandleAt creates a file, resolves its handle via name_to_handle_at,
 // then opens it via open_by_handle_at. Requires root (CAP_DAC_READ_SEARCH).
 // LockOSThread prevents goroutine migration between the two syscalls so that
diff --git a/integrationtests/truncate_test.go b/integrationtests/truncate_test.go
index 9b94eed..7d3f12e 100644
--- a/integrationtests/truncate_test.go
+++ b/integrationtests/truncate_test.go
@@ -23,3 +23,24 @@ func TestTruncateFtruncate(t *testing.T) {
 		},
 	})
 }
+
+func TestTruncateEnoent(t *testing.T) {
+	runScenario(t, "truncate-enoent", []ExpectedEvent{
+		{
+			PathContains: "truncate-enoent-missing.txt",
+			Tracepoint:   "enter_truncate",
+			Comm:         "ioworkload",
+			MinCount:     1,
+		},
+	})
+}
+
+func TestTruncateFtruncateEbadf(t *testing.T) {
+	runScenario(t, "truncate-ftruncate-ebadf", []ExpectedEvent{
+		{
+			Tracepoint: "enter_ftruncate",
+			Comm:       "ioworkload",
+			MinCount:   1,
+		},
+	})
+}