2 files changed, 113 insertions, 0 deletions
diff --git a/integrationtests/cmd/ioworkload/scenario_mmap.go b/integrationtests/cmd/ioworkload/scenario_mmap.go
new file mode 100644
index 0000000..e7b9f02
--- /dev/null
+++ b/integrationtests/cmd/ioworkload/scenario_mmap.go
@@ -0,0 +1,110 @@
+package main
+
+import (
+	"fmt"
+	"path/filepath"
+	"syscall"
+	"unsafe"
+)
+
+// mmapBasic creates a file-backed shared mapping.
+// mmap(2) allows closing the fd after mapping without invalidating the mapping.
+func mmapBasic() error {
+	dir, cleanup, err := makeTempDir("mmap-basic")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "mmapfile.txt")
+	fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT|syscall.O_TRUNC, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	defer syscall.Close(fd)
+
+	data := []byte("mmap shared page data")
+	if _, err := syscall.Write(fd, data); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+
+	mapped, err := syscall.Mmap(fd, 0, len(data), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
+	if err != nil {
+		return fmt.Errorf("mmap: %w", err)
+	}
+	defer syscall.Munmap(mapped)
+
+	copy(mapped[:4], []byte("MMAP"))
+	return nil
+}
+
+// mmapMsyncSync maps a file and flushes modifications via msync(2).
+// Per msync(2), callers should specify exactly one of MS_SYNC or MS_ASYNC.
+func mmapMsyncSync() error {
+	dir, cleanup, err := makeTempDir("mmap-msync-sync")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "msyncfile.txt")
+	fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT|syscall.O_TRUNC, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	defer syscall.Close(fd)
+
+	data := []byte("msync shared page data")
+	if _, err := syscall.Write(fd, data); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+
+	mapped, err := syscall.Mmap(fd, 0, len(data), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
+	if err != nil {
+		return fmt.Errorf("mmap: %w", err)
+	}
+	defer syscall.Munmap(mapped)
+
+	copy(mapped[:5], []byte("MSYNC"))
+
+	_, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(&mapped[0])), uintptr(len(mapped)), uintptr(syscall.MS_SYNC))
+	if errno != 0 {
+		return fmt.Errorf("msync: %w", errno)
+	}
+	return nil
+}
+
+// mmapMsyncInvalidFlags calls msync(2) with both MS_SYNC and MS_ASYNC.
+// The kernel returns EINVAL, but enter_msync should still be captured.
+func mmapMsyncInvalidFlags() error {
+	dir, cleanup, err := makeTempDir("mmap-msync-invalid-flags")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "msyncinvalidfile.txt")
+	fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT|syscall.O_TRUNC, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	defer syscall.Close(fd)
+
+	data := []byte("msync invalid flags data")
+	if _, err := syscall.Write(fd, data); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+
+	mapped, err := syscall.Mmap(fd, 0, len(data), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
+	if err != nil {
+		return fmt.Errorf("mmap: %w", err)
+	}
+	defer syscall.Munmap(mapped)
+
+	flags := syscall.MS_SYNC | syscall.MS_ASYNC
+	_, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(&mapped[0])), uintptr(len(mapped)), uintptr(flags))
+	if errno != syscall.EINVAL {
+		return fmt.Errorf("expected EINVAL from msync with both MS_SYNC|MS_ASYNC, got %v", errno)
+	}
+	return nil
+}
diff --git a/integrationtests/cmd/ioworkload/scenarios.go b/integrationtests/cmd/ioworkload/scenarios.go
index 4bd85b6..d99b584 100644
--- a/integrationtests/cmd/ioworkload/scenarios.go
+++ b/integrationtests/cmd/ioworkload/scenarios.go
@@ -82,6 +82,9 @@ var scenarios = map[string]func() error{
 	"sync-fsync-ebadf":            syncFsyncEbadf,
 	"sync-fdatasync-ebadf":        syncFdatasyncEbadf,
 	"sync-file-range-ebadf":       syncFileRangeEbadf,
+	"mmap-basic":                  mmapBasic,
+	"mmap-msync-sync":             mmapMsyncSync,
+	"mmap-msync-invalid-flags":    mmapMsyncInvalidFlags,
 	"truncate-basic":              truncateBasic,
 	"truncate-ftruncate":          truncateFtruncate,
 	"truncate-enoent":             truncateEnoent,