feat: add mount/fs management syscall tracing for c7

3 files changed, 122 insertions, 0 deletions

diff --git a/cmd/ioworkload/scenario_mountfs.go b/cmd/ioworkload/scenario_mountfs.go
new file mode 100644
index 0000000..4c48ded
--- /dev/null
+++ b/cmd/ioworkload/scenario_mountfs.go
@@ -0,0 +1,91 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+type mountIDReq struct {
+	Size  uint32
+	Pad   uint32
+	MntID uint64
+	Param uint64
+}
+
+func mountfsManagement() error {
+	dir, cleanup, err := makeTempDir("mountfs-management")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	mountPoint := filepath.Join(dir, "mnt")
+	if err := os.Mkdir(mountPoint, 0o755); err != nil {
+		return fmt.Errorf("mkdir mountpoint: %w", err)
+	}
+
+	swapFile := filepath.Join(dir, "swapfile")
+	if err := os.WriteFile(swapFile, []byte("swap"), 0o600); err != nil {
+		return fmt.Errorf("write swap file: %w", err)
+	}
+
+	mountPath := mustCStringPtr(mountPoint)
+	swapPath := mustCStringPtr(swapFile)
+	newRoot := mustCStringPtr(mountPoint)
+	putOld := mustCStringPtr(dir)
+	tmpfs := mustCStringPtr("tmpfs")
+	none := mustCStringPtr("none")
+	atFDCWDInt := int64(unix.AT_FDCWD)
+	atFDCWD := uintptr(atFDCWDInt)
+
+	// Best-effort coverage: these calls are expected to fail on most hosts
+	// without CAP_SYS_ADMIN, but still exercise syscall tracing paths.
+	_, _, _ = syscall.RawSyscall6(unix.SYS_MOUNT, uintptr(unsafe.Pointer(none)), uintptr(unsafe.Pointer(mountPath)), uintptr(unsafe.Pointer(tmpfs)), 0, 0, 0)
+	_, _, _ = syscall.RawSyscall(unix.SYS_UMOUNT2, uintptr(unsafe.Pointer(mountPath)), 0, 0)
+	_, _, _ = syscall.RawSyscall(unix.SYS_UMOUNT2, uintptr(unsafe.Pointer(mountPath)), uintptr(unix.MNT_DETACH), 0)
+	_, _, _ = syscall.RawSyscall6(unix.SYS_MOVE_MOUNT, atFDCWD, uintptr(unsafe.Pointer(mountPath)), atFDCWD, uintptr(unsafe.Pointer(mountPath)), 0, 0)
+	_, _, _ = syscall.RawSyscall(unix.SYS_FSMOUNT, ^uintptr(0), 0, 0)
+	_, _, _ = syscall.RawSyscall(unix.SYS_PIVOT_ROOT, uintptr(unsafe.Pointer(newRoot)), uintptr(unsafe.Pointer(putOld)), 0)
+	_, _, _ = syscall.RawSyscall6(unix.SYS_QUOTACTL, 0, uintptr(unsafe.Pointer(mountPath)), 0, 0, 0, 0)
+	_, _, _ = syscall.RawSyscall(unix.SYS_SWAPON, uintptr(unsafe.Pointer(swapPath)), 0, 0)
+	_, _, _ = syscall.RawSyscall(unix.SYS_SWAPOFF, uintptr(unsafe.Pointer(swapPath)), 0, 0)
+
+	req := mountIDReq{Size: uint32(unsafe.Sizeof(mountIDReq{}))}
+	var statBuf [256]byte
+	_, _, _ = syscall.RawSyscall6(unix.SYS_STATMOUNT, uintptr(unsafe.Pointer(&req)), uintptr(unsafe.Pointer(&statBuf[0])), uintptr(len(statBuf)), 0, 0, 0)
+
+	var mountIDs [8]uint64
+	_, _, _ = syscall.RawSyscall6(unix.SYS_LISTMOUNT, uintptr(unsafe.Pointer(&req)), uintptr(unsafe.Pointer(&mountIDs[0])), uintptr(len(mountIDs)), 0, 0, 0)
+
+	if nr, err := listnsSyscallNr(); err == nil {
+		var nsIDs [8]uint64
+		_, _, _ = syscall.RawSyscall6(nr, uintptr(unsafe.Pointer(&req)), uintptr(unsafe.Pointer(&nsIDs[0])), uintptr(len(nsIDs)), 0, 0, 0)
+	}
+
+	return nil
+}
+
+func listnsSyscallNr() (uintptr, error) {
+	return listnsSyscallNrForArch(runtime.GOARCH)
+}
+
+func listnsSyscallNrForArch(arch string) (uintptr, error) {
+	// __NR_listns was introduced from asm-generic numbering where amd64/arm64 use 470.
+	switch arch {
+	case "amd64", "arm64":
+		return 470, nil
+	default:
+		return 0, fmt.Errorf("listns syscall number not defined for GOARCH=%s", arch)
+	}
+}
+
+func mustCStringPtr(s string) *byte {
+	p, _ := unix.BytePtrFromString(s)
+	return p
+}
diff --git a/cmd/ioworkload/scenario_mountfs_test.go b/cmd/ioworkload/scenario_mountfs_test.go
new file mode 100644
index 0000000..c1c317a
--- /dev/null
+++ b/cmd/ioworkload/scenario_mountfs_test.go
@@ -0,0 +1,30 @@
+package main
+
+import "testing"
+
+func TestListnsSyscallNrForArch(t *testing.T) {
+	for _, tc := range []struct {
+		name    string
+		arch    string
+		want    uintptr
+		wantErr bool
+	}{
+		{name: "amd64", arch: "amd64", want: 470},
+		{name: "arm64", arch: "arm64", want: 470},
+		{name: "unsupported", arch: "riscv64", wantErr: true},
+	} {
+		got, err := listnsSyscallNrForArch(tc.arch)
+		if tc.wantErr {
+			if err == nil {
+				t.Fatalf("%s: expected error", tc.name)
+			}
+			continue
+		}
+		if err != nil {
+			t.Fatalf("%s: unexpected error: %v", tc.name, err)
+		}
+		if got != tc.want {
+			t.Fatalf("%s: got %d, want %d", tc.name, got, tc.want)
+		}
+	}
+}
diff --git a/cmd/ioworkload/scenarios.go b/cmd/ioworkload/scenarios.go
index e0827a5..79d4e6d 100644
--- a/cmd/ioworkload/scenarios.go
+++ b/cmd/ioworkload/scenarios.go
@@ -34,6 +34,7 @@ var scenarios = map[string]func() error{
 	"pipe2-basic":                   pipe2Basic,
 	"eventfd-basic":                 eventfdBasic,
 	"eventfd2-basic":                eventfd2Basic,
+	"mountfs-management":            mountfsManagement,
 	"polling-epoll":                 pollingEpoll,
 	"sleep-syscalls":                sleepSyscalls,
 	"family-mixed":                  familyMixed,