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authorJing Chen <chjing@google.com>2020-12-11 04:19:58 -0800
committergVisor bot <gvisor-bot@google.com>2020-12-11 04:22:04 -0800
commit73eccab91ec58aafd1ffdf038993b78a812ba30f (patch)
tree67d1a83d0c35fd264c2e2ce64466bc220959303a /pkg/sentry
parent0eb4acad37c448a298c77090b3475ce6903ecf18 (diff)
Make semctl IPC_INFO cmd return the index of highest used entry.
PiperOrigin-RevId: 346973338
Diffstat (limited to 'pkg/sentry')
-rw-r--r--pkg/sentry/kernel/semaphore/semaphore.go53
-rw-r--r--pkg/sentry/syscalls/linux/sys_sem.go7
2 files changed, 57 insertions, 3 deletions
diff --git a/pkg/sentry/kernel/semaphore/semaphore.go b/pkg/sentry/kernel/semaphore/semaphore.go
index 31198d772..3dd3953b3 100644
--- a/pkg/sentry/kernel/semaphore/semaphore.go
+++ b/pkg/sentry/kernel/semaphore/semaphore.go
@@ -52,6 +52,9 @@ type Registry struct {
mu sync.Mutex `state:"nosave"`
semaphores map[int32]*Set
lastIDUsed int32
+ // indexes maintains a mapping between a set's index in virtual array and
+ // its identifier.
+ indexes map[int32]int32
}
// Set represents a set of semaphores that can be operated atomically.
@@ -113,6 +116,7 @@ func NewRegistry(userNS *auth.UserNamespace) *Registry {
return &Registry{
userNS: userNS,
semaphores: make(map[int32]*Set),
+ indexes: make(map[int32]int32),
}
}
@@ -163,6 +167,9 @@ func (r *Registry) FindOrCreate(ctx context.Context, key, nsems int32, mode linu
}
// Apply system limits.
+ //
+ // Map semaphores and map indexes in a registry are of the same size,
+ // check map semaphores only here for the system limit.
if len(r.semaphores) >= setsMax {
return nil, syserror.EINVAL
}
@@ -192,6 +199,23 @@ func (r *Registry) IPCInfo() *linux.SemInfo {
}
}
+// HighestIndex returns the index of the highest used entry in
+// the kernel's array.
+func (r *Registry) HighestIndex() int32 {
+ r.mu.Lock()
+ defer r.mu.Unlock()
+
+ // By default, highest used index is 0 even though
+ // there is no semaphroe set.
+ var highestIndex int32
+ for index := range r.indexes {
+ if index > highestIndex {
+ highestIndex = index
+ }
+ }
+ return highestIndex
+}
+
// RemoveID removes set with give 'id' from the registry and marks the set as
// dead. All waiters will be awakened and fail.
func (r *Registry) RemoveID(id int32, creds *auth.Credentials) error {
@@ -202,6 +226,11 @@ func (r *Registry) RemoveID(id int32, creds *auth.Credentials) error {
if set == nil {
return syserror.EINVAL
}
+ index, found := r.findIndexByID(id)
+ if !found {
+ // Inconsistent state.
+ panic(fmt.Sprintf("unable to find an index for ID: %d", id))
+ }
set.mu.Lock()
defer set.mu.Unlock()
@@ -213,6 +242,7 @@ func (r *Registry) RemoveID(id int32, creds *auth.Credentials) error {
}
delete(r.semaphores, set.ID)
+ delete(r.indexes, index)
set.destroy()
return nil
}
@@ -236,6 +266,11 @@ func (r *Registry) newSet(ctx context.Context, key int32, owner, creator fs.File
continue
}
if r.semaphores[id] == nil {
+ index, found := r.findFirstAvailableIndex()
+ if !found {
+ panic("unable to find an available index")
+ }
+ r.indexes[index] = id
r.lastIDUsed = id
r.semaphores[id] = set
set.ID = id
@@ -263,6 +298,24 @@ func (r *Registry) findByKey(key int32) *Set {
return nil
}
+func (r *Registry) findIndexByID(id int32) (int32, bool) {
+ for k, v := range r.indexes {
+ if v == id {
+ return k, true
+ }
+ }
+ return 0, false
+}
+
+func (r *Registry) findFirstAvailableIndex() (int32, bool) {
+ for index := int32(0); index < setsMax; index++ {
+ if _, present := r.indexes[index]; !present {
+ return index, true
+ }
+ }
+ return 0, false
+}
+
func (r *Registry) totalSems() int {
totalSems := 0
for _, v := range r.semaphores {
diff --git a/pkg/sentry/syscalls/linux/sys_sem.go b/pkg/sentry/syscalls/linux/sys_sem.go
index a1601676f..a62a6b3b5 100644
--- a/pkg/sentry/syscalls/linux/sys_sem.go
+++ b/pkg/sentry/syscalls/linux/sys_sem.go
@@ -150,9 +150,10 @@ func Semctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
buf := args[3].Pointer()
r := t.IPCNamespace().SemaphoreRegistry()
info := r.IPCInfo()
- _, err := info.CopyOut(t, buf)
- // TODO(gvisor.dev/issue/137): Return the index of the highest used entry.
- return 0, nil, err
+ if _, err := info.CopyOut(t, buf); err != nil {
+ return 0, nil, err
+ }
+ return uintptr(r.HighestIndex()), nil, nil
case linux.SEM_INFO,
linux.SEM_STAT,