fix(swingset): add GC syscall stubs

This adda `syscall.retireImports` and `syscall.retireExports` to the
pre-existing `syscall.dropImports`. All three are no-ops, but vats should be
able to call them without ill effects, so kernel and liveslots development
can continue in parallel.

refs #2724

packages/SwingSet/src/kernel/kernelSyscall.js

@@ -119,6 +119,18 @@ export function makeKernelSyscallHandler(tools) {
     return OKNULL;
   }
 
+  function retireImports(koids) {
+    assert(Array.isArray(koids), X`retireImports given non-Array ${koids}`);
+    console.log(`-- kernel ignoring retireImports ${koids.join(',')}`);
+    return OKNULL;
+  }
+
+  function retireExports(koids) {
+    assert(Array.isArray(koids), X`retireExports given non-Array ${koids}`);
+    console.log(`-- kernel ignoring retireExports ${koids.join(',')}`);
+    return OKNULL;
+  }
+
   function doKernelSyscall(ksc) {
     const [type, ...args] = ksc;
     switch (type) {
@@ -140,16 +152,17 @@ export function makeKernelSyscallHandler(tools) {
         return vatstoreDelete(...args);
       case 'dropImports':
         return dropImports(...args);
+      case 'retireImports':
+        return retireImports(...args);
+      case 'retireExports':
+        return retireExports(...args);
       default:
         assert.fail(X`unknown vatSyscall type ${type}`);
     }
   }
 
   const kernelSyscallHandler = harden({
     send, // TODO remove these individual ones
-    invoke,
-    subscribe,
-    resolve,
     doKernelSyscall,
   });
   return kernelSyscallHandler;

packages/SwingSet/src/kernel/vatManager/supervisor-helper.js

@@ -158,6 +158,8 @@ function makeSupervisorSyscall(syscallToManager, workerCanBlock) {
     resolve: resolutions => doSyscall(['resolve', resolutions]),
     exit: (isFailure, data) => doSyscall(['exit', isFailure, data]),
     dropImports: vrefs => doSyscall(['dropImports', vrefs]),
+    retireImports: vrefs => doSyscall(['retireImports', vrefs]),
+    retireExports: vrefs => doSyscall(['retireExports', vrefs]),
 
     // These syscalls should be omitted if the worker cannot get a
     // synchronous return value back from the kernel, such as when the worker

packages/SwingSet/src/kernel/vatTranslator.js

@@ -185,20 +185,43 @@ function makeTranslateVatSyscallToKernelSyscall(vatID, kernelKeeper) {
   }
 
   function translateDropImports(vrefs) {
-    assert(Array.isArray(vrefs), X`dropImport() given non-Array ${vrefs}`);
-    // We delete clist entries as we translate, which will (TODO) decref the
-    // krefs. When we're done with that loop, we hand the set of krefs to
-    // kernelSyscall so it can (TODO) check newly-decremented refcounts
-    // against zero, and maybe delete even more.
+    assert(Array.isArray(vrefs), X`dropImports() given non-Array ${vrefs}`);
+    // TODO: dropImports does not affect the c-list, but makes the kernel
+    // calculate the refcount of a kref, possibly causing further action.
     const krefs = vrefs.map(vref => {
-      insistVatType('object', vref);
+      insistVatType('object', vref); // TODO: probably device nodes too
       const kref = mapVatSlotToKernelSlot(vref);
-      vatKeeper.deleteCListEntry(kref, vref);
       return kref;
     });
     return harden(['dropImports', krefs]);
   }
 
+  function translateRetireImports(vrefs) {
+    assert(Array.isArray(vrefs), X`retireImports() given non-Array ${vrefs}`);
+    // TODO: retireImports will delete clist entries as we translate, which
+    // will (TODO) decref the krefs. When we're done with that loop, we hand
+    // the set of krefs to kernelSyscall so it can (TODO) check
+    // newly-decremented refcounts against zero, and maybe delete even more.
+    const krefs = vrefs.map(vref => {
+      insistVatType('object', vref); // TODO: probably device nodes too
+      const kref = mapVatSlotToKernelSlot(vref);
+      // vatKeeper.deleteCListEntry(kref, vref);
+      return kref;
+    });
+    return harden(['retireImports', krefs]);
+  }
+
+  function translateRetireExports(vrefs) {
+    assert(Array.isArray(vrefs), X`retireExports() given non-Array ${vrefs}`);
+    // TODO: not sure how the kernel should react to this yet
+    const krefs = vrefs.map(vref => {
+      insistVatType('object', vref); // TODO: probably device nodes too
+      const kref = mapVatSlotToKernelSlot(vref);
+      return kref;
+    });
+    return harden(['retireExports', krefs]);
+  }
+
   function translateCallNow(target, method, args) {
     insistCapData(args);
     const dev = mapVatSlotToKernelSlot(target);
@@ -276,6 +299,10 @@ function makeTranslateVatSyscallToKernelSyscall(vatID, kernelKeeper) {
         return translateVatstoreDelete(...args);
       case 'dropImports':
         return translateDropImports(...args);
+      case 'retireImports':
+        return translateRetireImports(...args);
+      case 'retireExports':
+        return translateRetireExports(...args);
       default:
         assert.fail(X`unknown vatSyscall type ${type}`);
     }

packages/SwingSet/src/message.js

@@ -150,7 +150,9 @@ export function insistVatSyscallObject(vso) {
       assert.typeof(key, 'string');
       break;
     }
-    case 'dropImports': {
+    case 'dropImports':
+    case 'retireImports':
+    case 'retireExports': {
       const [slots] = rest;
       assert(Array.isArray(slots));
       for (const slot of slots) {

packages/SwingSet/src/types.js

@@ -82,10 +82,13 @@
  * @typedef { [tag: 'vatstoreSet', key: string, data: string ]} VatSyscallVatstoreSet
  * @typedef { [tag: 'vatstoreDelete', key: string ]} VatSyscallVatstoreDelete
  * @typedef { [tag: 'dropImports', slots: string[] ]} VatSyscallDropImports
+ * @typedef { [tag: 'retireImports', slots: string[] ]} VatSyscallRetireImports
+ * @typedef { [tag: 'retireExports', slots: string[] ]} VatSyscallRetireExports
  *
  * @typedef { VatSyscallSend | VatSyscallCallNow | VatSyscallSubscribe
  *    | VatSyscallResolve | VatSyscallVatstoreGet | VatSyscallVatstoreSet
  *    | VatSyscallVatstoreDelete | VatSyscallDropImports
+ *    | VatSyscallRetireImports | VatSyscallRetireExports
  * } VatSyscallObject
  *
  * @typedef { [tag: 'ok', data: SwingSetCapData | string | null ]} VatSyscallResultOk

packages/SwingSet/test/liveslots-helpers.js

@@ -17,6 +17,12 @@ export function buildSyscall() {
     dropImports(slots) {
       log.push({ type: 'dropImports', slots });
     },
+    retireImports(slots) {
+      log.push({ type: 'retireImports', slots });
+    },
+    retireExports(slots) {
+      log.push({ type: 'retireExports', slots });
+    },
     exit(isFailure, info) {
       log.push({ type: 'exit', isFailure, info });
     },