[Zion] Add the ability to delete a capability.

zion/capability/capability_table.cpp

@@ -17,7 +17,8 @@ uint64_t CapabilityTable::AddExistingCapability(
 glcr::RefPtr<Capability> CapabilityTable::GetCapability(uint64_t id) {
   MutexHolder h(lock_);
   if (!capabilities_.Contains(id)) {
-    panic("Bad cap access {}", id);
+    dbgln("Bad cap access {}", id);
+    return {};
   }
   return capabilities_.at(id);
 }
@@ -25,7 +26,8 @@ glcr::RefPtr<Capability> CapabilityTable::GetCapability(uint64_t id) {
 glcr::RefPtr<Capability> CapabilityTable::ReleaseCapability(uint64_t id) {
   MutexHolder h(lock_);
   if (!capabilities_.Contains(id)) {
-    panic("Bad cap release {}", id);
+    dbgln("Bad cap release {}", id);
+    return {};
   }
   auto cap = capabilities_.at(id);
   (void)capabilities_.Delete(id);

zion/include/zcall.h

@@ -56,6 +56,7 @@ SYS5(ReplyPortRecv, z_cap_t, reply_port_cap, uint64_t*, num_bytes, void*, data,
      uint64_t*, num_caps, z_cap_t*, caps);
 
 SYS3(CapDuplicate, z_cap_t, cap_in, z_perm_t, perm_mask, z_cap_t*, cap_out);
+SYS1(CapRelease, z_cap_t, cap);
 
 SYS1(MutexCreate, z_cap_t*, mutex_cap);
 SYS1(MutexLock, z_cap_t, mutex_cap);

zion/include/ztypes.h

@@ -53,6 +53,7 @@ const uint64_t kZionEndpointCall = 0x65;
 
 // Capability Calls
 const uint64_t kZionCapDuplicate = 0x70;
+const uint64_t kZionCapRelease = 0x71;
 
 // Syncronization Calls
 const uint64_t kZionMutexCreate = 0x80;

zion/syscall/capability.cpp

@@ -18,3 +18,11 @@ z_err_t CapDuplicate(ZCapDuplicateReq* req) {
                                         cap->permissions() & req->perm_mask);
   return glcr::OK;
 }
+
+z_err_t CapRelease(ZCapReleaseReq* req) {
+  auto& proc = gScheduler->CurrentProcess();
+  if (proc.ReleaseCapability(req->cap).empty()) {
+    return glcr::CAP_NOT_FOUND;
+  }
+  return glcr::OK;
+}

zion/syscall/capability.h

@@ -3,3 +3,4 @@
 #include "include/zcall.h"
 
 z_err_t CapDuplicate(ZCapDuplicateReq* req);
+z_err_t CapRelease(ZCapReleaseReq* req);

zion/syscall/syscall.cpp

@@ -81,6 +81,7 @@ extern "C" z_err_t SyscallHandler(uint64_t call_id, void* req) {
     CASE(ReplyPortRecv);
     // syscall/capability.h
     CASE(CapDuplicate);
+    CASE(CapRelease);
     // syscall/syncronization.h
     CASE(MutexCreate);
     CASE(MutexLock);