[zion] Add a syscall to duplicate capabilities

zion/include/zcall.h

@@ -46,6 +46,9 @@
 
 #define Z_IRQ_PCI_BASE 0x30
 
+// Capability Calls
+#define Z_CAP_DUPLICATE 0x60
+
 // Debugging Calls.
 #define Z_DEBUG_PRINT 0x10000000
 
@@ -101,4 +104,6 @@ void ZThreadExit();
                                 uint64_t* actual_bytes, uint64_t* actual_caps);
 [[nodiscard]] z_err_t ZIrqRegister(uint64_t irq_num, uint64_t* port_cap);
 
+[[nodiscard]] z_err_t ZCapDuplicate(uint64_t cap_in, uint64_t* cap_out);
+
 [[nodiscard]] z_err_t ZDebug(const char* message);

zion/syscall/syscall.cpp

@@ -239,6 +239,16 @@ z_err_t IrqRegister(ZIrqRegisterReq* req, ZIrqRegisterResp* resp) {
   return Z_OK;
 }
 
+z_err_t CapDuplicate(ZCapDuplicateReq* req, ZCapDuplicateResp* resp) {
+  auto& proc = gScheduler->CurrentProcess();
+  auto cap = proc.GetCapability(req->cap);
+  if (!cap) {
+    return Z_ERR_CAP_NOT_FOUND;
+  }
+  resp->cap = proc.AddExistingCapability(cap);
+  return Z_OK;
+}
+
 extern "C" z_err_t SyscallHandler(uint64_t call_id, void* req, void* resp) {
   RefPtr<Thread> thread = gScheduler->CurrentThread();
   switch (call_id) {
@@ -290,6 +300,9 @@ extern "C" z_err_t SyscallHandler(uint64_t call_id, void* req, void* resp) {
     case Z_IRQ_REGISTER:
       return IrqRegister(reinterpret_cast<ZIrqRegisterReq*>(req),
                          reinterpret_cast<ZIrqRegisterResp*>(resp));
+    case Z_CAP_DUPLICATE:
+      return CapDuplicate(reinterpret_cast<ZCapDuplicateReq*>(req),
+                          reinterpret_cast<ZCapDuplicateResp*>(resp));
     case Z_DEBUG_PRINT:
       dbgln("[Debug] %s", req);
       return Z_OK;

zion/usr/zcall.cpp

@@ -222,4 +222,14 @@ z_err_t ZIrqRegister(uint64_t irq_num, uint64_t* port_cap) {
   return ret;
 }
 
+z_err_t ZCapDuplicate(uint64_t cap_in, uint64_t* cap_out) {
+  ZCapDuplicateReq req{
+      .cap = cap_in,
+  };
+  ZCapDuplicateResp resp;
+  z_err_t ret = SysCall2(Z_CAP_DUPLICATE, &req, &resp);
+  *cap_out = resp.cap;
+  return ret;
+}
+
 z_err_t ZDebug(const char* message) { return SysCall1(Z_DEBUG_PRINT, message); }

zion/usr/zcall_internal.h

@@ -102,3 +102,11 @@ struct ZIrqRegisterReq {
 struct ZIrqRegisterResp {
   uint64_t port_cap;
 };
+
+struct ZCapDuplicateReq {
+  uint64_t cap;
+};
+
+struct ZCapDuplicateResp {
+  uint64_t cap;
+};