Add a Port poll operation

zion/include/zcall.h

@@ -46,6 +46,7 @@
 #define Z_PORT_CREATE 0x50
 #define Z_PORT_SEND 0x51
 #define Z_PORT_RECV 0x52
+#define Z_PORT_POLL 0x53
 
 #define Z_IRQ_REGISTER 0x58
 
@@ -99,6 +100,10 @@ void ZThreadExit();
                                 uint8_t* bytes, uint64_t num_caps,
                                 uint64_t* caps, uint64_t* type,
                                 uint64_t* actual_bytes, uint64_t* actual_caps);
+[[nodiscard]] z_err_t ZPortPoll(uint64_t port_cap, uint64_t num_bytes,
+                                uint8_t* bytes, uint64_t num_caps,
+                                uint64_t* caps, uint64_t* type,
+                                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 ZDebug(const char* message);

zion/include/zerrors.h

@@ -10,6 +10,7 @@
 #define Z_ERR_BUFF_SIZE 005
 #define Z_ERR_NULL 0x6
 #define Z_ERR_EXISTS 0x7
+#define Z_ERR_EMPTY 0x8
 
 #define Z_ERR_CAP_NOT_FOUND 0x100
 #define Z_ERR_CAP_TYPE 0x101

zion/object/port.cpp

@@ -73,3 +73,8 @@ z_err_t Port::Read(ZMessage& msg) {
 
   return Z_OK;
 }
+
+bool Port::HasMessages() {
+  MutexHolder h(mutex_);
+  return pending_messages_.size() != 0;
+}

zion/object/port.h

@@ -24,6 +24,8 @@ class Port : public KernelObject {
   z_err_t Write(const ZMessage& msg);
   z_err_t Read(ZMessage& msg);
 
+  bool HasMessages();
+
  private:
   struct Message {
     uint64_t type;

zion/syscall/syscall.cpp

@@ -208,6 +208,19 @@ z_err_t PortRecv(ZPortRecvReq* req) {
   return port->Read(req->message);
 }
 
+z_err_t PortPoll(ZPortRecvReq* req) {
+  auto& proc = gScheduler->CurrentProcess();
+  auto port_cap = proc.GetCapability(req->port_cap);
+  RET_ERR(ValidateCap(port_cap, ZC_READ));
+
+  auto port = port_cap->obj<Port>();
+  RET_IF_NULL(port);
+  if (!port->HasMessages()) {
+    return Z_ERR_EMPTY;
+  }
+  return port->Read(req->message);
+}
+
 z_err_t IrqRegister(ZIrqRegisterReq* req, ZIrqRegisterResp* resp) {
   auto& proc = gScheduler->CurrentProcess();
   if (req->irq_num != Z_IRQ_PCI_BASE) {
@@ -264,6 +277,8 @@ extern "C" z_err_t SyscallHandler(uint64_t call_id, void* req, void* resp) {
       return ChannelRecv(reinterpret_cast<ZChannelRecvReq*>(req));
     case Z_PORT_RECV:
       return PortRecv(reinterpret_cast<ZPortRecvReq*>(req));
+    case Z_PORT_POLL:
+      return PortPoll(reinterpret_cast<ZPortRecvReq*>(req));
     case Z_IRQ_REGISTER:
       return IrqRegister(reinterpret_cast<ZIrqRegisterReq*>(req),
                          reinterpret_cast<ZIrqRegisterResp*>(resp));

zion/usr/zcall.cpp

@@ -184,6 +184,27 @@ z_err_t ZPortRecv(uint64_t port_cap, uint64_t num_bytes, uint8_t* bytes,
   return ret;
 }
 
+z_err_t ZPortPoll(uint64_t port_cap, uint64_t num_bytes, uint8_t* bytes,
+                  uint64_t num_caps, uint64_t* caps, uint64_t* type,
+                  uint64_t* actual_bytes, uint64_t* actual_caps) {
+  ZPortRecvReq req{
+      .port_cap = port_cap,
+      .message =
+          {
+              .type = 0,
+              .num_bytes = num_bytes,
+              .bytes = bytes,
+              .num_caps = num_caps,
+              .caps = caps,
+          },
+  };
+  z_err_t ret = SysCall1(Z_PORT_POLL, &req);
+  *type = req.message.type;
+  *actual_bytes = req.message.num_bytes;
+  *actual_caps = req.message.num_caps;
+  return ret;
+}
+
 z_err_t ZIrqRegister(uint64_t irq_num, uint64_t* port_cap) {
   ZIrqRegisterReq req{
       .irq_num = irq_num,