From 636858dbbd48ed9f5073793b46740302aa202f43 Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Tue, 28 Nov 2023 20:07:50 +0100
Subject: Kernel: Add basic IPC and move to microkernel design.

The IPC design is currently a WIP and is nowhere near complete
---
 kernel/ipc.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 kernel/ipc.c

(limited to 'kernel/ipc.c')

diff --git a/kernel/ipc.c b/kernel/ipc.c
new file mode 100644
index 0000000..3422cc7
--- /dev/null
+++ b/kernel/ipc.c
@@ -0,0 +1,95 @@
+#include <assert.h>
+#include <ipc.h>
+#include <math.h>
+#include <sched/scheduler.h>
+#include <stdbool.h>
+#include <string.h>
+
+struct IpcEndpoint {
+  u8 in_use;
+  u32 pid;
+};
+
+struct IpcEndpoint ipc_endpoints[100];
+
+bool ipc_register_endpoint(u32 endpoint) {
+  if (endpoint >= 100)
+    return false;
+  if (ipc_endpoints[endpoint].in_use)
+    return false;
+  ipc_endpoints[endpoint].in_use = 1;
+  ipc_endpoints[endpoint].pid = get_current_task()->pid;
+  return true;
+}
+
+bool ipc_endpoint_to_pid(u32 endpoint, u32 *pid) {
+  if (endpoint >= 100)
+    return false;
+  if (!ipc_endpoints[endpoint].in_use)
+    return false;
+  *pid = ipc_endpoints[endpoint].pid;
+  return true;
+}
+
+int ipc_get_mailbox(u32 id, struct IpcMailbox **out) {
+  process_t *p;
+  if (!get_task_from_pid(id, &p))
+    return 0;
+  *out = &p->ipc_mailbox;
+  return 1;
+}
+
+int ipc_read(u8 *buffer, u32 length, u32 *sender_pid) {
+  struct IpcMailbox *handler = &get_current_task()->ipc_mailbox;
+
+  u32 read_ptr = handler->read_ptr;
+  struct IpcMessage *ipc_message = NULL;
+  for (;;) {
+    ipc_message = &handler->data[read_ptr];
+    if (!ipc_message->is_used) {
+      asm("sti");
+      continue;
+    }
+    break;
+  }
+  ipc_message->is_used = 0;
+  // TODO: Verify sender_pid is a valid address
+  if (sender_pid)
+    *sender_pid = ipc_message->sender_pid;
+
+  u32 len = min(length, ipc_message->size);
+  memcpy(buffer, ipc_message->buffer, len);
+
+  // Update read_ptr
+  read_ptr++;
+  if (read_ptr >= IPC_NUM_DATA)
+    read_ptr = 0;
+  handler->read_ptr = read_ptr;
+  return len;
+}
+
+int ipc_write_to_process(int pid, u8 *buffer, u32 length) {
+  struct IpcMailbox *handler;
+  assert(ipc_get_mailbox(pid, &handler));
+
+  u32 write_ptr = handler->write_ptr;
+  struct IpcMessage *ipc_message = &handler->data[write_ptr];
+  ipc_message->is_used = 1;
+  u32 len = min(IPC_BUFFER_SIZE, length);
+  ipc_message->sender_pid = get_current_task()->pid;
+  ipc_message->size = len;
+  memcpy(ipc_message->buffer, buffer, len);
+
+  // Update write_ptr
+  write_ptr++;
+  if (write_ptr >= IPC_NUM_DATA)
+    write_ptr = 0;
+  handler->write_ptr = write_ptr;
+  return len;
+}
+
+int ipc_write(int endpoint, u8 *buffer, u32 length) {
+  u32 pid;
+  assert(ipc_endpoint_to_pid(endpoint, &pid));
+  return ipc_write_to_process(pid, buffer, length);
+}
-- 
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