[project] Clean up src/ tree

A long overdue cleanup of the src/ tree.

- Moved src/drivers to src/user because it contains more than drivers
- Removed src/drivers/ahci because it's unused - will restore it when I
  make a real AHCI driver
- Removed unused src/tools
- Moved kernel.ld (the only used file under src/arch) to src/kernel for
  now, if/when there's a multi-platform effort that should be figured
  out as part of it
- Removed the rest of the unused src/arch
- Renamed 'fb' to 'drv.uefi_fb' and 'nulldrv' to 'testapp'

src/user/testapp/main.cpp

@@ -0,0 +1,152 @@
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "j6/types.h"
+#include "j6/errors.h"
+#include "j6/signals.h"
+#include "j6/syscalls.h"
+
+#include "io.h"
+#include "serial.h"
+
+char inbuf[1024];
+extern j6_handle_t __handle_sys;
+j6_handle_t endp = j6_handle_invalid;
+
+extern "C" {
+	int main(int, const char **);
+}
+
+void
+thread_proc()
+{
+	j6_system_log("sub thread starting");
+
+	char buffer[512];
+	size_t len = sizeof(buffer);
+	j6_tag_t tag = 0;
+	j6_status_t result = j6_endpoint_receive(endp, &tag, &len, (void*)buffer);
+	if (result != j6_status_ok)
+		j6_thread_exit(result);
+
+	j6_system_log("sub thread received message");
+
+	for (int i = 0; i < len; ++i)
+		if (buffer[i] >= 'A' && buffer[i] <= 'Z')
+			buffer[i] += 0x20;
+
+	tag++;
+	result = j6_endpoint_send(endp, tag, len, (void*)buffer);
+	if (result != j6_status_ok)
+		j6_thread_exit(result);
+
+	j6_system_log("sub thread sent message");
+
+	for (int i = 1; i < 5; ++i)
+		j6_thread_sleep(i*10);
+
+	j6_system_log("sub thread exiting");
+	j6_thread_exit(0);
+}
+
+int
+main(int argc, const char **argv)
+{
+	j6_handle_t children[2] = {j6_handle_invalid, j6_handle_invalid};
+	j6_signal_t out = 0;
+
+	j6_system_log("main thread starting");
+
+	for (int i = 0; i < argc; ++i)
+		j6_system_log(argv[i]);
+
+	void *base = malloc(0x1000);
+	if (!base)
+		return 1;
+
+	uint64_t *vma_ptr = reinterpret_cast<uint64_t*>(base);
+	for (int i = 0; i < 3; ++i)
+		vma_ptr[i*100] = uint64_t(i);
+
+	j6_system_log("main thread wrote to memory area");
+
+	j6_status_t result = j6_endpoint_create(&endp);
+	if (result != j6_status_ok)
+		return result;
+
+	j6_system_log("main thread created endpoint");
+
+	result = j6_thread_create(reinterpret_cast<void*>(&thread_proc), &children[1]);
+	if (result != j6_status_ok)
+		return result;
+
+	j6_system_log("main thread created sub thread");
+
+	char message[] = "MAIN THREAD SUCCESSFULLY CALLED SENDRECV IF THIS IS LOWERCASE";
+	size_t size = sizeof(message);
+	j6_tag_t tag = 16;
+	result = j6_endpoint_sendrecv(endp, &tag, &size, (void*)message);
+	if (result != j6_status_ok)
+		return result;
+
+	if (tag != 17)
+		j6_system_log("GOT WRONG TAG FROM SENDRECV");
+
+	result = j6_system_bind_irq(__handle_sys, endp, 3);
+	if (result != j6_status_ok)
+		return result;
+
+	j6_system_log(message);
+
+	j6_system_log("main thread creating a new process");
+	result = j6_process_create(&children[0]);
+	if (result != j6_status_ok)
+		return result;
+
+	j6_system_log("main thread waiting on children");
+
+	j6_handle_t outhandle;
+	result = j6_object_wait_many(children, 2, -1ull, &outhandle, &out);
+	if (result != j6_status_ok)
+		return result;
+
+	if (outhandle == children[1]) {
+		j6_system_log("   ok from child thread");
+	} else if (outhandle == children[0]) {
+		j6_system_log("   ok from child process");
+	} else {
+		j6_system_log("   ... got unknown handle");
+	}
+
+	j6_system_log("main testing irqs");
+
+
+	serial_port com2(COM2);
+
+	const char *fgseq = "\x1b[2J";
+	while (*fgseq)
+		com2.write(*fgseq++);
+
+	for (int i = 0; i < 10; ++i)
+		com2.write('%');
+
+	size_t len = 0;
+	while (true) {
+		result = j6_endpoint_receive(endp, &tag, &len, nullptr);
+		if (result != j6_status_ok)
+			return result;
+
+		if (j6_tag_is_irq(tag))
+			j6_system_log("main thread got irq!");
+	}
+
+	j6_system_log("main thread closing endpoint");
+
+	result = j6_object_close(endp);
+	if (result != j6_status_ok)
+		return result;
+
+	j6_system_log("main thread done, exiting");
+	return 0;
+}
+