From a33a72915e9fe0e198618a40efae5b32380072ea Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Thu, 5 Jan 2023 21:52:26 +0100
Subject: [PATCH] Scheduler: Creation, destruction and switching of userspace
 tasks :))

From a TarStream. Not optimal, but OK for the moment.
---
 kernel/src/thread/Scheduler.cpp | 93 +++++++++++++++++++++++++++++++--
 kernel/src/thread/Scheduler.h   |  3 ++
 2 files changed, 91 insertions(+), 5 deletions(-)

diff --git a/kernel/src/thread/Scheduler.cpp b/kernel/src/thread/Scheduler.cpp
index 8b498cd0..11b8366a 100644
--- a/kernel/src/thread/Scheduler.cpp
+++ b/kernel/src/thread/Scheduler.cpp
@@ -1,4 +1,5 @@
 #include "thread/Scheduler.h"
+#include "ELF.h"
 #include "Log.h"
 #include "arch/CPU.h"
 #include "arch/MMU.h"
@@ -19,6 +20,7 @@ namespace Scheduler
         g_idle.init_regs_kernel();
         g_idle.set_ip((u64)CPU::idle_loop);
         g_idle.state = ThreadState::Idle;
+        g_idle.is_kernel = true;
 
         g_idle.ticks_left = 1;
 
@@ -60,6 +62,8 @@ namespace Scheduler
 
         thread->stack = thread_stack;
 
+        thread->is_kernel = true;
+
         g_threads.append(thread);
 
         kinfoln("CREATED THREAD: id %lu with ip %lx and sp %lx", thread->id, thread->ip(), thread->sp());
@@ -95,13 +99,84 @@ namespace Scheduler
         return new_kernel_thread_impl(thread);
     }
 
+    static Result<void> create_stacks(Stack& user_stack, Stack& kernel_stack)
+    {
+        const u64 THREAD_STACK_BASE = 0x10000;
+
+        TRY(MemoryManager::alloc_at(THREAD_STACK_BASE, 4, MMU::ReadWrite | MMU::NoExecute | MMU::User));
+
+        auto guard = make_scope_guard([&] { MemoryManager::unmap_owned(THREAD_STACK_BASE, 4); });
+
+        u64 kernel_stack_base = TRY(MemoryManager::alloc_for_kernel(4, MMU::ReadWrite | MMU::NoExecute));
+
+        guard.deactivate();
+
+        user_stack = { THREAD_STACK_BASE, 4 * ARCH_PAGE_SIZE };
+        kernel_stack = { kernel_stack_base, 4 * ARCH_PAGE_SIZE };
+
+        return {};
+    }
+
+    Result<void> new_userspace_thread(const TarStream::Entry& entry, const TarStream& stream)
+    {
+        Thread* thread = TRY(new_thread());
+
+        thread->is_kernel = false;
+
+        auto guard = make_scope_guard([&] { delete thread; });
+
+        auto directory = TRY(MMU::create_page_directory_for_userspace());
+
+        auto directory_guard = make_scope_guard([&] {
+            MMU::switch_page_directory(MMU::kernel_page_directory());
+            MemoryManager::free_frame((u64)directory);
+        });
+
+        MMU::switch_page_directory(directory);
+
+        thread->init_regs_user();
+
+        auto data = TRY(ELFLoader::load(entry, stream));
+
+        thread->set_ip(data.entry);
+
+        TRY(create_stacks(thread->stack, thread->kernel_stack));
+        thread->set_sp(thread->stack.top());
+
+        thread->directory = directory;
+
+        guard.deactivate();
+        directory_guard.deactivate();
+
+        kinfoln("CREATED USERSPACE THREAD: id %lu with ip %lx and sp %lx (ksp %lx)", thread->id, thread->ip(),
+                thread->sp(), thread->kernel_stack.top());
+
+        g_threads.append(thread);
+
+        return {};
+    }
+
     void reap_thread(Thread* thread)
     {
         kinfoln("reap: reaping thread with id %zu", thread->id);
-        auto stack = thread->stack;
-        kinfoln("deleting thread stack @ %#lx, has %zu bytes of stack", stack.bottom(), stack.bytes());
-        // FIXME: Propagate errors I guess?
-        MemoryManager::unmap_owned_and_free_vm(stack.bottom(), stack.bytes() / ARCH_PAGE_SIZE).release_value();
+
+        if (thread->is_kernel)
+        {
+            auto stack = thread->stack;
+            // FIXME: Propagate errors I guess?
+            kinfoln("deleting stack @ %#lx", stack.bottom());
+            MemoryManager::unmap_owned_and_free_vm(stack.bottom(), stack.bytes() / ARCH_PAGE_SIZE).release_value();
+        }
+        else
+        {
+            auto stack = thread->kernel_stack;
+            kinfoln("deleting kstack @ %#lx", stack.bottom());
+            // FIXME: Propagate errors I guess?
+            MemoryManager::unmap_owned_and_free_vm(stack.bottom(), stack.bytes() / ARCH_PAGE_SIZE).release_value();
+        }
+
+        if (!thread->is_kernel) MMU::delete_userspace_page_directory(thread->directory);
+
         delete thread;
     }
 
@@ -138,7 +213,15 @@ namespace Scheduler
 
     void generic_switch_context(Thread* old_thread, Thread* new_thread, Registers* regs)
     {
-        if (old_thread != new_thread) switch_context(old_thread, new_thread, regs);
+        if (old_thread != new_thread)
+        {
+            switch_context(old_thread, new_thread, regs);
+            if (!new_thread->is_kernel)
+            {
+                MMU::switch_page_directory(new_thread->directory);
+                CPU::switch_kernel_stack(new_thread->kernel_stack.top());
+            }
+        }
 
         if (new_thread->is_idle())
         {
diff --git a/kernel/src/thread/Scheduler.h b/kernel/src/thread/Scheduler.h
index f818c731..c2dd4cfc 100644
--- a/kernel/src/thread/Scheduler.h
+++ b/kernel/src/thread/Scheduler.h
@@ -1,5 +1,6 @@
 #pragma once
 #include "thread/Thread.h"
+#include <luna/TarStream.h>
 
 namespace Scheduler
 {
@@ -12,6 +13,8 @@ namespace Scheduler
     Result<void> new_kernel_thread(void (*func)(void));
     Result<void> new_kernel_thread(void (*func)(void*), void* arg);
 
+    Result<void> new_userspace_thread(const TarStream::Entry& entry, const TarStream& stream);
+
     Thread* pick_task();
 
     void reap_thread(Thread* thread);