Kernel: Create CriticalScope and fix kmalloc

This disables interrupts for the current scope and restores them
after the scope. This is used in kmalloc, since scheduler might
call into kmalloc/kfree, but deadlock if some thread is currently
trying to allocate. This allows us to use kmalloc in Scheduler.

kernel/include/kernel/CriticalScope.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <BAN/NoCopyMove.h>
+
+#include <stddef.h>
+
+namespace Kernel
+{
+
+	class CriticalScope
+	{
+		BAN_NON_COPYABLE(CriticalScope);
+		BAN_NON_MOVABLE(CriticalScope);
+	
+	public:
+		CriticalScope()
+		{
+			asm volatile("pushf; cli; pop %0" : "=r"(m_flags) :: "memory");
+		}
+
+		~CriticalScope()
+		{
+			asm volatile("push %0; popf" :: "rm"(m_flags) : "memory", "cc");
+		}
+
+	private:
+		size_t m_flags;
+	};
+
+}

kernel/include/kernel/InterruptController.h

@@ -18,6 +18,4 @@ public:
 	static InterruptController& get();
 };
 
-uintptr_t disable_interrupts_and_get_flags();
-void restore_flags(uintptr_t);
 bool interrupts_enabled();

kernel/kernel/InterruptController.cpp

@@ -26,18 +26,6 @@ void InterruptController::initialize(bool force_pic)
 	s_instance = PIC::create();
 }
 
-uintptr_t disable_interrupts_and_get_flags()
-{
-	uintptr_t flags;
-	asm volatile("pushf; cli; pop %0" : "=r"(flags) :: "memory");
-	return flags;
-}
-
-void restore_flags(uintptr_t flags)
-{
-	asm volatile("push %0; popf" :: "rm"(flags) : "memory", "cc");
-}
-
 bool interrupts_enabled()
 {
 	uintptr_t flags;

kernel/kernel/Scheduler.cpp

@@ -1,10 +1,9 @@
 #include <kernel/Arch.h>
 #include <kernel/Attributes.h>
+#include <kernel/CriticalScope.h>
 #include <kernel/InterruptController.h>
 #include <kernel/Scheduler.h>
 
-#include <kernel/PCI.h>
-
 #if 1
 	#define VERIFY_STI() ASSERT(interrupts_enabled())
 	#define VERIFY_CLI() ASSERT(!interrupts_enabled())
@@ -89,10 +88,9 @@ namespace Kernel
 
 	BAN::ErrorOr<void> Scheduler::add_thread(BAN::RefPtr<Thread> thread)
 	{
-		auto flags = disable_interrupts_and_get_flags();
-		BAN::ErrorOr<void> result = m_active_threads.emplace_back(thread);
-		restore_flags(flags);
-		return result;
+		Kernel::CriticalScope critical;
+		TRY(m_active_threads.emplace_back(thread));
+		return {};
 	}
 
 	void Scheduler::advance_current_thread()

kernel/kernel/Shell.cpp

@@ -195,7 +195,7 @@ argument_done:
 			if (thread_or_error.is_error())
 				return TTY_PRINTLN("{}", thread_or_error.error());
 
-			MUST(Scheduler::get().add_thread(thread));
+			MUST(Scheduler::get().add_thread(thread_or_error.release_value()));
 
 			while (s_thread_spinlock.is_locked());
 		}

kernel/kernel/Thread.cpp

@@ -47,6 +47,7 @@ namespace Kernel
 
 	Thread::~Thread()
 	{
+		dprintln("thread {} destruct", tid());
 		kfree(m_stack_base);
 	}
 

kernel/kernel/kernel.cpp

@@ -103,7 +103,6 @@ extern "C" void kernel_main()
 
 	MUST(Scheduler::initialize());
 	Scheduler& scheduler = Scheduler::get();
-	#if 1
 	MUST(scheduler.add_thread(MUST(Thread::create(
 		[terminal_driver]
 		{
@@ -120,7 +119,6 @@ extern "C" void kernel_main()
 				terminal_driver->set_font(font_or_error.release_value());
 		}
 	))));
-	#endif
 	MUST(scheduler.add_thread(MUST(Thread::create(
 		[tty1]
 		{

kernel/kernel/kmalloc.cpp

@@ -1,21 +1,13 @@
 #include <BAN/Errors.h>
-#include <BAN/Math.h>
+#include <kernel/CriticalScope.h>
 #include <kernel/kmalloc.h>
 #include <kernel/kprint.h>
 #include <kernel/multiboot.h>
 
-#include <kernel/SpinLock.h>
-#include <kernel/LockGuard.h>
-
-#include <stdint.h>
-
 #define MB (1 << 20)
 
 static constexpr size_t s_kmalloc_min_align = alignof(max_align_t);
 
-static Kernel::SpinLock s_general_lock;
-static Kernel::SpinLock s_fixed_lock;
-
 struct kmalloc_node
 {
 	void set_align(ptrdiff_t align)			{ m_align = align; }
@@ -192,8 +184,6 @@ void kmalloc_dump_info()
 
 static void* kmalloc_fixed()
 {
-	Kernel::LockGuard guard(s_fixed_lock);
-
 	auto& info = s_kmalloc_fixed_info;
 
 	if (!info.free_list_head)
@@ -233,8 +223,6 @@ static void* kmalloc_fixed()
 
 static void* kmalloc_impl(size_t size, size_t align)
 {
-	Kernel::LockGuard guard(s_general_lock);
-
 	ASSERT(align % s_kmalloc_min_align == 0);
 	ASSERT(size % s_kmalloc_min_align == 0);
 
@@ -309,6 +297,7 @@ static constexpr bool is_power_of_two(size_t value)
 
 void* kmalloc(size_t size, size_t align)
 {
+
 	const kmalloc_info& info = s_kmalloc_info;
 
 	if (size == 0 || size >= info.size)
@@ -316,6 +305,8 @@ void* kmalloc(size_t size, size_t align)
 
 	ASSERT(is_power_of_two(align));
 	
+	Kernel::CriticalScope critical;
+
 	// if the size fits into fixed node, we will try to use that since it is faster
 	if (align == s_kmalloc_min_align && size <= sizeof(kmalloc_fixed_info::node::data))
 		if (void* result = kmalloc_fixed())
@@ -334,10 +325,10 @@ void kfree(void* address)
 	uintptr_t address_uint = (uintptr_t)address;
 	ASSERT(address_uint % s_kmalloc_min_align == 0);
 
+	Kernel::CriticalScope critical;
+
 	if (s_kmalloc_fixed_info.base <= address_uint && address_uint < s_kmalloc_fixed_info.end)
 	{
-		Kernel::LockGuard guard(s_fixed_lock);
-
 		auto& info = s_kmalloc_fixed_info;
 		ASSERT(info.used_list_head);
 
@@ -369,8 +360,6 @@ void kfree(void* address)
 	}
 	else if (s_kmalloc_info.base <= address_uint && address_uint < s_kmalloc_info.end)
 	{
-		Kernel::LockGuard guard(s_general_lock);
-
 		auto& info = s_kmalloc_info;
 		
 		auto* node = info.from_address(address);