Kernel: MMU::get() is now MMU::kernel

MMU is can now be locked with RecursiveSpinLock.

Scheduler now has get_current_tid() that works before the Scheduler
is initialized. This allows RecursiveSpinLock usage early on.

kernel/arch/x86_64/MMU.cpp

@@ -1,4 +1,6 @@
 #include <BAN/Errors.h>
+#include <kernel/Arch.h>
+#include <kernel/LockGuard.h>
 #include <kernel/Memory/kmalloc.h>
 #include <kernel/Memory/MMU.h>
 
@@ -6,33 +8,34 @@
 #define PAGE_MASK (~FLAGS_MASK)
 
 #define CLEANUP_STRUCTURE(s)				\
+	do {									\
 		for (uint64_t i = 0; i < 512; i++)	\
-		if (s[i] & Flags::Present)		\
+			if ((s)[i] & Flags::Present)	\
 				return;						\
-	kfree(s)
+		kfree(s);							\
-
+	} while (false)
 
 extern uint8_t g_kernel_end[];
 
 namespace Kernel
 {
 	
-	static MMU* s_instance = nullptr;
+	static MMU* s_kernel = nullptr;
 	static MMU* s_current = nullptr;
 
 	void MMU::initialize()
 	{
-		ASSERT(s_instance == nullptr);
+		ASSERT(s_kernel == nullptr);
-		s_instance = new MMU();
+		s_kernel = new MMU();
-		ASSERT(s_instance);
+		ASSERT(s_kernel);
-		s_instance->initialize_kernel();
+		s_kernel->initialize_kernel();
-		s_instance->load();
+		s_kernel->load();
 	}
 
-	MMU& MMU::get()
+	MMU& MMU::kernel()
 	{
-		ASSERT(s_instance);
+		ASSERT(s_kernel);
-		return *s_instance;
+		return *s_kernel;
 	}
 
 	MMU& MMU::current()
@@ -61,13 +64,15 @@ namespace Kernel
 
 	MMU::MMU()
 	{
-		if (s_instance == nullptr)
+		if (s_kernel == nullptr)
 			return;
 		
-		// Here we copy the s_instances paging structs since they are
+		// Here we copy the s_kernel paging structs since they are
 		// global for every process
 
-		uint64_t* global_pml4 = s_instance->m_highest_paging_struct;
+		LockGuard _(s_kernel->m_lock);
+
+		uint64_t* global_pml4 = s_kernel->m_highest_paging_struct;
 
 		uint64_t* pml4 = allocate_page_aligned_page();
 		for (uint32_t pml4e = 0; pml4e < 512; pml4e++)
@@ -136,6 +141,10 @@ namespace Kernel
 
 	void MMU::load()
 	{
+		uintptr_t rsp;
+		read_rsp(rsp);
+		ASSERT(!is_page_free(rsp & PAGE_MASK));
+
 		asm volatile("movq %0, %%cr3" :: "r"(m_highest_paging_struct));
 		s_current = this;
 	}
@@ -148,41 +157,39 @@ namespace Kernel
 
 	void MMU::identity_map_range(paddr_t address, size_t size, flags_t flags)
 	{
-		paddr_t s_page = address & PAGE_MASK;
+		LockGuard _(m_lock);
-		paddr_t e_page = (address + size - 1) & PAGE_MASK;
+
-		for (paddr_t page = s_page; page <= e_page; page += PAGE_SIZE)
+		paddr_t s_page = address / PAGE_SIZE;
-			identity_map_page(page, flags);
+		paddr_t e_page = (address + size - 1) / PAGE_SIZE;
+		for (paddr_t page = s_page; page <= e_page; page++)
+			identity_map_page(page * PAGE_SIZE, flags);
 	}
 
 	void MMU::unmap_page(vaddr_t address)
 	{
+		LockGuard _(m_lock);
+
 		ASSERT((address >> 48) == 0);
 
 		address &= PAGE_MASK;
 
+		if (is_page_free(address))
+		{
+			dwarnln("unmapping unmapped page {8H}", address);
+			return;
+		}
+
 		uint64_t pml4e = (address >> 39) & 0x1FF;
 		uint64_t pdpte = (address >> 30) & 0x1FF;
 		uint64_t pde   = (address >> 21) & 0x1FF;
 		uint64_t pte   = (address >> 12) & 0x1FF;
 		
 		uint64_t* pml4 = m_highest_paging_struct;
-		if (!(pml4[pml4e] & Flags::Present))
-			return;
-
 		uint64_t* pdpt = (uint64_t*)(pml4[pml4e] & PAGE_MASK);
-		if (!(pdpt[pdpte] & Flags::Present))
-			return;
-
 		uint64_t* pd   = (uint64_t*)(pdpt[pdpte] & PAGE_MASK);
-		if (!(pd[pde] & Flags::Present))
-			return;
-
 		uint64_t* pt   = (uint64_t*)(pd[pde]     & PAGE_MASK);
-		if (!(pt[pte] & Flags::Present))
-			return;
 
 		pt[pte] = 0;
-
 		CLEANUP_STRUCTURE(pt);
 		pd[pde] = 0;
 		CLEANUP_STRUCTURE(pd);
@@ -193,14 +200,18 @@ namespace Kernel
 
 	void MMU::unmap_range(vaddr_t address, size_t size)
 	{
-		vaddr_t s_page = address & PAGE_MASK;
+		LockGuard _(m_lock);
-		vaddr_t e_page = (address + size - 1) & PAGE_MASK;
+
-		for (vaddr_t page = s_page; page <= e_page; page += PAGE_SIZE)
+		vaddr_t s_page = address / PAGE_SIZE;
-			unmap_page(page);
+		vaddr_t e_page = (address + size - 1) / PAGE_SIZE;
+		for (vaddr_t page = s_page; page <= e_page; page++)
+			unmap_page(page * PAGE_SIZE);
 	}
 
 	void MMU::map_page_at(paddr_t paddr, vaddr_t vaddr, flags_t flags)
 	{
+		LockGuard _(m_lock);
+
 		ASSERT((paddr >> 48) == 0);
 		ASSERT((vaddr >> 48) == 0);
 
@@ -245,6 +256,8 @@ namespace Kernel
 
 	uint64_t MMU::get_page_data(vaddr_t address) const
 	{
+		LockGuard _(m_lock);
+
 		ASSERT((address >> 48) == 0);
 		ASSERT(address % PAGE_SIZE == 0);
 
@@ -284,6 +297,8 @@ namespace Kernel
 
 	vaddr_t MMU::get_free_page() const
 	{
+		LockGuard _(m_lock);
+
 		// Try to find free page that can be mapped without
 		// allocations (page table with unused entries)
 		vaddr_t* pml4 = m_highest_paging_struct;
@@ -332,6 +347,8 @@ namespace Kernel
 
 	vaddr_t MMU::get_free_contiguous_pages(size_t page_count) const
 	{
+		LockGuard _(m_lock);
+
 		for (vaddr_t address = PAGE_SIZE; !(address >> 48); address += PAGE_SIZE)
 		{
 			bool valid { true };
@@ -339,7 +356,7 @@ namespace Kernel
 			{
 				if (get_page_flags(address + page * PAGE_SIZE) & Flags::Present)
 				{
-					address += page;
+					address += page * PAGE_SIZE;
 					valid = false;
 					break;
 				}
@@ -359,8 +376,10 @@ namespace Kernel
 
 	bool MMU::is_range_free(vaddr_t start, size_t size) const
 	{
+		LockGuard _(m_lock);
+		
 		vaddr_t first_page = start / PAGE_SIZE;
-		vaddr_t last_page = BAN::Math::div_round_up<vaddr_t>(start + size, PAGE_SIZE);
+		vaddr_t last_page = (start + size - 1) / PAGE_SIZE;
 		for (vaddr_t page = first_page; page <= last_page; page++)
 			if (!is_page_free(page * PAGE_SIZE))
 				return false;

kernel/include/kernel/Memory/MMU.h

@@ -1,6 +1,7 @@
 #pragma once
 
-#include <kernel/Memory/Heap.h>
+#include <kernel/Memory/Types.h>
+#include <kernel/SpinLock.h>
 
 namespace Kernel
 {
@@ -18,7 +19,7 @@ namespace Kernel
 
 	public:
 		static void initialize();
-		static MMU& get();
+		static MMU& kernel();
 
 		static MMU& current();
 
@@ -44,12 +45,16 @@ namespace Kernel
 
 		void load();
 
+		void lock() const { m_lock.lock(); }
+		void unlock() const { m_lock.unlock(); }
+
 	private:
 		uint64_t get_page_data(vaddr_t) const;
 		void initialize_kernel();
 
 	private:
-		uint64_t* m_highest_paging_struct;
+		uint64_t*					m_highest_paging_struct { nullptr };
+		mutable RecursiveSpinLock	m_lock;
 	};
 
 }

kernel/include/kernel/Process.h

@@ -68,7 +68,7 @@ namespace Kernel
 
 		static Process& current() { return Thread::current().process(); }
 
-		MMU& mmu() { return m_mmu ? *m_mmu : MMU::get(); }
+		MMU& mmu() { return m_mmu ? *m_mmu : MMU::kernel(); }
 
 	private:
 		Process(pid_t);

kernel/include/kernel/Scheduler.h

@@ -26,6 +26,7 @@ namespace Kernel
 		void unblock_threads(Semaphore*);
 
 		Thread& current_thread();
+		static pid_t current_tid();
 
 	private:
 		Scheduler() = default;

kernel/include/kernel/Thread.h

@@ -49,6 +49,8 @@ namespace Kernel
 		uintptr_t interrupt_stack_size() const { return m_interrupt_stack_size; }
 
 		static Thread& current() ;
+		static pid_t current_tid();
+
 		Process& process();
 		bool has_process() const { return m_process; }
 

kernel/kernel/ACPI.cpp

@@ -105,8 +105,8 @@ namespace Kernel
 		if (rsdp->revision >= 2)
 		{
 			const XSDT* xsdt = (const XSDT*)rsdp->xsdt_address;
-			MMU::get().identity_map_page((uintptr_t)xsdt, MMU::Flags::Present);
+			MMU::kernel().identity_map_page((uintptr_t)xsdt, MMU::Flags::Present);
-			BAN::ScopeGuard _([xsdt] { MMU::get().unmap_page((uintptr_t)xsdt); });
+			BAN::ScopeGuard _([xsdt] { MMU::kernel().unmap_page((uintptr_t)xsdt); });
 
 			if (memcmp(xsdt->signature, "XSDT", 4) != 0)
 				return BAN::Error::from_error_code(ErrorCode::ACPI_RootInvalid);
@@ -120,8 +120,8 @@ namespace Kernel
 		else
 		{
 			const RSDT* rsdt = (const RSDT*)(uintptr_t)rsdp->rsdt_address;
-			MMU::get().identity_map_page((uintptr_t)rsdt, MMU::Flags::Present);
+			MMU::kernel().identity_map_page((uintptr_t)rsdt, MMU::Flags::Present);
-			BAN::ScopeGuard _([rsdt] { MMU::get().unmap_page((uintptr_t)rsdt); });
+			BAN::ScopeGuard _([rsdt] { MMU::kernel().unmap_page((uintptr_t)rsdt); });
 
 			if (memcmp(rsdt->signature, "RSDT", 4) != 0)
 				return BAN::Error::from_error_code(ErrorCode::ACPI_RootInvalid);
@@ -133,13 +133,13 @@ namespace Kernel
 			m_entry_count = (rsdt->length - sizeof(SDTHeader)) / 4;
 		}
 
-		MMU::get().identity_map_range(m_header_table, m_entry_count * m_entry_size, MMU::Flags::Present);
+		MMU::kernel().identity_map_range(m_header_table, m_entry_count * m_entry_size, MMU::Flags::Present);
 
 		for (uint32_t i = 0; i < m_entry_count; i++)
 		{
 			auto* header = get_header_from_index(i);
-			MMU::get().identity_map_page((uintptr_t)header, MMU::Flags::Present);
+			MMU::kernel().identity_map_page((uintptr_t)header, MMU::Flags::Present);
-			MMU::get().identity_map_range((uintptr_t)header, header->length, MMU::Flags::Present);
+			MMU::kernel().identity_map_range((uintptr_t)header, header->length, MMU::Flags::Present);
 		}
 
 		return {};

kernel/kernel/APIC.cpp

@@ -146,10 +146,10 @@ APIC* APIC::create()
 		return nullptr;
 	}
 
-	MMU::get().identity_map_page(apic->m_local_apic, MMU::Flags::ReadWrite | MMU::Flags::Present);
+	MMU::kernel().identity_map_page(apic->m_local_apic, MMU::Flags::ReadWrite | MMU::Flags::Present);
 	for (auto& io_apic : apic->m_io_apics)
 	{
-		MMU::get().identity_map_page(io_apic.address, MMU::Flags::ReadWrite | MMU::Flags::Present);
+		MMU::kernel().identity_map_page(io_apic.address, MMU::Flags::ReadWrite | MMU::Flags::Present);
 		io_apic.max_redirs = io_apic.read(IOAPIC_MAX_REDIRS);
 	}
 

kernel/kernel/Process.cpp

@@ -130,7 +130,7 @@ namespace Kernel
 		ASSERT(m_general_allocator == nullptr);
 		if (m_mmu)
 		{
-			MMU::get().load();
+			MMU::kernel().load();
 			delete m_mmu;
 		}
 		for (auto paddr : m_allocated_pages)

kernel/kernel/Scheduler.cpp

@@ -52,9 +52,17 @@ namespace Kernel
 		return m_current_thread ? *m_current_thread->thread : *m_idle_thread;
 	}
 
+	pid_t Scheduler::current_tid()
+	{
+		if (s_instance == nullptr)
+			return 0;
+		return Scheduler::get().current_thread().tid();
+	}
+
 	void Scheduler::reschedule()
 	{
 		VERIFY_CLI();
+
 		ASSERT(InterruptController::get().is_in_service(PIT_IRQ));
 		InterruptController::get().eoi(PIT_IRQ);
 
@@ -174,7 +182,7 @@ namespace Kernel
 			GDT::set_tss_stack(current.interrupt_stack_base() + current.interrupt_stack_size());
 		}
 		else
-			MMU::get().load();
+			MMU::kernel().load();
 
 		switch (current.state())
 		{

kernel/kernel/SpinLock.cpp

@@ -1,5 +1,5 @@
+#include <kernel/Scheduler.h>
 #include <kernel/SpinLock.h>
-#include <kernel/Thread.h>
 
 namespace Kernel
 {
@@ -25,7 +25,7 @@ namespace Kernel
 	void RecursiveSpinLock::lock()
 	{
 		// FIXME: is this thread safe?
-		if (m_locker == Thread::current().tid())
+		if (m_locker == Scheduler::current_tid())
 		{
 			m_lock_depth++;
 		}
@@ -33,13 +33,15 @@ namespace Kernel
 		{
 			m_lock.lock();
 			ASSERT(m_locker == 0);
-			m_locker = Thread::current().tid();
+			m_locker = Scheduler::current_tid();
 			m_lock_depth = 1;
 		}
 	}
 
 	void RecursiveSpinLock::unlock()
 	{
+		ASSERT(m_lock_depth > 0);
+
 		m_lock_depth--;
 		if (m_lock_depth == 0)
 		{

kernel/kernel/Terminal/VesaTerminalDriver.cpp

@@ -36,7 +36,7 @@ VesaTerminalDriver* VesaTerminalDriver::create()
 		return nullptr;
 	}
 
-	MMU::get().identity_map_range(framebuffer.addr, framebuffer.pitch * framebuffer.height, MMU::Flags::UserSupervisor | MMU::Flags::ReadWrite | MMU::Flags::Present);
+	MMU::kernel().identity_map_range(framebuffer.addr, framebuffer.pitch * framebuffer.height, MMU::Flags::UserSupervisor | MMU::Flags::ReadWrite | MMU::Flags::Present);
 
 	auto* driver = new VesaTerminalDriver(
 		framebuffer.width,
@@ -53,7 +53,7 @@ VesaTerminalDriver* VesaTerminalDriver::create()
 
 VesaTerminalDriver::~VesaTerminalDriver()
 {
-	MMU::get().unmap_range(m_address, m_pitch * m_height);
+	MMU::kernel().unmap_range(m_address, m_pitch * m_height);
 }
 
 void VesaTerminalDriver::set_pixel(uint32_t offset, Color color)