Kernel: kmalloc has now somewhat dynamic storage

Allocations bigger than PAGE_SIZE and those not forced to be identity
mapped are now done on a GeneralAllocator. This allows us to use kmalloc
for big allocations; bigger than the fixed 1 MiB storage.

This is still a hack and the whole kmalloc will have to be rewritten at
some point, but for now this does the job :D

kernel/arch/x86_64/IDT.cpp

@@ -137,6 +137,21 @@ namespace IDT
 
 	extern "C" void cpp_isr_handler(uint64_t isr, uint64_t error, const Registers* regs)
 	{
+		if (isr == ISR::PageFault)
+		{
+			using namespace Kernel;
+			
+			vaddr_t vaddr = regs->cr2 & PAGE_ADDR_MASK;
+
+			if (!PageTable::kernel().is_page_free(vaddr))
+			{
+				auto paddr = kmalloc_paddr_of(vaddr);
+				ASSERT(paddr.has_value());
+				PageTable::current().map_page_at(paddr.value(), vaddr, PageTable::Flags::ReadWrite | PageTable::Flags::Present);
+				return;
+			}
+		}
+
 		pid_t tid = Kernel::Scheduler::current_tid();
 		pid_t pid = tid ? Kernel::Process::current().pid() : 0;
 

kernel/arch/x86_64/PageTable.cpp

@@ -65,7 +65,7 @@ namespace Kernel
 
 	static uint64_t* allocate_page_aligned_page()
 	{
-		void* page = kmalloc(PAGE_SIZE, PAGE_SIZE);
+		void* page = kmalloc(PAGE_SIZE, PAGE_SIZE, true);
 		ASSERT(page);
 		memset(page, 0, PAGE_SIZE);
 		return (uint64_t*)page;

kernel/include/kernel/Memory/kmalloc.h

@@ -1,10 +1,15 @@
 #pragma once
 
+#include <BAN/Optional.h>
+#include <kernel/Memory/Types.h>
+
 #include <stddef.h>
 
 void kmalloc_initialize();
 void kmalloc_dump_info();
 
-void* kmalloc(size_t);
-void* kmalloc(size_t, size_t);
+void* kmalloc(size_t size);
+void* kmalloc(size_t size, size_t align, bool force_identity_map = false);
 void kfree(void*);
+
+BAN::Optional<Kernel::paddr_t> kmalloc_paddr_of(Kernel::vaddr_t);

kernel/kernel/Memory/kmalloc.cpp

@@ -1,16 +1,21 @@
 #include <BAN/Errors.h>
 #include <kernel/CriticalScope.h>
 #include <kernel/kprint.h>
+#include <kernel/Memory/GeneralAllocator.h>
 #include <kernel/Memory/kmalloc.h>
 
 #include <kernel/Thread.h>
 
 #define MB (1 << 20)
 
+extern uint8_t g_kernel_end[];
+
 static constexpr size_t s_kmalloc_min_align = alignof(max_align_t);
 
 static uint8_t s_kmalloc_storage[2 * MB];
 
+static BAN::UniqPtr<Kernel::GeneralAllocator> s_general_allocator;
+
 struct kmalloc_node
 {
 	void set_align(ptrdiff_t align)			{ m_align = align; }
@@ -277,7 +282,7 @@ static void* kmalloc_impl(size_t size, size_t align)
 
 void* kmalloc(size_t size)
 {
-	return kmalloc(size, s_kmalloc_min_align);
+	return kmalloc(size, s_kmalloc_min_align, false);
 }
 
 static constexpr bool is_power_of_two(size_t value)
@@ -287,16 +292,30 @@ static constexpr bool is_power_of_two(size_t value)
 	return (value & (value - 1)) == 0;
 }
 
-void* kmalloc(size_t size, size_t align)
+void* kmalloc(size_t size, size_t align, bool force_indentity_map)
 {
 	const kmalloc_info& info = s_kmalloc_info;
 
 	ASSERT(is_power_of_two(align));
 	if (align < s_kmalloc_min_align)
 		align = s_kmalloc_min_align;
+	ASSERT(align <= PAGE_SIZE);
 
 	Kernel::CriticalScope critical;
 
+	// FIXME: this is a hack to make more dynamic kmalloc memory
+	if (size > PAGE_SIZE && !force_indentity_map)
+	{
+		using namespace Kernel;
+
+		if (!s_general_allocator)
+			s_general_allocator = MUST(GeneralAllocator::create(PageTable::kernel(), (vaddr_t)g_kernel_end));
+		
+		auto vaddr = s_general_allocator->allocate(size);
+		if (vaddr)
+			return (void*)vaddr;
+	}
+
 	if (size == 0 || size >= info.size)
 		goto no_memory;
 
@@ -331,6 +350,9 @@ void kfree(void* address)
 
 	Kernel::CriticalScope critical;
 
+	if (s_general_allocator && s_general_allocator->deallocate((Kernel::vaddr_t)address))
+		return;
+
 	if (s_kmalloc_fixed_info.base <= address_uint && address_uint < s_kmalloc_fixed_info.end)
 	{
 		auto& info = s_kmalloc_fixed_info;
@@ -387,3 +409,20 @@ void kfree(void* address)
 	}
 
 }
+
+BAN::Optional<Kernel::paddr_t> kmalloc_paddr_of(Kernel::vaddr_t vaddr)
+{
+	using namespace Kernel;
+
+	if (s_general_allocator)
+	{
+		auto paddr = s_general_allocator->paddr_of(vaddr);
+		if (paddr.has_value())
+			return paddr.value();
+	}
+
+	if ((vaddr_t)s_kmalloc_storage <= vaddr && vaddr < (vaddr_t)s_kmalloc_storage + sizeof(s_kmalloc_storage))
+		return V2P(vaddr);
+
+	return {};
+}

kernel/kernel/kernel.cpp

@@ -133,6 +133,9 @@ extern "C" void kernel_main()
 	PageTable::initialize();
 	dprintln("PageTable initialized");
 
+	Heap::initialize();
+	dprintln("Heap initialzed");
+
 	TerminalDriver* terminal_driver = VesaTerminalDriver::create();
 	ASSERT(terminal_driver);
 	dprintln("VESA initialized");
@@ -141,9 +144,6 @@ extern "C" void kernel_main()
 	ASSERT(tty1);
 	dprintln("TTY initialized");
 
-	Heap::initialize();
-	dprintln("Heap initialzed");
-
 	parse_command_line();
 	dprintln("command line parsed, root='{}'", cmdline.root);