[kernel] Move pml4 create/delete into vm_space

vm_space and page_table continue to take over duties from
page_manager:

- creation and deletion of address spaces / pml4s
- cross-address-space copies for endpoints
- taking over pml4 ownership from process

Also fixed the bug where the wrong process was being set in the cpu
data.

To solve: now the kernel process has its own vm_space which is not
g_kernel_space.

src/kernel/objects/endpoint.cpp

@@ -1,7 +1,9 @@
 #include "objects/endpoint.h"
+#include "objects/process.h"
 #include "objects/thread.h"
 #include "page_manager.h"
 #include "scheduler.h"
+#include "vm_space.h"
 
 endpoint::endpoint() :
 	kobject(kobject::type::endpoint)
@@ -86,9 +88,9 @@ endpoint::do_message_copy(const endpoint::thread_data &sender, endpoint::thread_
 		return j6_err_insufficient;
 
 	page_manager *pm = page_manager::get();
-	void *send_data = pm->get_offset_from_mapped(sender.data, sender.th->tcb()->pml4);
-	void *recv_data = pm->get_offset_from_mapped(receiver.data, receiver.th->tcb()->pml4);
-	kutil::memcpy(recv_data, send_data, sender.len);
+	vm_space &source = sender.th->parent().space();
+	vm_space &dest = receiver.th->parent().space();
+	vm_space::copy(source, dest, sender.data, receiver.data, sender.len);
 	*receiver.len_p = sender.len;
 
 	// TODO: this will not work if non-contiguous pages are mapped!!

src/kernel/objects/process.cpp

@@ -7,10 +7,8 @@
 
 kutil::vector<process*> process::s_processes;
 
-process::process(page_table *pml4) :
+process::process() :
 	kobject(kobject::type::process),
-	m_pml4(pml4),
-	m_space(pml4),
 	m_next_handle(0),
 	m_state(state::running)
 {
@@ -41,7 +39,6 @@ process::exit(unsigned code)
 		thread->exit(code);
 	}
 	m_return_code = code;
-	page_manager::get()->delete_process_map(m_pml4);
 	assert_signal(j6_signal_process_exit);
 }
 
@@ -76,13 +73,7 @@ process::create_thread(uint8_t priority, bool user)
 
 	if (user) {
 		uintptr_t stack_top = stacks_top - (m_threads.count() * stack_size);
-		auto *pm = page_manager::get();
-		pm->map_pages(
-			stack_top - stack_size,
-			page_manager::page_count(stack_size),
-			true, // user stack
-			m_pml4);
-
+		m_space.allow(stack_top - stack_size, stack_size, true);
 		th->tcb()->rsp3 = stack_top;
 	}
 

src/kernel/objects/process.h

@@ -19,8 +19,7 @@ public:
 	constexpr static size_t stack_size = 0x4000;
 
 	/// Constructor.
-	/// \args pml4  Root of the process' page tables
-	process(page_table *pml4);
+	process();
 
 	/// Destructor.
 	virtual ~process();
@@ -35,9 +34,6 @@ public:
 	/// Update internal bookkeeping about threads.
 	void update();
 
-	/// Get the process' page table root
-	page_table * pml4() { return m_pml4; }
-
 	/// Get the process' virtual memory space
 	vm_space & space() { return m_space; }
 
@@ -75,7 +71,6 @@ public:
 private:
 	uint32_t m_return_code;
 
-	page_table *m_pml4;
 	vm_space m_space;
 
 	kutil::vector<thread*> m_threads;

src/kernel/objects/thread.cpp

@@ -17,7 +17,7 @@ thread::thread(process &parent, uint8_t pri, uintptr_t rsp0) :
 	m_wait_data(0),
 	m_wait_obj(0)
 {
-	m_tcb.pml4 = parent.pml4();
+	parent.space().initialize_tcb(m_tcb);
 	m_tcb.priority = pri;
 
 	if (!rsp0)

src/kernel/objects/thread.h

@@ -15,7 +15,7 @@ struct TCB
 	uintptr_t rsp;
 	uintptr_t rsp0;
 	uintptr_t rsp3;
-	page_table *pml4;
+	uintptr_t pml4;
 
 	uint8_t priority;
 	// note: 3 bytes padding

src/kernel/page_manager.cpp

@@ -45,55 +45,6 @@ page_manager::page_manager(frame_allocator &frames, page_table *pml4) :
 {
 }
 
-page_table *
-page_manager::create_process_map()
-{
-	page_table *table = page_table::get_table_page();
-
-	kutil::memset(table, 0, frame_size/2);
-	for (unsigned i = pml4e_kernel; i < table_entries; ++i)
-		table->entries[i] = m_kernel_pml4->entries[i];
-
-	return table;
-}
-
-void
-page_manager::delete_process_map(page_table *pml4)
-{
-	bool was_pml4 = (pml4 == get_pml4());
-	if (was_pml4)
-		set_pml4(m_kernel_pml4);
-
-	log::info(logs::paging, "Deleting process pml4 at %016lx%s",
-			pml4, was_pml4 ? " (was current)" : "");
-
-	unmap_table(pml4, page_table::level::pml4, true);
-}
-
-void *
-page_manager::get_offset_from_mapped(void *p, page_table *pml4)
-{
-	if (!pml4) pml4 = get_pml4();
-	uintptr_t v = reinterpret_cast<uintptr_t>(p);
-
-	page_table_indices idx{v};
-	page_table *tables[4] = {pml4, nullptr, nullptr, nullptr};
-
-	for (int i = 1; i < 4; ++i) {
-		tables[i] = tables[i-1]->get(idx[i-1]);
-		if (!tables[i])
-			return nullptr;
-	}
-
-	uintptr_t a = tables[3]->entries[idx[3]];
-	if (!(a & 1))
-		return nullptr;
-
-	return memory::to_virtual<void>(
-			(a & ~0xfffull) |
-			(v & 0xfffull));
-}
-
 void
 page_manager::dump_pml4(page_table *pml4, bool recurse)
 {

src/kernel/page_manager.h

@@ -49,15 +49,6 @@ public:
 		__asm__ __volatile__ ( "mov %0, %%cr3" :: "r" (p) );
 	}
 
-	/// Allocate but don't switch to a new PML4 table. This table
-	/// should only have global kernel pages mapped.
-	/// \returns      A pointer to the PML4 table
-	page_table * create_process_map();
-
-	/// Deallocate a process' PML4 table and entries.
-	/// \arg pml4  The process' PML4 table
-	void delete_process_map(page_table *pml4);
-
 	/// Allocate and map pages into virtual memory.
 	/// \arg address  The virtual address at which to map the pages
 	/// \arg count    The number of pages to map
@@ -72,11 +63,6 @@ public:
 	/// \arg pml4     The pml4 to unmap from - null for the current one
 	void unmap_pages(void *address, size_t count, page_table *pml4 = nullptr);
 
-	/// Get the offet-mapped virtual address of a normal virtual address
-	/// \arg p   Virtual address
-	/// \returns Virtual address in offset-mapped linear space
-	void * get_offset_from_mapped(void *p, page_table *pml4 = nullptr);
-
 	/// Dump the given or current PML4 to the console
 	/// \arg pml4     The page table to use, null for the current one
 	/// \arg recurse  Whether to print sub-tables

src/kernel/page_table.cpp

@@ -12,6 +12,7 @@ extern frame_allocator &g_frame_allocator;
 
 free_page_header * page_table::s_page_cache = nullptr;
 size_t page_table::s_cache_count = 0;
+constexpr size_t page_table::entry_sizes[4];
 
 // Flags: 0 0 0 0  0 0 0 0  0 0 1 1 = 0x0003
 //        IGNORED  | | | |  | | | +- Present
@@ -88,7 +89,7 @@ page_table::iterator::align() const
 page_table::level
 page_table::iterator::depth() const
 {
-	for (level i = level::pml4; i < level::pt; ++i)
+	for (level i = level::pml4; i < level::page; ++i)
 		if (!(entry(i) & 1)) return i;
 	return level::pt;
 }
@@ -248,6 +249,26 @@ page_table::fill_table_page_cache()
 	}
 }
 
+void
+page_table::free(page_table::level l)
+{
+	unsigned last = l == level::pml4
+		? memory::pml4e_kernel
+		: memory::table_entries;
+
+	for (unsigned i = 0; i < last; ++i) {
+		if (!is_present(i)) continue;
+		if (is_page(l, i)) {
+			size_t count = memory::page_count(entry_sizes[unsigned(l)]);
+			g_frame_allocator.free(entries[i] & ~0xfffull, count);
+		} else {
+			get(i)->free(l + 1);
+		}
+	}
+
+	free_table_page(this);
+}
+
 void
 page_table::dump(page_table::level lvl, bool recurse)
 {

src/kernel/page_table.h

@@ -76,7 +76,7 @@ struct page_table
 		/// Get a *non-const* reference to the current table entry of
 		/// the table at the given level.
 		inline uint64_t & entry(level l) {
-			for (unsigned i = 1; i < unsigned(l); ++i) ensure_table(level(i));
+			for (unsigned i = 1; i <= unsigned(l); ++i) ensure_table(level(i));
 			return table(l)->entries[index(l)];
 		}
 
@@ -149,6 +149,10 @@ struct page_table
 	/// Check if the given entry represents a page (of any size)
 	inline bool is_page(level l, int i) const { return (l == level::pt) || is_large_page(l, i); }
 
+	/// Free this page table and all resources it references
+	/// \arg l  The level of this page table
+	void free(level l);
+
 	/// Print this table to the debug console.
 	void dump(level lvl = level::pml4, bool recurse = true);
 

src/kernel/scheduler.cpp

@@ -42,7 +42,7 @@ scheduler::scheduler(lapic *apic) :
 	s_instance = this;
 
 	page_table *pml4 = page_manager::get_pml4();
-	process *kp = new process(pml4);
+	process *kp = new process;
 	m_kernel_process = kp;
 
 	log::debug(logs::task, "Kernel process koid %llx", kp->koid());
@@ -136,9 +136,9 @@ load_process_image(const void *image_start, size_t bytes, TCB *tcb)
 }
 
 thread *
-scheduler::create_process(page_table *pml4, bool user)
+scheduler::create_process(bool user)
 {
-	process *p = new process(pml4);
+	process *p = new process;
 	thread *th = p->create_thread(default_priority, user);
 	auto *tcb = th->tcb();
 
@@ -160,10 +160,7 @@ scheduler::load_process(const char *name, const void *data, size_t size)
 	uint16_t kss = (2 << 3) | 0; // Kernel SS is GDT entry 2, ring 0
 	uint16_t ss = (4 << 3) | 3;  // User SS is GDT entry 4, ring 3
 
-	// Set up the page tables - this also allocates an initial user stack
-	page_table *pml4 = page_manager::get()->create_process_map();
-
-	thread* th = create_process(pml4, true);
+	thread* th = create_process(true);
 	auto *tcb = th->tcb();
 
 	// Create an initial kernel stack space
@@ -348,10 +345,11 @@ scheduler::schedule()
 	m_apic->reset_timer(next->time_left);
 
 	if (next != m_current) {
+		thread *next_thread = thread::from_tcb(next);
+
+		bsp_cpu_data.t = next_thread;
+		bsp_cpu_data.p = &next_thread->parent();
 		m_current = next;
-		bsp_cpu_data.t = thread::from_tcb(m_current);
-		bsp_cpu_data.p = &th->parent();
-		thread *next_thread = thread::from_tcb(m_current);
 
 		log::debug(logs::task, "Scheduler switching threads %llx->%llx",
 				th->koid(), next_thread->koid());

src/kernel/scheduler.h

@@ -83,10 +83,9 @@ private:
 
 	/// Create a new process object. This process will have its pid
 	/// set but nothing else.
-	/// \arg pml4 The root page table of the process
 	/// \arg user True if this thread will enter userspace
 	/// \returns  The new process' main thread
-	thread * create_process(page_table *pml4, bool user);
+	thread * create_process(bool user);
 
 	void prune(uint64_t now);
 	void check_promotions(uint64_t now);

src/kernel/vm_space.cpp

@@ -1,5 +1,5 @@
 #include "log.h"
-#include "objects/process.h"
+#include "objects/thread.h"
 #include "objects/vm_area.h"
 #include "page_manager.h"
 #include "vm_space.h"
@@ -24,12 +24,29 @@ vm_space::vm_space(page_table *p) : m_kernel(true), m_pml4(p) {}
 vm_space::vm_space() :
 	m_kernel(false)
 {
+	m_pml4 = page_table::get_table_page();
+	page_table *kpml4 = kernel_space().m_pml4;
+
+	kutil::memset(m_pml4, 0, memory::frame_size/2);
+	for (unsigned i = memory::pml4e_kernel; i < memory::table_entries; ++i)
+		m_pml4->entries[i] = kpml4->entries[i];
 }
 
 vm_space::~vm_space()
 {
 	for (auto &a : m_areas)
 		a.area->remove_from(this);
+
+	kassert(!is_kernel(), "Kernel vm_space destructor!");
+
+	vm_space &kernel = kernel_space();
+
+	if (active())
+		kernel.activate();
+
+	// All VMAs have been removed by now, so just
+	// free all remaining pages and tables
+	m_pml4->free(page_table::level::pml4);
 }
 
 vm_space &
@@ -104,6 +121,30 @@ vm_space::allow(uintptr_t start, size_t length, bool allow)
 	}
 }
 
+bool
+vm_space::active() const
+{
+	uintptr_t pml4 = 0;
+	__asm__ __volatile__ ( "mov %%cr3, %0" : "=r" (pml4) );
+	return memory::to_virtual<page_table>(pml4 & ~0xfffull) == m_pml4;
+}
+
+void
+vm_space::activate() const
+{
+	constexpr uint64_t phys_mask = ~memory::page_offset & ~0xfffull;
+	uintptr_t p = reinterpret_cast<uintptr_t>(m_pml4) & phys_mask;
+	__asm__ __volatile__ ( "mov %0, %%cr3" :: "r" (p) );
+}
+
+void
+vm_space::initialize_tcb(TCB &tcb)
+{
+	tcb.pml4 =
+		reinterpret_cast<uintptr_t>(m_pml4) &
+		~memory::page_offset;
+}
+
 bool
 vm_space::handle_fault(uintptr_t addr, fault_type fault)
 {
@@ -124,3 +165,22 @@ vm_space::handle_fault(uintptr_t addr, fault_type fault)
 
 	return true;
 }
+
+size_t
+vm_space::copy(vm_space &source, vm_space &dest, void *from, void *to, size_t length)
+{
+	uintptr_t ifrom = reinterpret_cast<uintptr_t>(from);
+	uintptr_t ito = reinterpret_cast<uintptr_t>(to);
+
+	page_table::iterator sit {ifrom, source.m_pml4};
+	page_table::iterator dit {ito, dest.m_pml4};
+
+	// TODO: iterate page mappings and continue copying. For now i'm blindly
+	// assuming both buffers are fully contained within single pages
+	kutil::memcpy(
+		memory::to_virtual<void>((*dit & ~0xfffull) | (ito & 0xffful)),
+		memory::to_virtual<void>((*sit & ~0xfffull) | (ifrom & 0xffful)),
+		length);
+
+	return length;
+}

src/kernel/vm_space.h

@@ -8,6 +8,7 @@
 
 struct page_table;
 class process;
+struct TCB;
 class vm_area;
 
 /// Tracks a region of virtual memory address space
@@ -64,6 +65,12 @@ public:
 	/// \arg allow  True if allocation should be allowed
 	void allow(uintptr_t start, size_t length, bool allow);
 
+	/// Check if this space is the current active space
+	bool active() const;
+
+	/// Set this space as the current active space
+	void activate() const;
+
 	enum class fault_type : uint8_t {
 		none     = 0x00,
 		present  = 0x01,
@@ -79,11 +86,22 @@ public:
 	/// \returns   True if the fault was successfully handled
 	bool handle_fault(uintptr_t addr, fault_type fault);
 
+	/// Set up a TCB to operate in this address space.
+	void initialize_tcb(TCB &tcb);
+
+	/// Copy data from one address space to another
+	/// \arg source The address space data is being copied from
+	/// \arg dest   The address space data is being copied to
+	/// \arg from   Pointer to the data in the source address space
+	/// \arg to     Pointer to the destination in the dest address space
+	/// \arg length Amount of data to copy, in bytes
+	/// \returnd    The number of bytes copied
+	static size_t copy(vm_space &source, vm_space &dest, void *from, void *to, size_t length);
+
 private:
 	bool m_kernel;
 	page_table *m_pml4;
 
-
 	struct area {
 		uintptr_t base;
 		vm_area *area;