Kernel: Add bareboness fork() function

kernel/CMakeLists.txt

@@ -48,6 +48,7 @@ set(KERNEL_SOURCES
 	kernel/Storage/ATADevice.cpp
 	kernel/Storage/StorageDevice.cpp
 	kernel/Syscall.cpp
+	kernel/Syscall.S
 	kernel/Thread.cpp
 	kernel/Terminal/TTY.cpp
 	kernel/Terminal/VesaTerminalDriver.cpp

kernel/include/kernel/Arch.h

@@ -17,4 +17,8 @@
 	#define read_rsp(rsp) asm volatile("movl %%esp, %0" : "=r"(rsp))
 	#define push_callee_saved() asm volatile("pushal")
 	#define pop_callee_saved() asm volatile("popal")
-#endif
+#endif
+
+#include <stdint.h>
+
+extern "C" uintptr_t read_rip();

kernel/include/kernel/Process.h

@@ -41,6 +41,8 @@ namespace Kernel
 
 		pid_t pid() const { return m_pid; }
 
+		BAN::ErrorOr<Process*> fork(uintptr_t rsp, uintptr_t rip);
+
 		BAN::ErrorOr<int> open(BAN::StringView, int);
 		BAN::ErrorOr<void> close(int fd);
 		BAN::ErrorOr<size_t> read(int fd, void* buffer, size_t count);

kernel/include/kernel/Thread.h

@@ -31,6 +31,8 @@ namespace Kernel
 		static BAN::ErrorOr<Thread*> create_userspace(uintptr_t, Process*, int, char**);
 		~Thread();
 
+		BAN::ErrorOr<Thread*> clone(Process*, uintptr_t rsp, uintptr_t rip);
+
 		pid_t tid() const { return m_tid; }
 
 		void set_rsp(uintptr_t rsp) { m_rsp = rsp; validate_stack(); }

kernel/kernel/Memory/VirtualRange.cpp

@@ -83,9 +83,11 @@ namespace Kernel
 		for (size_t i = 0; i < result->m_physical_pages.size(); i++)
 		{
 			m_mmu.map_page_at(result->m_physical_pages[i], 0, MMU::Flags::ReadWrite | MMU::Flags::Present);
+			m_mmu.invalidate(0);
 			memcpy((void*)0, (void*)(vaddr() + i * PAGE_SIZE), PAGE_SIZE);
 		}
 		m_mmu.unmap_page(0);
+		m_mmu.invalidate(0);
 
 		return result;
 	}

kernel/kernel/Process.cpp

@@ -129,6 +129,8 @@ namespace Kernel
 			MMU::kernel().load();
 			delete m_mmu;
 		}
+
+		dprintln("process {} exit", pid());
 	}
 
 	void Process::add_thread(Thread* thread)
@@ -167,8 +169,6 @@ namespace Kernel
 			m_general_allocator = nullptr;
 		}
 
-		dprintln("process {} exit", pid());
-
 		s_process_lock.lock();
 		for (size_t i = 0; i < s_processes.size(); i++)
 			if (s_processes[i] == this)
@@ -197,6 +197,40 @@ namespace Kernel
 		return {};
 	}
 
+	BAN::ErrorOr<Process*> Process::fork(uintptr_t rsp, uintptr_t rip)
+	{
+		LockGuard _(m_lock);
+		
+		Process* forked = create_process();
+
+		forked->m_tty = m_tty;
+		forked->m_working_directory = m_working_directory;
+
+		forked->m_open_files = m_open_files;
+
+		forked->m_mmu = new MMU();
+		ASSERT(forked->m_mmu);
+
+		for (auto* mapped_range : m_mapped_ranges)
+			MUST(forked->m_mapped_ranges.push_back(mapped_range->clone(forked->mmu())));
+
+		ASSERT(m_threads.size() == 1);
+		ASSERT(m_threads.front() == &Thread::current());
+
+		//for (auto& allocator : m_fixed_width_allocators)
+		//	MUST(forked->m_fixed_width_allocators.push_back(allocator.clone()));
+
+		//if (m_general_allocator)
+		//	forked->m_general_allocator = m_general_allocator->clone();
+
+		Thread* thread = MUST(m_threads.front()->clone(forked, rsp, rip));
+		forked->add_thread(thread);
+		
+		register_process(forked);
+
+		return forked;
+	}
+
 	BAN::ErrorOr<int> Process::open(BAN::StringView path, int flags)
 	{
 		if (flags & ~O_RDWR)

kernel/kernel/Scheduler.cpp

@@ -19,7 +19,6 @@ namespace Kernel
 
 	extern "C" [[noreturn]] void start_thread(uintptr_t rsp, uintptr_t rip);
 	extern "C" [[noreturn]] void continue_thread(uintptr_t rsp, uintptr_t rip);
-	extern "C" uintptr_t read_rip();
 
 	static Scheduler* s_instance = nullptr;
 

kernel/kernel/Syscall.S

@@ -0,0 +1,22 @@
+.global sys_fork_trampoline
+sys_fork_trampoline:
+	pushq %rbx
+	pushq %rbp
+	pushq %r12
+	pushq %r13
+	pushq %r14
+	pushq %r15
+	call read_rip
+	testq %rax, %rax
+	je .done
+	movq %rax, %rsi
+	movq %rsp, %rdi
+	call sys_fork
+.done:
+	popq %r15
+	popq %r14
+	popq %r13
+	popq %r12
+	popq %rbp
+	popq %rbx
+	ret

kernel/kernel/Syscall.cpp

@@ -98,6 +98,16 @@ namespace Kernel
 		return 0;
 	}
 
+	extern "C" long sys_fork(uintptr_t rsp, uintptr_t rip)
+	{
+		auto ret = Process::current().fork(rsp, rip);
+		if (ret.is_error())
+			return -ret.error().get_error_code();
+		return ret.value()->pid();
+	}
+
+	extern "C" long sys_fork_trampoline();
+
 	extern "C" long cpp_syscall_handler(int syscall, uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4, uintptr_t arg5)
 	{
 		Thread::current().set_in_syscall(true);
@@ -149,6 +159,9 @@ namespace Kernel
 		case SYS_SET_TERMIOS:
 			ret = sys_set_termios((const ::termios*)arg1);
 			break;
+		case SYS_FORK:
+			ret = sys_fork_trampoline();
+			break;
 		default:
 			Kernel::panic("Unknown syscall {}", syscall);
 		}

kernel/kernel/Thread.cpp

@@ -111,13 +111,38 @@ namespace Kernel
 
 	Thread::~Thread()
 	{
-		dprintln("thread {} ({}) exit", tid(), m_process->pid());
 		if (m_stack)
 			delete m_stack;
 		m_stack = nullptr;
 		if (m_interrupt_stack)
 			delete m_interrupt_stack;
 		m_interrupt_stack = nullptr;
+		
+		dprintln("thread {} ({}) exit", tid(), m_process->pid());
+	}
+
+	BAN::ErrorOr<Thread*> Thread::clone(Process* new_process, uintptr_t rsp, uintptr_t rip)
+	{
+		ASSERT(m_is_userspace);
+		ASSERT(m_state == State::Executing);
+
+		Thread* thread = new Thread(s_next_tid++, new_process);
+		if (thread == nullptr)
+			return BAN::Error::from_errno(ENOMEM);
+		thread->m_is_userspace = true;
+
+		thread->m_interrupt_stack = m_interrupt_stack->clone(new_process->mmu());
+		thread->m_stack = m_stack->clone(new_process->mmu());
+
+		thread->m_state = State::Executing;
+		thread->m_in_syscall = true;
+
+		thread->m_rip = rip;
+		thread->m_rsp = rsp;
+
+		thread->m_userspace_entry = {};
+
+		return thread;
 	}
 
 	void Thread::validate_stack() const

kernel/kernel/kernel.cpp

@@ -126,7 +126,7 @@ extern "C" void kernel_main()
 	dprintln("GDT initialized");
 
 	IDT::initialize();
-	dprintln("IDT initialized");	
+	dprintln("IDT initialized");
 
 	MMU::initialize();
 	dprintln("MMU initialized");
@@ -180,7 +180,7 @@ static void init2(void* tty1)
 
 	((TTY*)tty1)->initialize_device();
 
-	MUST(Process::create_userspace("/usr/bin/Shell"sv));
+	MUST(Process::create_userspace("/usr/bin/test"sv));
 	return;
 
 	Process::create_kernel(

libc/include/sys/syscall.h

@@ -17,6 +17,7 @@ __BEGIN_DECLS
 #define SYS_TELL 10
 #define SYS_GET_TERMIOS 11
 #define SYS_SET_TERMIOS 12
+#define SYS_FORK 13
 
 __END_DECLS
 

libc/unistd.cpp

@@ -103,6 +103,11 @@ long syscall(long syscall, ...)
 			ret = Kernel::syscall(SYS_SET_TERMIOS, (uintptr_t)termios);
 			break;
 		}
+		case SYS_FORK:
+		{
+			ret = Kernel::syscall(SYS_FORK);
+			break;
+		}
 		default:
 			puts("LibC: Unhandeled syscall");
 			ret = -ENOSYS;
@@ -122,25 +127,5 @@ long syscall(long syscall, ...)
 
 pid_t fork(void)
 {
-	return -1;
-}
-
-int execv(const char*, char* const[])
-{
-	return -1;
-}
-
-int execve(const char*, char* const[], char* const[])
-{
-	return -1;
-}
-
-int execvp(const char*, char* const[])
-{
-	return -1;
-}
-
-pid_t getpid(void)
-{
-	return -1;
+	return syscall(SYS_FORK);
 }

userspace/test/test.cpp

@@ -1,31 +1,22 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #define ERROR(msg) { perror(msg); return 1; }
 #define BUF_SIZE 1024
 
 int main()
 {
-	FILE* fp = fopen("/usr/include/stdio.h", "r");
-	if (fp == NULL)
-		ERROR("fopen");
+	printf("forking\n");
 
-	char* buffer = (char*)malloc(BUF_SIZE);
-	if (buffer == NULL)
-		ERROR("malloc");
-
-	for (;;)
+	pid_t pid = fork();
+	if (pid == 0)
 	{
-		size_t n_read = fread(buffer, 1, BUF_SIZE - 1, fp);
-		if (n_read == 0)
-			break;
-		buffer[n_read] = '\0';
-		printf("%s", buffer);
+		printf("child\n");
+		return 0;
 	}
-
-	free(buffer);
-	fclose(fp);
+	printf("parent\n");
 
 	return 0;
 }