Kernel/LibC: add mmap for private anonymous mappings

This will be used by the userspace to get more memory. Currently
kernel handles all allocations, which is not preferable.

kernel/include/kernel/Process.h

@@ -15,6 +15,7 @@
 #include <kernel/Terminal/TTY.h>
 #include <kernel/Thread.h>
 
+#include <sys/mman.h>
 #include <termios.h>
 
 namespace LibELF { class ELF; }
@@ -115,6 +116,9 @@ namespace Kernel
 
 		BAN::ErrorOr<long> sys_read_dir_entries(int fd, DirectoryEntryList* buffer, size_t buffer_size);
 
+		BAN::ErrorOr<long> sys_mmap(const sys_mmap_t&);
+		BAN::ErrorOr<long> sys_munmap(void* addr, size_t len);
+
 		BAN::ErrorOr<long> sys_alloc(size_t);
 		BAN::ErrorOr<long> sys_free(void*);
 
@@ -177,6 +181,8 @@ namespace Kernel
 		BAN::String m_working_directory;
 		BAN::Vector<Thread*> m_threads;
 
+		BAN::Vector<BAN::UniqPtr<VirtualRange>> m_private_anonymous_mappings;
+
 		BAN::Vector<BAN::UniqPtr<FixedWidthAllocator>> m_fixed_width_allocators;
 		BAN::UniqPtr<GeneralAllocator> m_general_allocator;
 

kernel/kernel/Process.cpp

@@ -159,6 +159,7 @@ namespace Kernel
 		ASSERT(m_threads.empty());
 		ASSERT(m_fixed_width_allocators.empty());
 		ASSERT(!m_general_allocator);
+		ASSERT(m_private_anonymous_mappings.empty());
 		ASSERT(m_mapped_ranges.empty());
 		ASSERT(m_exit_status.waiting == 0);
 		ASSERT(&PageTable::current() != m_page_table.ptr());
@@ -192,6 +193,7 @@ namespace Kernel
 		m_open_file_descriptors.close_all();
 
 		// NOTE: We must unmap ranges while the page table is still alive
+		m_private_anonymous_mappings.clear();
 		m_mapped_ranges.clear();
 
 		// NOTE: We must clear allocators while the page table is still alive
@@ -358,6 +360,11 @@ namespace Kernel
 		OpenFileDescriptorSet open_file_descriptors(m_credentials);
 		TRY(open_file_descriptors.clone_from(m_open_file_descriptors));
 
+		BAN::Vector<BAN::UniqPtr<VirtualRange>> private_anonymous_mappings;
+		TRY(private_anonymous_mappings.reserve(m_private_anonymous_mappings.size()));
+		for (auto& private_anonymous_mapping : m_private_anonymous_mappings)
+			MUST(private_anonymous_mappings.push_back(TRY(private_anonymous_mapping->clone(*page_table))));
+
 		BAN::Vector<BAN::UniqPtr<VirtualRange>> mapped_ranges;
 		TRY(mapped_ranges.reserve(m_mapped_ranges.size()));
 		for (auto& mapped_range : m_mapped_ranges)
@@ -378,6 +385,7 @@ namespace Kernel
 		forked->m_working_directory = BAN::move(working_directory);
 		forked->m_page_table = BAN::move(page_table);
 		forked->m_open_file_descriptors = BAN::move(open_file_descriptors);
+		forked->m_private_anonymous_mappings = BAN::move(private_anonymous_mappings);
 		forked->m_mapped_ranges = BAN::move(mapped_ranges);
 		forked->m_fixed_width_allocators = BAN::move(fixed_width_allocators);
 		forked->m_general_allocator = BAN::move(general_allocator);
@@ -428,6 +436,7 @@ namespace Kernel
 
 			m_fixed_width_allocators.clear();
 			m_general_allocator.clear();
+			m_private_anonymous_mappings.clear();
 			m_mapped_ranges.clear();
 
 			load_elf_to_memory(*elf);
@@ -811,6 +820,66 @@ namespace Kernel
 		return (long)buffer;
 	}
 
+	BAN::ErrorOr<long> Process::sys_mmap(const sys_mmap_t& args)
+	{
+		if (args.prot != PROT_NONE && args.prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC))
+			return BAN::Error::from_errno(EINVAL);
+
+		PageTable::flags_t flags = PageTable::Flags::UserSupervisor;
+		if (args.prot & PROT_READ)
+			flags |= PageTable::Flags::Present;
+		if (args.prot & PROT_WRITE)
+			flags |= PageTable::Flags::ReadWrite | PageTable::Flags::Present;
+		if (args.prot & PROT_EXEC)
+			flags |= PageTable::Flags::Execute | PageTable::Flags::Present;
+
+		if (args.flags == (MAP_ANONYMOUS | MAP_PRIVATE))
+		{
+			if (args.addr != nullptr)
+				return BAN::Error::from_errno(ENOTSUP);
+			if (args.off != 0)
+				return BAN::Error::from_errno(EINVAL);
+			if (args.len % PAGE_SIZE != 0)
+				return BAN::Error::from_errno(EINVAL);
+
+			auto range = TRY(VirtualRange::create_to_vaddr_range(
+				page_table(),
+				0x400000, KERNEL_OFFSET,
+				args.len,
+				PageTable::Flags::UserSupervisor | PageTable::Flags::ReadWrite | PageTable::Flags::Present
+			));
+			range->set_zero();
+
+			LockGuard _(m_lock);
+			TRY(m_private_anonymous_mappings.push_back(BAN::move(range)));
+			return m_private_anonymous_mappings.back()->vaddr();
+		}
+
+		return BAN::Error::from_errno(ENOTSUP);
+	}
+
+	BAN::ErrorOr<long> Process::sys_munmap(void* addr, size_t len)
+	{
+		if (len == 0)
+			return BAN::Error::from_errno(EINVAL);
+
+		vaddr_t vaddr = (vaddr_t)addr;
+		if (vaddr % PAGE_SIZE != 0)
+			return BAN::Error::from_errno(EINVAL);
+
+		LockGuard _(m_lock);
+
+		for (size_t i = 0; i < m_private_anonymous_mappings.size(); i++)
+		{
+			auto& mapping = m_private_anonymous_mappings[i];
+			if (vaddr + len < mapping->vaddr() || vaddr >= mapping->vaddr() + mapping->size())
+				continue;
+			m_private_anonymous_mappings.remove(i);
+		}
+
+		return 0;
+	}
+
 	static constexpr size_t allocator_size_for_allocation(size_t value)
 	{
 		if (value <= 256) {

kernel/kernel/Syscall.cpp

@@ -194,6 +194,12 @@ namespace Kernel
 		case SYS_SYNC:
 			ret = Process::current().sys_sync();
 			break;
+		case SYS_MMAP:
+			ret = Process::current().sys_mmap(*(const sys_mmap_t*)arg1);
+			break;
+		case SYS_MUNMAP:
+			ret = Process::current().sys_munmap((void*)arg1, (size_t)arg2);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;

libc/CMakeLists.txt

@@ -13,6 +13,7 @@ set(LIBC_SOURCES
 	stdio.cpp
 	stdlib.cpp
 	string.cpp
+	sys/mman.cpp
 	sys/stat.cpp
 	sys/wait.cpp
 	termios.cpp

libc/include/sys/mman.h

@@ -46,6 +46,16 @@ struct posix_typed_mem_info
 	size_t posix_tmi_length;	/* Maximum length which may be allocated from a typed memory object. */
 };
 
+struct sys_mmap_t
+{
+	void* addr;
+	size_t len;
+	int prot;
+	int flags;
+	int fildes;
+	off_t off;
+};
+
 int		mlock(const void* addr, size_t len);
 int		mlockall(int flags);
 void*	mmap(void* addr, size_t len, int prot, int flags, int fildes, off_t off);

libc/include/sys/syscall.h

@@ -55,6 +55,8 @@ __BEGIN_DECLS
 #define SYS_FSTATAT 48
 #define SYS_STAT 49 // stat/lstat
 #define SYS_SYNC 50
+#define SYS_MMAP 51
+#define SYS_MUNMAP 52
 
 __END_DECLS
 

libc/sys/mman.cpp

@@ -0,0 +1,23 @@
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+void* mmap(void* addr, size_t len, int prot, int flags, int fildes, off_t off)
+{
+	sys_mmap_t args {
+		.addr = addr,
+		.len = len,
+		.prot = prot,
+		.flags = flags,
+		.off = off
+	};
+	long ret = syscall(SYS_MMAP, &args);
+	if (ret == -1)
+		return nullptr;
+	return (void*)ret;
+}
+
+int munmap(void* addr, size_t len)
+{
+	return syscall(SYS_MUNMAP, addr, len);
+}