Kernel/LibC: Implement very basic msync

kernel/include/kernel/Memory/FileBackedRegion.h

@@ -10,6 +10,8 @@ namespace Kernel
 	{
 		~SharedFileData();
 
+		void sync(size_t page_index);
+
 		// FIXME: this should probably be ordered tree like map
 		//        for fast lookup and less memory usage
 		BAN::Vector<paddr_t> pages;
@@ -26,6 +28,8 @@ namespace Kernel
 		static BAN::ErrorOr<BAN::UniqPtr<FileBackedRegion>> create(BAN::RefPtr<Inode>, PageTable&, off_t offset, size_t size, AddressRange address_range, Type, PageTable::flags_t);
 		~FileBackedRegion();
 
+		virtual BAN::ErrorOr<void> msync(vaddr_t, size_t, int) override;
+
 		virtual BAN::ErrorOr<BAN::UniqPtr<MemoryRegion>> clone(PageTable& new_page_table) override;
 
 	protected:

kernel/include/kernel/Memory/MemoryBackedRegion.h

@@ -14,9 +14,10 @@ namespace Kernel
 		static BAN::ErrorOr<BAN::UniqPtr<MemoryBackedRegion>> create(PageTable&, size_t size, AddressRange, Type, PageTable::flags_t);
 		~MemoryBackedRegion();
 
-
 		virtual BAN::ErrorOr<BAN::UniqPtr<MemoryRegion>> clone(PageTable& new_page_table) override;
 
+		virtual BAN::ErrorOr<void> msync(vaddr_t, size_t, int) override { return {}; }
+
 		// Copy data from buffer into this region
 		// This can fail if no memory is mapped and no free memory was available
 		BAN::ErrorOr<void> copy_data_to_region(size_t offset_into_region, const uint8_t* buffer, size_t buffer_size);

kernel/include/kernel/Memory/MemoryRegion.h

@@ -40,6 +40,8 @@ namespace Kernel
 		size_t virtual_page_count() const { return BAN::Math::div_round_up<size_t>(m_size, PAGE_SIZE); }
 		size_t physical_page_count() const { return m_physical_page_count; }
 
+		virtual BAN::ErrorOr<void> msync(vaddr_t, size_t, int) = 0;
+
 		// Returns error if no memory was available
 		// Returns true if page was succesfully allocated
 		// Returns false if page was already allocated

kernel/include/kernel/Process.h

@@ -130,6 +130,7 @@ namespace Kernel
 
 		BAN::ErrorOr<long> sys_mmap(const sys_mmap_t*);
 		BAN::ErrorOr<long> sys_munmap(void* addr, size_t len);
+		BAN::ErrorOr<long> sys_msync(void* addr, size_t len, int flags);
 
 		BAN::ErrorOr<long> sys_tty_ctrl(int fildes, int command, int flags);
 

kernel/kernel/Memory/FileBackedRegion.cpp

@@ -3,6 +3,8 @@
 #include <kernel/Memory/FileBackedRegion.h>
 #include <kernel/Memory/Heap.h>
 
+#include <sys/mman.h>
+
 namespace Kernel
 {
 
@@ -70,17 +72,43 @@ namespace Kernel
 		{
 			if (pages[i] == 0)
 				continue;
+			sync(i);
+		}
+	}
+
+	void SharedFileData::sync(size_t page_index)
+	{
+		// FIXME: should this be locked?
+
+		if (pages[page_index] == 0)
+			return;
 
 		{
 			CriticalScope _;
-				PageTable::map_fast_page(pages[i]);
+			PageTable::with_fast_page(pages[page_index], [&] {
 				memcpy(page_buffer, PageTable::fast_page_as_ptr(), PAGE_SIZE);
-				PageTable::unmap_fast_page();
+			});
 		}
 
-			if (auto ret = inode->write(i * PAGE_SIZE, BAN::ConstByteSpan::from(page_buffer)); ret.is_error())
+		if (auto ret = inode->write(page_index * PAGE_SIZE, BAN::ConstByteSpan::from(page_buffer)); ret.is_error())
 			dwarnln("{}", ret.error());
 	}
+
+	BAN::ErrorOr<void> FileBackedRegion::msync(vaddr_t address, size_t size, int flags)
+	{
+		if (flags != MS_SYNC)
+			return BAN::Error::from_errno(ENOTSUP);
+		if (m_type != Type::SHARED)
+			return {};
+		
+		vaddr_t first_page	= address & PAGE_ADDR_MASK;
+		vaddr_t last_page	= BAN::Math::div_round_up<vaddr_t>(address + size, PAGE_SIZE) * PAGE_SIZE;
+
+		for (vaddr_t page_addr = first_page; page_addr < last_page; page_addr += PAGE_SIZE)
+			if (contains(page_addr))
+				m_shared_data->sync((page_addr - m_vaddr) / PAGE_SIZE);
+
+		return {};
 	}
 
 	BAN::ErrorOr<bool> FileBackedRegion::allocate_page_containing_impl(vaddr_t address)

kernel/kernel/Process.cpp

@@ -1098,6 +1098,24 @@ namespace Kernel
 		return 0;
 	}
 
+	BAN::ErrorOr<long> Process::sys_msync(void* addr, size_t len, int flags)
+	{
+		if (flags != MS_SYNC && flags != MS_ASYNC && flags != MS_INVALIDATE)
+			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 (auto& mapped_region : m_mapped_regions)
+			if (mapped_region->overlaps(vaddr, len))
+				TRY(mapped_region->msync(vaddr, len, flags));
+
+		return 0;
+	}
+
 	BAN::ErrorOr<long> Process::sys_tty_ctrl(int fildes, int command, int flags)
 	{
 		LockGuard _(m_lock);

kernel/kernel/Syscall.cpp

@@ -217,6 +217,9 @@ namespace Kernel
 		case SYS_READLINKAT:
 			ret = Process::current().sys_readlinkat((int)arg1, (const char*)arg2, (char*)arg3, (size_t)arg4);
 			break;
+		case SYS_MSYNC:
+			ret = Process::current().sys_msync((void*)arg1, (size_t)arg2, (int)arg3);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;

libc/include/sys/syscall.h

@@ -61,6 +61,7 @@ __BEGIN_DECLS
 #define SYS_UNLINK 58
 #define SYS_READLINK 59
 #define SYS_READLINKAT 60
+#define SYS_MSYNC 61
 
 __END_DECLS
 

libc/sys/mman.cpp

@@ -22,3 +22,8 @@ int munmap(void* addr, size_t len)
 {
 	return syscall(SYS_MUNMAP, addr, len);
 }
+
+int msync(void* addr, size_t len, int flags)
+{
+	return syscall(SYS_MSYNC, addr, len, flags);
+}