Kernel/LibC: Implement pread()

kernel/include/kernel/Process.h

@@ -105,6 +105,8 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_readlink(const char* path, char* buffer, size_t bufsize);
 		BAN::ErrorOr<long> sys_readlinkat(int fd, const char* path, char* buffer, size_t bufsize);
 
+		BAN::ErrorOr<long> sys_pread(int fd, void* buffer, size_t count, off_t offset);
+
 		BAN::ErrorOr<long> sys_chmod(const char*, mode_t);
 
 		BAN::ErrorOr<long> sys_pipe(int fildes[2]);

kernel/kernel/Process.cpp

@@ -823,6 +823,14 @@ namespace Kernel
 		return readlink_impl(absolute_path.sv(), buffer, bufsize);
 	}
 
+	BAN::ErrorOr<long> Process::sys_pread(int fd, void* buffer, size_t count, off_t offset)
+	{
+		LockGuard _(m_lock);
+		validate_pointer_access(buffer, count);
+		auto inode = TRY(m_open_file_descriptors.inode_of(fd));
+		return TRY(inode->read(offset, { (uint8_t*)buffer, count }));
+	}
+
 	BAN::ErrorOr<long> Process::sys_chmod(const char* path, mode_t mode)
 	{
 		if (mode & S_IFMASK)

kernel/kernel/Syscall.cpp

@@ -220,6 +220,9 @@ namespace Kernel
 		case SYS_MSYNC:
 			ret = Process::current().sys_msync((void*)arg1, (size_t)arg2, (int)arg3);
 			break;
+		case SYS_PREAD:
+			ret = Process::current().sys_pread((int)arg1, (void*)arg2, (size_t)arg3, (off_t)arg4);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;