diff --git a/kernel/src/filesystem/vfs/core.rs b/kernel/src/filesystem/vfs/core.rs index 18ec6555..10aacdd1 100644 --- a/kernel/src/filesystem/vfs/core.rs +++ b/kernel/src/filesystem/vfs/core.rs @@ -4,10 +4,7 @@ use alloc::{format, string::ToString, sync::Arc}; use system_error::SystemError; use crate::{ - driver::{ - base::block::disk_info::Partition, - disk::ahci::{self}, - }, + driver::{base::block::disk_info::Partition, disk::ahci}, filesystem::{ devfs::devfs_init, fat::fs::FATFileSystem, @@ -23,7 +20,7 @@ use crate::{ use super::{ file::FileMode, utils::{rsplit_path, user_path_at}, - IndexNode, InodeId, MAX_PATHLEN, VFS_MAX_FOLLOW_SYMLINK_TIMES, + IndexNode, InodeId, VFS_MAX_FOLLOW_SYMLINK_TIMES, }; /// @brief 原子地生成新的Inode号。 @@ -181,10 +178,7 @@ pub fn mount_root_fs() -> Result<(), SystemError> { /// @brief 创建文件/文件夹 pub fn do_mkdir(path: &str, _mode: FileMode) -> Result { - // 文件名过长 - if path.len() > MAX_PATHLEN as usize { - return Err(SystemError::ENAMETOOLONG); - } + let path = path.trim(); let inode: Result, SystemError> = ROOT_INODE().lookup(path); @@ -213,10 +207,7 @@ pub fn do_mkdir(path: &str, _mode: FileMode) -> Result { /// @brief 删除文件夹 pub fn do_remove_dir(dirfd: i32, path: &str) -> Result { - // 文件名过长 - if path.len() > MAX_PATHLEN as usize { - return Err(SystemError::ENAMETOOLONG); - } + let path = path.trim(); let pcb = ProcessManager::current_pcb(); let (inode_begin, remain_path) = user_path_at(&pcb, dirfd, path)?; @@ -249,10 +240,8 @@ pub fn do_remove_dir(dirfd: i32, path: &str) -> Result { /// @brief 删除文件 pub fn do_unlink_at(dirfd: i32, path: &str) -> Result { - // 文件名过长 - if path.len() > MAX_PATHLEN as usize { - return Err(SystemError::ENAMETOOLONG); - } + let path = path.trim(); + let pcb = ProcessManager::current_pcb(); let (inode_begin, remain_path) = user_path_at(&pcb, dirfd, path)?; let inode: Result, SystemError> = diff --git a/kernel/src/filesystem/vfs/open.rs b/kernel/src/filesystem/vfs/open.rs index bbe37351..33db06e4 100644 --- a/kernel/src/filesystem/vfs/open.rs +++ b/kernel/src/filesystem/vfs/open.rs @@ -36,10 +36,6 @@ pub(super) fn do_faccessat( let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; - if path.len() == 0 { - return Err(SystemError::EINVAL); - } - let (inode, path) = user_path_at(&ProcessManager::current_pcb(), dirfd, &path)?; // 如果找不到文件，则返回错误码ENOENT @@ -52,10 +48,6 @@ pub(super) fn do_faccessat( pub fn do_fchmodat(dirfd: i32, path: *const u8, _mode: ModeType) -> Result { let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; - if path.len() == 0 { - return Err(SystemError::EINVAL); - } - let (inode, path) = user_path_at(&ProcessManager::current_pcb(), dirfd, &path)?; // 如果找不到文件，则返回错误码ENOENT @@ -85,10 +77,8 @@ fn do_sys_openat2( follow_symlink: bool, ) -> Result { // kdebug!("open: path: {}, mode: {:?}", path, mode); - // 文件名过长 - if path.len() > MAX_PATHLEN as usize { - return Err(SystemError::ENAMETOOLONG); - } + let path = path.trim(); + let (inode_begin, path) = user_path_at(&ProcessManager::current_pcb(), dirfd, path)?; let inode: Result, SystemError> = inode_begin.lookup_follow_symlink( &path, diff --git a/kernel/src/filesystem/vfs/syscall.rs b/kernel/src/filesystem/vfs/syscall.rs index 871b5294..44ce7f80 100644 --- a/kernel/src/filesystem/vfs/syscall.rs +++ b/kernel/src/filesystem/vfs/syscall.rs @@ -1,21 +1,16 @@ -use core::ffi::CStr; +use core::mem::size_of; -use alloc::{ - string::{String, ToString}, - sync::Arc, - vec::Vec, -}; +use alloc::{string::String, sync::Arc, vec::Vec}; use system_error::SystemError; use crate::{ driver::base::{block::SeekFrom, device::device_number::DeviceNumber}, filesystem::vfs::file::FileDescriptorVec, - kerror, libs::rwlock::RwLockWriteGuard, mm::{verify_area, VirtAddr}, process::ProcessManager, syscall::{ - user_access::{check_and_clone_cstr, UserBufferReader, UserBufferWriter}, + user_access::{check_and_clone_cstr, UserBufferWriter}, Syscall, }, time::TimeSpec, @@ -86,6 +81,7 @@ bitflags! { } #[repr(C)] +#[derive(Clone, Copy)] /// # 文件信息结构体 pub struct PosixKstat { /// 硬件设备ID @@ -248,22 +244,34 @@ impl Syscall { /// /// @return 文件描述符编号，或者是错误码 pub fn open( - path: &str, - flags: FileMode, - mode: ModeType, + path: *const u8, + o_flags: u32, + mode: u32, follow_symlink: bool, ) -> Result { - return do_sys_open(AtFlags::AT_FDCWD.bits(), path, flags, mode, follow_symlink); + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + let open_flags: FileMode = FileMode::from_bits(o_flags).ok_or(SystemError::EINVAL)?; + let mode = ModeType::from_bits(mode as u32).ok_or(SystemError::EINVAL)?; + return do_sys_open( + AtFlags::AT_FDCWD.bits(), + &path, + open_flags, + mode, + follow_symlink, + ); } pub fn openat( dirfd: i32, - path: &str, - o_flags: FileMode, - mode: ModeType, + path: *const u8, + o_flags: u32, + mode: u32, follow_symlink: bool, ) -> Result { - return do_sys_open(dirfd, path, o_flags, mode, follow_symlink); + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + let open_flags: FileMode = FileMode::from_bits(o_flags).ok_or(SystemError::EINVAL)?; + let mode = ModeType::from_bits(mode as u32).ok_or(SystemError::EINVAL)?; + return do_sys_open(dirfd, &path, open_flags, mode, follow_symlink); } /// @brief 关闭文件 @@ -351,7 +359,15 @@ impl Syscall { /// /// @return Ok(usize) 调整后，文件访问指针相对于文件头部的偏移量 /// @return Err(SystemError) 调整失败，返回posix错误码 - pub fn lseek(fd: i32, seek: SeekFrom) -> Result { + pub fn lseek(fd: i32, offset: i64, seek: u32) -> Result { + let seek = match seek { + SEEK_SET => Ok(SeekFrom::SeekSet(offset)), + SEEK_CUR => Ok(SeekFrom::SeekCurrent(offset)), + SEEK_END => Ok(SeekFrom::SeekEnd(offset)), + SEEK_MAX => Ok(SeekFrom::SeekEnd(0)), + _ => Err(SystemError::EINVAL), + }?; + let binding = ProcessManager::current_pcb().fd_table(); let fd_table_guard = binding.read(); let file = fd_table_guard @@ -429,10 +445,14 @@ impl Syscall { /// EFAULT | 错误的地址 /// /// ENAMETOOLONG | 路径过长 - pub fn chdir(dest_path: &str) -> Result { + pub fn chdir(path: *const u8) -> Result { + if path.is_null() { + return Err(SystemError::EFAULT); + } + + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; let proc = ProcessManager::current_pcb(); // Copy path to kernel space to avoid some security issues - let path = dest_path.to_string(); let mut new_path = String::from(""); if path.len() > 0 { let cwd = match path.as_bytes()[0] { @@ -461,8 +481,7 @@ impl Syscall { } let inode = match ROOT_INODE().lookup_follow_symlink(&new_path, VFS_MAX_FOLLOW_SYMLINK_TIMES) { - Err(e) => { - kerror!("Change Directory Failed, Error = {:?}", e); + Err(_) => { return Err(SystemError::ENOENT); } Ok(i) => i, @@ -534,8 +553,9 @@ impl Syscall { /// @param path(r8) 路径 / mode(r9) 模式 /// /// @return uint64_t 负数错误码 / 0表示成功 - pub fn mkdir(path: &str, mode: usize) -> Result { - return do_mkdir(path, FileMode::from_bits_truncate(mode as u32)).map(|x| x as usize); + pub fn mkdir(path: *const u8, mode: usize) -> Result { + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + return do_mkdir(&path, FileMode::from_bits_truncate(mode as u32)).map(|x| x as usize); } /// **删除文件夹、取消文件的链接、删除文件的系统调用** @@ -547,14 +567,15 @@ impl Syscall { /// - `flags`：标志位 /// /// - pub fn unlinkat(dirfd: i32, pathname: &str, flags: u32) -> Result { + pub fn unlinkat(dirfd: i32, path: *const u8, flags: u32) -> Result { let flags = AtFlags::from_bits(flags as i32).ok_or(SystemError::EINVAL)?; + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + if flags.contains(AtFlags::AT_REMOVEDIR) { // kdebug!("rmdir"); - match do_remove_dir(dirfd, &pathname) { + match do_remove_dir(dirfd, &path) { Err(err) => { - kerror!("Failed to Remove Directory, Error Code = {:?}", err); return Err(err); } Ok(_) => { @@ -563,9 +584,8 @@ impl Syscall { } } - match do_unlink_at(dirfd, &pathname) { + match do_unlink_at(dirfd, &path) { Err(err) => { - kerror!("Failed to Remove Directory, Error Code = {:?}", err); return Err(err); } Ok(_) => { @@ -574,32 +594,14 @@ impl Syscall { } } - pub fn rmdir(pathname: *const u8) -> Result { - let pathname: String = check_and_clone_cstr(pathname, Some(MAX_PATHLEN))?; - if pathname.len() >= MAX_PATHLEN { - return Err(SystemError::ENAMETOOLONG); - } - let pathname = pathname.as_str().trim(); - return do_remove_dir(AtFlags::AT_FDCWD.bits(), pathname).map(|v| v as usize); + pub fn rmdir(path: *const u8) -> Result { + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + return do_remove_dir(AtFlags::AT_FDCWD.bits(), &path).map(|v| v as usize); } - pub fn unlink(pathname: *const u8) -> Result { - if pathname.is_null() { - return Err(SystemError::EFAULT); - } - let ureader = UserBufferReader::new(pathname, MAX_PATHLEN, true)?; - - let buf: &[u8] = ureader.buffer(0).unwrap(); - - let pathname: &CStr = CStr::from_bytes_until_nul(buf).map_err(|_| SystemError::EINVAL)?; - - let pathname: &str = pathname.to_str().map_err(|_| SystemError::EINVAL)?; - if pathname.len() >= MAX_PATHLEN { - return Err(SystemError::ENAMETOOLONG); - } - let pathname = pathname.trim(); - - return do_unlink_at(AtFlags::AT_FDCWD.bits(), pathname).map(|v| v as usize); + pub fn unlink(path: *const u8) -> Result { + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + return do_unlink_at(AtFlags::AT_FDCWD.bits(), &path).map(|v| v as usize); } /// # 修改文件名 @@ -892,45 +894,44 @@ impl Syscall { } pub fn fstat(fd: i32, usr_kstat: *mut PosixKstat) -> Result { + let mut writer = UserBufferWriter::new(usr_kstat, size_of::(), true)?; let kstat = Self::do_fstat(fd)?; - if usr_kstat.is_null() { - return Err(SystemError::EFAULT); - } - unsafe { - *usr_kstat = kstat; - } + + writer.copy_one_to_user(&kstat, 0)?; return Ok(0); } - pub fn stat(path: &str, user_kstat: *mut PosixKstat) -> Result { - let fd = Self::open(path, FileMode::O_RDONLY, ModeType::empty(), true)?; + pub fn stat(path: *const u8, user_kstat: *mut PosixKstat) -> Result { + let fd = Self::open( + path, + FileMode::O_RDONLY.bits(), + ModeType::empty().bits(), + true, + )?; let r = Self::fstat(fd as i32, user_kstat); Self::close(fd).ok(); return r; } - pub fn lstat(path: &str, user_kstat: *mut PosixKstat) -> Result { - let fd = Self::open(path, FileMode::O_RDONLY, ModeType::empty(), false)?; + pub fn lstat(path: *const u8, user_kstat: *mut PosixKstat) -> Result { + let fd = Self::open( + path, + FileMode::O_RDONLY.bits(), + ModeType::empty().bits(), + false, + )?; let r = Self::fstat(fd as i32, user_kstat); Self::close(fd).ok(); return r; } pub fn mknod( - path_ptr: *const i8, + path: *const u8, mode: ModeType, dev_t: DeviceNumber, ) -> Result { - // 安全检验 - let len = unsafe { CStr::from_ptr(path_ptr).to_bytes().len() }; - let user_buffer = UserBufferReader::new(path_ptr, len, true)?; - let buf = user_buffer.read_from_user::(0)?; - let path = core::str::from_utf8(buf).map_err(|_| SystemError::EINVAL)?; - - // 文件名过长 - if path.len() > MAX_PATHLEN as usize { - return Err(SystemError::ENAMETOOLONG); - } + let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + let path = path.as_str().trim(); let inode: Result, SystemError> = ROOT_INODE().lookup_follow_symlink(path, VFS_MAX_FOLLOW_SYMLINK_TIMES); @@ -980,12 +981,9 @@ impl Syscall { buf_size: usize, ) -> Result { let path = check_and_clone_cstr(path, Some(MAX_PATHLEN))?; + let path = path.as_str().trim(); let mut user_buf = UserBufferWriter::new(user_buf, buf_size, true)?; - if path.len() == 0 { - return Err(SystemError::EINVAL); - } - let (inode, path) = user_path_at(&ProcessManager::current_pcb(), dirfd, &path)?; let inode = inode.lookup(path.as_str())?; diff --git a/kernel/src/syscall/mod.rs b/kernel/src/syscall/mod.rs index 58ae1576..2e896472 100644 --- a/kernel/src/syscall/mod.rs +++ b/kernel/src/syscall/mod.rs @@ -1,5 +1,5 @@ use core::{ - ffi::{c_char, c_int, c_void, CStr}, + ffi::{c_int, c_void}, sync::atomic::{AtomicBool, Ordering}, }; @@ -22,14 +22,13 @@ use system_error::SystemError; use crate::{ arch::{cpu::cpu_reset, interrupt::TrapFrame, MMArch}, - driver::base::block::SeekFrom, filesystem::vfs::{ fcntl::{AtFlags, FcntlCommand}, file::FileMode, - syscall::{ModeType, PosixKstat, SEEK_CUR, SEEK_END, SEEK_MAX, SEEK_SET}, + syscall::{ModeType, PosixKstat}, MAX_PATHLEN, }, - include::bindings::bindings::{PAGE_2M_SIZE, PAGE_4K_SIZE}, + include::bindings::bindings::PAGE_4K_SIZE, kinfo, libs::align::page_align_up, mm::{verify_area, MemoryManagementArch, VirtAddr}, @@ -90,21 +89,11 @@ impl Syscall { } #[cfg(target_arch = "x86_64")] SYS_OPEN => { - let path: &CStr = unsafe { CStr::from_ptr(args[0] as *const c_char) }; - let path: Result<&str, core::str::Utf8Error> = path.to_str(); - let res = if path.is_err() { - Err(SystemError::EINVAL) - } else { - let path: &str = path.unwrap(); + let path = args[0] as *const u8; + let flags = args[1] as u32; + let mode = args[2] as u32; - let flags = args[1]; - let mode = args[2]; - - let open_flags: FileMode = FileMode::from_bits_truncate(flags as u32); - let mode = ModeType::from_bits(mode as u32).ok_or(SystemError::EINVAL)?; - Self::open(path, open_flags, mode, true) - }; - res + Self::open(path, flags, mode, true) } SYS_RENAME => { @@ -138,22 +127,11 @@ impl Syscall { SYS_OPENAT => { let dirfd = args[0] as i32; - let path: &CStr = unsafe { CStr::from_ptr(args[1] as *const c_char) }; - let flags = args[2]; - let mode = args[3]; + let path = args[1] as *const u8; + let flags = args[2] as u32; + let mode = args[3] as u32; - let path: Result<&str, core::str::Utf8Error> = path.to_str(); - let res = if path.is_err() { - Err(SystemError::EINVAL) - } else { - let path: &str = path.unwrap(); - - let open_flags: FileMode = - FileMode::from_bits(flags as u32).ok_or(SystemError::EINVAL)?; - let mode = ModeType::from_bits(mode as u32).ok_or(SystemError::EINVAL)?; - Self::openat(dirfd, path, open_flags, mode, true) - }; - res + Self::openat(dirfd, path, flags, mode, true) } SYS_CLOSE => { let fd = args[0]; @@ -187,15 +165,7 @@ impl Syscall { let offset = args[1] as i64; let whence = args[2] as u32; - let w = match whence { - SEEK_SET => Ok(SeekFrom::SeekSet(offset)), - SEEK_CUR => Ok(SeekFrom::SeekCurrent(offset)), - SEEK_END => Ok(SeekFrom::SeekEnd(offset)), - SEEK_MAX => Ok(SeekFrom::SeekEnd(0)), - _ => Err(SystemError::EINVAL), - }?; - - Self::lseek(fd, w) + Self::lseek(fd, offset, whence) } SYS_PREAD64 => { @@ -248,32 +218,7 @@ impl Syscall { SYS_REBOOT => Self::reboot(), SYS_CHDIR => { - // Closure for checking arguments - let chdir_check = |arg0: usize| { - if arg0 == 0 { - return Err(SystemError::EFAULT); - } - let path_ptr = arg0 as *const c_char; - let virt_addr = VirtAddr::new(path_ptr as usize); - // 权限校验 - if path_ptr.is_null() - || (frame.from_user() - && verify_area(virt_addr, PAGE_2M_SIZE as usize).is_err()) - { - return Err(SystemError::EINVAL); - } - let dest_path: &CStr = unsafe { CStr::from_ptr(path_ptr) }; - let dest_path: &str = dest_path.to_str().map_err(|_| SystemError::EINVAL)?; - if dest_path.len() == 0 { - return Err(SystemError::EINVAL); - } else if dest_path.len() > MAX_PATHLEN as usize { - return Err(SystemError::ENAMETOOLONG); - } - - return Ok(dest_path); - }; - - let r = chdir_check(args[0])?; + let r = args[0] as *const u8; Self::chdir(r) } @@ -340,31 +285,10 @@ impl Syscall { } #[cfg(target_arch = "x86_64")] SYS_MKDIR => { - let path_ptr = args[0] as *const c_char; + let path = args[0] as *const u8; let mode = args[1]; - let virt_path_ptr = VirtAddr::new(path_ptr as usize); - let security_check = || { - if path_ptr.is_null() - || (frame.from_user() - && verify_area(virt_path_ptr, PAGE_2M_SIZE as usize).is_err()) - { - return Err(SystemError::EINVAL); - } - let path: &CStr = unsafe { CStr::from_ptr(path_ptr) }; - let path: &str = path.to_str().map_err(|_| SystemError::EINVAL)?.trim(); - if path == "" { - return Err(SystemError::EINVAL); - } - return Ok(path); - }; - - let path = security_check(); - if path.is_err() { - Err(path.unwrap_err()) - } else { - Self::mkdir(path.unwrap(), mode) - } + Self::mkdir(path, mode) } SYS_NANOSLEEP => { @@ -407,43 +331,21 @@ impl Syscall { SYS_UNLINKAT => { let dirfd = args[0] as i32; - let pathname = args[1] as *const c_char; + let path = args[1] as *const u8; let flags = args[2] as u32; - let virt_pathname = VirtAddr::new(pathname as usize); - if frame.from_user() && verify_area(virt_pathname, PAGE_4K_SIZE as usize).is_err() { - Err(SystemError::EFAULT) - } else if pathname.is_null() { - Err(SystemError::EFAULT) - } else { - let get_path = || { - let pathname: &CStr = unsafe { CStr::from_ptr(pathname) }; - - let pathname: &str = pathname.to_str().map_err(|_| SystemError::EINVAL)?; - if pathname.len() >= MAX_PATHLEN { - return Err(SystemError::ENAMETOOLONG); - } - return Ok(pathname.trim()); - }; - let pathname = get_path(); - if pathname.is_err() { - Err(pathname.unwrap_err()) - } else { - // kdebug!("sys unlinkat: dirfd: {}, pathname: {}", dirfd, pathname.as_ref().unwrap()); - Self::unlinkat(dirfd, pathname.unwrap(), flags) - } - } + Self::unlinkat(dirfd, path, flags) } #[cfg(target_arch = "x86_64")] SYS_RMDIR => { - let pathname = args[0] as *const u8; - Self::rmdir(pathname) + let path = args[0] as *const u8; + Self::rmdir(path) } #[cfg(target_arch = "x86_64")] SYS_UNLINK => { - let pathname = args[0] as *const u8; - Self::unlink(pathname) + let path = args[0] as *const u8; + Self::unlink(path) } SYS_KILL => { let pid = Pid::new(args[0]); @@ -736,7 +638,7 @@ impl Syscall { let flags = args[1]; let dev_t = args[2]; let flags: ModeType = ModeType::from_bits_truncate(flags as u32); - Self::mknod(path as *const i8, flags, DeviceNumber::from(dev_t as u32)) + Self::mknod(path as *const u8, flags, DeviceNumber::from(dev_t as u32)) } SYS_CLONE => { @@ -788,40 +690,16 @@ impl Syscall { #[cfg(target_arch = "x86_64")] SYS_LSTAT => { - let path: &CStr = unsafe { CStr::from_ptr(args[0] as *const c_char) }; - let path: Result<&str, core::str::Utf8Error> = path.to_str(); - let res = if path.is_err() { - Err(SystemError::EINVAL) - } else { - let path: &str = path.unwrap(); - let kstat = args[1] as *mut PosixKstat; - let vaddr = VirtAddr::new(kstat as usize); - match verify_area(vaddr, core::mem::size_of::()) { - Ok(_) => Self::lstat(path, kstat), - Err(e) => Err(e), - } - }; - - res + let path = args[0] as *const u8; + let kstat = args[1] as *mut PosixKstat; + Self::lstat(path, kstat) } #[cfg(target_arch = "x86_64")] SYS_STAT => { - let path: &CStr = unsafe { CStr::from_ptr(args[0] as *const c_char) }; - let path: Result<&str, core::str::Utf8Error> = path.to_str(); - let res = if path.is_err() { - Err(SystemError::EINVAL) - } else { - let path: &str = path.unwrap(); - let kstat = args[1] as *mut PosixKstat; - let vaddr = VirtAddr::new(kstat as usize); - match verify_area(vaddr, core::mem::size_of::()) { - Ok(_) => Self::stat(path, kstat), - Err(e) => Err(e), - } - }; - - res + let path = args[0] as *const u8; + let kstat = args[1] as *mut PosixKstat; + Self::stat(path, kstat) } SYS_EPOLL_CREATE => Self::epoll_create(args[0] as i32), @@ -958,10 +836,10 @@ impl Syscall { SYS_READLINKAT => { let dirfd = args[0] as i32; - let pathname = args[1] as *const u8; + let path = args[1] as *const u8; let buf = args[2] as *mut u8; let bufsiz = args[3]; - Self::readlink_at(dirfd, pathname, buf, bufsiz) + Self::readlink_at(dirfd, path, buf, bufsiz) } SYS_PRLIMIT64 => { diff --git a/kernel/src/syscall/user_access.rs b/kernel/src/syscall/user_access.rs index 9f83a30d..8dcfe4ab 100644 --- a/kernel/src/syscall/user_access.rs +++ b/kernel/src/syscall/user_access.rs @@ -75,7 +75,7 @@ pub fn check_and_clone_cstr( max_length: Option, ) -> Result { if user.is_null() { - return Ok(String::new()); + return Err(SystemError::EFAULT); } // 从用户态读取，直到遇到空字符 '\0' 或者达到最大长度