Backwards-compatibly rewrite getdents to use special syscall.

src/header/dirent/mod.rs

@@ -1,29 +1,114 @@
 //! dirent implementation following http://pubs.opengroup.org/onlinepubs/009695399/basedefs/dirent.h.html
 
-use alloc::boxed::Box;
+use alloc::{boxed::Box, vec::Vec};
 use core::{mem, ptr};
 
 use crate::{
     c_str::CStr,
     c_vec::CVec,
+    error::{Errno, ResultExtPtrMut},
     fs::File,
-    header::{errno, fcntl, stdlib, string},
-    io::{Seek, SeekFrom},
+    header::{fcntl, stdlib, string},
     platform::{self, types::*, Pal, Sys},
 };
 
-const DIR_BUF_SIZE: usize = mem::size_of::<dirent>() * 3;
+use super::errno::{EINVAL, EIO, ENOMEM};
 
-// No repr(C) needed, C won't see the content
+const INITIAL_BUFSIZE: usize = 512;
+
+// No repr(C) needed, as this is a completely opaque struct. Being accessed as a pointer, in C it's
+// just defined as `struct DIR`.
 pub struct DIR {
     file: File,
-    buf: [c_char; DIR_BUF_SIZE],
-    // index and len are specified in bytes
-    index: usize,
-    len: usize,
+    buf: Vec<u8>,
+    buf_offset: usize,
 
     // The last value of d_off, used by telldir
-    offset: usize,
+    opaque_offset: u64,
+}
+impl DIR {
+    pub fn new(path: CStr) -> Result<Box<Self>, Errno> {
+        Ok(Box::new(Self {
+            file: File::open(
+                path,
+                fcntl::O_RDONLY | fcntl::O_DIRECTORY | fcntl::O_CLOEXEC,
+            )?,
+            buf: Vec::with_capacity(INITIAL_BUFSIZE),
+            buf_offset: 0,
+            opaque_offset: 0,
+        }))
+    }
+    fn next_dirent(&mut self) -> Result<*mut dirent, Errno> {
+        let mut this_dent = self.buf.get(self.buf_offset..).ok_or(Errno(EIO))?;
+        if this_dent.is_empty() {
+            let size = loop {
+                self.buf.resize(self.buf.capacity(), 0_u8);
+                // TODO: uninitialized memory?
+                match Sys::getdents(*self.file, &mut self.buf, self.opaque_offset) {
+                    Ok(size) => break size,
+                    Err(Errno(EINVAL)) => {
+                        self.buf
+                            .try_reserve_exact(self.buf.len())
+                            .map_err(|_| Errno(ENOMEM))?;
+                        continue;
+                    }
+                    Err(Errno(other)) => return Err(Errno(other)),
+                }
+            };
+            self.buf.truncate(size);
+            self.buf_offset = 0;
+
+            if size == 0 {
+                return Ok(core::ptr::null_mut());
+            }
+            this_dent = &self.buf;
+        }
+        let (this_reclen, this_next_opaque) =
+            unsafe { Sys::dent_reclen_offset(this_dent, self.buf_offset).ok_or(Errno(EIO))? };
+
+        //println!("CDENT {} {}+{}", self.opaque_offset, self.buf_offset, this_reclen);
+
+        let next_off = self
+            .buf_offset
+            .checked_add(usize::from(this_reclen))
+            .ok_or(Errno(EIO))?;
+        if next_off > self.buf.len() {
+            return Err(Errno(EIO));
+        }
+        if this_dent.len() < usize::from(this_reclen) {
+            // Don't want memory corruption if a scheme is adversarial.
+            return Err(Errno(EIO));
+        }
+        let dent_ptr = this_dent.as_ptr() as *mut dirent;
+
+        self.opaque_offset = this_next_opaque;
+        self.buf_offset = next_off;
+        Ok(dent_ptr)
+    }
+    fn seek(&mut self, off: u64) {
+        let Ok(_) = Sys::dir_seek(*self.file, off) else {
+            return;
+        };
+        self.buf.clear();
+        self.buf_offset = 0;
+        self.opaque_offset = off;
+    }
+    fn rewind(&mut self) {
+        self.opaque_offset = 0;
+        let Ok(_) = Sys::dir_seek(*self.file, 0) else {
+            return;
+        };
+        self.buf.clear();
+        self.buf_offset = 0;
+        self.opaque_offset = 0;
+    }
+    fn close(mut self) -> c_int {
+        // Reference files aren't closed when dropped
+        self.file.reference = true;
+
+        // TODO: result
+        Sys::close(*self.file)
+    }
 }
 
 #[repr(C)]
@@ -36,68 +121,50 @@ pub struct dirent {
     pub d_name: [c_char; 256],
 }
 
+#[cfg(target_os = "redox")]
+const _: () = {
+    use core::mem::{offset_of, size_of};
+    use syscall::dirent::DirentHeader;
+
+    if offset_of!(dirent, d_ino) != offset_of!(DirentHeader, inode) {
+        panic!("struct dirent layout mismatch (inode)");
+    }
+    if offset_of!(dirent, d_off) != offset_of!(DirentHeader, next_opaque_id) {
+        panic!("struct dirent layout mismatch (inode)");
+    }
+    if offset_of!(dirent, d_reclen) != offset_of!(DirentHeader, record_len) {
+        panic!("struct dirent layout mismatch (len)");
+    }
+    if offset_of!(dirent, d_type) != offset_of!(DirentHeader, kind) {
+        panic!("struct dirent layout mismatch (kind)");
+    }
+    if offset_of!(dirent, d_name) != size_of::<DirentHeader>() {
+        panic!("struct dirent layout mismatch (name)");
+    }
+};
+
 #[no_mangle]
 pub unsafe extern "C" fn opendir(path: *const c_char) -> *mut DIR {
     let path = CStr::from_ptr(path);
-    let file = match File::open(
-        path,
-        fcntl::O_RDONLY | fcntl::O_DIRECTORY | fcntl::O_CLOEXEC,
-    ) {
-        Ok(file) => file,
-        Err(_) => return ptr::null_mut(),
-    };
 
-    Box::into_raw(Box::new(DIR {
-        file,
-        buf: [0; DIR_BUF_SIZE],
-        index: 0,
-        len: 0,
-        offset: 0,
-    }))
+    DIR::new(path).or_errno_null_mut()
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn closedir(dir: *mut DIR) -> c_int {
-    let mut dir = Box::from_raw(dir);
-
-    let ret = Sys::close(*dir.file);
-
-    // Reference files aren't closed when dropped
-    dir.file.reference = true;
-
-    ret
+pub extern "C" fn closedir(dir: Box<DIR>) -> c_int {
+    dir.close()
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn dirfd(dir: *mut DIR) -> c_int {
-    *((*dir).file)
+pub extern "C" fn dirfd(dir: &mut DIR) -> c_int {
+    *dir.file
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn readdir(dir: *mut DIR) -> *mut dirent {
-    if (*dir).index >= (*dir).len {
-        let read = Sys::getdents(
-            *(*dir).file,
-            (*dir).buf.as_mut_ptr() as *mut dirent,
-            (*dir).buf.len(),
-        );
-        if read <= 0 {
-            if read != 0 && read != -errno::ENOENT {
-                platform::ERRNO.set(-read);
-            }
-            return ptr::null_mut();
-        }
-
-        (*dir).index = 0;
-        (*dir).len = read as usize;
-    }
-
-    let ptr = (*dir).buf.as_mut_ptr().add((*dir).index) as *mut dirent;
-
-    (*dir).offset = (*ptr).d_off as usize;
-    (*dir).index += (*ptr).d_reclen as usize;
-    ptr
+pub extern "C" fn readdir(dir: &mut DIR) -> *mut dirent {
+    dir.next_dirent().or_errno_null_mut()
 }
+
 // #[no_mangle]
 pub extern "C" fn readdir_r(
     _dir: *mut DIR,
@@ -108,19 +175,19 @@ pub extern "C" fn readdir_r(
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn telldir(dir: *mut DIR) -> c_long {
-    (*dir).offset as c_long
+pub extern "C" fn telldir(dir: &mut DIR) -> c_long {
+    dir.opaque_offset as c_long
 }
 #[no_mangle]
-pub unsafe extern "C" fn seekdir(dir: *mut DIR, off: c_long) {
-    let _ = (*dir).file.seek(SeekFrom::Start(off as u64));
-    (*dir).offset = off as usize;
-    (*dir).index = 0;
-    (*dir).len = 0;
+pub extern "C" fn seekdir(dir: &mut DIR, off: c_long) {
+    dir.seek(
+        off.try_into()
+            .expect("off must come from telldir, thus never negative"),
+    );
 }
 #[no_mangle]
-pub unsafe extern "C" fn rewinddir(dir: *mut DIR) {
-    seekdir(dir, 0)
+pub extern "C" fn rewinddir(dir: &mut DIR) {
+    dir.rewind();
 }
 
 #[no_mangle]
@@ -149,7 +216,7 @@ pub unsafe extern "C" fn scandir(
     platform::ERRNO.set(0);
 
     loop {
-        let entry: *mut dirent = readdir(dir);
+        let entry: *mut dirent = readdir(&mut *dir);
         if entry.is_null() {
             break;
         }
@@ -170,7 +237,7 @@ pub unsafe extern "C" fn scandir(
         }
     }
 
-    closedir(dir);
+    closedir(Box::from_raw(dir));
 
     let len = vec.len();
     if let Err(_) = vec.shrink_to_fit() {

src/header/fcntl/cbindgen.toml

@@ -6,9 +6,5 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true

src/header/signal/cbindgen.toml

@@ -6,10 +6,6 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true
 

src/header/stdlib/cbindgen.toml

@@ -6,9 +6,6 @@ style = "Type"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_pointer_width=64" = "__LP64__"
-
 [enum]
 prefix_with_name = true
 

src/header/sys_epoll/cbindgen.toml

@@ -5,10 +5,5 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-"target_pointer_width=64" = "__LP64__"
-
 [enum]
 prefix_with_name = true

src/header/sys_ioctl/cbindgen.toml

@@ -4,10 +4,6 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true
 

src/header/sys_mman/cbindgen.toml

@@ -6,9 +6,5 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true

src/header/sys_resource/cbindgen.toml

@@ -6,10 +6,6 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true
 

src/header/sys_socket/cbindgen.toml

@@ -6,10 +6,6 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true
 

src/header/termios/cbindgen.toml

@@ -5,10 +5,6 @@ style = "Tag"
 no_includes = true
 cpp_compat = true
 
-[defines]
-"target_os=linux" = "__linux__"
-"target_os=redox" = "__redox__"
-
 [enum]
 prefix_with_name = true
 

src/header/time/cbindgen.toml

@@ -7,7 +7,3 @@ cpp_compat = true
 
 [enum]
 prefix_with_name = true
-
-[defines]
-"target_os = linux" = "__linux__"
-"target_os = redox" = "__redox__"

src/header/unistd/cbindgen.toml

@@ -8,7 +8,3 @@ cpp_compat = true
 
 [enum]
 prefix_with_name = true
-
-[defines]
-"target_os = linux" = "__linux__"
-"target_os = redox" = "__redox__"