hermit/syscalls/

mod.rs

#![allow(clippy::result_unit_err)]

use alloc::ffi::CString;
#[cfg(all(target_os = "none", not(feature = "common-os")))]
use core::alloc::{GlobalAlloc, Layout};
use core::ffi::{CStr, c_char};
use core::marker::PhantomData;
use core::{ptr, slice};

use dirent_display::Dirent64Display;
use hermit_sync::Lazy;

pub use self::condvar::*;
pub use self::entropy::*;
pub use self::futex::*;
pub use self::processor::*;
#[cfg(feature = "newlib")]
pub use self::recmutex::*;
pub use self::semaphore::*;
pub use self::spinlock::*;
pub use self::system::*;
pub use self::tasks::*;
pub use self::timer::*;
use crate::env;
use crate::errno::{Errno, ToErrno};
use crate::executor::block_on;
use crate::fd::{
	self, AccessOption, AccessPermission, EventFlags, OpenOption, PollFd, RawFd, dup_object,
	dup_object2, get_object, isatty, remove_object,
};
use crate::fs::{self, FileAttr, SeekWhence};
#[cfg(all(target_os = "none", not(feature = "common-os")))]
use crate::mm::ALLOCATOR;
use crate::syscalls::interfaces::SyscallInterface;

mod condvar;
mod entropy;
mod futex;
pub(crate) mod interfaces;
#[cfg(feature = "mman")]
pub mod mman;
mod processor;
#[cfg(feature = "newlib")]
mod recmutex;
mod semaphore;
#[cfg(any(feature = "net", feature = "virtio-vsock"))]
pub mod socket;
mod spinlock;
mod system;
#[cfg(feature = "common-os")]
pub(crate) mod table;
mod tasks;
mod timer;

pub(crate) static SYS: Lazy<&'static dyn SyscallInterface> = Lazy::new(|| {
	if env::is_uhyve() {
		&self::interfaces::Uhyve
	} else {
		&self::interfaces::Generic
	}
});

#[repr(C)]
#[derive(Debug, Clone, Copy)]
/// Describes  a  region  of  memory, beginning at `iov_base` address and with the size of `iov_len` bytes.
struct iovec {
	/// Starting address
	pub iov_base: *mut u8,
	/// Size of the memory pointed to by iov_base.
	pub iov_len: usize,
}

const IOV_MAX: usize = 1024;

pub(crate) fn init() {
	Lazy::force(&SYS);

	// Perform interface-specific initialization steps.
	SYS.init();

	init_entropy();
}

/// Interface to allocate memory from system heap
///
/// # Errors
/// Returning a null pointer indicates that either memory is exhausted or
/// `size` and `align` do not meet this allocator's size or alignment constraints.
///
#[cfg(all(target_os = "none", not(feature = "common-os")))]
#[hermit_macro::system]
#[unsafe(no_mangle)]
pub extern "C" fn sys_alloc(size: usize, align: usize) -> *mut u8 {
	let layout_res = Layout::from_size_align(size, align);
	if layout_res.is_err() || size == 0 {
		warn!("__sys_alloc called with size {size:#x}, align {align:#x} is an invalid layout!");
		return ptr::null_mut();
	}
	let layout = layout_res.unwrap();
	let ptr = unsafe { ALLOCATOR.alloc(layout) };

	trace!("__sys_alloc: allocate memory at {ptr:p} (size {size:#x}, align {align:#x})");

	ptr
}

#[cfg(all(target_os = "none", not(feature = "common-os")))]
#[hermit_macro::system]
#[unsafe(no_mangle)]
pub extern "C" fn sys_alloc_zeroed(size: usize, align: usize) -> *mut u8 {
	let layout_res = Layout::from_size_align(size, align);
	if layout_res.is_err() || size == 0 {
		warn!(
			"__sys_alloc_zeroed called with size {size:#x}, align {align:#x} is an invalid layout!"
		);
		return ptr::null_mut();
	}
	let layout = layout_res.unwrap();
	let ptr = unsafe { ALLOCATOR.alloc_zeroed(layout) };

	trace!("__sys_alloc_zeroed: allocate memory at {ptr:p} (size {size:#x}, align {align:#x})");

	ptr
}

#[cfg(all(target_os = "none", not(feature = "common-os")))]
#[hermit_macro::system]
#[unsafe(no_mangle)]
pub extern "C" fn sys_malloc(size: usize, align: usize) -> *mut u8 {
	let layout_res = Layout::from_size_align(size, align);
	if layout_res.is_err() || size == 0 {
		warn!("__sys_malloc called with size {size:#x}, align {align:#x} is an invalid layout!");
		return ptr::null_mut();
	}
	let layout = layout_res.unwrap();
	let ptr = unsafe { ALLOCATOR.alloc(layout) };

	trace!("__sys_malloc: allocate memory at {ptr:p} (size {size:#x}, align {align:#x})");

	ptr
}

/// Shrink or grow a block of memory to the given `new_size`. The block is described by the given
/// ptr pointer and layout. If this returns a non-null pointer, then ownership of the memory block
/// referenced by ptr has been transferred to this allocator. The memory may or may not have been
/// deallocated, and should be considered unusable (unless of course it was transferred back to the
/// caller again via the return value of this method). The new memory block is allocated with
/// layout, but with the size updated to new_size.
/// If this method returns null, then ownership of the memory block has not been transferred to this
/// allocator, and the contents of the memory block are unaltered.
///
/// # Safety
/// This function is unsafe because undefined behavior can result if the caller does not ensure all
/// of the following:
/// - `ptr` must be currently allocated via this allocator,
/// - `size` and `align` must be the same layout that was used to allocate that block of memory.
/// ToDO: verify if the same values for size and align always lead to the same layout
///
/// # Errors
/// Returns null if the new layout does not meet the size and alignment constraints of the
/// allocator, or if reallocation otherwise fails.
#[cfg(all(target_os = "none", not(feature = "common-os")))]
#[hermit_macro::system]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_realloc(
	ptr: *mut u8,
	size: usize,
	align: usize,
	new_size: usize,
) -> *mut u8 {
	unsafe {
		let layout_res = Layout::from_size_align(size, align);
		if layout_res.is_err() || size == 0 || new_size == 0 {
			warn!(
				"__sys_realloc called with ptr {ptr:p}, size {size:#x}, align {align:#x}, new_size {new_size:#x} is an invalid layout!"
			);
			return ptr::null_mut();
		}
		let layout = layout_res.unwrap();
		let new_ptr = ALLOCATOR.realloc(ptr, layout, new_size);

		if new_ptr.is_null() {
			debug!(
				"__sys_realloc failed to resize ptr {ptr:p} with size {size:#x}, align {align:#x}, new_size {new_size:#x} !"
			);
		} else {
			trace!("__sys_realloc: resized memory at {ptr:p}, new address {new_ptr:p}");
		}
		new_ptr
	}
}

/// Interface to deallocate a memory region from the system heap
///
/// # Safety
/// This function is unsafe because undefined behavior can result if the caller does not ensure all of the following:
/// - ptr must denote a block of memory currently allocated via this allocator,
/// - `size` and `align` must be the same values that were used to allocate that block of memory
/// ToDO: verify if the same values for size and align always lead to the same layout
///
/// # Errors
/// May panic if debug assertions are enabled and invalid parameters `size` or `align` where passed.
#[cfg(all(target_os = "none", not(feature = "common-os")))]
#[hermit_macro::system]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_dealloc(ptr: *mut u8, size: usize, align: usize) {
	unsafe {
		let layout_res = Layout::from_size_align(size, align);
		if layout_res.is_err() || size == 0 {
			warn!(
				"__sys_dealloc called with size {size:#x}, align {align:#x} is an invalid layout!"
			);
			debug_assert!(layout_res.is_err(), "__sys_dealloc error: Invalid layout");
			debug_assert_ne!(size, 0, "__sys_dealloc error: size cannot be 0");
		} else {
			trace!("sys_free: deallocate memory at {ptr:p} (size {size:#x})");
		}
		let layout = layout_res.unwrap();
		ALLOCATOR.dealloc(ptr, layout);
	}
}

#[cfg(all(target_os = "none", not(feature = "common-os")))]
#[hermit_macro::system]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_free(ptr: *mut u8, size: usize, align: usize) {
	unsafe {
		let layout_res = Layout::from_size_align(size, align);
		if layout_res.is_err() || size == 0 {
			warn!("__sys_free called with size {size:#x}, align {align:#x} is an invalid layout!");
			debug_assert!(layout_res.is_err(), "__sys_free error: Invalid layout");
			debug_assert_ne!(size, 0, "__sys_free error: size cannot be 0");
		} else {
			trace!("sys_free: deallocate memory at {ptr:p} (size {size:#x})");
		}
		let layout = layout_res.unwrap();
		ALLOCATOR.dealloc(ptr, layout);
	}
}

pub(crate) fn get_application_parameters() -> (i32, *const *const u8, *const *const u8) {
	SYS.get_application_parameters()
}

pub(crate) fn shutdown(arg: i32) -> ! {
	// print some performance statistics
	crate::arch::kernel::print_statistics();

	SYS.shutdown(arg)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_unlink(name: *const c_char) -> i32 {
	let name = unsafe { CStr::from_ptr(name) }.to_str().unwrap();

	fs::unlink(name).map_or_else(|e| -i32::from(e), |()| 0)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_mkdir(name: *const c_char, mode: u32) -> i32 {
	let name = unsafe { CStr::from_ptr(name) }.to_str().unwrap();
	let Some(mode) = AccessPermission::from_bits(mode) else {
		return -i32::from(Errno::Inval);
	};

	crate::fs::create_dir(name, mode).map_or_else(|e| -i32::from(e), |()| 0)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_rmdir(name: *const c_char) -> i32 {
	let name = unsafe { CStr::from_ptr(name) }.to_str().unwrap();

	crate::fs::remove_dir(name).map_or_else(|e| -i32::from(e), |()| 0)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_stat(name: *const c_char, stat: *mut FileAttr) -> i32 {
	let name = unsafe { CStr::from_ptr(name) }.to_str().unwrap();

	match fs::read_stat(name) {
		Ok(attr) => unsafe {
			*stat = attr;
			0
		},
		Err(e) => -i32::from(e),
	}
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_lstat(name: *const c_char, stat: *mut FileAttr) -> i32 {
	let name = unsafe { CStr::from_ptr(name) }.to_str().unwrap();

	match fs::read_lstat(name) {
		Ok(attr) => unsafe {
			*stat = attr;
			0
		},
		Err(e) => -i32::from(e),
	}
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_fstat(fd: RawFd, stat: *mut FileAttr) -> i32 {
	if stat.is_null() {
		return -i32::from(Errno::Inval);
	}

	crate::fd::fstat(fd).map_or_else(
		|e| -i32::from(e),
		|v| unsafe {
			*stat = v;
			0
		},
	)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_opendir(name: *const c_char) -> RawFd {
	let Ok(name) = unsafe { CStr::from_ptr(name) }.to_str() else {
		return -i32::from(Errno::Inval);
	};

	crate::fs::opendir(name).unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_open(name: *const c_char, flags: i32, mode: u32) -> RawFd {
	let Some(flags) = OpenOption::from_bits(flags) else {
		return -i32::from(Errno::Inval);
	};
	let Some(mode) = AccessPermission::from_bits(mode) else {
		return -i32::from(Errno::Inval);
	};

	let Ok(name) = unsafe { CStr::from_ptr(name) }.to_str() else {
		return -i32::from(Errno::Inval);
	};

	crate::fs::open(name, flags, mode).unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_getcwd(buf: *mut c_char, size: usize) -> *const c_char {
	let error = |e: Errno| {
		e.set_errno();
		ptr::null::<c_char>()
	};

	if size == 0 {
		return error(Errno::Inval);
	}

	if buf.is_null() {
		// Behavior unspecified
		return error(Errno::Noent);
	}

	let cwd = match fs::get_cwd() {
		Err(e) => {
			return error(e);
		}
		Ok(cwd) => cwd,
	};

	let Ok(cwd) = CString::new(cwd) else {
		return error(Errno::Noent);
	};

	if (cwd.count_bytes() + 1) > size {
		return error(Errno::Range);
	}

	unsafe {
		buf.copy_from(cwd.as_ptr(), size);
	}

	buf
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_fchdir(_fd: RawFd) -> i32 {
	-i32::from(Errno::Nosys)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_chdir(path: *mut c_char) -> i32 {
	let Ok(name) = unsafe { CStr::from_ptr(path) }.to_str() else {
		return -i32::from(Errno::Inval);
	};

	crate::fs::set_cwd(name)
		.map(|()| 0)
		.unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_umask(umask: u32) -> u32 {
	crate::fs::umask(AccessPermission::from_bits_truncate(umask)).bits()
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_faccessat(
	dirfd: RawFd,
	name: *const c_char,
	_mode: i32,
	flags: i32,
) -> i32 {
	let Some(access_option) = AccessOption::from_bits(flags) else {
		return -i32::from(Errno::Inval);
	};

	let Ok(name) = unsafe { CStr::from_ptr(name) }.to_str() else {
		return -i32::from(Errno::Inval);
	};

	const AT_SYMLINK_NOFOLLOW: i32 = 0x100;
	const AT_FDCWD: i32 = -100;

	let stat = if name.starts_with("/") || dirfd == AT_FDCWD {
		let no_follow: bool = (flags & AT_SYMLINK_NOFOLLOW) != 0;

		if no_follow {
			fs::read_stat(name)
		} else {
			fs::read_lstat(name)
		}
	} else {
		warn!("faccessat with directory relative to fd is not implemented!");
		return -i32::from(Errno::Nosys);
	};

	match stat {
		Err(e) => -i32::from(e),
		Ok(stat) if access_option.can_access(stat.st_mode) => 0,
		Ok(_) => -i32::from(Errno::Acces),
	}
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_access(name: *const c_char, flags: i32) -> i32 {
	let Some(access_option) = AccessOption::from_bits(flags) else {
		return -i32::from(Errno::Inval);
	};

	if access_option.contains(AccessOption::F_OK) && access_option != AccessOption::F_OK {
		return -i32::from(Errno::Inval);
	}

	let Ok(name) = unsafe { CStr::from_ptr(name) }.to_str() else {
		return -i32::from(Errno::Inval);
	};

	match crate::fs::read_lstat(name) {
		Err(e) => -i32::from(e),
		Ok(stat) if access_option.can_access(stat.st_mode) => 0,
		Ok(_) => -i32::from(Errno::Acces),
	}
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_fchmod(fd: RawFd, mode: u32) -> i32 {
	let Some(access_permission) = AccessPermission::from_bits(mode) else {
		return -i32::from(Errno::Inval);
	};

	crate::fd::chmod(fd, access_permission)
		.map(|()| 0)
		.unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_close(fd: RawFd) -> i32 {
	let obj = remove_object(fd);
	obj.map_or_else(|e| -i32::from(e), |_| 0)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_read(fd: RawFd, buf: *mut u8, len: usize) -> isize {
	let slice = unsafe { slice::from_raw_parts_mut(buf.cast(), len) };
	crate::fd::read(fd, slice).map_or_else(
		|e| isize::try_from(-i32::from(e)).unwrap(),
		|v| v.try_into().unwrap(),
	)
}

/// `read()` attempts to read `nbyte` of data to the object referenced by the
/// descriptor `fd` from a buffer. `read()` performs the same
/// action, but scatters the input data from the `iovcnt` buffers specified by the
/// members of the iov array: `iov[0], iov[1], ..., iov[iovcnt-1]`.
///
/// ```
/// struct iovec {
///     char   *iov_base;  /* Base address. */
///     size_t iov_len;    /* Length. */
/// };
/// ```
///
/// Each `iovec` entry specifies the base address and length of an area in memory from
/// which data should be written.  `readv()` will always fill an completely
/// before proceeding to the next.
#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_readv(fd: i32, iov: *const iovec, iovcnt: usize) -> isize {
	if !(0..=IOV_MAX).contains(&iovcnt) {
		return (-i32::from(Errno::Inval)).try_into().unwrap();
	}

	let mut read_bytes: isize = 0;
	let iovec_buffers = unsafe { slice::from_raw_parts(iov, iovcnt) };

	for iovec_buf in iovec_buffers {
		let buf =
			unsafe { slice::from_raw_parts_mut(iovec_buf.iov_base.cast(), iovec_buf.iov_len) };

		let len = crate::fd::read(fd, buf).map_or_else(
			|e| isize::try_from(-i32::from(e)).unwrap(),
			|v| v.try_into().unwrap(),
		);

		if len < 0 {
			return len;
		}

		read_bytes += len;

		if len < isize::try_from(iovec_buf.iov_len).unwrap() {
			return read_bytes;
		}
	}

	read_bytes
}

unsafe fn write(fd: RawFd, buf: *const u8, len: usize) -> isize {
	let slice = unsafe { slice::from_raw_parts(buf, len) };
	crate::fd::write(fd, slice).map_or_else(
		|e| isize::try_from(-i32::from(e)).unwrap(),
		|v| v.try_into().unwrap(),
	)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_write(fd: RawFd, buf: *const u8, len: usize) -> isize {
	unsafe { write(fd, buf, len) }
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_ftruncate(fd: RawFd, size: usize) -> i32 {
	fd::truncate(fd, size).map_or_else(|e| -i32::from(e), |()| 0)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_truncate(path: *const c_char, size: usize) -> i32 {
	let Ok(path) = unsafe { CStr::from_ptr(path) }.to_str() else {
		return -i32::from(Errno::Inval);
	};

	fs::truncate(path, size).map_or_else(|e| -i32::from(e), |()| 0)
}

/// `write()` attempts to write `nbyte` of data to the object referenced by the
/// descriptor `fd` from a buffer. `writev()` performs the same
/// action, but gathers the output data from the `iovcnt` buffers specified by the
/// members of the iov array: `iov[0], iov[1], ..., iov[iovcnt-1]`.
///
/// ```
/// struct iovec {
///     char   *iov_base;  /* Base address. */
///     size_t iov_len;    /* Length. */
/// };
/// ```
///
/// Each `iovec` entry specifies the base address and length of an area in memory from
/// which data should be written.  `writev()` will always write a
/// complete area before proceeding to the next.
#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_writev(fd: RawFd, iov: *const iovec, iovcnt: usize) -> isize {
	if !(0..=IOV_MAX).contains(&iovcnt) {
		return (-i32::from(Errno::Inval)).try_into().unwrap();
	}

	let mut written_bytes: isize = 0;
	let iovec_buffers = unsafe { slice::from_raw_parts(iov, iovcnt) };

	for iovec_buf in iovec_buffers {
		let buf = unsafe { slice::from_raw_parts(iovec_buf.iov_base, iovec_buf.iov_len) };

		let len = crate::fd::write(fd, buf).map_or_else(
			|e| isize::try_from(-i32::from(e)).unwrap(),
			|v| v.try_into().unwrap(),
		);

		if len < 0 {
			return len;
		}

		written_bytes += len;

		if len < isize::try_from(iovec_buf.iov_len).unwrap() {
			return written_bytes;
		}
	}

	written_bytes
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_ioctl(fd: RawFd, cmd: i32, argp: *mut core::ffi::c_void) -> i32 {
	const FIONBIO: i32 = 0x8008_667eu32 as i32;

	if cmd == FIONBIO {
		let value = unsafe { *(argp as *const i32) };
		let status_flags = if value != 0 {
			fd::StatusFlags::O_NONBLOCK
		} else {
			fd::StatusFlags::empty()
		};

		let obj = get_object(fd);
		obj.map_or_else(
			|e| -i32::from(e),
			|v| {
				block_on(
					async { v.write().await.set_status_flags(status_flags).await },
					None,
				)
				.map_or_else(|e| -i32::from(e), |()| 0)
			},
		)
	} else {
		-i32::from(Errno::Inval)
	}
}

/// Manipulate file descriptor
#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_fcntl(fd: i32, cmd: i32, arg: i32) -> i32 {
	const F_SETFD: i32 = 2;
	const F_GETFL: i32 = 3;
	const F_SETFL: i32 = 4;
	const FD_CLOEXEC: i32 = 1;

	if cmd == F_SETFD && arg == FD_CLOEXEC {
		0
	} else if cmd == F_GETFL {
		let obj = get_object(fd);
		obj.map_or_else(
			|e| -i32::from(e),
			|v| {
				block_on(async { v.read().await.status_flags().await }, None)
					.map_or_else(|e| -i32::from(e), |status_flags| status_flags.bits())
			},
		)
	} else if cmd == F_SETFL {
		let obj = get_object(fd);
		obj.map_or_else(
			|e| -i32::from(e),
			|v| {
				block_on(
					async {
						v.write()
							.await
							.set_status_flags(fd::StatusFlags::from_bits_retain(arg))
							.await
					},
					None,
				)
				.map_or_else(|e| -i32::from(e), |()| 0)
			},
		)
	} else {
		-i32::from(Errno::Inval)
	}
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_lseek(fd: RawFd, offset: isize, whence: i32) -> isize {
	let whence = u8::try_from(whence).unwrap();
	let whence = SeekWhence::try_from(whence).unwrap();
	crate::fd::lseek(fd, offset, whence).unwrap_or_else(|e| isize::try_from(-i32::from(e)).unwrap())
}

#[repr(C)]
pub struct Dirent64 {
	/// 64-bit inode number
	pub d_ino: u64,
	/// Field without meaning. Kept for BW compatibility.
	pub d_off: i64,
	/// Size of this dirent
	pub d_reclen: u16,
	/// File type
	pub d_type: fs::FileType,
	/// Filename (null-terminated)
	pub d_name: PhantomData<c_char>,
}
impl Dirent64 {
	/// Creates a [`Dirent64Display`] struct for debug printing.
	///
	/// # Safety
	/// The bytes following the `d_name` must form a valid zero terminated `CStr`. Else we have an
	/// out-of-bounds read.
	#[allow(dead_code)]
	unsafe fn display<'a>(&'a self) -> Dirent64Display<'a> {
		unsafe { Dirent64Display::new(self) }
	}
}

mod dirent_display {
	use core::ffi::{CStr, c_char};
	use core::fmt;

	use super::Dirent64;

	/// [`Display`] adapter for [`Dirent64`].
	///
	/// [`Display`]: fmt::Display
	pub(super) struct Dirent64Display<'a> {
		dirent: &'a Dirent64,
	}

	impl<'a> Dirent64Display<'a> {
		/// # Safety
		/// The `d_name` ptr of `dirent` must be valid and zero-terminated.
		pub(super) unsafe fn new(dirent: &'a Dirent64) -> Self {
			Self { dirent }
		}
	}

	impl<'a> fmt::Debug for Dirent64Display<'a> {
		fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
			let cstr = unsafe { CStr::from_ptr((&raw const self.dirent.d_name).cast::<c_char>()) };

			f.debug_struct("Dirent64")
				.field("d_ino", &self.dirent.d_ino)
				.field("d_off", &self.dirent.d_off)
				.field("d_reclen", &self.dirent.d_reclen)
				.field("d_type", &self.dirent.d_type)
				.field("d_name", &cstr)
				.finish()
		}
	}
}

/// Read the entries of a directory.
/// Similar as the Linux system-call, this reads up to `count` bytes and returns the number of
/// bytes written. If the size was not sufficient to list all directory entries, subsequent calls
/// to this fn return the next entries.
///
/// Parameters:
///
/// - `fd`: File Descriptor of the directory in question.
/// -`dirp`: Memory for the kernel to store the filled `Dirent64` objects including the c-strings with the filenames to.
/// - `count`: Size of the memory region described by `dirp` in bytes.
///
/// Return:
///
/// The number of bytes read into `dirp` on success. Zero indicates that no more entries remain and
/// the directories readposition needs to be reset using `sys_lseek`.
/// Negative numbers encode errors.
#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_getdents64(fd: RawFd, dirp: *mut Dirent64, count: usize) -> i64 {
	debug!("getdents for fd {fd:?} - count: {count}");
	if dirp.is_null() || count == 0 {
		return (-i32::from(Errno::Inval)).into();
	}

	let slice = unsafe { slice::from_raw_parts_mut(dirp.cast(), count) };

	let obj = get_object(fd);
	obj.map_or_else(
		|_| (-i32::from(Errno::Inval)).into(),
		|v| {
			block_on(async { v.read().await.getdents(slice).await }, None)
				.map_or_else(|e| (-i32::from(e)).into(), |cnt| cnt as i64)
		},
	)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_dup(fd: i32) -> i32 {
	dup_object(fd).unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_dup2(fd1: i32, fd2: i32) -> i32 {
	dup_object2(fd1, fd2).unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_isatty(fd: i32) -> i32 {
	match isatty(fd) {
		Err(e) => -i32::from(e),
		Ok(v) => {
			if v {
				1
			} else {
				0
			}
		}
	}
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_poll(fds: *mut PollFd, nfds: usize, timeout: i32) -> i32 {
	let slice = unsafe { slice::from_raw_parts_mut(fds, nfds) };
	let timeout = if timeout >= 0 {
		Some(core::time::Duration::from_millis(
			timeout.try_into().unwrap(),
		))
	} else {
		None
	};

	crate::fd::poll(slice, timeout).map_or_else(
		|e| {
			if e == Errno::Time { 0 } else { -i32::from(e) }
		},
		|v| v.try_into().unwrap(),
	)
}

#[hermit_macro::system(errno)]
#[unsafe(no_mangle)]
pub extern "C" fn sys_eventfd(initval: u64, flags: i16) -> i32 {
	let Some(flags) = EventFlags::from_bits(flags) else {
		return -i32::from(Errno::Inval);
	};

	crate::fd::eventfd(initval, flags).unwrap_or_else(|e| -i32::from(e))
}

#[hermit_macro::system]
#[unsafe(no_mangle)]
pub extern "C" fn sys_image_start_addr() -> usize {
	crate::mm::kernel_start_address().as_usize()
}

#[cfg(test)]
mod tests {
	use super::*;

	#[cfg(target_os = "none")]
	#[test_case]
	fn test_get_application_parameters() {
		crate::env::init();
		let (argc, argv, _envp) = get_application_parameters();
		assert_ne!(argc, 0);
		assert_ne!(argv, ptr::null());
	}
}