Add minimal support for Hermit OS

Cargo.toml

@@ -274,3 +274,6 @@ check-cfg = [
     'cfg(target_arch, values("xtensa"))',
     'cfg(target_os, values("cygwin"))',
 ]
+
+[patch.crates-io]
+libc = { git = "https://github.com/rust-lang/libc", branch = "libc-0.2" }

src/backend/libc/event/syscalls.rs

@@ -572,7 +572,7 @@ pub(crate) unsafe fn epoll_wait(
         if let Some(epoll_pwait2_func) = epoll_pwait2.get() {
             return ret_u32(epoll_pwait2_func(
                 borrowed_fd(epoll),
-                events.0.cast::<c::epoll_event>(),
+                events.0.cast(),
                 events.1.try_into().unwrap_or(i32::MAX),
                 crate::utils::option_as_ptr(timeout).cast(),
                 null(),
@@ -596,7 +596,7 @@ pub(crate) unsafe fn epoll_wait(
 
         ret_u32(epoll_pwait2(
             borrowed_fd(epoll),
-            events.0.cast::<c::epoll_event>(),
+            events.0.cast(),
             events.1.try_into().unwrap_or(i32::MAX),
             crate::utils::option_as_ptr(timeout).cast(),
             null(),
@@ -614,7 +614,7 @@ pub(crate) unsafe fn epoll_wait(
 
         ret_u32(c::epoll_wait(
             borrowed_fd(epoll),
-            events.0.cast::<c::epoll_event>(),
+            events.0.cast(),
             events.1.try_into().unwrap_or(i32::MAX),
             timeout,
         ))

src/backend/libc/fs/syscalls.rs

@@ -328,7 +328,7 @@ pub(crate) fn getdents_uninit(
     unsafe {
         ret_usize(getdents64(
             borrowed_fd(fd),
-            buf.as_mut_ptr().cast::<c::c_void>(),
+            buf.as_mut_ptr().cast(),
             buf.len(),
         ))
     }
@@ -2387,7 +2387,7 @@ pub(crate) unsafe fn getxattr(
         ret_usize(c::getxattr(
             path.as_ptr(),
             name.as_ptr(),
-            value.0.cast::<c::c_void>(),
+            value.0.cast(),
             value.1,
         ))
     }
@@ -2399,7 +2399,7 @@ pub(crate) unsafe fn getxattr(
         let ptr = if value.1 == 0 {
             core::ptr::null_mut()
         } else {
-            value.0.cast::<c::c_void>()
+            value.0.cast()
         };
         ret_usize(c::getxattr(
             path.as_ptr(),
@@ -2423,7 +2423,7 @@ pub(crate) unsafe fn lgetxattr(
         ret_usize(c::lgetxattr(
             path.as_ptr(),
             name.as_ptr(),
-            value.0.cast::<c::c_void>(),
+            value.0.cast(),
             value.1,
         ))
     }
@@ -2435,7 +2435,7 @@ pub(crate) unsafe fn lgetxattr(
         let ptr = if value.1 == 0 {
             core::ptr::null_mut()
         } else {
-            value.0.cast::<c::c_void>()
+            value.0.cast()
         };
 
         ret_usize(c::getxattr(
@@ -2460,7 +2460,7 @@ pub(crate) unsafe fn fgetxattr(
         ret_usize(c::fgetxattr(
             borrowed_fd(fd),
             name.as_ptr(),
-            value.0.cast::<c::c_void>(),
+            value.0.cast(),
             value.1,
         ))
     }
@@ -2472,7 +2472,7 @@ pub(crate) unsafe fn fgetxattr(
         let ptr = if value.1 == 0 {
             core::ptr::null_mut()
         } else {
-            value.0.cast::<c::c_void>()
+            value.0.cast()
         };
         ret_usize(c::fgetxattr(
             borrowed_fd(fd),
@@ -2497,7 +2497,7 @@ pub(crate) fn setxattr(
         ret(c::setxattr(
             path.as_ptr(),
             name.as_ptr(),
-            value.as_ptr().cast::<c::c_void>(),
+            value.as_ptr().cast(),
             value.len(),
             flags.bits() as i32,
         ))
@@ -2508,7 +2508,7 @@ pub(crate) fn setxattr(
         ret(c::setxattr(
             path.as_ptr(),
             name.as_ptr(),
-            value.as_ptr().cast::<c::c_void>(),
+            value.as_ptr().cast(),
             value.len(),
             0,
             flags.bits() as i32,
@@ -2528,7 +2528,7 @@ pub(crate) fn lsetxattr(
         ret(c::lsetxattr(
             path.as_ptr(),
             name.as_ptr(),
-            value.as_ptr().cast::<c::c_void>(),
+            value.as_ptr().cast(),
             value.len(),
             flags.bits() as i32,
         ))
@@ -2539,7 +2539,7 @@ pub(crate) fn lsetxattr(
         ret(c::setxattr(
             path.as_ptr(),
             name.as_ptr(),
-            value.as_ptr().cast::<c::c_void>(),
+            value.as_ptr().cast(),
             value.len(),
             0,
             flags.bits() as i32 | c::XATTR_NOFOLLOW,
@@ -2559,7 +2559,7 @@ pub(crate) fn fsetxattr(
         ret(c::fsetxattr(
             borrowed_fd(fd),
             name.as_ptr(),
-            value.as_ptr().cast::<c::c_void>(),
+            value.as_ptr().cast(),
             value.len(),
             flags.bits() as i32,
         ))
@@ -2570,7 +2570,7 @@ pub(crate) fn fsetxattr(
         ret(c::fsetxattr(
             borrowed_fd(fd),
             name.as_ptr(),
-            value.as_ptr().cast::<c::c_void>(),
+            value.as_ptr().cast(),
             value.len(),
             0,
             flags.bits() as i32,
@@ -2582,40 +2582,27 @@ pub(crate) fn fsetxattr(
 pub(crate) unsafe fn listxattr(path: &CStr, list: (*mut u8, usize)) -> io::Result<usize> {
     #[cfg(not(apple))]
     {
-        ret_usize(c::listxattr(
-            path.as_ptr(),
-            list.0.cast::<ffi::c_char>(),
-            list.1,
-        ))
+        ret_usize(c::listxattr(path.as_ptr(), list.0.cast(), list.1))
     }
 
     #[cfg(apple)]
     {
-        ret_usize(c::listxattr(
-            path.as_ptr(),
-            list.0.cast::<ffi::c_char>(),
-            list.1,
-            0,
-        ))
+        ret_usize(c::listxattr(path.as_ptr(), list.0.cast(), list.1, 0))
     }
 }
 
 #[cfg(any(apple, linux_kernel, target_os = "hurd"))]
 pub(crate) unsafe fn llistxattr(path: &CStr, list: (*mut u8, usize)) -> io::Result<usize> {
     #[cfg(not(apple))]
     {
-        ret_usize(c::llistxattr(
-            path.as_ptr(),
-            list.0.cast::<ffi::c_char>(),
-            list.1,
-        ))
+        ret_usize(c::llistxattr(path.as_ptr(), list.0.cast(), list.1))
     }
 
     #[cfg(apple)]
     {
         ret_usize(c::listxattr(
             path.as_ptr(),
-            list.0.cast::<ffi::c_char>(),
+            list.0.cast(),
             list.1,
             c::XATTR_NOFOLLOW,
         ))
@@ -2628,12 +2615,12 @@ pub(crate) unsafe fn flistxattr(fd: BorrowedFd<'_>, list: (*mut u8, usize)) -> i
 
     #[cfg(not(apple))]
     {
-        ret_usize(c::flistxattr(fd, list.0.cast::<ffi::c_char>(), list.1))
+        ret_usize(c::flistxattr(fd, list.0.cast(), list.1))
     }
 
     #[cfg(apple)]
     {
-        ret_usize(c::flistxattr(fd, list.0.cast::<ffi::c_char>(), list.1, 0))
+        ret_usize(c::flistxattr(fd, list.0.cast(), list.1, 0))
     }
 }
 

src/backend/libc/io/errno.rs

@@ -791,7 +791,7 @@ impl Errno {
     #[cfg(not(target_os = "l4re"))]
     pub const NOTSOCK: Self = Self(c::ENOTSOCK);
     /// `ENOTSUP`
-    #[cfg(not(any(windows, target_os = "redox")))]
+    #[cfg(not(any(windows, target_os = "hermit", target_os = "redox")))]
     pub const NOTSUP: Self = Self(c::ENOTSUP);
     /// `ENOTTY`
     #[cfg(not(windows))]

src/backend/libc/io/syscalls.rs

@@ -43,6 +43,7 @@ pub(crate) fn write(fd: BorrowedFd<'_>, buf: &[u8]) -> io::Result<usize> {
     }
 }
 
+#[cfg(not(target_os = "hermit"))]
 pub(crate) unsafe fn pread(
     fd: BorrowedFd<'_>,
     buf: (*mut u8, usize),
@@ -59,6 +60,7 @@ pub(crate) unsafe fn pread(
     ret_usize(c::pread(borrowed_fd(fd), buf.0.cast(), len, offset))
 }
 
+#[cfg(not(target_os = "hermit"))]
 pub(crate) fn pwrite(fd: BorrowedFd<'_>, buf: &[u8], offset: u64) -> io::Result<usize> {
     let len = min(buf.len(), READ_LIMIT);
 
@@ -76,8 +78,8 @@ pub(crate) fn readv(fd: BorrowedFd<'_>, bufs: &mut [IoSliceMut<'_>]) -> io::Resu
     unsafe {
         ret_usize(c::readv(
             borrowed_fd(fd),
-            bufs.as_ptr().cast::<c::iovec>(),
-            min(bufs.len(), MAX_IOV) as c::c_int,
+            bufs.as_ptr().cast(),
+            min(bufs.len(), MAX_IOV) as _,
         ))
     }
 }
@@ -87,8 +89,8 @@ pub(crate) fn writev(fd: BorrowedFd<'_>, bufs: &[IoSlice<'_>]) -> io::Result<usi
     unsafe {
         ret_usize(c::writev(
             borrowed_fd(fd),
-            bufs.as_ptr().cast::<c::iovec>(),
-            min(bufs.len(), MAX_IOV) as c::c_int,
+            bufs.as_ptr().cast(),
+            min(bufs.len(), MAX_IOV) as _,
         ))
     }
 }
@@ -97,6 +99,7 @@ pub(crate) fn writev(fd: BorrowedFd<'_>, bufs: &[IoSlice<'_>]) -> io::Result<usi
     target_os = "cygwin",
     target_os = "espidf",
     target_os = "haiku",
+    target_os = "hermit",
     target_os = "horizon",
     target_os = "nto",
     target_os = "redox",
@@ -117,7 +120,7 @@ pub(crate) fn preadv(
     unsafe {
         ret_usize(c::preadv(
             borrowed_fd(fd),
-            bufs.as_ptr().cast::<c::iovec>(),
+            bufs.as_ptr().cast(),
             min(bufs.len(), MAX_IOV) as c::c_int,
             offset,
         ))
@@ -128,6 +131,7 @@ pub(crate) fn preadv(
     target_os = "cygwin",
     target_os = "espidf",
     target_os = "haiku",
+    target_os = "hermit",
     target_os = "nto",
     target_os = "horizon",
     target_os = "redox",
@@ -144,7 +148,7 @@ pub(crate) fn pwritev(fd: BorrowedFd<'_>, bufs: &[IoSlice<'_>], offset: u64) ->
     unsafe {
         ret_usize(c::pwritev(
             borrowed_fd(fd),
-            bufs.as_ptr().cast::<c::iovec>(),
+            bufs.as_ptr().cast(),
             min(bufs.len(), MAX_IOV) as c::c_int,
             offset,
         ))
@@ -163,7 +167,7 @@ pub(crate) fn preadv2(
     unsafe {
         ret_usize(c::preadv2(
             borrowed_fd(fd),
-            bufs.as_ptr().cast::<c::iovec>(),
+            bufs.as_ptr().cast(),
             min(bufs.len(), MAX_IOV) as c::c_int,
             offset,
             bitflags_bits!(flags),
@@ -183,7 +187,7 @@ pub(crate) fn pwritev2(
     unsafe {
         ret_usize(c::pwritev2(
             borrowed_fd(fd),
-            bufs.as_ptr().cast::<c::iovec>(),
+            bufs.as_ptr().cast(),
             min(bufs.len(), MAX_IOV) as c::c_int,
             offset,
             bitflags_bits!(flags),
@@ -234,16 +238,18 @@ pub(crate) unsafe fn ioctl_readonly(
     ioctl(fd, request, arg)
 }
 
+#[cfg(not(target_os = "hermit"))]
 pub(crate) fn fcntl_getfd(fd: BorrowedFd<'_>) -> io::Result<FdFlags> {
     let flags = unsafe { ret_c_int(c::fcntl(borrowed_fd(fd), c::F_GETFD))? };
     Ok(FdFlags::from_bits_retain(bitcast!(flags)))
 }
 
+#[cfg(not(target_os = "hermit"))]
 pub(crate) fn fcntl_setfd(fd: BorrowedFd<'_>, flags: FdFlags) -> io::Result<()> {
     unsafe { ret(c::fcntl(borrowed_fd(fd), c::F_SETFD, flags.bits())) }
 }
 
-#[cfg(not(any(target_os = "espidf", target_os = "wasi")))]
+#[cfg(not(any(target_os = "espidf", target_os = "hermit", target_os = "wasi")))]
 pub(crate) fn fcntl_dupfd_cloexec(fd: BorrowedFd<'_>, min: RawFd) -> io::Result<OwnedFd> {
     unsafe { ret_owned_fd(c::fcntl(borrowed_fd(fd), c::F_DUPFD_CLOEXEC, min)) }
 }
@@ -259,7 +265,7 @@ pub(crate) fn dup(fd: BorrowedFd<'_>) -> io::Result<OwnedFd> {
 }
 
 #[allow(clippy::needless_pass_by_ref_mut)]
-#[cfg(not(target_os = "wasi"))]
+#[cfg(not(any(target_os = "hermit", target_os = "wasi")))]
 pub(crate) fn dup2(fd: BorrowedFd<'_>, new: &mut OwnedFd) -> io::Result<()> {
     unsafe { ret_discarded_fd(c::dup2(borrowed_fd(fd), borrowed_fd(new.as_fd()))) }
 }
@@ -272,6 +278,7 @@ pub(crate) fn dup2(fd: BorrowedFd<'_>, new: &mut OwnedFd) -> io::Result<()> {
     target_os = "dragonfly",
     target_os = "espidf",
     target_os = "haiku",
+    target_os = "hermit",
     target_os = "horizon",
     target_os = "nto",
     target_os = "redox",

src/backend/libc/io/types.rs

@@ -55,6 +55,7 @@ bitflags! {
             apple,
             target_os = "aix",
             target_os = "android",
+            target_os = "hermit",
             target_os = "redox",
         )))] // Android 5.0 has dup3, but libc doesn't have bindings
         const CLOEXEC = bitcast!(c::O_CLOEXEC);

src/backend/libc/net/addr.rs

@@ -321,7 +321,7 @@ impl SocketAddrStorage {
         // SAFETY: `self.0` is a `sockaddr_storage` so it has enough space.
         unsafe {
             AddressFamily::from_raw(crate::backend::net::read_sockaddr::read_sa_family(
-                crate::utils::as_ptr(&self.0).cast::<c::sockaddr>(),
+                crate::utils::as_ptr(&self.0).cast(),
             ))
         }
     }
@@ -332,7 +332,7 @@ impl SocketAddrStorage {
         // SAFETY: `self.0` is a `sockaddr_storage` so it has enough space.
         unsafe {
             crate::backend::net::read_sockaddr::initialize_family_to_unspec(
-                crate::utils::as_mut_ptr(&mut self.0).cast::<c::sockaddr>(),
+                crate::utils::as_mut_ptr(&mut self.0).cast(),
             )
         }
     }

src/backend/libc/net/read_sockaddr.rs

@@ -122,7 +122,7 @@ pub(crate) unsafe fn sockaddr_nonempty(storage: *const c::sockaddr, len: SocketA
     }
 
     assert!(len as usize >= size_of::<c::sa_family_t>());
-    let family: c::c_int = read_sa_family(storage.cast::<c::sockaddr>()).into();
+    let family: c::c_int = read_sa_family(storage.cast()).into();
     if family == c::AF_UNSPEC {
         return false;
     }
@@ -240,7 +240,7 @@ pub(crate) fn read_sockaddr_xdp(addr: &SocketAddrAny) -> Result<SocketAddrXdp, E
         return Err(Errno::AFNOSUPPORT);
     }
     assert!(addr.addr_len() as usize >= size_of::<c::sockaddr_xdp>());
-    let decode = unsafe { &*addr.as_ptr().cast::<c::sockaddr_xdp>() };
+    let decode: &c::sockaddr_xdp = unsafe { &*addr.as_ptr().cast() };
 
     // This ignores the `sxdp_shared_umem_fd` field, which is only expected to
     // be significant in `bind` calls, and not returned from `acceptfrom` or
@@ -259,6 +259,6 @@ pub(crate) fn read_sockaddr_netlink(addr: &SocketAddrAny) -> Result<SocketAddrNe
         return Err(Errno::AFNOSUPPORT);
     }
     assert!(addr.addr_len() as usize >= size_of::<c::sockaddr_nl>());
-    let decode = unsafe { &*addr.as_ptr().cast::<c::sockaddr_nl>() };
+    let decode: &c::sockaddr_nl = unsafe { &*addr.as_ptr().cast() };
     Ok(SocketAddrNetlink::new(decode.nl_pid, decode.nl_groups))
 }