Remove the shim kernel crate

kernel/src/syscall/pread64.rs

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::SyscallReturn;
+use crate::{fs::file_table::FileDesc, prelude::*};
+
+pub fn sys_pread64(
+    fd: FileDesc,
+    user_buf_ptr: Vaddr,
+    user_buf_len: usize,
+    offset: i64,
+    ctx: &Context,
+) -> Result<SyscallReturn> {
+    debug!(
+        "fd = {}, buf = 0x{:x}, user_buf_len = 0x{:x}, offset = 0x{:x}",
+        fd, user_buf_ptr, user_buf_len, offset
+    );
+
+    if offset < 0 {
+        return_errno_with_message!(Errno::EINVAL, "offset cannot be negative");
+    }
+    let file = {
+        let filetable = ctx.process.file_table().lock();
+        filetable.get_file(fd)?.clone()
+    };
+    // TODO: Check (f.file->f_mode & FMODE_PREAD); We don't have f_mode in our FileLike trait
+    if user_buf_len == 0 {
+        return Ok(SyscallReturn::Return(0));
+    }
+    if offset.checked_add(user_buf_len as i64).is_none() {
+        return_errno_with_message!(Errno::EINVAL, "offset + user_buf_len overflow");
+    }
+
+    let read_len = {
+        let mut writer = ctx
+            .process
+            .root_vmar()
+            .vm_space()
+            .writer(user_buf_ptr, user_buf_len)?;
+        file.read_at(offset as usize, &mut writer)?
+    };
+
+    Ok(SyscallReturn::Return(read_len as _))
+}