fix: replace UserPtr with starry-vm in sys_clone

[AsakuraMizu]

No description provided.

[Copilot]

Pull request overview

This PR refactors user space memory access in the sys_clone implementation by replacing the custom UserPtr wrapper with the starry-vm library's VmMutPtr trait. This change modernizes the codebase to use a more standardized approach for user memory operations.

Key changes:

• Replaced UserPtr wrapper and access_user_memory with direct raw pointer usage and starry-vm's VmMutPtr trait
• Changed new_user_task parameter from Option<&'static mut Pid> to usize for better consistency with other syscall parameters
• Updated sys_clone to use vm_write() method instead of UserPtr::get_as_mut()

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/entry.rs	Updated new_user_task call to pass 0 instead of None for the set_child_tid parameter
api/src/task.rs	Refactored new_user_task to use VmMutPtr trait methods (nullable() and vm_write()) instead of UserPtr and access_user_memory; removed import of access_user_memory
api/src/syscall/task/clone.rs	Replaced UserPtr usage with raw pointer casts and vm_write() calls for parent_tid and child_tid parameters; updated imports to use VmMutPtr instead of UserPtr

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[Copilot]

Silently discarding vm_write errors with .ok() may lead to unexpected behavior. If set_child_tid points to an invalid address, the old code (which used direct pointer dereference within access_user_memory) would trigger a page fault that could terminate the task. The new code silently ignores write failures, allowing the task to continue. Consider handling errors by at least logging them, or by raising a signal similar to how line 162 in do_exit checks is_ok() but takes conditional action based on the result.

Suggested change

	tid.vm_write(curr.id().as_u64() as Pid).ok();
	if let Err(err) = tid.vm_write(curr.id().as_u64() as Pid) {
	warn!(
	"Failed to write child TID to user memory at {:p}: {:?}",
	tid.as_ptr(),
	err
	);
	// Mirror the behavior for serious memory faults by raising SIGSEGV.
	raise_signal_fatal(SignalInfo::new_kernel(Signo::SIGSEGV))
	.expect("Failed to send SIGSEGV");
	}