refactor: remove UserPtr and UserConstPtr usages

[Ticonderoga2017]

#39

Description

• Remove UserPtr/UserConstPtr and their supporting memory validation functions to implement a unified user-space memory access interface.
• Introduce primitives like VmPtr/VmMutPtr, vm_read_slice, vm_write_slice, and vm_load_until_nul from starry_vm, covering scenarios such as read/write operations and string loading.
• Uniformly adapt system call paths and file I/O interfaces to the axio framework's Read/Write and IoBuf/IoBufMut models, avoiding inconsistencies caused by custom pointer types.

[AsakuraMizu]

Good job 👍

[AsakuraMizu]

Sorry, there were too many files, and I haven't had time to look at a few of them myself.

[Copilot]

Pull request overview

This pull request refactors the codebase to remove custom UserPtr and UserConstPtr types in favor of a unified memory access interface from starry_vm. The changes introduce VmPtr/VmMutPtr primitives and helper functions like vm_read_slice, vm_write_slice, and vm_load_until_nul for safer user-space memory operations.

Key Changes:

• Replaced all UserPtr/UserConstPtr usages with raw pointers and starry_vm primitives
• Updated system call signatures to accept raw pointers instead of custom wrapper types
• Refactored CMsgBuilder to work with raw pointers and return Result from constructor
• Simplified syscall dispatcher by replacing .into() calls with as _ casts

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
api/src/mm.rs	Removed UserPtr/UserConstPtr implementations; kept VmBytes/VmBytesMut wrappers and vm_load_string helper
api/src/vfs/dev/event.rs	Converted event device ioctls to use vm_write_slice and allocate temporary buffers
api/src/syscall/net/socket.rs	Updated socket syscalls to use raw pointers with VmPtr/VmMutPtr traits
api/src/syscall/net/opt.rs	Refactored getsockopt/setsockopt to use vm_read/vm_write with temporary variables
api/src/syscall/net/name.rs	Simplified getsockname/getpeername to use raw pointers
api/src/syscall/net/io.rs	Updated sendmsg/recvmsg to use vm_read_uninit and addr_of_mut for field access
api/src/syscall/net/cmsg.rs	Refactored CMsgBuilder to use raw pointers and made constructor fallible
api/src/syscall/mod.rs	Replaced .into() conversions with as _ casts throughout syscall dispatcher
api/src/syscall/ipc/shm.rs	Updated shmctl to use vm_read/vm_write with nullable pointer handling
api/src/syscall/io_mpx/select.rs	Converted select/pselect6 to read/write local copies and use nullable pattern
api/src/syscall/io_mpx/poll.rs	Updated poll/ppoll to use local Vec buffers with vm_read/vm_write
api/src/syscall/io_mpx/epoll.rs	Converted epoll functions to use temporary buffers and vm_write
api/src/syscall/fs/memfd.rs	Changed memfd_create signature to use raw pointer
api/src/syscall/fs/io.rs	Updated truncate to use vm_load_string
api/src/syscall/fs/fd_ops.rs	Modified fcntl to use vm_read_uninit/vm_write for flock64
api/src/socket.rs	Updated SocketAddrExt trait to use raw pointers; refactored read/write methods

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