Re: [RFC] proposed libc interface and man page for listmount

[Miklos Szeredi <miklos@szeredi.hu>]

On Tue, 5 Dec 2023 at 18:51, Matthew House <mattlloydhouse@gmail.com> wrote:
>
> On Tue, Dec 5, 2023 at 11:28 AM Miklos Szeredi <miklos@szeredi.hu> wrote:
> > Attaching the proposed man page for listing mounts (based on the new
> > listmount() syscall).
> >
> > The raw interface is:
> >
> >        syscall(__NR_listmount, const struct mnt_id_req __user *, req,
> >                   u64 __user *, buf, size_t, bufsize, unsigned int, flags);
> >
> > The proposed libc API is.
> >
> >        struct listmount *listmount_start(uint64_t mnt_id, unsigned int flags);
> >        uint64_t listmount_next(struct listmount *lm);
> >        void listmount_end(struct listmount *lm);
> >
> > I'm on the opinion that no wrapper is needed for the raw syscall, just
> > like there isn't one for getdents(2).
> >
> > Comments?
>
> One use case I've been thinking of involves inspecting the mount list
> between syscall(__NR_clone3) and _exit(), so it has to be async-signal-
> safe. It would be nice if there were a libc wrapper that accepted a user-
> provided buffer and was async-signal-safe, so that I wouldn't have to add
> yet another syscall wrapper and redefine the kernel types just for this
> use case. (I can't trust the libc not to make its own funny versions of the
> types' layouts for its own ends.)

You can just #include <linux/mount.h> directly.

Thanks,
Miklos