On Fri, Aug 14, 2020 at 05:30:58PM -0700, Andrew Morton wrote:
> From: Minchan Kim <minchan@xxxxxxxxxx>
> Subject: mm/madvise: introduce process_madvise() syscall: an external memory hinting API
>
<snip>
> +SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
> + unsigned long, vlen, int, behavior, unsigned int, flags)
> +{
> + ssize_t ret;
> + struct iovec iovstack[UIO_FASTIOV];
> + struct iovec *iov = iovstack;
> + struct iov_iter iter;
> +
> + ret = import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
> + if (ret >= 0) {
> + ret = do_process_madvise(pidfd, &iter, behavior, flags);
> + kfree(iov);
> + }
> + return ret;
> +}
> +
> +#ifdef CONFIG_COMPAT
> +COMPAT_SYSCALL_DEFINE5(process_madvise, compat_int_t, pidfd,
> + const struct compat_iovec __user *, vec,
> + compat_ulong_t, vlen,
> + compat_int_t, behavior,
> + compat_uint_t, flags)
> +
> +{
> + ssize_t ret;
> + struct iovec iovstack[UIO_FASTIOV];
> + struct iovec *iov = iovstack;
> + struct iov_iter iter;
> +
> + ret = compat_import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack),
> + &iov, &iter);
> + if (ret >= 0) {
> + ret = do_process_madvise(pidfd, &iter, behavior, flags);
> + kfree(iov);
> + }
> + return ret;
> +}
> +#endif
Note, I'm only commenting on this patch because it has already been
dropped for this merge window. Otherwise I wouldn't interfer with stuff
that has already been sent for inclusion.
I haven't noticed this before but why do you need this
COMPAT_SYSCALL_DEFINE5()? New code we add today tries pretty hard to
avoid the compat syscall definitions. (See what we did for
pidfd_send_signal(), seccomp, and in io_uring and in various other places.)
Afaict, this could just be sm like (__completely untested__):
static inline int madv_import_iovec(int type, const struct iovec __user *uvec, unsigned nr_segs,
unsigned fast_segs, struct iovec **iov, struct iov_iter *i)
{
#ifdef CONFIG_COMPAT
if (in_compat_syscall())
return compat_import_iovec(type, (struct compat_iovec __user *)uvec, nr_segs,
fast_segs, iov, i);
#endif
return import_iovec(type, uvec, nr_segs, fast_segs, iov, i);
}
SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
unsigned long, vlen, int, behavior, unsigned int, flags)
{
ssize_t ret;
struct iovec iovstack[UIO_FASTIOV];
struct iovec *iov = iovstack;
struct iov_iter iter;
ret = madv_import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
if (ret < 0)
return ret;
ret = do_process_madvise(pidfd, &iter, behavior, flags);
kfree(iov);
return ret;
}
or is there are specific reason this wouldn't work here?
Christian
