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 <20200526140027.GC24212@redhat.com>
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From:   Greentime Hu <greentime.hu@sifive.com>
Date:   Wed, 27 May 2020 14:34:05 +0800
Message-ID: <CAHCEehK7BnWUhjOAynCLP6puRo8EguMvf=N8iG5UMQmaD8ekCQ@mail.gmail.com>
Subject: Re: [RFC PATCH v4 01/13] ptrace: Use regset_size() for dynamic regset size.
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     Guo Ren <guoren@linux.alibaba.com>,
        Vincent Chen <vincent.chen@sifive.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Oleg Nesterov <oleg@redhat.com> =E6=96=BC 2020=E5=B9=B45=E6=9C=8826=E6=97=
=A5 =E9=80=B1=E4=BA=8C =E4=B8=8B=E5=8D=8810:00=E5=AF=AB=E9=81=93=EF=BC=9A
>
> On 05/26, Greentime Hu wrote:
> >
> > @@ -882,13 +882,18 @@ static int ptrace_regset(struct task_struct *task=
, int req, unsigned int type,
> >       const struct user_regset_view *view =3D task_user_regset_view(tas=
k);
> >       const struct user_regset *regset =3D find_regset(view, type);
> >       int regset_no;
> > +     unsigned int size;
> >
> > -     if (!regset || (kiov->iov_len % regset->size) !=3D 0)
> > +     if (!regset)
> >               return -EINVAL;
> >
> >       regset_no =3D regset - view->regsets;
> > -     kiov->iov_len =3D min(kiov->iov_len,
> > -                         (__kernel_size_t) (regset->n * regset->size))=
;
> > +     size =3D regset_size(task, regset);
> > +
> > +     if ((kiov->iov_len % size) !=3D 0)
> > +             return -EINVAL;
>
> Hmm. this doesn't look right.
>
> Before this patch we check "iov_len % regset->size", this is not the same
> as "iov_len % regset_size()".
>
> IOW, currently you can read/write, say, only the 1st register, you patch
> breaks this?
>

Hi Oleg,

Thank you. I misunderstood the meaning of regset->size
It seems I only needs to update this line, right?
- kiov->iov_len =3D min(kiov->iov_len,  (__kernel_size_t) (regset->n *
regset->size));
+ kiov->iov_len =3D min(kiov->iov_len,  (__kernel_size_t)
regset_size(task, regset));