Date: Fri, 16 Apr 2010 08:18:28 -0400 From: John Baldwin <jhb@freebsd.org> To: Fernando =?iso-8859-1?q?Apestegu=EDa?= <fernando.apesteguia@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Understanding proc_rwmem Message-ID: <201004160818.28944.jhb@freebsd.org> In-Reply-To: <r2u1bd550a01004160511t5886d215gb78e5556a755626d@mail.gmail.com> References: <x2l1bd550a01004141322m420065fbj742800c3e4a81927@mail.gmail.com> <201004141721.00254.jhb@freebsd.org> <r2u1bd550a01004160511t5886d215gb78e5556a755626d@mail.gmail.com>
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On Friday 16 April 2010 8:11:25 am Fernando Apestegu=EDa wrote:
> 2010/4/14 John Baldwin <jhb@freebsd.org>:
> > On Wednesday 14 April 2010 4:22:56 pm Fernando Apestegu=EDa wrote:
> >> Hi all,
> >>
> >> I'm trying to read process memory other than the current process in
> >> kernel. I was told to use the proc_rwmem function, however I can't get
> >> it working properly. At first, I'm trying to read how many elements
> >> the environment variables vector has. To do this I tried this from a
> >> linprocfs filler function:
> >>
> >>
> >> struct iovec iov;
> >> struct uio tmp_uio;
> >> struct ps_strings *pss;
> >> int ret_code;
> >>
> >> buff =3D malloc(sizeof(struct ps_strings), M_TEMP, M_WAITOK);
> >> memset(buff, 0, sizeof(struct ps_strings));
> >>
> >> PROC_LOCK_ASSERT(td->td_proc, MA_NOTOWNED);
> >> iov.iov_base =3D (caddr_t) buff;
> >> iov.iov_len =3D sizeof(struct ps_strings);
> >> tmp_uio.uio_iov =3D &iov;
> >> tmp_uio.uio_iovcnt =3D 1;
> >> tmp_uio.uio_offset =3D (off_t)(p->p_sysent->sv_psstrings);
> >> tmp_uio.uio_resid =3D sizeof(struct ps_strings);
> >> tmp_uio.uio_segflg =3D UIO_USERSPACE;
> >> tmp_uio.uio_rw =3D UIO_READ;
> >> tmp_uio.uio_td =3D td;
> >> ret_code =3D proc_rwmem(td->td_proc, &tmp_uio);
> >
> > I think you want to use 'p' instead of 'td->td_proc' here. As it is yo=
u=20
are
> > reading from the current process instead of the target process I believ=
e.
>=20
> Thank you. You are right.
>=20
> I made the changes suggested by both you and Kostik. I still have
> random data when reading.
> I'm trying to to the same thing using kern/sys_generic.c::read and
> kern/sys_process.c::kern_ptrace
> as examples, but I'm missing something...
> After reading with proc_rwmem, is it possible to do something like the
> following?
>=20
> if (ret_code =3D=3D 0) {
> sbuf_printf(sb, "proc_rwmem successfully executed: %d\n", ret_code);
> } else {
> sbuf_printf(sb, "Error in proc_rwmem: %d\n", ret_code);
> }
>=20
> pss =3D (struct ps_strings *)(iov.iov_base);
> sbuf_printf(sb, "ps_nargvstr =3D %d\nps_nenvstr =3D %d\n",
> pss->ps_nargvstr, pss->ps_nenvstr);
>=20
> Thanks in advance.
No, functions like uiomove() modify the iovec structures. Just use 'buff'=
=20
instead of iov.iov_base.
=2D-=20
John Baldwin
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