Date: Fri, 16 Apr 2010 14:37:14 +0200 From: =?ISO-8859-1?Q?Fernando_Apestegu=EDa?= <fernando.apesteguia@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: Understanding proc_rwmem Message-ID: <z2i1bd550a01004160537heaabda33t8bc50d6a4d8cc59e@mail.gmail.com> In-Reply-To: <201004160818.28944.jhb@freebsd.org> References: <x2l1bd550a01004141322m420065fbj742800c3e4a81927@mail.gmail.com> <201004141721.00254.jhb@freebsd.org> <r2u1bd550a01004160511t5886d215gb78e5556a755626d@mail.gmail.com> <201004160818.28944.jhb@freebsd.org>
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2010/4/16 John Baldwin <jhb@freebsd.org>:
> 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 ge=
t
>> >> 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:
>> >>
>> >>
>> >> =A0 =A0 =A0 =A0 struct iovec iov;
>> >> =A0 =A0 =A0 struct uio tmp_uio;
>> >> =A0 =A0 =A0 struct ps_strings *pss;
>> >> =A0 =A0 =A0 int ret_code;
>> >>
>> >> =A0 =A0 =A0 buff =3D malloc(sizeof(struct ps_strings), M_TEMP, M_WAIT=
OK);
>> >> =A0 =A0 =A0 memset(buff, 0, sizeof(struct ps_strings));
>> >>
>> >> =A0 =A0 =A0 PROC_LOCK_ASSERT(td->td_proc, MA_NOTOWNED);
>> >> =A0 =A0 =A0 iov.iov_base =3D (caddr_t) buff;
>> >> =A0 =A0 =A0 iov.iov_len =3D sizeof(struct ps_strings);
>> >> =A0 =A0 =A0 tmp_uio.uio_iov =3D &iov;
>> >> =A0 =A0 =A0 tmp_uio.uio_iovcnt =3D 1;
>> >> =A0 =A0 =A0 tmp_uio.uio_offset =3D (off_t)(p->p_sysent->sv_psstrings)=
;
>> >> =A0 =A0 =A0 tmp_uio.uio_resid =3D sizeof(struct ps_strings);
>> >> =A0 =A0 =A0 tmp_uio.uio_segflg =3D UIO_USERSPACE;
>> >> =A0 =A0 =A0 tmp_uio.uio_rw =3D UIO_READ;
>> >> =A0 =A0 =A0 tmp_uio.uio_td =3D td;
>> >> =A0 =A0 =A0 ret_code =3D proc_rwmem(td->td_proc, &tmp_uio);
>> >
>> > I think you want to use 'p' instead of 'td->td_proc' here. =A0As it is=
you
> are
>> > reading from the current process instead of the target process I belie=
ve.
>>
>> Thank you. You are right.
>>
>> 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?
>>
>> if (ret_code =3D=3D 0) {
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 sbuf_printf(sb, "proc_rwmem successfully exe=
cuted: %d\n", ret_code);
>> } else {
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 sbuf_printf(sb, "Error in proc_rwmem: %d\n",=
ret_code);
>> }
>>
>> 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);
>>
>> Thanks in advance.
>
> No, functions like uiomove() modify the iovec structures. =A0Just use 'bu=
ff'
> instead of iov.iov_base.
Ah! That was it!
Thanks!
>
> --
> John Baldwin
>
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