Date: Fri, 16 Apr 2010 14:11:25 +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: <r2u1bd550a01004160511t5886d215gb78e5556a755626d@mail.gmail.com> In-Reply-To: <201004141721.00254.jhb@freebsd.org> References: <x2l1bd550a01004141322m420065fbj742800c3e4a81927@mail.gmail.com> <201004141721.00254.jhb@freebsd.org>
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2010/4/14 John Baldwin <jhb@freebsd.org>:
> On Wednesday 14 April 2010 4:22:56 pm Fernando Apesteguía 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 = 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 = (caddr_t) buff;
>> iov.iov_len = sizeof(struct ps_strings);
>> tmp_uio.uio_iov = &iov;
>> tmp_uio.uio_iovcnt = 1;
>> tmp_uio.uio_offset = (off_t)(p->p_sysent->sv_psstrings);
>> tmp_uio.uio_resid = sizeof(struct ps_strings);
>> tmp_uio.uio_segflg = UIO_USERSPACE;
>> tmp_uio.uio_rw = UIO_READ;
>> tmp_uio.uio_td = td;
>> ret_code = proc_rwmem(td->td_proc, &tmp_uio);
>
> I think you want to use 'p' instead of 'td->td_proc' here. As it is you are
> reading from the current process instead of the target process I believe.
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 == 0) {
sbuf_printf(sb, "proc_rwmem successfully executed: %d\n", ret_code);
} else {
sbuf_printf(sb, "Error in proc_rwmem: %d\n", ret_code);
}
pss = (struct ps_strings *)(iov.iov_base);
sbuf_printf(sb, "ps_nargvstr = %d\nps_nenvstr = %d\n",
pss->ps_nargvstr, pss->ps_nenvstr);
Thanks in advance.
>
> --
> John Baldwin
>
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