Understanding proc_rwmem

[John Baldwin]

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.

-- 
John Baldwin