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proc_rwmem help

Discussion in 'FreeBSD Development' started by fernape, Apr 7, 2010.

  1. fernape

    fernape New Member

    Messages:
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    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:


    Code:
    	char *buff;
    	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);
    
    	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);
    
    	free(buff, M_TEMP);

    proc_rwmem returns 0 indicating no failure, but when I try to print the result, I get random stuff. I thought maybe the problem is in the uio_offset field, but p->p_sysent->sv_psstrings is a vm_offset_t. Is the offset properly specified? If not, what else could be the problem?

    Thanks in advance.