Passing STDOUT_FILENO to spec_write()

[Paul Goyette <paul%vps1.whooppee.com@localhost>]

I'm trying to debug a reported problem with filemon(4), and to make 
things a bit easier I tried to pass STDOUT_FILENO as the place where 
filemon should write its output.  Running this on a "console terminal" 
within qemu, the code in filemon_output() sets up a struct iovec and 
initializes a struct uio by calling uio_setup_sysspace(iovec).  It then 
calls (*filemon->fm_fp->f_ops->fo_write) which ends up in spec_write().

For some reason, spec_write() doesn't like something, and the code at

#ifdef DIAGNOSTIC
        if (uio->uio_rw != UIO_WRITE)
                panic("spec_write mode");
        if (&uio->uio_vmspace->vm_map != kernel_map &&
            uio->uio_vmspace != curproc->p_vmspace)
                panic("spec_write proc");
#endif

ends up by calling the panic("spec_write proc").

It's not clear to me what the DIAGNOSTIC code is supposed to prevent, 
nor is it clear why the call to uio_setup_sysspace() doesn't set up 
everything needed.

The same code in filemon seems to work just fine when it is passed a 
file descriptor that refers to a "real" file.

Can someone enlighten me here?


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| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
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