Function vmmdev_rw

freebsd/amd64/vmm/vmm_dev.c:195–250

}

static int
vmmdev_rw(struct cdev *cdev, struct uio *uio, int flags)
{
	int error, off, c, prot;
	vm_paddr_t gpa, maxaddr;
	void *hpa, *cookie;
	struct vmmdev_softc *sc;
	uint16_t lastcpu;

	error = vmm_priv_check(curthread->td_ucred);
	if (error)
		return (error);

	sc = vmmdev_lookup2(cdev);
	if (sc == NULL)
		return (ENXIO);

	/*
	 * Get a read lock on the guest memory map by freezing any vcpu.
	 */
	lastcpu = vm_get_maxcpus(sc->vm) - 1;
	error = vcpu_lock_one(sc, lastcpu);
	if (error)
		return (error);

	prot = (uio->uio_rw == UIO_WRITE ? VM_PROT_WRITE : VM_PROT_READ);
	maxaddr = vmm_sysmem_maxaddr(sc->vm);
	while (uio->uio_resid > 0 && error == 0) {
		gpa = uio->uio_offset;
		off = gpa & PAGE_MASK;
		c = min(uio->uio_resid, PAGE_SIZE - off);

		/*
		 * The VM has a hole in its physical memory map. If we want to
		 * use 'dd' to inspect memory beyond the hole we need to
		 * provide bogus data for memory that lies in the hole.
		 *
		 * Since this device does not support lseek(2), dd(1) will
		 * read(2) blocks of data to simulate the lseek(2).
		 */
		hpa = vm_gpa_hold(sc->vm, lastcpu, gpa, c,
		    prot, &cookie);
		if (hpa == NULL) {
			if (uio->uio_rw == UIO_READ && gpa < maxaddr)
				error = uiomove(__DECONST(void *, zero_region),
				    c, uio);
			else
				error = EFAULT;
		} else {
			error = uiomove(hpa, c, uio);
			vm_gpa_release(cookie);
		}
	}
	vcpu_unlock_one(sc, lastcpu);
	return (error);
}

CTASSERT(sizeof(((struct vm_memseg *)0)->name) >= VM_MAX_SUFFIXLEN + 1);