Le Wed, 30 Jul 2008 17:21:31 -0700, Greg KH <greg@xxxxxxxxx> a écrit : > That's a fault of the hardware, nothing the os can do about that, > sorry. Yes, however some recent chips provide an IOMMU, «a memory management unit (MMU) that connects a DMA-capable I/O bus to the main memory». And one of its advantage is: « Memory protection from malicious or misbehaving devices: a device cannot read or write to memory that hasn't been explicitly allocated (mapped) for it. The memory protection is based on the fact that OS running on the CPU (see figure) exclusively controls both the MMU and the IOMMU. The devices are physically unable to circumvent or corrupt configured memory management tables. » Using that kind of hardware, the OS has control over which parts of the physical memory is visible to a particular device. So the OS can protect itself against malicious devices. However, I don't know what chips are currently available with an IOMMU, and what's the status of Linux's support for IOMMU (I've seen several times patches being worked on, but I don't know if they have been merged). A rather old (2004) James Bottomley's article has more detail about DMA, <http://www.linuxjournal.com/node/7104/print>. Sincerly, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
