Messages in this thread | | | Subject | Re: [RFC] [PATCH] Add memcpy32 function | From | Bryan O'Sullivan <> | Date | Wed, 28 Dec 2005 07:00:25 -0800 |
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On Wed, 2005-12-28 at 12:01 +0100, Andi Kleen wrote:
> What irritates me is that the original author said this copy > would happen from user space in ipath.
I'm afraid there may have been some miscommunication there.
All of our uses of memcpy_toio32 (which uses memcpy32 on x86_64) copy from kernel virtual addresses to MMIO space. There's no direct copying from userspace to MMIO space through the driver.
However, we do let userspace code directly access portions of our chip. That code uses a routine that is exactly the same as memcpy32 to perform MMIO writes. That's where I think the confusion arose on the part of whoever responded to you.
> In that case you would need > exception handling for all memory accesses to return EFAULT, > otherwise everybody can crash the kernel.
Just to be clear: we use copy_{to,from}_user for all copies between userspace and driver, and we return -EFAULT on short copies, so we're already doing the right thing in that sort of case.
Sorry for the confusion. I hope this clears that business up.
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