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Date: Fri, 16 Oct 2020 07:54:03 +0100
From: Christoph Hellwig <hch@infradead.org>
To: "Christopher M. Riedl" <cmr@codefail.de>
Subject: Re: [PATCH 1/8] powerpc/uaccess: Add unsafe_copy_from_user
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On Thu, Oct 15, 2020 at 10:01:52AM -0500, Christopher M. Riedl wrote:
> Implement raw_copy_from_user_allowed() which assumes that userspace read
> access is open. Use this new function to implement raw_copy_from_user().
> Finally, wrap the new function to follow the usual "unsafe_" convention
> of taking a label argument. The new raw_copy_from_user_allowed() calls
> __copy_tofrom_user() internally, but this is still safe to call in user
> access blocks formed with user_*_access_begin()/user_*_access_end()
> since asm functions are not instrumented for tracing.

Please also add a fallback unsafe_copy_from_user to linux/uaccess.h
so this can be used as a generic API.