linux-kernel - Re: [PATCH 1/8] powerpc/uaccess: Add unsafe_copy_from

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Date:   Fri, 16 Oct 2020 07:54:03 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     "Christopher M. Riedl" <cmr@...efail.de>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        viro@...iv.linux.org.uk
Subject: Re: [PATCH 1/8] powerpc/uaccess: Add unsafe_copy_from_user

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.