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Date:   Mon, 25 May 2020 15:19:12 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Christoph Hellwig <hch@lst.de>
Cc:     x86@kernel.org, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-parisc@vger.kernel.org, linux-um@lists.infradead.org,
        netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: clean up and streamline probe_kernel_* and friends v4
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On Thu, 21 May 2020 17:22:38 +0200 Christoph Hellwig <hch@lst.de> wrote:

> this series start cleaning up the safe kernel and user memory probing
> helpers in mm/maccess.c, and then allows architectures to implement
> the kernel probing without overriding the address space limit and
> temporarily allowing access to user memory.  It then switches x86
> over to this new mechanism by reusing the unsafe_* uaccess logic.
> 
> This version also switches to the saner copy_{from,to}_kernel_nofault
> naming suggested by Linus.
> 
> I kept the x86 helpers as-is without calling unsage_{get,put}_user as
> that avoids a number of hard to trace casts, and it will still work
> with the asm-goto based version easily.

hm.  Applying linux-next to this series generates a lot of rejects against
powerpc:

-rw-rw-r-- 1 akpm akpm  493 May 25 15:06 arch/powerpc/kernel/kgdb.c.rej
-rw-rw-r-- 1 akpm akpm 6461 May 25 15:06 arch/powerpc/kernel/trace/ftrace.c.rej
-rw-rw-r-- 1 akpm akpm  447 May 25 15:06 arch/powerpc/mm/fault.c.rej
-rw-rw-r-- 1 akpm akpm  623 May 25 15:06 arch/powerpc/perf/core-book3s.c.rej
-rw-rw-r-- 1 akpm akpm 1408 May 25 15:06 arch/riscv/kernel/patch.c.rej

the arch/powerpc/kernel/trace/ftrace.c ones aren't very trivial.

It's -rc7.  Perhaps we should park all this until 5.8-rc1?