linux-kernel - Re: [PATCH v2 0/2] Replace and improve "mcsafe" with copy

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Date:   Thu, 30 Apr 2020 12:22:58 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        stable <stable@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Erwin Tsaur <erwin.tsaur@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] Replace and improve "mcsafe" with copy_safe()

On Thu, Apr 30, 2020 at 11:42:20AM -0700, Andy Lutomirski wrote:
> I suppose there could be a consistent naming like this:
> 
> copy_from_user()
> copy_to_user()
> 
> copy_from_unchecked_kernel_address() [what probe_kernel_read() is]
> copy_to_unchecked_kernel_address() [what probe_kernel_write() is]
> 
> copy_from_fallible() [from a kernel address that can fail to a kernel
> address that can't fail]
> copy_to_fallible() [the opposite, but hopefully identical to memcpy() on x86]
> 
> copy_from_fallible_to_user()
> copy_from_user_to_fallible()
> 
> These names are fairly verbose and could probably be improved.

How about

	try_copy_catch(void *dst, void *src, size_t count, int *fault)

returns number of bytes not-copied (like copy_to_user etc).

if return is not zero, "fault" tells you what type of fault
cause the early stop (#PF, #MC).

-Tony