linux-kernel - Re: [PATCH] powerpc/bpf: Enable bpf_probe

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Date:   Thu, 28 May 2020 17:06:30 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Petr Mladek <pmladek@...e.com>
Cc:     Miroslav Benes <mbenes@...e.cz>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Christoph Hellwig <hch@....de>, bpf@...r.kernel.org
Subject: Re: [PATCH] powerpc/bpf: Enable bpf_probe_read{, str}() on powerpc
 again

On 5/28/20 2:23 PM, Michael Ellerman wrote:
> Petr Mladek <pmladek@...e.com> writes:
>> On Thu 2020-05-28 11:03:43, Michael Ellerman wrote:
>>> Petr Mladek <pmladek@...e.com> writes:
>>>> The commit 0ebeea8ca8a4d1d453a ("bpf: Restrict bpf_probe_read{, str}() only
>>>> to archs where they work") caused that bpf_probe_read{, str}() functions
>>>> were not longer available on architectures where the same logical address
>>>> might have different content in kernel and user memory mapping. These
>>>> architectures should use probe_read_{user,kernel}_str helpers.
>>>>
>>>> For backward compatibility, the problematic functions are still available
>>>> on architectures where the user and kernel address spaces are not
>>>> overlapping. This is defined CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE.
>>>>
>>>> At the moment, these backward compatible functions are enabled only
>>>> on x86_64, arm, and arm64. Let's do it also on powerpc that has
>>>> the non overlapping address space as well.
>>>>
>>>> Signed-off-by: Petr Mladek <pmladek@...e.com>
>>>
>>> This seems like it should have a Fixes: tag and go into v5.7?
>>
>> Good point:
>>
>> Fixes: commit 0ebeea8ca8a4d1d4 ("bpf: Restrict bpf_probe_read{, str}() only to archs where they work")
>>
>> And yes, it should ideally go into v5.7 either directly or via stable.
>>
>> Should I resend the patch with Fixes and
>> Cc: stable@...r.kernel.org #v45.7 lines, please?
> 
> If it goes into v5.7 then it doesn't need a Cc: stable, and I guess a
> Fixes: tag is nice to have but not so important as it already mentions
> the commit that caused the problem. So a resend probably isn't
> necessary.
> 
> Acked-by: Michael Ellerman <mpe@...erman.id.au>
> 
> Daniel can you pick this up, or should I?

Yeah I'll take it into bpf tree for v5.7.

Thanks everyone,
Daniel