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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Daniel Borkmann <daniel@iogearbox.net>,
        Petr Mladek <pmladek@suse.com>
Cc:     Miroslav Benes <mbenes@suse.cz>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Brendan Gregg <brendan.d.gregg@gmail.com>,
        Christoph Hellwig <hch@lst.de>, bpf@vger.kernel.org
Subject: Re: [PATCH] powerpc/bpf: Enable bpf_probe_read{, str}() on powerpc again
In-Reply-To: <aace2e9e-c63c-a1a2-a1e1-c7a46904e8c5@iogearbox.net>
References: <20200527122844.19524-1-pmladek@suse.com> <87ftbkkh00.fsf@mpe.ellerman.id.au> <20200528091351.GE3529@linux-b0ei> <87d06ojlib.fsf@mpe.ellerman.id.au> <aace2e9e-c63c-a1a2-a1e1-c7a46904e8c5@iogearbox.net>
Date:   Fri, 29 May 2020 10:05:05 +1000
Message-ID: <87y2pbip1q.fsf@mpe.ellerman.id.au>
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Sender: linux-kernel-owner@vger.kernel.org
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Daniel Borkmann <daniel@iogearbox.net> writes:
> On 5/28/20 2:23 PM, Michael Ellerman wrote:
>> Petr Mladek <pmladek@suse.com> writes:
>>> On Thu 2020-05-28 11:03:43, Michael Ellerman wrote:
>>>> Petr Mladek <pmladek@suse.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@suse.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@vger.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@ellerman.id.au>
>> 
>> Daniel can you pick this up, or should I?
>
> Yeah I'll take it into bpf tree for v5.7.

Thanks.

cheers