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

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Date:   Thu, 28 May 2020 22:23:56 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     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,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Brendan Gregg <brendan.d.gregg@...il.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] powerpc/bpf: Enable bpf_probe_read{, str}() on powerpc again

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?

cheers