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

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Message-ID: <87ftbkkh00.fsf@mpe.ellerman.id.au>
Date:   Thu, 28 May 2020 11:03:43 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>,
        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:
> 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?

cheers

> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index d13b5328ca10..b29d7cb38368 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -126,6 +126,7 @@ config PPC
>  	select ARCH_HAS_MMIOWB			if PPC64
>  	select ARCH_HAS_PHYS_TO_DMA
>  	select ARCH_HAS_PMEM_API
> +	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>  	select ARCH_HAS_PTE_DEVMAP		if PPC_BOOK3S_64
>  	select ARCH_HAS_PTE_SPECIAL
>  	select ARCH_HAS_MEMBARRIER_CALLBACKS
> -- 
> 2.26.2