linux-kernel - Re: [PATCH v2] MIPS/bpf: Enable bpf_probe

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Message-ID: <20210322071240.GD3440@lst.de>
Date:   Mon, 22 Mar 2021 08:12:40 +0100
From:   Christoph Hellwig <hch@....de>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] MIPS/bpf: Enable bpf_probe_read{, str}() on MIPS
 again

On Mon, Mar 22, 2021 at 05:46:56AM +0100, Maciej W. Rozycki wrote:
> On Thu, 18 Mar 2021, Tiezhu Yang wrote:
> 
> > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> > index 160b3a8..4b94ec7 100644
> > --- a/arch/mips/Kconfig
> > +++ b/arch/mips/Kconfig
> > @@ -6,6 +6,7 @@ config MIPS
> >  	select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
> >  	select ARCH_HAS_FORTIFY_SOURCE
> >  	select ARCH_HAS_KCOV
> > +	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> 
>  Hmm, documentation on ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE seems rather 
> scarce, but based on my guess shouldn't this be "if !EVA"?

ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE means the any given virtual
address in a task context can either be a valid kernel or user address
space, but not both.

Note that the bpf probe really is a legacy use case and should not be
used in new code independent of that.