Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 22 Mar 2021 08:12:40 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc:     Tiezhu Yang <yangtiezhu@loongson.cn>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        linux-mips@vger.kernel.org, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, Xuefeng Li <lixuefeng@loongson.cn>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] MIPS/bpf: Enable bpf_probe_read{, str}() on MIPS
 again
Message-ID: <20210322071240.GD3440@lst.de>
References: <1616034557-5844-1-git-send-email-yangtiezhu@loongson.cn> <alpine.DEB.2.21.2103220540591.21463@angie.orcam.me.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.21.2103220540591.21463@angie.orcam.me.uk>
User-Agent: Mutt/1.5.17 (2007-11-01)
Precedence: bulk

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.