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Date:   Fri, 24 Apr 2020 13:22:30 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@linux-mips.org>
To:     Jiaxun Yang <jiaxun.yang@flygoat.com>
cc:     linux-mips@vger.kernel.org, clang-built-linux@googlegroups.com,
        Fangrui Song <maskray@google.com>,
        Kees Cook <keescook@chromium.org>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Paul Burton <paulburton@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Jouni Hogander <jouni.hogander@unikie.com>,
        Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>,
        Borislav Petkov <bp@suse.de>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] MIPS: Truncate link address into 32bit for 32bit
 kernel
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Message-ID: <alpine.LFD.2.21.2004241316360.851719@eddie.linux-mips.org>
References: <20200413062651.3992652-1-jiaxun.yang@flygoat.com> <20200422143258.1250960-1-jiaxun.yang@flygoat.com> <alpine.LFD.2.21.2004230036480.851719@eddie.linux-mips.org> <B307BFAC-9973-4444-B69A-40B054210E84@flygoat.com>
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On Thu, 23 Apr 2020, Jiaxun Yang wrote:

> > Alternatively, have you made any attempt to verify if actually replacing 
> >the setting for VMLINUX_LOAD_ADDRESS would be safe?  Glancing over its use 
> >there do not appear to be many places.
> 
> Limited experiments showed it should be fine...
> 
> But MIPS kernel has some design I'm not really familiar with like SYM32 for
> 64-bit kernel and special address space design for Trap-and-emul KVM.

 This only affects CONFIG_32BIT kernels, so SYM32 does not apply; I can't 
comment on KVM.  There's still that bunch of:

$(shell expr $(...) \< 0xffffffff80000000)

constructs I mentioned before, so let's leave your change as it stands at 
this time.  Please do rename the variable as I suggested though, I hope 
that's not a big deal.

  Maciej