linux-kernel - Re: [PATCH -fixes] riscv: Fix relocatable kernels with early alternatives using -fno-pie

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Message-ID: <20230526-clergyman-wriggly-accc659a3fad@spud>
Date:   Fri, 26 May 2023 17:24:37 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Alexandre Ghiti <alexghiti@...osinc.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -fixes] riscv: Fix relocatable kernels with early
 alternatives using -fno-pie

On Fri, May 26, 2023 at 05:46:30PM +0200, Alexandre Ghiti wrote:
> Early alternatives are called with the mmu disabled, and then should not
> access any global symbols through the GOT since it requires relocations,
> relocations that we do before but *virtually*. So only use medany code
> model for this early code.
> 
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> ---
> 
> Note that I'm not very happy with this fix, I think we need to put more
> effort into "harmonizing" this very early code (ie before the mmu is
> enabled) as it is spread between different locations and compiled
> differently.

Totally & I'll happily spend the time trying to review that work.

> I'll work on that later, but for now, this fix does what is
> needed to work (from my testing at least). Any Tested-by on the Unmatched
> and T-head boards is welcome!

On 6.4-rc1 & v6.4-rc1 + this patch, with CONFIG_RELOCATABLE added to my
config, my Nezha fails to boot. There is no output whatsoever from the
kernel. Turning off CONFIG_RELOCATABLE boots again.

I didn't test on my unmatched.

Thanks,
Conor.

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