linux-kernel - Re: [PATCH] riscv: code patching only works on !XIP

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Message-ID: <20210511181033.580c1eba@xhacker.debian>
Date:   Tue, 11 May 2021 18:10:33 +0800
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Vitaly Wool <vitaly.wool@...sulko.com>
Cc:     Jisheng Zhang <jszhang3@...l.ustc.edu.cn>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] riscv: code patching only works on !XIP_KERNEL

On Mon, 10 May 2021 20:19:30 +0200 Vitaly Wool <vitaly.wool@...sulko.com> wrote:


> 
> 
> On Mon, May 10, 2021 at 6:35 PM Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
> >
> > From: Jisheng Zhang <jszhang@...nel.org>
> >
> > Some features which need code patching such as KPROBES, DYNAMIC_FTRACE
> > KGDB can only work on !XIP_KERNEL. Add dependencies for these features
> > that rely on code patching.  
> 
> Since we can define extra RW sections to place some tiny code bits in

I knew this discussion on maillist recently, that's the
reason why ERRATA_ALTERNATIVE related part isn't touched

> RAM, I would suggest that you hold back this patch for a while.
> I am not going to support the idea of e. g. compiling KGDB support
> into a XIP kernel, but disabling the whole HAVE_ARCH_JUMP_LABEL is
> hardly the way to go.
> 

I'm not sure whether the solution "extra RW sections to place some tiny code
bits" can work for JUMP_LABEL or not. But obviously, in JUMP_LABEL users
such as static keys, the patching is taken on the .text section unless
patching the common implementation kernel/jump_label.c. IMHO it's impossible.

However, I can hold back this patch for a while as you suggested.

Thanks