linux-kernel - Re: [PATCH -fixes] riscv: Fix RISCV_ALTERNATIVE_EARLY

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Message-ID: <14d633c5-804b-4be9-8329-751a2ac08c7a@ghiti.fr>
Date: Tue, 27 Aug 2024 11:13:16 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Conor Dooley <conor@...nel.org>, Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Guo Ren <guoren@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
 Philipp Tomsich <philipp.tomsich@...ll.eu>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH -fixes] riscv: Fix RISCV_ALTERNATIVE_EARLY

Hi Conor,

On 27/08/2024 10:38, Conor Dooley wrote:
> On Mon, Aug 26, 2024 at 12:57:37PM +0200, Alexandre Ghiti wrote:
>> RISCV_ALTERNATIVE_EARLY will issue sbi_ecall() very early in the boot
>> process, before the first memory mapping is setup so we can't have any
>> instrumentation happening here.
>>
>> In addition, when the kernel is relocatable, we must also not issue any
>> relocation this early since they would have been patched virtually only.
>>
>> So, instead of disabling instrumentation for the whole kernel/sbi.c file
>> and compiling it with -fno-pie, simply move __sbi_ecall() and
>> __sbi_base_ecall() into their own file where this is fixed.
> IOW, this should fix the issue that we discussed here
> https://lore.kernel.org/linux-riscv/abec162e-f3f2-488c-83d9-be17257a5df8@ghiti.fr/
> also?

Yes, as a side effect it also fixes TRACEPOINTS + [KASAN|RELOCATABLE] as 
I reported in this thread since I moved the tracepoints in a file where 
instrumentation is disabled and compiled with no-pie.

> I'm sorry I didn't get to test that yet, we had some pretty bad IT
> issues in the office the last weeks and I have been avoiding going
> there. I'll try to test this one instead..
>
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