linux-kernel - Re: [PATCH v2 1/6] riscv: ftrace: support fastcc in Clang for WITH

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Message-ID: <877cckadci.fsf@all.your.base.are.belong.to.us>
Date: Tue, 13 Aug 2024 13:09:33 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Andy Chiu <andy.chiu@...ive.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
 <aou@...s.berkeley.edu>, Alexandre Ghiti <alexghiti@...osinc.com>, Zong Li
 <zong.li@...ive.com>, Steven Rostedt <rostedt@...dmis.org>, Masami
 Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers
 <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, Justin Stitt
 <justinstitt@...gle.com>, Puranjay Mohan <puranjay@...nel.org>
Cc: Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 llvm@...ts.linux.dev, Evgenii Shatokhin <e.shatokhin@...ro.com>, Andy Chiu
 <andy.chiu@...ive.com>
Subject: Re: [PATCH v2 1/6] riscv: ftrace: support fastcc in Clang for
 WITH_ARGS

Andy Chiu <andy.chiu@...ive.com> writes:

> Some caller-saved registers which are not defined as function arguments
> in the ABI can still be passed as arguments when the kernel is compiled
> with Clang. As a result, we must save and restore those registers to
> prevent ftrace from clobbering them.
>
> - [1]: https://reviews.llvm.org/D68559
>
> Reported-by: Evgenii Shatokhin <e.shatokhin@...ro.com>
> Closes: https://lore.kernel.org/linux-riscv/7e7c7914-445d-426d-89a0-59a9199c45b1@yadro.com/
> Acked-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Andy Chiu <andy.chiu@...ive.com>

Shouldn't this be a separate fix? Still reading the details, but it
smells like something what should be disabled when building w/ LLVM, no?


Björn