linux-kernel - Re: [PATCH 05/24] x86/entry: Introduce __entry

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Message-ID: <20210831193430.GL4353@worktop.programming.kicks-ass.net>
Date:   Tue, 31 Aug 2021 21:34:30 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 05/24] x86/entry: Introduce __entry_text for entry code
 written in C

On Wed, Sep 01, 2021 at 01:50:06AM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@...ux.alibaba.com>
> 
> Some entry code will be implemented in traps.c.  We need __entry_text
> to set them in .entry.text section.
> 
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> ---
>  arch/x86/entry/traps.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/x86/entry/traps.c b/arch/x86/entry/traps.c
> index f71db7934f90..ef07ae5fb3a0 100644
> --- a/arch/x86/entry/traps.c
> +++ b/arch/x86/entry/traps.c
> @@ -69,6 +69,11 @@
>  extern unsigned char native_irq_return_iret[];
>  extern unsigned char asm_load_gs_index_gs_change[];
>  
> +/* Entry code written in C. Must be only used in traps.c */
> +#define __entry_text							\
> +	noinline notrace __attribute((__section__(".entry.text")))	\
> +	__no_kcsan __no_sanitize_address __no_profile __no_sanitize_coverage

Urgh, that's bound to get out of sync with noinstr.. How about you make
noinstr something like:

#define __noinstr_section(section) \
	noinline notrace __attribute((__section__(section)))	\
	__no_kcsan __no_sanitize_address __no_profile __no_sanitize_coverage

#define noinstr __noinstr_section(".noinstr.text")

and then write the above like:

#define __entry_text __noinstr_section(".entry.text")