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

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Date:   Wed, 1 Sep 2021 08:23:06 +0800
From:   Lai Jiangshan <laijs@...ux.alibaba.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, 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 2021/9/1 03:34, Peter Zijlstra wrote:
> 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")

It is a good idea.  There was no "__no_profile __no_sanitize_coverage"
when I first made the patch several month ago.  I added it after I recheck
the definition of "noinstr" yesterday which means we really need __noinstr_section()
to keep them sync.

>