linux-kernel - Re: [PATCH v4 2/5] LoongArch: Use la.pcrel instead of la.abs for exception handlers

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Date:   Thu, 16 Feb 2023 16:03:10 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Xi Ruoyao <xry111@...111.site>, Jinyang He <hejinyang@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>
Cc:     Xuerui Wang <kernel@...0n.name>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>,
        Jianmin lv <lvjianmin@...ngson.cn>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH v4 2/5] LoongArch: Use la.pcrel instead of la.abs for
 exception handlers



On 02/16/2023 03:10 PM, Xi Ruoyao wrote:
> On Thu, 2023-02-16 at 14:59 +0800, Jinyang He wrote:
>> +.macro la.abs reg, sym
>> +766:
>> +    nop
>> +    nop
>> +    nop
>> +    nop
>
> In the "formal" version we can code
>
> lu12i.w		reg, 0
> ori		reg, reg, 0
> lu32i.d		reg, 0
> lu52i.d		reg, reg, 0
>
> here.  Then we only need to fixup the immediate slot so we can avoid
> using parse_r.
>
>
>> +    .pushsection ".laabs", "aw", %progbits
>> +768:
>> +    .word 768b-766b
>> +    parse_r regno, \reg
>> +    .word regno
>> +    .dword \sym
>> +    .popsection
>> +.endm

I will try to modify a version for testing, using the following
definition, when the RELOCATABLE is turned on, the "la.abs macro" is
used, otherwise the "la.abs pseudo instruction" is still used as before.

#ifdef CONFIG_RELOCATABLE
.macro la.abs reg, sym
lu12i.w		reg, 0
ori		reg, reg, 0
lu32i.d		reg, 0
lu52i.d		reg, reg, 0
.endm
#endif

Youling.