From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D55C01101 for ; Thu, 28 Jul 2022 09:14:59 +0000 (UTC) Received: from localhost.localdomain (unknown [111.9.175.10]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9Dx39CPU+Jij70+AA--.203S3; Thu, 28 Jul 2022 17:14:57 +0800 (CST) Subject: Re: [PATCH 3/5] LoongArch: Support relocation against _GLOBAL_OFFSET_TABLE_ To: Xi Ruoyao , loongarch@lists.linux.dev References: <385f63bcbee8e37c42f479ce9cdc7e7d731d419b.camel@xry111.site> <99733532831377ab6585d43ee40bf314a2d4c5a3.camel@xry111.site> <10c1e0f9-8409-a0f4-9b18-a5f56dfb14e1@loongson.cn> <9a79a424a11339ae025539c38fe121104ff00804.camel@xry111.site> Cc: linux-kernel@vger.kernel.org, WANG Xuerui , Huacai Chen From: Jinyang He Message-ID: Date: Thu, 28 Jul 2022 17:14:55 +0800 User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <9a79a424a11339ae025539c38fe121104ff00804.camel@xry111.site> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-CM-TRANSID:AQAAf9Dx39CPU+Jij70+AA--.203S3 X-Coremail-Antispam: 1UD129KBjvJXoW7Ww1xWFyUAF47WFWDAFyftFb_yoW8CFWkpr ZFkr4kKanrGrn5Gw17tw18ur1jka97ur4fKFZ8X3y8ArnYqryDur48tr90vF47X34kKw40 qa4v9348Wa98ZwUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkmb7Iv0xC_Kw4lb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26F4UJVW0owA2z4x0Y4 vEx4A2jsIEc7CjxVAFwI0_GcCE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xv F2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r 4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwCYjI0SjxkI62AI1cAE67vIY487 MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr 0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUAVWUtwCIc40Y0x0E wIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJV W8JwCI42IY6xAIw20EY4v20xvaj40_WFyUJVCq3wCI42IY6I8E87Iv67AKxVWUJVW8JwCI 42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxUgg_TUUUUU X-CM-SenderInfo: pkhmx0p1dqwqxorr0wxvrqhubq/ On 07/28/2022 02:41 PM, Xi Ruoyao wrote: > On Thu, 2022-07-28 at 09:02 +0800, Jinyang He wrote: > >> Hi, Ruoyao, >> >> It is possible to create a symbol when linking, which means >> maybe we can add _GLOBAL_OFFSET_TABLE_ in 'module.lds.h'. >> What do you think about it? > Hi Jinyang, > > I think you are right, this patch can be replaced with the following, > which is much simpler. > > -- >8 -- > > With the stack-based relocations, the assembler emits three relocations > to push the PC-relative offset of a GOT entry: > > R_LARCH_SOP_PUSH_PCREL _GLOBAL_OFFSET_TABLE_ > R_LARCH_SOP_PUSH_GPREL foo > R_LARCH_SOP_ADD > > In normal relocatable ELF object files, "_GLOBAL_OFFSET_TABLE_" is > undefined in the symtab and the BFD linker generates it on final link. > Define it for kernel modules so we will be able to really use > R_LARCH_SOP_PUSH_GPREL relocation. > > Note that we need to use "HIDDEN" to make it a local symbol because each > kernel module has its own GOT and the reference to it should not be > resolved to the GOT in the main kernel image. > > Suggested-by: Jinyang He > Signed-off-by: Xi Ruoyao > --- > arch/loongarch/include/asm/module.lds.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/loongarch/include/asm/module.lds.h b/arch/loongarch/include/asm/module.lds.h > index 57bbd0cedd26..42b7cca0b947 100644 > --- a/arch/loongarch/include/asm/module.lds.h > +++ b/arch/loongarch/include/asm/module.lds.h > @@ -4,5 +4,5 @@ SECTIONS { > . = ALIGN(4); > .plt : { BYTE(0) } > .plt.idx : { BYTE(0) } > - .got : { BYTE(0) } > + .got : { HIDDEN(_GLOBAL_OFFSET_TABLE_ = .); BYTE(0) } Not sure but maybe re-align is needed here. Since '{BYTE(0)}' actually use 1byte. _GLOABL_OFFSET_TABLE_ may have difference with really GOT table entry. Have no machine and without test... :-( Thanks, Jinyang > }