From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BFE86C4332F for ; Sat, 23 Oct 2021 18:32:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A00C60ED3 for ; Sat, 23 Oct 2021 18:32:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230516AbhJWSev (ORCPT ); Sat, 23 Oct 2021 14:34:51 -0400 Received: from angie.orcam.me.uk ([78.133.224.34]:34350 "EHLO angie.orcam.me.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230051AbhJWSeu (ORCPT ); Sat, 23 Oct 2021 14:34:50 -0400 Received: by angie.orcam.me.uk (Postfix, from userid 500) id 94E5592009C; Sat, 23 Oct 2021 20:32:29 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by angie.orcam.me.uk (Postfix) with ESMTP id 85BB192009B; Sat, 23 Oct 2021 20:32:29 +0200 (CEST) Date: Sat, 23 Oct 2021 20:32:29 +0200 (CEST) From: "Maciej W. Rozycki" To: Jinyang He cc: Thomas Bogendoerfer , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Burton , Jun-Ru Chang Subject: Re: [PATCH 4/4] MIPS: Add is_jr_ra_ins() to end the loop early In-Reply-To: <1610454557-25867-5-git-send-email-hejinyang@loongson.cn> Message-ID: References: <1610454557-25867-1-git-send-email-hejinyang@loongson.cn> <1610454557-25867-5-git-send-email-hejinyang@loongson.cn> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Jan 2021, Jinyang He wrote: > For those leaf functions, they are likely to have no stack operations. > Add is_jr_ra_ins() to determine whether jr ra has been touched before > the frame_size is found. Without this patch, the get frame_size operation > may be out of range and get the frame_size from the next nested function. > > Signed-off-by: Jinyang He > --- > arch/mips/kernel/process.c | 34 +++++++++++++++++++++++++++++++++- > 1 file changed, 33 insertions(+), 1 deletion(-) > > diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c > index bef8f8d..9e6f194 100644 > --- a/arch/mips/kernel/process.c > +++ b/arch/mips/kernel/process.c > @@ -205,6 +205,36 @@ struct mips_frame_info { > #define J_TARGET(pc,target) \ > (((unsigned long)(pc) & 0xf0000000) | ((target) << 2)) > > +static inline int is_jr_ra_ins(union mips_instruction *ip) > +{ > +#ifdef CONFIG_CPU_MICROMIPS > + /* > + * jr16 ra > + * jr ra > + */ > + if (mm_insn_16bit(ip->word >> 16)) { > + if (ip->mm16_r5_format.opcode == mm_pool16c_op && > + ip->mm16_r5_format.rt == mm_jr16_op && > + ip->mm16_r5_format.imm == 31) > + return 1; > + return 0; > + } > + > + if (ip->r_format.opcode == mm_pool32a_op && > + ip->r_format.func == mm_pool32axf_op && > + ((ip->u_format.uimmediate >> 6) & GENMASK(9,0)) == mm_jalr_op && > + ip->r_format.rs == 31) > + return 1; > + return 0; > +#else Without looking into it much, this is likely missing the point, because while technically inteed JR and JR16 can be used with $ra in microMIPS machine code (there's JRS too), in reality either JRC or JRADDIUSP will. [Wading through e-mail recovered from mid-Jan linux-mips.org crash.] Maciej