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 A53F9C433F5 for ; Thu, 21 Oct 2021 11:43:10 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5F58C610CB for ; Thu, 21 Oct 2021 11:43:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 5F58C610CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:CC:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=e83RfXkThtEAQmMzyfmATI6b/Gkx7EGm7QEmBgHB6nI=; b=l00xeZ0c3MblMD 4XPtU1PKD/fEPbV+JOVeVh3roZJpgu0d1No7Ru7PupvsHeAtzH7zi95vf5Xq/dcSQ8LTC/nwChl1c pL5lY7CEJbg3SKUp3t5iEI/gVmt9wFLvuASkLISOBV+V3M7zWe3yL7rnrgOw2rVwjUNh/1CEej19v AGe9mVprmtp4Yu5BDdCMEddd6k5wn5aV3A6L7ICiFYAEIsVeEVjvhWf4gK2B4ZSxUVgY812OuHVJS RRnzaCHzKvKN7FBCFjuZoeFwhjaUJijq8qHoDRWWLWYKxm4rR0V9NQ8ZL3dspqXvtIX5K1mqU1zjM llYEg0u84XYqzfaa6xJw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mdWTJ-007NFM-KL; Thu, 21 Oct 2021 11:42:57 +0000 Received: from szxga01-in.huawei.com ([45.249.212.187]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mdWTG-007NEd-IN for linux-riscv@lists.infradead.org; Thu, 21 Oct 2021 11:42:56 +0000 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4HZlt60JQCzWlZk; Thu, 21 Oct 2021 19:41:02 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Thu, 21 Oct 2021 19:42:50 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.15; Thu, 21 Oct 2021 19:42:49 +0800 Message-ID: <352c54e1-b164-38d9-43fb-dbc28ab38ac7@huawei.com> Date: Thu, 21 Oct 2021 19:42:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v2 2/2] riscv: switch to relative exception tables Content-Language: en-US To: Jisheng Zhang , Paul Walmsley , Palmer Dabbelt , Albert Ou , Masahiro Yamada , Michal Marek , Nick Desaulniers CC: , , References: <20211020220529.54ccf4e9@xhacker> <20211020220700.04bcdeca@xhacker> From: Kefeng Wang In-Reply-To: <20211020220700.04bcdeca@xhacker> X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggeme709-chm.china.huawei.com (10.1.199.105) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211021_044254_988458_491342FD X-CRM114-Status: GOOD ( 17.48 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 2021/10/20 22:07, Jisheng Zhang wrote: > From: Jisheng Zhang > > Similar as other architectures such as arm64, x86 and so on, use > offsets relative to the exception table entry values rather than > absolute addresses for both the exception locationand the fixup. > > However, RISCV label difference will actually produce two relocations, > a pair of R_RISCV_ADD32 and R_RISCV_SUB32. Take below simple code for > example: > > $ cat test.S > .section .text > 1: > nop > .section __ex_table,"a" > .balign 4 > .long (1b - .) > .previous > > $ riscv64-linux-gnu-gcc -c test.S > $ riscv64-linux-gnu-readelf -r test.o > Relocation section '.rela__ex_table' at offset 0x100 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + Addend > 000000000000 000600000023 R_RISCV_ADD32 0000000000000000 .L1^B1 + 0 > 000000000000 000500000027 R_RISCV_SUB32 0000000000000000 .L0 + 0 > > The modpost will complain the R_RISCV_SUB32 relocation, so we need to > patch modpost.c to skip this relocation for .rela__ex_table section. > > After this patch, the __ex_table section size of defconfig vmlinux is > reduced from 7072 Bytes to 3536 Bytes. > > Signed-off-by: Jisheng Zhang > --- ... > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index cb8ab7d91d30..0aa14b5bd124 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -1830,6 +1830,27 @@ static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > return 0; > } > > +#ifndef EM_RISCV > +#define EM_RISCV 243 > +#endif > + > +#ifndef R_RISCV_SUB32 > +#define R_RISCV_SUB32 39 > +#endif > + > +static int addend_riscv_rela(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > +{ > + unsigned int r_typ = ELF_R_TYPE(r->r_info); > + const char *fromsec; > + > + fromsec = sech_name(elf, sechdr); > + fromsec += strlen(".rela"); > + > + if (!strcmp("__ex_table", fromsec) && r_typ == R_RISCV_SUB32) > + return 1; /* skip this */ > + return 0; > +} > + > static void section_rela(const char *modname, struct elf_info *elf, > Elf_Shdr *sechdr) > { > @@ -1866,6 +1887,12 @@ static void section_rela(const char *modname, struct elf_info *elf, > r_sym = ELF_R_SYM(r.r_info); > #endif > r.r_addend = TO_NATIVE(rela->r_addend); > + switch (elf->hdr->e_machine) { > + case EM_RISCV: > + if (addend_riscv_rela(elf, sechdr, &r)) directly use if (!strcmp("__ex_table", fromsec) && ELF_R_TYPE(r.r_info) == R_RISCV_SUB32) > + continue; > + break; > + } > sym = elf->symtab_start + r_sym; > /* Skip special sections */ > if (is_shndx_special(sym->st_shndx)) > diff --git a/scripts/sorttable.c b/scripts/sorttable.c > index 6ee4fa882919..39e86e4acea3 100644 > --- a/scripts/sorttable.c > +++ b/scripts/sorttable.c > @@ -346,6 +346,7 @@ static int do_file(char const *const fname, void *addr) > case EM_PARISC: > case EM_PPC: > case EM_PPC64: > + case EM_RISCV: > custom_sort = sort_relative_table; > break; > case EM_ARCOMPACT: > @@ -353,7 +354,6 @@ static int do_file(char const *const fname, void *addr) > case EM_ARM: > case EM_MICROBLAZE: > case EM_MIPS: > - case EM_RISCV: > case EM_XTENSA: > break; > default: > _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv