From nobody Fri Dec 19 07:03:39 2025 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 88F375B216 for ; Sat, 7 Dec 2024 01:59:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=114.242.206.163 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733536770; cv=none; b=D6Z1VbytiJPmypITfsxGgIAxY4Qd+a+gaxUISd+UohoZflAnzrrPtyClwxjwTqEBINpWgwupZ652j/4TVChc3dZdcqmBzuiUFh+b4xHh5nn9MASJFjHAp9ATdcPjVOCmfhwMO7SBmfzmrWVlEdvnY77m+RIpJAyvv9I5K73Mrn8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733536770; c=relaxed/simple; bh=QVmrM8f3nhhAJnyGl7OMrM8qjRlcA+7PGC0I6StoDhM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q+r1Rb+col/vM5ib4MGieLr6tnYdgT70GyUjqv9czqq70ikyoPKsTUILiNXFbhbxhK+k34IcF+ktvqwMPwulwlZag8C93l0iTY5tlocTLqch8p8Yw41xYAYHkMFGzIAp0u76JiXjfaflL2uBQzhFsIwxXOJvaMtte1M2hhLzOdg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn; spf=pass smtp.mailfrom=loongson.cn; arc=none smtp.client-ip=114.242.206.163 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=loongson.cn Received: from loongson.cn (unknown [113.200.148.30]) by gateway (Coremail) with SMTP id _____8CxSOH+q1NnIq1SAA--.29183S3; Sat, 07 Dec 2024 09:59:26 +0800 (CST) Received: from linux.localdomain (unknown [113.200.148.30]) by front1 (Coremail) with SMTP id qMiowMBx_uD1q1Nn3Wd5AA--.42544S7; Sat, 07 Dec 2024 09:59:23 +0800 (CST) From: Tiezhu Yang To: Huacai Chen , Josh Poimboeuf , Peter Zijlstra Cc: loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v5 05/10] objtool/LoongArch: Add support for switch table Date: Sat, 7 Dec 2024 09:59:10 +0800 Message-ID: <20241207015915.1159-6-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20241207015915.1159-1-yangtiezhu@loongson.cn> References: <20241207015915.1159-1-yangtiezhu@loongson.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: qMiowMBx_uD1q1Nn3Wd5AA--.42544S7 X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Coremail-Antispam: 1Uk129KBj93XoWxCw4rWw18Wr1fWr43Zw43Jwc_yoWrXryDpF W7C345Kr45XryfWw13ta18uryakws7WFy7Jry3Kr93Aw4aqF1rtF4Sy3Z0yFy5ArsYyr4I qr4fKr4UCF4DAabCm3ZEXasCq-sJn29KB7ZKAUJUUUUr529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUU9jb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_ Gr0_Gr1UM2kKe7AKxVWUXVWUAwAS0I0E0xvYzxvE52x082IY62kv0487Mc804VCY07AIYI kI8VC2zVCFFI0UMc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AKxVWUtVWr XwAv7VC2z280aVAFwI0_Gr0_Cr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI4 8JMxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMxCIbckI1I0E14v26r1Y 6r17MI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7 AF67AKxVWUAVWUtwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26ryj6F1UMIIF0xvE 2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcV C2z280aVAFwI0_Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2Kfnx nUUI43ZEXa7IU8EeHDUUUUU== Content-Type: text/plain; charset="utf-8" The objtool program need to analysis the control flow of each object file generated by compiler toolchain, it needs to know all the locations that a branch instruction may jump into, if a jump table is used, objtool has to correlate the jump instruction with the table. On x86 (which is the only port supported by objtool before LoongArch), there is a relocation type on the jump instruction and directly points to the table. But on LoongArch, the relocation is on another kind of instruction prior to the jump instruction, and also with scheduling it is not very easy to tell the offset of that instruction from the jump instruction. Furthermore, because LoongArch has -fsection-anchors (often enabled at -O1 or above) the relocation may actually points to a section anchor instead of the table itself. The good news is that after continuous analysis and discussion, at last a GCC patch "LoongArch: Add support to annotate tablejump" and a Clang patch "[LoongArch] Add options for annotate tablejump" have been merged into the upstream mainline, the compiler changes make life much easier for switch table support of objtool on LoongArch. By now, there is an additional section ".discard.tablejump_annotate" to store the jump info as pairs of addresses, each pair contains the address of jump instruction and the address of jump table. In order to find switch table, it is easy to parse the relocation section ".rela.discard.tablejump_annotate" to get table_sec and table_offset, the rest process is somehow like x86. Link: https://gcc.gnu.org/git/?p=3Dgcc.git;a=3Dcommit;h=3D0ee028f55640 Link: https://github.com/llvm/llvm-project/commit/4c2c17756739 Signed-off-by: Tiezhu Yang --- tools/objtool/arch/loongarch/special.c | 53 +++++++++++++++++++++++++- 1 file changed, 52 insertions(+), 1 deletion(-) diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/lo= ongarch/special.c index 87230ed570fd..f933f6b5bac6 100644 --- a/tools/objtool/arch/loongarch/special.c +++ b/tools/objtool/arch/loongarch/special.c @@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0-or-later +#include #include =20 bool arch_support_alt_relocation(struct special_alt *special_alt, @@ -8,9 +9,59 @@ bool arch_support_alt_relocation(struct special_alt *speci= al_alt, return false; } =20 +static struct reloc *find_reloc_by_table_annotate(struct objtool_file *fil= e, + struct instruction *insn, + unsigned long *table_size) +{ + struct section *rsec; + struct reloc *reloc; + unsigned long offset; + + rsec =3D find_section_by_name(file->elf, ".rela.discard.tablejump_annotat= e"); + if (!rsec) + return NULL; + + for_each_reloc(rsec, reloc) { + if (reloc->sym->sec->rodata) + continue; + + if (strcmp(insn->sec->name, reloc->sym->sec->name)) + continue; + + offset =3D reloc->sym->offset + reloc_addend(reloc); + if (insn->offset =3D=3D offset) { + reloc++; + return reloc; + } + } + + return NULL; +} + struct reloc *arch_find_switch_table(struct objtool_file *file, struct instruction *insn, unsigned long *table_size) { - return NULL; + struct reloc *annotate_reloc; + struct reloc *rodata_reloc; + struct section *table_sec; + unsigned long table_offset; + + annotate_reloc =3D find_reloc_by_table_annotate(file, insn, table_size); + if (!annotate_reloc) + return NULL; + + table_sec =3D annotate_reloc->sym->sec; + table_offset =3D annotate_reloc->sym->offset + reloc_addend(annotate_relo= c); + + /* + * Each table entry has a rela associated with it. The rela + * should reference text in the same function as the original + * instruction. + */ + rodata_reloc =3D find_reloc_by_dest(file->elf, table_sec, table_offset); + if (!rodata_reloc) + return NULL; + + return rodata_reloc; } --=20 2.42.0