From nobody Thu Dec 18 10:05:15 2025 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9AEA41FAC49 for ; Tue, 11 Feb 2025 11:50:26 +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=1739274629; cv=none; b=NY8JibR5vWMH6DfbO6hj9VOpIOph48PPKk/IgYZJPssYVidJHoKZGw8hsogRoeS/ofh1ntjbWYfiPajLwhKSXS3yV6fJkNhMHyJxVC3qFa0F4lhGXSAk9sVR7zO4Q+gT6OKPChqdC64for760MWq5DnzzTtymITzzb3vgvwzq5k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739274629; c=relaxed/simple; bh=lFIV0tp5kTgIjQqFoy4l3pEQtpR+NFoU2d6a4ga6vfE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BfD9iAGIBatMPBXWoQlCyhYtm5GWLfIJqUHujsjQK4I6foSaBEMDBXNIJa9lc82G8lHoTTLGzrTTozWswWMXcFrtuSYCZqz0DiTfIBl+qzHC4YPclJINXuGgRDc5jaiqTX41sStpYP3LCeFVmAnR/RUXtNNvl+4i+QBjCkvFWqk= 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 _____8BxJHCAOatnYCJyAA--.2042S3; Tue, 11 Feb 2025 19:50:24 +0800 (CST) Received: from linux.localdomain (unknown [113.200.148.30]) by front1 (Coremail) with SMTP id qMiowMBx3MR6OatnNPMLAA--.43600S6; Tue, 11 Feb 2025 19:50:22 +0800 (CST) From: Tiezhu Yang To: Josh Poimboeuf , Peter Zijlstra , Huacai Chen Cc: loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v7 4/7] objtool/LoongArch: Add support for switch table Date: Tue, 11 Feb 2025 19:50:13 +0800 Message-ID: <20250211115016.26913-5-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20250211115016.26913-1-yangtiezhu@loongson.cn> References: <20250211115016.26913-1-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: qMiowMBx3MR6OatnNPMLAA--.43600S6 X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Coremail-Antispam: 1Uk129KBj93XoW3GF1DXF4rur4xuw43Cw43XFc_yoWxZw43pF y3C3s8trWYqFyrWr47tF4I9rW3Aw4kWry7Gr9xG34rA343tryFqayavasIkas5GrZ8Ar4I qrW5Kr1xCF4kAFXCm3ZEXasCq-sJn29KB7ZKAUJUUUUr529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUvEb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_ GcCE3s1ln4kS14v26r1Y6r17M2AIxVAIcxkEcVAq07x20xvEncxIr21l57IF6xkI12xvs2 x26I8E6xACxx1l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1q6rW5 McIj6I8E87Iv67AKxVW8JVWxJwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr4 1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1l4IxYO2xFxVAFwI0_Jrv_ JF1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17 CE14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Gr0_Xr1lIxAIcVC0 I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I 8E87Iv67AKxVW8JVWxJwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73 UjIFyTuYvjxU4AhLUUUUU 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. Additionally, it needs to get each table size. When compiling on LoongArch, there are unsorted table offsets of rodata if there exist many jump tables, it will get the wrong table end and find the wrong table jump destination instructions in add_jump_table(). Sort the rodata table offset by parsing ".rela.discard.tablejump_annotate" and then get each table size of rodata corresponded with each table jump instruction, it is used to check the table end and will break the process when parsing ".rela.rodata" to avoid getting the wrong jump destination instructions. 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 | 131 ++++++++++++++++++++++++- 1 file changed, 130 insertions(+), 1 deletion(-) diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/lo= ongarch/special.c index 87230ed570fd..4fa6877d5b2b 100644 --- a/tools/objtool/arch/loongarch/special.c +++ b/tools/objtool/arch/loongarch/special.c @@ -1,5 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-or-later +#include #include +#include =20 bool arch_support_alt_relocation(struct special_alt *special_alt, struct instruction *insn, @@ -8,9 +10,136 @@ bool arch_support_alt_relocation(struct special_alt *spe= cial_alt, return false; } =20 +struct table_info { + struct list_head jump_info; + unsigned long insn_offset; + unsigned long rodata_offset; +}; + +static void get_rodata_table_size_by_table_annotate(struct objtool_file *f= ile, + struct instruction *insn, + unsigned long *table_size) +{ + struct section *rsec; + struct reloc *reloc; + struct list_head table_list; + struct table_info *orig_table; + struct table_info *next_table; + unsigned long tmp_insn_offset; + unsigned long tmp_rodata_offset; + + rsec =3D find_section_by_name(file->elf, ".rela.discard.tablejump_annotat= e"); + if (!rsec) + return; + + INIT_LIST_HEAD(&table_list); + + for_each_reloc(rsec, reloc) { + orig_table =3D malloc(sizeof(struct table_info)); + if (!orig_table) { + WARN("malloc failed"); + return; + } + + orig_table->insn_offset =3D reloc->sym->offset + reloc_addend(reloc); + reloc++; + orig_table->rodata_offset =3D reloc->sym->offset + reloc_addend(reloc); + + list_add_tail(&orig_table->jump_info, &table_list); + + if (reloc_idx(reloc) + 1 =3D=3D sec_num_entries(rsec)) + break; + } + + list_for_each_entry(orig_table, &table_list, jump_info) { + next_table =3D list_next_entry(orig_table, jump_info); + list_for_each_entry_from(next_table, &table_list, jump_info) { + if (next_table->rodata_offset < orig_table->rodata_offset) { + tmp_insn_offset =3D next_table->insn_offset; + tmp_rodata_offset =3D next_table->rodata_offset; + next_table->insn_offset =3D orig_table->insn_offset; + next_table->rodata_offset =3D orig_table->rodata_offset; + orig_table->insn_offset =3D tmp_insn_offset; + orig_table->rodata_offset =3D tmp_rodata_offset; + } + } + } + + list_for_each_entry(orig_table, &table_list, jump_info) { + if (insn->offset =3D=3D orig_table->insn_offset) { + next_table =3D list_next_entry(orig_table, jump_info); + if (&next_table->jump_info =3D=3D &table_list) { + *table_size =3D 0; + return; + } + + while (next_table->rodata_offset =3D=3D orig_table->rodata_offset) { + next_table =3D list_next_entry(next_table, jump_info); + if (&next_table->jump_info =3D=3D &table_list) { + *table_size =3D 0; + return; + } + } + + *table_size =3D next_table->rodata_offset - orig_table->rodata_offset; + } + } +} + +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) { + get_rodata_table_size_by_table_annotate(file, insn, table_size); + 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