From nobody Thu Dec 18 00:27:12 2025 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 91D0013D8B4 for ; Tue, 17 Dec 2024 01:09:17 +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=1734397759; cv=none; b=ZbfyLifCpttv4X5GJyXilTn1oDLvXOiS+Wj/7CwsrIiHAaS/NceCV494teKuaK7v0QBjViMWlbReqN0u9Ep6PEauE6fiIZJPwx0OzwSwvdI+uqqWzzN0PdmER5Wti3NlK0afW8uPo+k2mj8eQcDIYAy8PhOX9gxlnXDg+YZM7nU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734397759; c=relaxed/simple; bh=VNhZx1RSKoKpE+uds6M9R6tlg953Re2Ndu7s2C/UrQs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bBi4waKX0+AZiQut25yBgdL8XeTgMdB4wLZckcjcETZq5ibhfc5g0F0hZPUpxM9OE/DptKZml9LYIA8H75pzl9nqcbMBq+d/IRo/tGPxqeplx6qUmnJ+KYzuu0Yu+ItNz5CeiFRoN17UR13dbp8p5d6asRemKRiHKCHB5u9Jgks= 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 _____8BxIK88z2BnO5dXAA--.15964S3; Tue, 17 Dec 2024 09:09:16 +0800 (CST) Received: from linux.localdomain (unknown [113.200.148.30]) by front1 (Coremail) with SMTP id qMiowMDxPEcyz2BnXNeFAA--.16436S8; Tue, 17 Dec 2024 09:09:15 +0800 (CST) From: Tiezhu Yang To: Huacai Chen , Josh Poimboeuf , Peter Zijlstra Cc: loongarch@lists.linux.dev, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 6/9] objtool/LoongArch: Add support for goto table Date: Tue, 17 Dec 2024 09:09:02 +0800 Message-ID: <20241217010905.13054-7-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20241217010905.13054-1-yangtiezhu@loongson.cn> References: <20241217010905.13054-1-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: qMiowMDxPEcyz2BnXNeFAA--.16436S8 X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Coremail-Antispam: 1Uk129KBj93XoWxCw4rWw18Wr1fWr43Zw43Jwc_yoWrXFy5pF W3C345Kr45ZrWSgr47tay09ryaya1IgFy7JrW7t34fAw43Xr1FyF1SvF9IyFWrCrZ5Jr4I qrs5Kr18CF4DAacCm3ZEXasCq-sJn29KB7ZKAUJUUUU7529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUBFb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVWxJVW8Jr1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6r4j6r4UJwAaw2AFwI0_Jrv_JF1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqjxCEc2xF0c Ia020Ex4CE44I27wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Wrv_ ZF1lYx0Ex4A2jsIE14v26r4j6F4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwI xGrwCY1x0262kKe7AKxVWUAVWUtwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWU JVW8JwCFI7km07C267AKxVWUXVWUAwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4 vE14v26r106r1rMI8E67AF67kF1VAFwI0_JF0_Jw1lIxkGc2Ij64vIr41lIxAIcVC0I7IY x2IY67AKxVW5JVW7JwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26c xKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r4j6F4UMIIF0xvEx4A2jsIEc7CjxVAF wI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07jqRRiUUUUU= 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. For the jump table of switch cases, 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, it can parse the additional section ".discard.tablejump_annotate" which stores the jump info as pairs of addresses, each pair contains the address of jump instruction and the address of jump table. For the jump table of computed gotos, it is indeed not easy to implement in the compiler, especially if there is more than one computed goto in a function such as ___bpf_prog_run(). objdump kernel/bpf/core.o shows that there are many table jump instructions in ___bpf_prog_run(), but there are no relocations on the table jump instructions and to the table directly on LoongArch. Without the help of compiler, in order to figure out the address of goto table for the special case of ___bpf_prog_run(), since the instruction sequence is relatively single and stable, it makes sense to add a helper find_reloc_of_rodata_c_jump_table() to find the relocation which points to the section ".rodata..c_jump_table". If find_reloc_by_table_annotate() failed, it means there is no relocation info of switch table address in ".rela.discard.tablejump_annotate", then objtool may find the relocation info of goto table ".rodata..c_jump_table" with find_reloc_of_rodata_c_jump_table(). Signed-off-by: Tiezhu Yang --- tools/objtool/arch/loongarch/special.c | 32 ++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/lo= ongarch/special.c index 4fa6877d5b2b..27c6473608f3 100644 --- a/tools/objtool/arch/loongarch/special.c +++ b/tools/objtool/arch/loongarch/special.c @@ -116,6 +116,30 @@ static struct reloc *find_reloc_by_table_annotate(stru= ct objtool_file *file, return NULL; } =20 +static struct reloc *find_reloc_of_rodata_c_jump_table(struct section *sec, + unsigned long offset, + unsigned long *table_size) +{ + struct section *rsec; + struct reloc *reloc; + + rsec =3D sec->rsec; + if (!rsec) + return NULL; + + for_each_reloc(rsec, reloc) { + if (reloc_offset(reloc) > offset) + break; + + if (!strncmp(reloc->sym->sec->name, ".rodata..c_jump_table", 21)) { + *table_size =3D 0; + return reloc; + } + } + + return NULL; +} + struct reloc *arch_find_switch_table(struct objtool_file *file, struct instruction *insn, unsigned long *table_size) @@ -126,8 +150,12 @@ struct reloc *arch_find_switch_table(struct objtool_fi= le *file, unsigned long table_offset; =20 annotate_reloc =3D find_reloc_by_table_annotate(file, insn, table_size); - if (!annotate_reloc) - return NULL; + if (!annotate_reloc) { + annotate_reloc =3D find_reloc_of_rodata_c_jump_table( + insn->sec, insn->offset, table_size); + if (!annotate_reloc) + return NULL; + } =20 table_sec =3D annotate_reloc->sym->sec; table_offset =3D annotate_reloc->sym->offset + reloc_addend(annotate_relo= c); --=20 2.42.0