From nobody Sat Nov 23 17:53:53 2024 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9006C19CCEA for ; Tue, 19 Nov 2024 06:57:07 +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=1731999429; cv=none; b=k8eCZSc5LMZhIliFv4XIfmNHf85WkJke5lpEsOGCTc4+Eve3uqpSZUGiTi+CuENmptExu/F1GyC6z6YLgUAGqongraHZk1V/0QvhOE94KhDViuQNH0Re+lDFtf633oaoP3dbNiDoZuzbuXCNl7rxE/KhLlvQNopBpCBaMyNEkTE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731999429; c=relaxed/simple; bh=vo+nyHm4J5Y/nSI2tKzgttln0FQjBwZYWDnBlKp3wlU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SsqAUiEKDZwVCNzr1AqtxLvf91IOXNrmE/f4F7HN8Jv9UaiXd6pxF+RZjweyfBwfQ+ZGeKinLybSeLrMSz0EYqoUXm0ayWm7ZINLanA8C6CuNyt8QQzL0xeV9fodWc8Ie1k9eFd5JHTRNMusx5r8Rgq0IVRzv2hJkENWs5w+Xws= 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 _____8DxG+LCNjxnejZCAA--.64019S3; Tue, 19 Nov 2024 14:57:06 +0800 (CST) Received: from linux.localdomain (unknown [113.200.148.30]) by front1 (Coremail) with SMTP id qMiowMCxDuG4NjxnB_5cAA--.5437S11; Tue, 19 Nov 2024 14:57:05 +0800 (CST) From: Tiezhu Yang To: Huacai Chen , Josh Poimboeuf , Peter Zijlstra Cc: loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v3 09/10] objtool/LoongArch: Add support for goto table Date: Tue, 19 Nov 2024 14:56:54 +0800 Message-ID: <20241119065655.21123-10-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20241119065655.21123-1-yangtiezhu@loongson.cn> References: <20241119065655.21123-1-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: qMiowMCxDuG4NjxnB_5cAA--.5437S11 X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Coremail-Antispam: 1Uk129KBj93XoWxCw4rWw18Wr1fGr1kCw4kuFX_yoWrGryfpF W3C345Kr45Xr4Sgr47tay09ryaya1IgFy7GrWDt34rAw43Xr1rtF1SqF9IyFy8urZ5Ar4I qr4rKr48CF4DAacCm3ZEXasCq-sJn29KB7ZKAUJUUUUr529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUU9Ib4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIEc7CjxVAF wI0_Gr1j6F4UJwAaw2AFwI0_Jrv_JF1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqjxCEc2 xF0cIa020Ex4CE44I27wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_ Wrv_ZF1lYx0Ex4A2jsIE14v26r4j6F4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x 0EwIxGrwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwCFI7km07C267AK xVWUXVWUAwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67 AF67kF1VAFwI0_JF0_Jw1lIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVW7JVWDJwCI 42IY6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCw CI42IY6I8E87Iv67AKxVW8JVWxJwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnI WIevJa73UjIFyTuYvjxUVCD7UUUUU Content-Type: text/plain; charset="utf-8" The objtool program needs 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 on the jump instruction and to the table directly. But on LoongArch, the relocation is on some kind of instruction prior to the jump instruction, and also with scheduling it is not 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 | 28 ++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/lo= ongarch/special.c index 366517deb35b..c5f4217df3a7 100644 --- a/tools/objtool/arch/loongarch/special.c +++ b/tools/objtool/arch/loongarch/special.c @@ -114,6 +114,27 @@ 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) +{ + 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)) + return reloc; + } + + return NULL; +} + struct reloc *arch_find_switch_table(struct objtool_file *file, struct instruction *insn) { @@ -123,8 +144,11 @@ 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); - if (!annotate_reloc) - return NULL; + if (!annotate_reloc) { + annotate_reloc =3D find_reloc_of_rodata_c_jump_table(insn->sec, insn->of= fset); + if (!annotate_reloc) + return NULL; + } =20 table_sec =3D annotate_reloc->sym->sec; if (annotate_reloc->sym->type =3D=3D STT_SECTION) --=20 2.42.0