From nobody Fri Dec 19 07:03:46 2025 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 14E777F460 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=1733536771; cv=none; b=TIQI3qW1CgpeWklGxIMMJP7Cb2zC42uXW55aAPbbPnAOepGdba354YsFMHOIFEUdfQ/w5bjDYp1+iWb/Aj93khjACqzOcqCcBMBV+P/8/AT9BI7j/6b4PBibJ2zEpp1STlkjpSK1dUDMWibX/P2h1178WaGXEI/4fx4R3acdx9w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733536771; c=relaxed/simple; bh=eqaduniEyXH5k1KEnULm9YE0PxuykGi4EFID1nVVyOI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SqPbeXsL198i+fUfa5E0dbUiI3rRFPt4e69bQF/T282eiRhlSQWDbATNiw3tMCBldL2GhtTAncOiQ9fIDOFh3egE3MbID28dntKChJC16MzHZ6TYEVhI+vaIQdRb5q32Q/g6Ww/wxG0EM5LVw3N40miXu4uPi1snhL70r6aQIVk= 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+L_q1NnKq1SAA--.29225S3; Sat, 07 Dec 2024 09:59:27 +0800 (CST) Received: from linux.localdomain (unknown [113.200.148.30]) by front1 (Coremail) with SMTP id qMiowMBx_uD1q1Nn3Wd5AA--.42544S9; Sat, 07 Dec 2024 09:59:26 +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 07/10] objtool/LoongArch: Add support for goto table Date: Sat, 7 Dec 2024 09:59:12 +0800 Message-ID: <20241207015915.1159-8-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--.42544S9 X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Coremail-Antispam: 1Uk129KBj93XoWxCw4rWw18Wr1fWr43Zw43Jwc_yoWrXFy5pF W3C345Kr45Zr4Igr47tay09ryaya1IgFy7JrW7t34fAw43Xr1FyF1SvF9IyFWrCrZ5tr4I qr18Kr48CF4DAacCm3ZEXasCq-sJn29KB7ZKAUJUUUUr529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUU9jb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r126r13M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v 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 nUUI43ZEXa7IU8XyCJUUUUU== 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 c1db0c59f9a1..7dbdf3d388a6 100644 --- a/tools/objtool/arch/loongarch/special.c +++ b/tools/objtool/arch/loongarch/special.c @@ -121,6 +121,30 @@ 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) @@ -131,8 +155,12 @@ 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