From nobody Tue Dec 2 00:26:06 2025 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 726D728C862 for ; Tue, 25 Nov 2025 06:33:55 +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=1764052441; cv=none; b=tQs/SX80RcyDvvC5yKhm0ZkagfQ7PwmvH+Bs05/2D3ktJLYCZNOtKQewtiHz9A7B9lS/BSrJdW1ho2219vEUJoB3U86WoGyigR3re8tffvWhwp83Gkd5IOW71OAZmM7qzVi8uOAeVcArd2YDLsZlEei5L+C6rtH+vqc08SCW034= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764052441; c=relaxed/simple; bh=itml4WuMwKy7zy/ENIm4fPju3xgWXyBBNowvVqsOXd0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=pYORKT65236q44Yq2sBt9S1tzBNLlVfC50H7tsMh/F143UwFTxydm0VfoYdhSCks054HYdJo9i3MHcOSJhqBj6FlXsHRmeoaaPgDCGE/xJSVUbO1ynQ+UxY8tUNGnLcg4bvHhhxY/8BM7a2Ln+sUgjDCsNnaGImH6aztN4CodyM= 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 _____8Dxb_DKTSVp2cgnAA--.21111S3; Tue, 25 Nov 2025 14:33:46 +0800 (CST) Received: from linux.localdomain (unknown [113.200.148.30]) by front1 (Coremail) with SMTP id qMiowJDx_8PGTSVpc2w+AQ--.40949S2; Tue, 25 Nov 2025 14:33:43 +0800 (CST) From: Tiezhu Yang To: Huacai Chen Cc: Xi Zhang , Xianglai Li , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v1] LoongArch: Handle special PC in unwind_next_frame() Date: Tue, 25 Nov 2025 14:33:27 +0800 Message-ID: <20251125063327.31586-1-yangtiezhu@loongson.cn> X-Mailer: git-send-email 2.42.0 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: qMiowJDx_8PGTSVpc2w+AQ--.40949S2 X-CM-SenderInfo: p1dqw3xlh2x3gn0dqz5rrqw2lrqou0/ X-Coremail-Antispam: 1Uk129KBj93XoW7Kry3Gr1rtF1kWrWxAw1rKrX_yoW8KrWxpF yDArn5Kr48GF90qa4DC34xuryDXw4DG34agasrt34ruFn0v3W3Xw10vwnrZa1qq3yvgayI qF95Cry2kayUAabCm3ZEXasCq-sJn29KB7ZKAUJUUUU5529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUkYb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Jr0_Gr1l84ACjcxK6I8E87Iv67AKxVWxJVW8Jr1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6r4UJVWxJr1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqjxCEc2xF0cIa020Ex4CE44I27w Aqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jrv_JF1lYx0Ex4A2jsIE 14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwCF04k20xvY0x 0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E 7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_JF0_Jw1lIxkGc2Ij64vIr41lIxAIcV C0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr0_Gr1lIxAIcVCF 04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7 CjxVAFwI0_Jr0_GrUvcSsGvfC2KfnxnUUI43ZEXa7IU8zwZ7UUUUU== Content-Type: text/plain; charset="utf-8" When running virtual machine before testing the kernel live patching with "modprobe livepatch-sample", there is a timeout over 15 seconds, the dmesg command shows "unreliable stack" for user tasks in debug mode. The "unreliable stack" is because it can not unwind from kvm_handle_exit() to its previous frame kvm_exc_entry() due to the PC is not a valid kernel address, the root cause is that the code of kvm_exc_entry() was copied to the DMW area in kvm_loongarch_env_init(), so it should check the PC range and then finish unwinding for this special case. How to test: (1) Update kernel with LIVEPATCH git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.= git cd linux && make mrproper defconfig scripts/config -e FTRACE -e FUNCTION_TRACER \ -e LIVEPATCH -e SAMPLES -m SAMPLE_LIVEPATCH make olddefconfig all -j"$(nproc)" sudo make modules_install sudo make install sudo reboot (2) Set up a VM with "-accel kvm", no need to specify kernel and initrd sudo yum -y install edk2-loongarch64 qemu qemu-system-loongarch64 -serial stdio \ -machine virt -cpu la464 -smp 8 -m 4G \ -bios /usr/share/edk2/loongarch64/QEMU_EFI.fd \ -nodefaults -no-reboot -nographic -accel kvm (3) Test the kernel live patching cat /proc/cmdline sudo modprobe livepatch-sample cat /proc/cmdline sudo sh -c "echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled" sudo rmmod livepatch_sample cat /proc/cmdline dmesg -T Cc: stable@vger.kernel.org # v6.9+ Fixes: cb8a2ef0848c ("LoongArch: Add ORC stack unwinder support") Reported-by: Xi Zhang Reported-by: Xianglai Li Signed-off-by: Tiezhu Yang --- arch/loongarch/kernel/unwind_orc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/loongarch/kernel/unwind_orc.c b/arch/loongarch/kernel/unw= ind_orc.c index 0d5fa64a2225..1d60a593479a 100644 --- a/arch/loongarch/kernel/unwind_orc.c +++ b/arch/loongarch/kernel/unwind_orc.c @@ -506,6 +506,9 @@ bool unwind_next_frame(struct unwind_state *state) goto err; } =20 + if (pc >=3D (unsigned long)_end && pc < (unsigned long)XKVRANGE) + goto end; + state->pc =3D bt_address(pc); if (!state->pc) { pr_err("cannot find unwind pc at %p\n", (void *)pc); --=20 2.42.0