From nobody Sat Apr 11 14:13:30 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1FF28C19F2D for ; Thu, 11 Aug 2022 07:42:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234384AbiHKHmM (ORCPT ); Thu, 11 Aug 2022 03:42:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234439AbiHKHmE (ORCPT ); Thu, 11 Aug 2022 03:42:04 -0400 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3826F8E44E; Thu, 11 Aug 2022 00:42:01 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R501e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=xianting.tian@linux.alibaba.com;NM=1;PH=DS;RN=23;SR=0;TI=SMTPD_---0VLyDALP_1660203715; Received: from localhost(mailfrom:xianting.tian@linux.alibaba.com fp:SMTPD_---0VLyDALP_1660203715) by smtp.aliyun-inc.com; Thu, 11 Aug 2022 15:41:56 +0800 From: Xianting Tian To: paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, anup@brainfault.org, heiko@sntech.de, guoren@kernel.org, mick@ics.forth.gr, alexandre.ghiti@canonical.com, bhe@redhat.com, vgoyal@redhat.com, dyoung@redhat.com, corbet@lwn.net, Conor.Dooley@microchip.com Cc: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, crash-utility@redhat.com, heinrich.schuchardt@canonical.com, k-hagio-ab@nec.com, hschauhan@nulltrace.org, yixun.lan@gmail.com, Xianting Tian Subject: [PATCH V6 2/6] RISC-V: Fixup get incorrect user mode PC for kernel mode regs Date: Thu, 11 Aug 2022 15:41:46 +0800 Message-Id: <20220811074150.3020189-3-xianting.tian@linux.alibaba.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220811074150.3020189-1-xianting.tian@linux.alibaba.com> References: <20220811074150.3020189-1-xianting.tian@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" When use 'echo c > /proc/sysrq-trigger' to trigger kdump, riscv_crash_save_= regs() will be called to save regs for vmcore, we found "epc" value 00ffffffa55374= 00 is not a valid kernel virtual address, but is a user virtual address. Other regs(eg, ra, sp, gp...) are correct kernel virtual address. Actually 0x00ffffffb0dd9400 is the user mode PC of 'PID: 113 Comm: sh', whi= ch is saved in the task's stack. [ 21.201701] CPU: 0 PID: 113 Comm: sh Kdump: loaded Not tainted 5.18.9 #45 [ 21.201979] Hardware name: riscv-virtio,qemu (DT) [ 21.202160] epc : 00ffffffa5537400 ra : ffffffff80088640 sp : ff20000010= 333b90 [ 21.202435] gp : ffffffff810dde38 tp : ff6000000226c200 t0 : ffffffff80= 32be7c [ 21.202707] t1 : 0720072007200720 t2 : 30203a7375746174 s0 : ff20000010= 333cf0 [ 21.202973] s1 : 0000000000000000 a0 : ff20000010333b98 a1 : 0000000000= 000001 [ 21.203243] a2 : 0000000000000010 a3 : 0000000000000000 a4 : 28c8f0aeff= ea4e00 [ 21.203519] a5 : 28c8f0aeffea4e00 a6 : 0000000000000009 a7 : ffffffff80= 35c9b8 [ 21.203794] s2 : ffffffff810df0a8 s3 : ffffffff810df718 s4 : ff20000010= 333b98 [ 21.204062] s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80= c4a468 [ 21.204331] s8 : 00ffffffef451410 s9 : 0000000000000007 s10: 00aaaaaac0= 510700 [ 21.204606] s11: 0000000000000001 t3 : ff60000001218f00 t4 : ff60000001= 218f00 [ 21.204876] t5 : ff60000001218000 t6 : ff200000103338b8 [ 21.205079] status: 0000000200000020 badaddr: 0000000000000000 cause: 00= 00000000000008 With the incorrect PC, the backtrace showed by crash tool as below, the fir= st stack frame is abnormal, crash> bt PID: 113 TASK: ff60000002269600 CPU: 0 COMMAND: "sh" #0 [ff2000001039bb90] __efistub_.Ldebug_info0 at 00ffffffa5537400 <-- Abno= rmal #1 [ff2000001039bcf0] panic at ffffffff806578ba #2 [ff2000001039bd50] sysrq_reset_seq_param_set at ffffffff8038c030 #3 [ff2000001039bda0] __handle_sysrq at ffffffff8038c5f8 #4 [ff2000001039be00] write_sysrq_trigger at ffffffff8038cad8 #5 [ff2000001039be20] proc_reg_write at ffffffff801b7edc #6 [ff2000001039be40] vfs_write at ffffffff80152ba6 #7 [ff2000001039be80] ksys_write at ffffffff80152ece #8 [ff2000001039bed0] sys_write at ffffffff80152f46 With the patch, we can get current kernel mode PC, the output as below, [ 17.607658] CPU: 0 PID: 113 Comm: sh Kdump: loaded Not tainted 5.18.9 #42 [ 17.607937] Hardware name: riscv-virtio,qemu (DT) [ 17.608150] epc : ffffffff800078f8 ra : ffffffff8008862c sp : ff20000010= 333b90 [ 17.608441] gp : ffffffff810dde38 tp : ff6000000226c200 t0 : ffffffff80= 32be68 [ 17.608741] t1 : 0720072007200720 t2 : 666666666666663c s0 : ff20000010= 333cf0 [ 17.609025] s1 : 0000000000000000 a0 : ff20000010333b98 a1 : 0000000000= 000001 [ 17.609320] a2 : 0000000000000010 a3 : 0000000000000000 a4 : 0000000000= 000000 [ 17.609601] a5 : ff60000001c78000 a6 : 000000000000003c a7 : ffffffff80= 35c9a4 [ 17.609894] s2 : ffffffff810df0a8 s3 : ffffffff810df718 s4 : ff20000010= 333b98 [ 17.610186] s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80= c4a468 [ 17.610469] s8 : 00ffffffca281410 s9 : 0000000000000007 s10: 00aaaaaab5= bb6700 [ 17.610755] s11: 0000000000000001 t3 : ff60000001218f00 t4 : ff60000001= 218f00 [ 17.611041] t5 : ff60000001218000 t6 : ff20000010333988 [ 17.611255] status: 0000000200000020 badaddr: 0000000000000000 cause: 00= 00000000000008 With the correct PC, the backtrace showed by crash tool as below, crash> bt PID: 113 TASK: ff6000000226c200 CPU: 0 COMMAND: "sh" #0 [ff20000010333b90] riscv_crash_save_regs at ffffffff800078f8 <--- Normal #1 [ff20000010333cf0] panic at ffffffff806578c6 #2 [ff20000010333d50] sysrq_reset_seq_param_set at ffffffff8038c03c #3 [ff20000010333da0] __handle_sysrq at ffffffff8038c604 #4 [ff20000010333e00] write_sysrq_trigger at ffffffff8038cae4 #5 [ff20000010333e20] proc_reg_write at ffffffff801b7ee8 #6 [ff20000010333e40] vfs_write at ffffffff80152bb2 #7 [ff20000010333e80] ksys_write at ffffffff80152eda #8 [ff20000010333ed0] sys_write at ffffffff80152f52 Fixes: e53d28180d4d ("RISC-V: Add kdump support") Co-developed-by: Guo Ren Signed-off-by: Xianting Tian --- arch/riscv/kernel/crash_save_regs.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/kernel/crash_save_regs.S b/arch/riscv/kernel/crash_= save_regs.S index 7832fb763aba..b2a1908c0463 100644 --- a/arch/riscv/kernel/crash_save_regs.S +++ b/arch/riscv/kernel/crash_save_regs.S @@ -44,7 +44,7 @@ SYM_CODE_START(riscv_crash_save_regs) REG_S t6, PT_T6(a0) /* x31 */ =20 csrr t1, CSR_STATUS - csrr t2, CSR_EPC + auipc t2, 0x0 csrr t3, CSR_TVAL csrr t4, CSR_CAUSE =20 --=20 2.17.1