From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1B38C43441 for ; Tue, 27 Nov 2018 03:51:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96D9120989 for ; Tue, 27 Nov 2018 03:51:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="akJ85xQr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96D9120989 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728494AbeK0OsW (ORCPT ); Tue, 27 Nov 2018 09:48:22 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:36492 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728357AbeK0OsV (ORCPT ); Tue, 27 Nov 2018 09:48:21 -0500 Received: by mail-pg1-f195.google.com with SMTP id n2so7201242pgm.3 for ; Mon, 26 Nov 2018 19:51:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=TleW3aeT6Xi4cOXs3xUyW4j3M/zHD1gzfQ3Vy2FkFYk=; b=akJ85xQr6gnyWGE3F30/+sbUPOZt2tdFS9SeB4qr4iXc7twWyi6Dk43nnUNRguYrCt trkSwDTY/bQ+0yEAW0bqadjUwmJ2Y1iW3imUFzC94z5narmwWP2nYo2XwRMwjQLbPr80 FLMqANVL7pwDqpTYzjXJfShYHN+bTRVLWn7fU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=TleW3aeT6Xi4cOXs3xUyW4j3M/zHD1gzfQ3Vy2FkFYk=; b=sp/ERwJzv1hwAoWo/mLMT/VuouSi6AhW6OVQxA1WFDquafmD/Y/t4VAsbEDRVC195p BRkCRg/NmouYygEZHHcgauKFjdWQ41fNT8oEL6ijB8Cj3JEGVpzyyOvZd4qWd82sC8hP Njz5W/7iCeTK8EVOCWnuk9sM404TCn6S109JqRtFxQy1Px0JVzDhNqr758ww+XuGviKz mogA6AGzq30Z+Ch0rU8LZXJYQuVRw0YYtImUgHPWn/B38T5/fQf/O1m9VAd1hBycHbyz iR/j6J7wiHArPWrRb0kTthqUdlPRxBPXHv+vQfPuDkAGb/+b43eHRrlss4NPC96+PCXM qFOw== X-Gm-Message-State: AA+aEWYD3K2D/5KnMZoiiAXy9NMqhXFQjUkXZzz6HzOgk8/5OWk+aE2s +3apbFdS+5ktMB0i1U8enIxjCw== X-Google-Smtp-Source: AFSGD/V5khO/zUqc7cefdlDDPfJix5FEqRi5/WVNPGLdH3heSIoEDW2U88rf1pQCA81YR6blocj/wA== X-Received: by 2002:a63:7b06:: with SMTP id w6mr27581466pgc.288.1543290711251; Mon, 26 Nov 2018 19:51:51 -0800 (PST) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:c8e0:70d7:4be7:a36]) by smtp.gmail.com with ESMTPSA id i4sm2690112pfj.82.2018.11.26.19.51.50 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 26 Nov 2018 19:51:50 -0800 (PST) From: Douglas Anderson To: Jason Wessel , Daniel Thompson Cc: Will Deacon , kgdb-bugreport@lists.sourceforge.net, Peter Zijlstra , Douglas Anderson , Christophe Leroy , linux-kernel@vger.kernel.org Subject: [PATCH v5 4/4] kdb: Don't back trace on a cpu that didn't round up Date: Mon, 26 Nov 2018 19:51:33 -0800 Message-Id: <20181127035133.225592-5-dianders@chromium.org> X-Mailer: git-send-email 2.20.0.rc0.387.gc7a69e6b6c-goog In-Reply-To: <20181127035133.225592-1-dianders@chromium.org> References: <20181127035133.225592-1-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If you have a CPU that fails to round up and then run 'btc' you'll end up crashing in kdb becaue we dereferenced NULL. Let's add a check. It's wise to also set the task to NULL when leaving the debugger so that if we fail to round up on a later entry into the debugger we won't backtrace a stale task. Signed-off-by: Douglas Anderson --- Changes in v5: None Changes in v4: - Also clear out .debuggerinfo. - Also clear out .debuggerinfo and .task for the master. - Remove clearing out in kdb_stub for offline CPUs; it's now redundant. Changes in v3: - Don't back trace on a cpu that didn't round up new for v3. Changes in v2: None kernel/debug/debug_core.c | 4 ++++ kernel/debug/kdb/kdb_bt.c | 11 ++++++++++- kernel/debug/kdb/kdb_debugger.c | 7 ------- 3 files changed, 14 insertions(+), 8 deletions(-) diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 1fb8b239e567..5cc608de6883 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -592,6 +592,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, arch_kgdb_ops.correct_hw_break(); if (trace_on) tracing_on(); + kgdb_info[cpu].debuggerinfo = NULL; + kgdb_info[cpu].task = NULL; kgdb_info[cpu].exception_state &= ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); kgdb_info[cpu].enter_kgdb--; @@ -724,6 +726,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, if (trace_on) tracing_on(); + kgdb_info[cpu].debuggerinfo = NULL; + kgdb_info[cpu].task = NULL; kgdb_info[cpu].exception_state &= ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); kgdb_info[cpu].enter_kgdb--; diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c index 7921ae4fca8d..7e2379aa0a1e 100644 --- a/kernel/debug/kdb/kdb_bt.c +++ b/kernel/debug/kdb/kdb_bt.c @@ -186,7 +186,16 @@ kdb_bt(int argc, const char **argv) kdb_printf("btc: cpu status: "); kdb_parse("cpu\n"); for_each_online_cpu(cpu) { - sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu)); + void *kdb_tsk = KDB_TSK(cpu); + + /* If a CPU failed to round up we could be here */ + if (!kdb_tsk) { + kdb_printf("WARNING: no task for cpu %ld\n", + cpu); + continue; + } + + sprintf(buf, "btt 0x%px\n", kdb_tsk); kdb_parse(buf); touch_nmi_watchdog(); } diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c index 15e1a7af5dd0..53a0df6e4d92 100644 --- a/kernel/debug/kdb/kdb_debugger.c +++ b/kernel/debug/kdb/kdb_debugger.c @@ -118,13 +118,6 @@ int kdb_stub(struct kgdb_state *ks) kdb_bp_remove(); KDB_STATE_CLEAR(DOING_SS); KDB_STATE_SET(PAGER); - /* zero out any offline cpu data */ - for_each_present_cpu(i) { - if (!cpu_online(i)) { - kgdb_info[i].debuggerinfo = NULL; - kgdb_info[i].task = NULL; - } - } if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) { ks->pass_exception = 1; KDB_FLAG_SET(CATASTROPHIC); -- 2.20.0.rc0.387.gc7a69e6b6c-goog