From nobody Wed Sep 17 22:34:53 2025 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 0115AC4332F for ; Thu, 15 Dec 2022 14:29:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229939AbiLOO3g (ORCPT ); Thu, 15 Dec 2022 09:29:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229844AbiLOO31 (ORCPT ); Thu, 15 Dec 2022 09:29:27 -0500 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C26ED2CE1B for ; Thu, 15 Dec 2022 06:29:26 -0800 (PST) Received: by mail-pj1-x102f.google.com with SMTP id t11-20020a17090a024b00b0021932afece4so2884534pje.5 for ; Thu, 15 Dec 2022 06:29:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=FuxPSSo3Y0HNcsTRiv4LvjgP5Z2vwZbV6xJtY/KrG9Q=; b=GH+o3xGpbeSkSiHU4ZhFMZ9jkmwSgjEShmS+hkyC7LNuC+FLDPkFdCt39W2pFj3AEq 3As93RhfetUr/a7+HyILd1yr1jzNA4jL3g65bSUssPV3DXNsyRiz7MB4Q1IZMNyHQdX0 KdKsXm+wpuXZumoARgb0dOpHO6JxWQXv3nabufiTcvvLq6C/KV29jIjx6SzomLlD3CiL cdoIvLW6MjHKI32o3jL/M6+DbJaMmhAHE3iNhv8LQxF0tqxqQJjUq/W3D0jzhC0oKL1F tjpZFM6Dv21s0Dp9a6xoJGxJmlCzbNMtmDDN3LEC4KyS+J3XtdDbTB03jQdaw5kLlIce EKjQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=FuxPSSo3Y0HNcsTRiv4LvjgP5Z2vwZbV6xJtY/KrG9Q=; b=2YcjGme5bEdqa0NkgrMRS7FEf5Xz9F4Q3GjsTTawiopblKITzAs3dlx4MyobPWQjo+ W19NMJUYySHK9rRCu+HQQ25ZQQy61ABsqCj4NClF+mpLogBhrVxxLLDaT+1M5UZEhfwb aR3FFaXTDwkd/+a5L4ViwUyv9s/0e43ooHdELAasL/irMHQ1D+HhdaIM+vLCDG0DeDQz nby7rZ6LrbQ0LoGgXghRlMtnzzZPf5x94PcTOxNIQ0wtZhj/pJ++DsCVoB+FH+JzTkh0 pG3wFYrgeKBVRDRqxcD8b2+BsjUlGEWh+jxV0yLHl+Z6md+iHoFqTp0HUA0qE3UtPyzH wiJQ== X-Gm-Message-State: ANoB5pkJLYnqkDVYLXlr1dalQs3ejywDHyODcvtLlawfnUFZ7lgXXyOO JlkZ0u7nCxdISDL+LG9V4iIY2Q== X-Google-Smtp-Source: AA0mqf6Fe2RSsBxw7IoI8CLHsSgyH2bi7UGfEUMoabxqwYlOQ8jx9uJ48AQ0FQtFljyOfs1EiF8dQA== X-Received: by 2002:a17:903:251:b0:189:7891:574d with SMTP id j17-20020a170903025100b001897891574dmr32757233plh.47.1671114566259; Thu, 15 Dec 2022 06:29:26 -0800 (PST) Received: from sumit-X1.. ([223.178.208.45]) by smtp.gmail.com with ESMTPSA id z1-20020a170902d54100b0017f5ad327casm3922010plf.103.2022.12.15.06.29.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Dec 2022 06:29:25 -0800 (PST) From: Sumit Garg To: will@kernel.org, catalin.marinas@arm.com, daniel.thompson@linaro.org, dianders@chromium.org Cc: liwei391@huawei.com, mark.rutland@arm.com, mhiramat@kernel.org, maz@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sumit Garg Subject: [PATCH v4 2/2] arm64: kgdb: Set PSTATE.SS to 1 to re-enable single-step Date: Thu, 15 Dec 2022 19:59:03 +0530 Message-Id: <20221215142903.2624142-3-sumit.garg@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221215142903.2624142-1-sumit.garg@linaro.org> References: <20221215142903.2624142-1-sumit.garg@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Currently only the first attempt to single-step has any effect. After that all further stepping remains "stuck" at the same program counter value. Refer to the ARM Architecture Reference Manual (ARM DDI 0487E.a) D2.12, PSTATE.SS=3D1 should be set at each step before transferring the PE to the 'Active-not-pending' state. The problem here is PSTATE.SS=3D1 is not set since the second single-step. After the first single-step, the PE transferes to the 'Inactive' state, with PSTATE.SS=3D0 and MDSCR.SS=3D1, thus PSTATE.SS won't be set to 1 due to kernel_active_single_step()=3Dtrue. Then the PE transferes to the 'Active-pending' state when ERET and returns to the debugger by step exception. Before this patch: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Entering kdb (current=3D0xffff3376039f0000, pid 1) on processor 0 due to Ke= yboard Entry [0]kdb> [0]kdb> [0]kdb> bp write_sysrq_trigger Instruction(i) BP #0 at 0xffffa45c13d09290 (write_sysrq_trigger) is enabled addr at ffffa45c13d09290, hardtype=3D0 installed=3D0 [0]kdb> go $ echo h > /proc/sysrq-trigger Entering kdb (current=3D0xffff4f7e453f8000, pid 175) on processor 1 due to = Breakpoint @ 0xffffad651a309290 [1]kdb> ss Entering kdb (current=3D0xffff4f7e453f8000, pid 175) on processor 1 due to = SS trap @ 0xffffad651a309294 [1]kdb> ss Entering kdb (current=3D0xffff4f7e453f8000, pid 175) on processor 1 due to = SS trap @ 0xffffad651a309294 [1]kdb> After this patch: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Entering kdb (current=3D0xffff6851c39f0000, pid 1) on processor 0 due to Ke= yboard Entry [0]kdb> bp write_sysrq_trigger Instruction(i) BP #0 at 0xffffc02d2dd09290 (write_sysrq_trigger) is enabled addr at ffffc02d2dd09290, hardtype=3D0 installed=3D0 [0]kdb> go $ echo h > /proc/sysrq-trigger Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = Breakpoint @ 0xffffc02d2dd09290 [1]kdb> ss Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = SS trap @ 0xffffc02d2dd09294 [1]kdb> ss Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = SS trap @ 0xffffc02d2dd09298 [1]kdb> ss Entering kdb (current=3D0xffff6851c53c1840, pid 174) on processor 1 due to = SS trap @ 0xffffc02d2dd0929c [1]kdb> Fixes: 44679a4f142b ("arm64: KGDB: Add step debugging support") Co-developed-by: Wei Li Signed-off-by: Wei Li Signed-off-by: Sumit Garg Tested-by: Douglas Anderson --- arch/arm64/include/asm/debug-monitors.h | 1 + arch/arm64/kernel/debug-monitors.c | 5 +++++ arch/arm64/kernel/kgdb.c | 2 ++ 3 files changed, 8 insertions(+) diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/a= sm/debug-monitors.h index 7b7e05c02691..ce3875ad5cd3 100644 --- a/arch/arm64/include/asm/debug-monitors.h +++ b/arch/arm64/include/asm/debug-monitors.h @@ -104,6 +104,7 @@ void user_regs_reset_single_step(struct user_pt_regs *r= egs, void kernel_enable_single_step(struct pt_regs *regs); void kernel_disable_single_step(void); int kernel_active_single_step(void); +void kernel_regs_reset_single_step(struct pt_regs *regs); =20 #ifdef CONFIG_HAVE_HW_BREAKPOINT int reinstall_suspended_bps(struct pt_regs *regs); diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-m= onitors.c index 3da09778267e..9af898b22ed4 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -438,6 +438,11 @@ int kernel_active_single_step(void) } NOKPROBE_SYMBOL(kernel_active_single_step); =20 +void kernel_regs_reset_single_step(struct pt_regs *regs) +{ + set_regs_spsr_ss(regs); +} + /* ptrace API */ void user_enable_single_step(struct task_struct *task) { diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c index cda9c1e9864f..51f204bbcf87 100644 --- a/arch/arm64/kernel/kgdb.c +++ b/arch/arm64/kernel/kgdb.c @@ -224,6 +224,8 @@ int kgdb_arch_handle_exception(int exception_vector, in= t signo, */ if (!kernel_active_single_step()) kernel_enable_single_step(linux_regs); + else + kernel_regs_reset_single_step(linux_regs); err =3D 0; break; default: --=20 2.34.1