From patchwork Mon Aug 15 17:41:56 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 1068652 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by demeter1.kernel.org (8.14.4/8.14.4) with ESMTP id p7FHhIDA020567 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 15 Aug 2011 17:43:39 GMT Received: from canuck.infradead.org ([2001:4978:20e::1]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1Qt1BY-0004Jx-1w; Mon, 15 Aug 2011 17:42:50 +0000 Received: from localhost ([127.0.0.1] helo=canuck.infradead.org) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Qt1BX-00075E-CF; Mon, 15 Aug 2011 17:42:47 +0000 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Qt1Av-0006xH-Fw for linux-arm-kernel@lists.infradead.org; Mon, 15 Aug 2011 17:42:10 +0000 Received: from localhost.localdomain (e102144-lin.cambridge.arm.com [10.1.69.60]) by cam-admin0.cambridge.arm.com (8.12.6/8.12.6) with ESMTP id p7FHf915009946; Mon, 15 Aug 2011 18:41:09 +0100 (BST) From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 4/5] ARM: hw_breakpoint: trap undef instruction exceptions in reset_ctrl_regs Date: Mon, 15 Aug 2011 18:41:56 +0100 Message-Id: <1313430117-3439-5-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 1.7.0.4 MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1313430117-3439-1-git-send-email-will.deacon@arm.com> References: <1313430117-3439-1-git-send-email-will.deacon@arm.com> X-CRM114-Version: 20090807-BlameThorstenAndJenny ( TRE 0.7.6 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20110815_134209_795956_D94BE713 X-CRM114-Status: GOOD ( 19.99 ) X-Spam-Score: -3.3 (---) X-Spam-Report: SpamAssassin version 3.3.1 on canuck.infradead.org summary: Content analysis details: (-3.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [217.140.96.50 listed in list.dnswl.org] -1.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain Cc: Will Deacon X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Mon, 15 Aug 2011 17:43:39 +0000 (UTC) The ARM debug registers can only be accessed if the DBGSWENABLE signal to the core is driven HIGH by the DAP. The architecture does not provide a way to detect the value of this signal, so the best we can do is register an undef_hook to trap debug register co-processor accesses and then fail if the trap is taken. Signed-off-by: Will Deacon --- arch/arm/kernel/hw_breakpoint.c | 46 +++++++++++++++++++++++++++++++------- 1 files changed, 37 insertions(+), 9 deletions(-) diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 448143e..64ac5c6 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -857,11 +857,31 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr, /* * One-time initialisation. */ -static void reset_ctrl_regs(void *info) +static cpumask_t debug_err_mask; + +static int debug_reg_trap(struct pt_regs *regs, unsigned int instr) +{ + int cpu = smp_processor_id(); + + pr_warning("Debug register access (0x%x) caused undefined instruction on CPU %d\n", + instr, cpu); + + /* Set the error flag for this CPU and skip the faulting instruction. */ + cpumask_set_cpu(cpu, &debug_err_mask); + instruction_pointer(regs) += 4; + return 0; +} + +static struct undef_hook debug_reg_hook = { + .instr_mask = 0x0fe80f10, + .instr_val = 0x0e000e10, + .fn = debug_reg_trap, +}; + +static void reset_ctrl_regs(void *unused) { int i, raw_num_brps, err = 0, cpu = smp_processor_id(); u32 dbg_power; - cpumask_t *cpumask = info; /* * v7 debug contains save and restore registers so that debug state @@ -893,7 +913,7 @@ static void reset_ctrl_regs(void *info) if (err) { pr_warning("CPU %d debug is powered down!\n", cpu); - cpumask_or(cpumask, cpumask, cpumask_of(cpu)); + cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu)); return; } @@ -932,6 +952,7 @@ static int __cpuinit dbg_reset_notify(struct notifier_block *self, { if (action == CPU_ONLINE) smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1); + return NOTIFY_OK; } @@ -942,7 +963,6 @@ static struct notifier_block __cpuinitdata dbg_reset_nb = { static int __init arch_hw_breakpoint_init(void) { u32 dscr; - cpumask_t cpumask = { CPU_BITS_NONE }; debug_arch = get_debug_arch(); @@ -955,21 +975,29 @@ static int __init arch_hw_breakpoint_init(void) core_num_brps = get_num_brps(); core_num_wrps = get_num_wrps(); - pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n", - core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " : - "", core_num_wrps); + /* + * We need to tread carefully here because DBGSWENABLE may be + * driven low on this core and there isn't an architected way to + * determine that. + */ + register_undef_hook(&debug_reg_hook); /* * Reset the breakpoint resources. We assume that a halting * debugger will leave the world in a nice state for us. */ - on_each_cpu(reset_ctrl_regs, &cpumask, 1); - if (!cpumask_empty(&cpumask)) { + on_each_cpu(reset_ctrl_regs, NULL, 1); + unregister_undef_hook(&debug_reg_hook); + if (!cpumask_empty(&debug_err_mask)) { core_num_brps = 0; core_num_wrps = 0; return 0; } + pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n", + core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " : + "", core_num_wrps); + ARM_DBG_READ(c1, 0, dscr); if (dscr & ARM_DSCR_HDBGEN) { max_watchpoint_len = 4;