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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 272F9C5B552 for ; Mon, 9 Jun 2025 19:20:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:To:From:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=dMpt8nW9d3gImYpXx1daCaoXyKaTXCBPPwRYBpS3Jbc=; b=X1YArExoVjPaYn gg+XEtSsEsANkDeoFn9lhUZii8QoAWQRZK/XqkUhu/XaV6zD4GBvCjB1Js5SE6pRSobspxMnXf0rZ vKkLeUmurUUiEcswiD1V6MNU2hk/4SKTyjY4s9hf1sLymuO7b2TNzPu0hPxaMFlEHeN7WvgPGJTLb vyjOYHcF2Chomnwnhva1K+zLNRN2alTnX5+o4Doq9EVfS9D19Cc4DNH0NZSaWCbyMc6ejC1gZd7Ro yVoXMCsaom6iNsxy5cdjsauCntAgAy7JLdRBYq29Z+XB/TYEdk/5ozYLeSRMjPFULgSW0zZJvMKXX aArQfThSHAEerFVjIZyA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uOi2t-000000050RK-1mYQ; Mon, 09 Jun 2025 19:20:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uOgPC-00000004oxK-1Hbp for linux-arm-kernel@lists.infradead.org; Mon, 09 Jun 2025 17:35:31 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D96951515; Mon, 9 Jun 2025 10:35:10 -0700 (PDT) Received: from e137867.cambridge.arm.com (e137867.arm.com [10.1.32.173]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 971573F66E; Mon, 9 Jun 2025 10:35:28 -0700 (PDT) From: Ada Couprie Diaz To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v3 12/13] arm64: debug: split bkpt32 exception entry Date: Mon, 9 Jun 2025 18:34:12 +0100 Message-ID: <20250609173413.132168-13-ada.coupriediaz@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250609173413.132168-1-ada.coupriediaz@arm.com> References: <20250609173413.132168-1-ada.coupriediaz@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250609_103530_435917_F60129BF X-CRM114-Status: GOOD ( 15.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Catalin Marinas , Will Deacon , "Luis Claudio R. Goncalves" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Currently all debug exceptions share common entry code and are routed to `do_debug_exception()`, which calls dynamically-registered handlers for each specific debug exception. This is unfortunate as different debug exceptions have different entry handling requirements, and it would be better to handle these distinct requirements earlier. The BKPT32 exception can only be triggered by a BKPT instruction. Thus, we know that the PC is a legitimate address and isn't being used to train a branch predictor with a bogus address : we don't need to call `arm64_apply_bp_hardening()`. The handler for this exception only pends a signal and doesn't depend on any per-CPU state : we don't need to inhibit preemption, nor do we need to keep the DAIF exceptions masked, so we can unmask them earlier. Split the BKPT32 exception entry and adjust function signatures and its behaviour to match its relaxed constraints compared to other debug exceptions. This replaces the last usage of `el0_dbg()`, so remove it. Signed-off-by: Ada Couprie Diaz --- arch/arm64/include/asm/exception.h | 1 + arch/arm64/kernel/debug-monitors.c | 8 ++++++++ arch/arm64/kernel/entry-common.c | 21 +++++++++------------ 3 files changed, 18 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h index 6500c378d2d3..1c41b6e3d3be 100644 --- a/arch/arm64/include/asm/exception.h +++ b/arch/arm64/include/asm/exception.h @@ -66,6 +66,7 @@ void do_softstep(unsigned long esr, struct pt_regs *regs); void do_watchpoint(unsigned long addr, unsigned long esr, struct pt_regs *regs); void do_brk64(unsigned long esr, struct pt_regs *regs); +void do_bkpt32(unsigned long esr, struct pt_regs *regs); void do_fpsimd_acc(unsigned long esr, struct pt_regs *regs); void do_sve_acc(unsigned long esr, struct pt_regs *regs); void do_sme_acc(unsigned long esr, struct pt_regs *regs); diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index 10f6a8a15954..5490a4f32e85 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -286,6 +286,14 @@ void do_brk64(unsigned long esr, struct pt_regs *regs) } NOKPROBE_SYMBOL(do_brk64); +#ifdef CONFIG_COMPAT +void do_bkpt32(unsigned long esr, struct pt_regs *regs) +{ + arm64_notify_die("aarch32 BKPT", regs, SIGTRAP, TRAP_BRKPT, regs->pc, esr); +} +NOKPROBE_SYMBOL(do_bkpt32); +#endif /* CONFIG_COMPAT */ + bool try_handle_aarch32_break(struct pt_regs *regs) { u32 arm_instr; diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index c0dcca825383..90ee140052c5 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -866,17 +866,6 @@ static void noinstr el0_brk64(struct pt_regs *regs, unsigned long esr) exit_to_user_mode(regs); } -static void noinstr el0_dbg(struct pt_regs *regs, unsigned long esr) -{ - /* Only watchpoints write FAR_EL1, otherwise its UNKNOWN */ - unsigned long far = read_sysreg(far_el1); - - enter_from_user_mode(regs); - do_debug_exception(far, esr, regs); - local_daif_restore(DAIF_PROCCTX); - exit_to_user_mode(regs); -} - static void noinstr el0_svc(struct pt_regs *regs) { enter_from_user_mode(regs); @@ -1037,6 +1026,14 @@ static void noinstr el0_svc_compat(struct pt_regs *regs) exit_to_user_mode(regs); } +static void noinstr el0_bkpt32(struct pt_regs *regs, unsigned long esr) +{ + enter_from_user_mode(regs); + local_daif_restore(DAIF_PROCCTX); + do_bkpt32(esr, regs); + exit_to_user_mode(regs); +} + asmlinkage void noinstr el0t_32_sync_handler(struct pt_regs *regs) { unsigned long esr = read_sysreg(esr_el1); @@ -1080,7 +1077,7 @@ asmlinkage void noinstr el0t_32_sync_handler(struct pt_regs *regs) el0_watchpt(regs, esr); break; case ESR_ELx_EC_BKPT32: - el0_dbg(regs, esr); + el0_bkpt32(regs, esr); break; default: el0_inv(regs, esr); -- 2.43.0