From patchwork Thu Jul 25 08:15:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 11058199 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B76A114DB for ; Thu, 25 Jul 2019 08:16:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A59B6287E2 for ; Thu, 25 Jul 2019 08:16:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9963D287FE; Thu, 25 Jul 2019 08:16:49 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 1F43C287E2 for ; Thu, 25 Jul 2019 08:16:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=O/MEGUMeRw0yy4F8Q+draGQCmUjmBL33BP3fSUcVFeg=; b=Cmf1Qj3rJnnkYm rGPp7sfqrplFiiudaFJ9DjpahtS4MJ4VF7WMgT1b88015A0UO5VchJagqJWC18HvXizAfPXMzfIBd cd26VL1iyCYSF9dPFuGsKVKUF4EsV8mL2OEWJUvkxbqLTFQswIccCu7e+ZRf9/tvZpVaUSH8mltfn 8pHpMa6oCZxKUrd6oqWTS+g2K0NPG/JHGvxQ3whIRKZgiZ2Nr3pucgnt2X6fcys9I/d5Jn+FLs1xf FPrC1BlffSSkztQe2CUXzg3wr283QPIZJmD98uyuiGWsajJ7Z09IHnn5PQDbKQWpDorPisiO7Csjl sc6NyU2Dpb3ImBFro6PA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hqYvS-00042H-W8; Thu, 25 Jul 2019 08:16:36 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hqYut-0003ri-Mk for linux-arm-kernel@lists.infradead.org; Thu, 25 Jul 2019 08:16:05 +0000 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BB0C822BEF; Thu, 25 Jul 2019 08:15:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564042559; bh=zvOD/NhJ1ppVzvGI+gKJSff+TbgtbifjjIqRMfaYbSw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xuJVs+Bl5fZsnaeLJ5Ogn8iQitL7ImTW5M4la/vpTqCk0G1jhsQbZoVSIVqlwnZ1O tT1b+sQqx2Q2ZP8NAm2NO/Q5wbzH7qt+VtNdrnCE9R6egArit5iUNmWRkFLARRf34R jd3w+w5L+uX4PpBjahoidymviPGC3dn5Ff95kkZQ= From: Masami Hiramatsu To: Catalin Marinas , Will Deacon Subject: [PATCH v3 1/4] arm64: kprobes: Recover pstate.D in single-step exception handler Date: Thu, 25 Jul 2019 17:15:54 +0900 Message-Id: <156404255444.2020.3301023170351823334.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <156404254387.2020.886452004489353899.stgit@devnote2> References: <156404254387.2020.886452004489353899.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_011600_499947_0E64498C X-CRM114-Status: GOOD ( 16.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dan Rue , Daniel Diaz , Anders Roxell , Naresh Kamboju , linux-kernel@vger.kernel.org, James Morse , Matt Hart , linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP kprobes manipulates the interrupted PSTATE for single step, and doesn't restore it. Thus, if we put a kprobe where the pstate.D (debug) masked, the mask will be cleared after the kprobe hits. Moreover, in the most complicated case, this can lead a kernel crash with below message when a nested kprobe hits. [ 152.118921] Unexpected kernel single-step exception at EL1 When the 1st kprobe hits, do_debug_exception() will be called. At this point, debug exception (= pstate.D) must be masked (=1). But if another kprobes hits before single-step of the first kprobe (e.g. inside user pre_handler), it unmask the debug exception (pstate.D = 0) and return. Then, when the 1st kprobe setting up single-step, it saves current DAIF, mask DAIF, enable single-step, and restore DAIF. However, since "D" flag in DAIF is cleared by the 2nd kprobe, the single-step exception happens soon after restoring DAIF. This has been introduced by commit 7419333fa15e ("arm64: kprobe: Always clear pstate.D in breakpoint exception handler") To solve this issue, this stores all DAIF bits and restore it after single stepping. Reported-by: Naresh Kamboju Fixes: commit 7419333fa15e ("arm64: kprobe: Always clear pstate.D in breakpoint exception handler") Reviewed-by: James Morse Tested-by: James Morse Signed-off-by: Masami Hiramatsu --- Changes in v3: - Update patch description - move PSR_DAIF_MASK in daifflags.h Changes in v2: - Save and restore all DAIF flags. - Operate pstate directly and remove spsr_set_debug_flag(). --- arch/arm64/include/asm/daifflags.h | 2 ++ arch/arm64/kernel/probes/kprobes.c | 39 +++++------------------------------- 2 files changed, 7 insertions(+), 34 deletions(-) diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h index 987926ed535e..063c964af705 100644 --- a/arch/arm64/include/asm/daifflags.h +++ b/arch/arm64/include/asm/daifflags.h @@ -13,6 +13,8 @@ #define DAIF_PROCCTX 0 #define DAIF_PROCCTX_NOIRQ PSR_I_BIT #define DAIF_ERRCTX (PSR_I_BIT | PSR_A_BIT) +#define DAIF_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT) + /* mask/save/unmask/restore all exceptions, including interrupts. */ static inline void local_daif_mask(void) diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index bd5dfffca272..bf2259651b67 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -167,33 +167,6 @@ static void __kprobes set_current_kprobe(struct kprobe *p) __this_cpu_write(current_kprobe, p); } -/* - * When PSTATE.D is set (masked), then software step exceptions can not be - * generated. - * SPSR's D bit shows the value of PSTATE.D immediately before the - * exception was taken. PSTATE.D is set while entering into any exception - * mode, however software clears it for any normal (none-debug-exception) - * mode in the exception entry. Therefore, when we are entering into kprobe - * breakpoint handler from any normal mode then SPSR.D bit is already - * cleared, however it is set when we are entering from any debug exception - * mode. - * Since we always need to generate single step exception after a kprobe - * breakpoint exception therefore we need to clear it unconditionally, when - * we become sure that the current breakpoint exception is for kprobe. - */ -static void __kprobes -spsr_set_debug_flag(struct pt_regs *regs, int mask) -{ - unsigned long spsr = regs->pstate; - - if (mask) - spsr |= PSR_D_BIT; - else - spsr &= ~PSR_D_BIT; - - regs->pstate = spsr; -} - /* * Interrupts need to be disabled before single-step mode is set, and not * reenabled until after single-step mode ends. @@ -205,17 +178,17 @@ spsr_set_debug_flag(struct pt_regs *regs, int mask) static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, struct pt_regs *regs) { - kcb->saved_irqflag = regs->pstate; + kcb->saved_irqflag = regs->pstate & DAIF_MASK; regs->pstate |= PSR_I_BIT; + /* Unmask PSTATE.D for enabling software step exceptions. */ + regs->pstate &= ~PSR_D_BIT; } static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, struct pt_regs *regs) { - if (kcb->saved_irqflag & PSR_I_BIT) - regs->pstate |= PSR_I_BIT; - else - regs->pstate &= ~PSR_I_BIT; + regs->pstate &= ~DAIF_MASK; + regs->pstate |= kcb->saved_irqflag; } static void __kprobes @@ -252,8 +225,6 @@ static void __kprobes setup_singlestep(struct kprobe *p, set_ss_context(kcb, slot); /* mark pending ss */ - spsr_set_debug_flag(regs, 0); - /* IRQs and single stepping do not mix well. */ kprobes_save_local_irqflag(kcb, regs); kernel_enable_single_step(regs); From patchwork Thu Jul 25 08:16:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 11058201 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 249AC14DB for ; Thu, 25 Jul 2019 08:17:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0F67F287E2 for ; Thu, 25 Jul 2019 08:17:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F0258287FE; Thu, 25 Jul 2019 08:17:15 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 83EDF287E2 for ; Thu, 25 Jul 2019 08:17:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; 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Thu, 25 Jul 2019 08:16:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564042569; bh=lpvJdO31en1wcj0t6J2VjwvDEWvWEgYER3oV5jINp3k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yCBi3i5GNbP+BcE7uzuOnYI8PH4hvoK5Lt/RiP2fH/9Deft2CUfD/wr6auPp71Z1i h1CxJs+S620wwqO1qPW3WJnCdi5LsmUJdPlB8dG7e76rgNhdplMD0xTPuwbK1JuvaL dADXYfUpDnu80TGFFkfpwas36rIkqVTBS6sFk/XQ= From: Masami Hiramatsu To: Catalin Marinas , Will Deacon Subject: [PATCH v3 2/4] arm64: unwind: Prohibit probing on return_address() Date: Thu, 25 Jul 2019 17:16:05 +0900 Message-Id: <156404256479.2020.11810441013424601533.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <156404254387.2020.886452004489353899.stgit@devnote2> References: <156404254387.2020.886452004489353899.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_011610_183447_6DC39D6E X-CRM114-Status: GOOD ( 12.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dan Rue , Daniel Diaz , Anders Roxell , Naresh Kamboju , linux-kernel@vger.kernel.org, Matt Hart , linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Prohibit probing on return_address() and subroutines which is called from return_address(), since the it is invoked from trace_hardirqs_off() which is also kprobe blacklisted. Reported-by: Naresh Kamboju Signed-off-by: Masami Hiramatsu --- Changes in v3: - Fix to use NOKPROBE_SYMBOL() for save_return_addr instead of nokprobe_inline. --- arch/arm64/kernel/return_address.c | 3 +++ arch/arm64/kernel/stacktrace.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c index b21cba90f82d..491184a9f081 100644 --- a/arch/arm64/kernel/return_address.c +++ b/arch/arm64/kernel/return_address.c @@ -8,6 +8,7 @@ #include #include +#include #include #include @@ -29,6 +30,7 @@ static int save_return_addr(struct stackframe *frame, void *d) return 0; } } +NOKPROBE_SYMBOL(save_return_addr); void *return_address(unsigned int level) { @@ -52,3 +54,4 @@ void *return_address(unsigned int level) return NULL; } EXPORT_SYMBOL_GPL(return_address); +NOKPROBE_SYMBOL(return_address); diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 62d395151abe..cd7dab54d17b 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -73,6 +74,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) return 0; } +NOKPROBE_SYMBOL(unwind_frame); void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, int (*fn)(struct stackframe *, void *), void *data) @@ -87,6 +89,7 @@ void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, break; } } +NOKPROBE_SYMBOL(walk_stackframe); #ifdef CONFIG_STACKTRACE struct stack_trace_data { From patchwork Thu Jul 25 08:16:15 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 11058203 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1BAF96C5 for ; Thu, 25 Jul 2019 08:17:48 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 07DBD287E2 for ; Thu, 25 Jul 2019 08:17:48 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EEB1F287FE; 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Thu, 25 Jul 2019 08:16:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564042580; bh=bj3ACEoZ6fDvnv1h+J3z/wBLkf8p5zMTGUIo4Wk+ZbU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EJe39KJtwxbdMs5ze4dzVIZEiyDiuRL8bAF0F1JsVXCckiHtr5y+rfprBxUxYRfUP nNosXfoOTaqmG4u/SGfaHftz0E/P3gZRYNcLye1Ui0NFGgxDKPgF4wbZ07TSp19YlH dirjXWebPq2q/yOXI9cHdibBOCKlkZhT5Hlq+IE0= From: Masami Hiramatsu To: Catalin Marinas , Will Deacon Subject: [PATCH v3 3/4] arm64: Make debug exception handlers visible from RCU Date: Thu, 25 Jul 2019 17:16:15 +0900 Message-Id: <156404257493.2020.7940525305482369976.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <156404254387.2020.886452004489353899.stgit@devnote2> References: <156404254387.2020.886452004489353899.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_011621_575903_13AAAEC2 X-CRM114-Status: GOOD ( 14.70 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dan Rue , Daniel Diaz , Anders Roxell , Naresh Kamboju , linux-kernel@vger.kernel.org, Matt Hart , "Paul E . McKenney" , linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Make debug exceptions visible from RCU so that synchronize_rcu() correctly track the debug exception handler. This also introduces sanity checks for user-mode exceptions as same as x86's ist_enter()/ist_exit(). The debug exception can interrupt in idle task. For example, it warns if we put a kprobe on a function called from idle task as below. The warning message showed that the rcu_read_lock() caused this problem. But actually, this means the RCU is lost the context which is already in NMI/IRQ. /sys/kernel/debug/tracing # echo p default_idle_call >> kprobe_events /sys/kernel/debug/tracing # echo 1 > events/kprobes/enable /sys/kernel/debug/tracing # [ 135.122237] [ 135.125035] ============================= [ 135.125310] WARNING: suspicious RCU usage [ 135.125581] 5.2.0-08445-g9187c508bdc7 #20 Not tainted [ 135.125904] ----------------------------- [ 135.126205] include/linux/rcupdate.h:594 rcu_read_lock() used illegally while idle! [ 135.126839] [ 135.126839] other info that might help us debug this: [ 135.126839] [ 135.127410] [ 135.127410] RCU used illegally from idle CPU! [ 135.127410] rcu_scheduler_active = 2, debug_locks = 1 [ 135.128114] RCU used illegally from extended quiescent state! [ 135.128555] 1 lock held by swapper/0/0: [ 135.128944] #0: (____ptrval____) (rcu_read_lock){....}, at: call_break_hook+0x0/0x178 [ 135.130499] [ 135.130499] stack backtrace: [ 135.131192] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0-08445-g9187c508bdc7 #20 [ 135.131841] Hardware name: linux,dummy-virt (DT) [ 135.132224] Call trace: [ 135.132491] dump_backtrace+0x0/0x140 [ 135.132806] show_stack+0x24/0x30 [ 135.133133] dump_stack+0xc4/0x10c [ 135.133726] lockdep_rcu_suspicious+0xf8/0x108 [ 135.134171] call_break_hook+0x170/0x178 [ 135.134486] brk_handler+0x28/0x68 [ 135.134792] do_debug_exception+0x90/0x150 [ 135.135051] el1_dbg+0x18/0x8c [ 135.135260] default_idle_call+0x0/0x44 [ 135.135516] cpu_startup_entry+0x2c/0x30 [ 135.135815] rest_init+0x1b0/0x280 [ 135.136044] arch_call_rest_init+0x14/0x1c [ 135.136305] start_kernel+0x4d4/0x500 [ 135.136597] So make debug exception visible to RCU can fix this warning. Reported-by: Naresh Kamboju Acked-by: Paul E. McKenney Signed-off-by: Masami Hiramatsu --- Changes in v3: - Make a comment for debug_exception_enter() clearer. --- arch/arm64/mm/fault.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 9568c116ac7f..ed6c55c87fdc 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -777,6 +777,42 @@ void __init hook_debug_fault_code(int nr, debug_fault_info[nr].name = name; } +/* + * In debug exception context, we explicitly disable preemption. + * This serves two purposes: it makes it much less likely that we would + * accidentally schedule in exception context and it will force a warning + * if we somehow manage to schedule by accident. + */ +static void debug_exception_enter(struct pt_regs *regs) +{ + if (user_mode(regs)) { + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); + } else { + /* + * We might have interrupted pretty much anything. In + * fact, if we're a debug exception, we can even interrupt + * NMI processing. We don't want this code makes in_nmi() + * to return true, but we need to notify RCU. + */ + rcu_nmi_enter(); + } + + preempt_disable(); + + /* This code is a bit fragile. Test it. */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "exception_enter didn't work"); +} +NOKPROBE_SYMBOL(debug_exception_enter); + +static void debug_exception_exit(struct pt_regs *regs) +{ + preempt_enable_no_resched(); + + if (!user_mode(regs)) + rcu_nmi_exit(); +} +NOKPROBE_SYMBOL(debug_exception_exit); + #ifdef CONFIG_ARM64_ERRATUM_1463225 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa); @@ -824,6 +860,8 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint, if (interrupts_enabled(regs)) trace_hardirqs_off(); + debug_exception_enter(regs); + if (user_mode(regs) && !is_ttbr0_addr(pc)) arm64_apply_bp_hardening(); @@ -832,6 +870,8 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint, inf->sig, inf->code, (void __user *)pc, esr); } + debug_exception_exit(regs); + if (interrupts_enabled(regs)) trace_hardirqs_on(); } From patchwork Thu Jul 25 08:16:25 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 11058205 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AFF6D13AC for ; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9FEB4287E2 for ; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 90B89287FE; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 3AF8A287E2 for ; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=sPMEhCBq7kyKq00eA01e8EA5Tz9m3ZfLthXVKbgRJFo=; b=pNWv49uB8w+CT3 2YPqUt+3wt/8Si7GOb4R4nyhGSWK1wl4piFjG2a6mGi6ZitCngqZTLSkpdxSEDAHWWtMCLR3IdAEj LXAousCFJ0PxCcs4HM+WzfmE823xMh+25iiCEm3L4jTNyndibgf08eJc3tp/VC8gh9gPswcL+vkoN D8vxR9ik/TbGjESROQBcUD6gWdJqkXh4vAWjE/i4dkAwwKL8ri5n7o1vQmtxga61G5x8+bg0V87cE OF6Wf3SYzYEIMZ0+vz59bj1qQdxkagVKP9LTVjLaym/w0EcJQfSvC3G5zYr71hYR629V8hU605G3n NoHdEpzay4ajMNeKhxvw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hqYwi-0004q3-EM; Thu, 25 Jul 2019 08:17:52 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hqYvO-00043m-MO for linux-arm-kernel@lists.infradead.org; Thu, 25 Jul 2019 08:16:34 +0000 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F351820657; Thu, 25 Jul 2019 08:16:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564042590; bh=U5JsQy9M6SP8lvveNoBirJFjzlJL4CpLUxow+e3YRvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bXA7Rl4m1FdAnDljrSpbxyNrTH2z8iih7Q6dNDIACq/JZ2YEq6oyUBvUr6O4tztZK 0C++xAFHag/f4QcJPiuQfC4xCDiH0v4SAqAfBopH46lPyCOKPKYs/Q4YwUtX8nD+SE p5/l8oVtssyFD3TRWXmyN0IPESb1pyg1C8xqZyeE= From: Masami Hiramatsu To: Catalin Marinas , Will Deacon Subject: [PATCH v3 4/4] arm64: Remove unneeded rcu_read_lock from debug handlers Date: Thu, 25 Jul 2019 17:16:25 +0900 Message-Id: <156404258547.2020.3652813018925680357.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <156404254387.2020.886452004489353899.stgit@devnote2> References: <156404254387.2020.886452004489353899.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_011632_440479_DBA79078 X-CRM114-Status: GOOD ( 11.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dan Rue , Daniel Diaz , Anders Roxell , Naresh Kamboju , linux-kernel@vger.kernel.org, Matt Hart , "Paul E . McKenney" , linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Remove rcu_read_lock()/rcu_read_unlock() from debug exception handlers since we are sure those are not preemptible and interrupts are off. Acked-by: Paul E. McKenney Signed-off-by: Masami Hiramatsu --- arch/arm64/kernel/debug-monitors.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index f8719bd30850..48222a4760c2 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -207,16 +207,16 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr) list = user_mode(regs) ? &user_step_hook : &kernel_step_hook; - rcu_read_lock(); - + /* + * Since single-step exception disables interrupt, this function is + * entirely not preemptible, and we can use rcu list safely here. + */ list_for_each_entry_rcu(hook, list, node) { retval = hook->fn(regs, esr); if (retval == DBG_HOOK_HANDLED) break; } - rcu_read_unlock(); - return retval; } NOKPROBE_SYMBOL(call_step_hook); @@ -305,14 +305,16 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) list = user_mode(regs) ? &user_break_hook : &kernel_break_hook; - rcu_read_lock(); + /* + * Since brk exception disables interrupt, this function is + * entirely not preemptible, and we can use rcu list safely here. + */ list_for_each_entry_rcu(hook, list, node) { unsigned int comment = esr & ESR_ELx_BRK64_ISS_COMMENT_MASK; if ((comment & ~hook->mask) == hook->imm) fn = hook->fn; } - rcu_read_unlock(); return fn ? fn(regs, esr) : DBG_HOOK_ERROR; }