From patchwork Thu Jul 18 05:43:37 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: 11048507 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 85420112C for ; Thu, 18 Jul 2019 05:43:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 716AE287AD for ; Thu, 18 Jul 2019 05:43:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6531E287AA; Thu, 18 Jul 2019 05:43:56 +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 041BE287AA for ; Thu, 18 Jul 2019 05:43:56 +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=U8pFMRjAkRfAC2pTFZ4eQjh6ZeclJ7BkaGZNwwsXKo4=; b=mfEqWtH9h/1jXY quhRt5XRcz2hgfgfPyzdtWayVFlUYyzhhnw9aeuPoWDCJ7YTbFXY2OR64qNWgroesDhzRSg0SD5jy pdUNEH3ZaBianVGcT13/QERlipJIcmrovej1ftFJeaT8XRTGOPlP1yvdrfxh1xttRe9k1FpNczUnu viKxzVD58W/HJCxa9Pn1FOoh8dbyGsj1UNSyOsvgi4VxnuRgSdQOwdqEuequqoA4L25fvn2JWvfkM 8WHxugvVwBzsZAuhE0VZU2NhtQ90JuCViRFdokktaRcTI8ee06Ul0bPy5tGhbwekfkZxxlu0adzRp GeLuFxjFLJQ/5/i5WDVg==; 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 1hnzCt-0007Jp-79; Thu, 18 Jul 2019 05:43:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hnzCg-0007B1-S9 for linux-arm-kernel@lists.infradead.org; Thu, 18 Jul 2019 05:43:44 +0000 Received: from localhost.localdomain (115.42.148.210.bf.2iij.net [210.148.42.115]) (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 1F2A02077C; Thu, 18 Jul 2019 05:43:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563428622; bh=0SNEK6gGwQn1OWea04NP26kwWDvWXL2LRO0v9+iQPRw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FChIDXQr68auUYmY3OgLk0ibepVLmrXp3Sw70Mq/TXZPW8cJmf7mYY6vV/ZGh0zF7 whI67PGrR0cy6dMai+4+696YLsdqTuovUYa4DcZoXLe2Yn7w9lsNxN8P61Z7xUuMdK /7pBZwRxT+hpWsJqJyLkosQ72efnQsS+uQmo7yts= From: Masami Hiramatsu To: Catalin Marinas , Will Deacon Subject: [PATCH 1/3] arm64: kprobes: Recover pstate.D in single-step exception handler Date: Thu, 18 Jul 2019 14:43:37 +0900 Message-Id: <156342861775.8565.9122725195458920037.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <156342860634.8565.14804606041960884732.stgit@devnote2> References: <156342860634.8565.14804606041960884732.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-20190717_224343_270125_5141D65A X-CRM114-Status: GOOD ( 13.05 ) 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 On arm64, if a nested kprobes hit, it can crash the kernel with below error message. [ 152.118921] Unexpected kernel single-step exception at EL1 This is because commit 7419333fa15e ("arm64: kprobe: Always clear pstate.D in breakpoint exception handler") clears pstate.D always in the nested kprobes. That is correct *unless* any nested kprobes (single-stepping) runs inside other kprobes (including kprobes in user handler). When the 1st kprobe hits, do_debug_exception() will be called. At this point, debug exception (= pstate.D) must be masked (=1). When the 2nd (nested) kprobe is hit before single-step of the first kprobe, it modifies debug exception clear (pstate.D = 0). 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. To solve this issue, this refers saved pstate register to check the previous pstate.D and recover it if needed. Reported-by: Naresh Kamboju Fixes: commit 7419333fa15e ("arm64: kprobe: Always clear pstate.D in breakpoint exception handler") Signed-off-by: Masami Hiramatsu --- arch/arm64/kernel/probes/kprobes.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index bd5dfffca272..6e1dc0bb4c82 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -201,12 +201,14 @@ spsr_set_debug_flag(struct pt_regs *regs, int mask) * interrupt occurrence in the period of exception return and start of * out-of-line single-step, that result in wrongly single stepping * into the interrupt handler. + * This also controls debug flag, so that we can refer the saved pstate. */ static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, struct pt_regs *regs) { kcb->saved_irqflag = regs->pstate; regs->pstate |= PSR_I_BIT; + spsr_set_debug_flag(regs, 0); } static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, @@ -216,6 +218,10 @@ static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, regs->pstate |= PSR_I_BIT; else regs->pstate &= ~PSR_I_BIT; + + /* Recover pstate.D mask if needed */ + if (kcb->saved_irqflag & PSR_D_BIT) + spsr_set_debug_flag(regs, 1); } static void __kprobes @@ -245,15 +251,12 @@ static void __kprobes setup_singlestep(struct kprobe *p, kcb->kprobe_status = KPROBE_HIT_SS; } - if (p->ainsn.api.insn) { /* prepare for single stepping */ slot = (unsigned long)p->ainsn.api.insn; 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);