From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Tue, 31 May 2022 10:08:27 +0200 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nvwvT-00G1X3-4N for lore@lore.pengutronix.de; Tue, 31 May 2022 10:08:27 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nvwvR-0007ZJ-QQ for lore@pengutronix.de; Tue, 31 May 2022 10:08:26 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=JUprWzp+FzmtbueRQqTqZ8SlsTlm90ZF7Y1vQvQM9KY=; b=0SZ37uKqowz3kn 5267wwxOBA1x89ZP4/WHe1Fp3Y8V4k9mloW8DTSZkv9zQZE8yp0vZbU1qErQ5gEYIAuevF5myA4yz j9ua9cnT2y8/5r5srhPGPH+ItUAzlMNWmD1Sv+V5LkNxw7B+p3QJO8yVWlQMa8a/xK9lmDlYpqcDW prIuXmvoYd2WlHGUwstpgJgnSrSCYrUOlao+NMAOJUv8g5x38rUvFuu/4Ri67t1k94yzWrhsv+bjg C7VPn2EVkpbS4voWf9sypL8MWOm6PJx5lyDCFKaXi6B1CY2F4N7EQwpwmCp0Dy89XvSIHEjn5RU5v 4MeslvX2LLf6r7IaHo8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nvwtc-009mIa-BH; Tue, 31 May 2022 08:06:32 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nvwtX-009mH2-FD for barebox@lists.infradead.org; Tue, 31 May 2022 08:06:29 +0000 Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nvwtQ-0007Ql-5Q; Tue, 31 May 2022 10:06:20 +0200 Received: from sha by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1nvwtP-0001uq-SZ; Tue, 31 May 2022 10:06:19 +0200 Date: Tue, 31 May 2022 10:06:19 +0200 From: Sascha Hauer To: Ahmad Fatoum Cc: barebox@lists.infradead.org, lst@pengutronix.de Message-ID: <20220531080619.GQ1615@pengutronix.de> References: <20220530073948.632014-1-a.fatoum@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220530073948.632014-1-a.fatoum@pengutronix.de> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-Accept-Language: de,en X-Accept-Content-Type: text/plain User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220531_010627_551574_8A8B7B29 X-CRM114-Status: GOOD ( 29.30 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.ext.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-3.9 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH master] ARM: cpu: don't clobber sp when booted in HYP mode X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.ext.pengutronix.de) On Mon, May 30, 2022 at 09:39:48AM +0200, Ahmad Fatoum wrote: > arm_cpu_lowlevel_init() is usually called first thing and will ensure > barebox runs in SVC mode. If barebox is started in HYP mode instead, > like is the case on Raspberry Pi 2-3, it will do an exception return > into SVC mode, which will bank the previously used SP_Hyp and > restore SP_Svc that may not have been properly initialized by barebox. > > This wasn't too bad so far, because arm_setup_stack was usually called > after arm_cpu_lowlevel_init, but with ENTRY_FUNCTION_WITHSTACK, SP is > initialized early on in the naked entry point with > arm_cpu_lowlevel_init() being called after that. > > This can lead to spurious boot hangs in the Raspberry Pi 2 and 3 entry > points. Fix this by always saving sp to r3 and restoring it, like we do > with lr. This is safe to do, because r3 isn't clobbered by any > instruction in arm_cpu_lowlevel_init() and because it's an argument > register, callers have to expect it being overwritten by the callee. > > Fixes: b267578d0567 ("ARM: rpi: use ENTRY_FUNCTION_WITHSTACK to prepare for ARM64 support") > Fixes: 41292192c01b ("ARM: safely switch from HYP to SVC mode if required") > Signed-off-by: Ahmad Fatoum > --- > arch/arm/cpu/lowlevel.S | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/arm/cpu/lowlevel.S b/arch/arm/cpu/lowlevel.S > index 5a7dd3c2093f..2199d9416cb3 100644 > --- a/arch/arm/cpu/lowlevel.S > +++ b/arch/arm/cpu/lowlevel.S > @@ -9,6 +9,7 @@ > ENTRY(arm_cpu_lowlevel_init) > /* save lr, since it may be banked away with a processor mode change */ > mov r2, lr > + mov r3, sp Can you add a comment why this is necessary? We can look at the commit message for the elaborated description, but a reminder in the code still seems useful, otherwise I might be trapped into applying a "remove useless code" patch. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox