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 44A91ECAAA1 for ; Mon, 12 Sep 2022 09:33:29 +0000 (UTC) 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=0LnZo0uof2egI9z8FroNjFKatcIPiqRuTVPm8YIGR8o=; b=Lr0dPu4A+d3Ywm +Z7DkcPSCXhxEujTtUNsL7Jp3Z1MgU/msuqRIw3BoHEcozYYcDw4QUfVIyQ61api4eXX6hpFTLbg/ O2KKeA2+3UK1rWWNdN6mfn9yk82TS+AE7EIlfQUDUv07sxeMlXi+sKuPf4ErMo8UI7DtOATTqTUTY cM76uLJLsuIfviHS2n5UfjrLWJBHD2etQuHvVNkW5K3N7u1u111mQDGOUo0/leFxfswymSDVa2HwO upU8yZ4cJJKrS8CQC09No3ErFHHyLBabeaMwiUNd+gYFN0jwUzPb0ivaUSRIx7bv5vKvEo+4fdJV6 D3afiYOZRpvHvATQ+uNA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oXfne-008HrW-32; Mon, 12 Sep 2022 09:32:18 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oXfnY-008Hng-OU for linux-arm-kernel@lists.infradead.org; Mon, 12 Sep 2022 09:32:16 +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 8457D113E; Mon, 12 Sep 2022 02:32:15 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 642F53F73D; Mon, 12 Sep 2022 02:32:07 -0700 (PDT) Date: Mon, 12 Sep 2022 10:31:55 +0100 From: Mark Rutland To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, james.morse@arm.com, joey.gouly@arm.com, maz@kernel.org, will@kernel.org Subject: Re: [PATCH 5/9] arm64: alternatives: make alt_region const Message-ID: References: <20220901151403.1735836-1-mark.rutland@arm.com> <20220901151403.1735836-6-mark.rutland@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220912_023212_940970_7C404103 X-CRM114-Status: GOOD ( 33.91 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Sep 06, 2022 at 05:18:54PM +0200, Ard Biesheuvel wrote: > Hi Mark, > > On Thu, 1 Sept 2022 at 17:14, Mark Rutland wrote: > > > > We never alter a struct alt_region after creation, and we open-code the > > bounds of the kernel alternatives region in two functions. > > > > This patch adds a shared struct alt_region, and marks the alt regions as > > const to prevent unintentional modification. > > > > What is the point of struct alt_region? Can we just get rid of it > entirely? It seems its only purpose is to carry a tuple > that could easily be converted into start and end arguments to > __apply_alternatives(). We could right now, but I'm intending to fix some noinstr issues (and make debugging easier) by splitting the alternatives sanity-checking & patching into distinct initcalls (alnog with some extra debug), and having the structure for the common definition is quite nice to avoid open-coding the start and end value in a bunch of places. So I'd prefer to keep it for now, but I can follow up and delete it if the above doesn't turn out to need it, if that's ok? Mark. > > There should be no functional change as a result of this patch. > > > > Signed-off-by: Mark Rutland > > Cc: Ard Biesheuvel > > Cc: Catalin Marinas > > Cc: James Morse > > Cc: Joey Gouly > > Cc: Marc Zyngier > > Cc: Will Deacon > > --- > > arch/arm64/kernel/alternative.c | 26 ++++++++++++-------------- > > 1 file changed, 12 insertions(+), 14 deletions(-) > > > > diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c > > index d94d97cb4a0bf..2e18c9c0f612b 100644 > > --- a/arch/arm64/kernel/alternative.c > > +++ b/arch/arm64/kernel/alternative.c > > @@ -133,8 +133,9 @@ static void clean_dcache_range_nopatch(u64 start, u64 end) > > } while (cur += d_size, cur < end); > > } > > > > -static void __nocfi __apply_alternatives(struct alt_region *region, bool is_module, > > - unsigned long *feature_mask) > > +static void __nocfi __apply_alternatives(const struct alt_region *region, > > + bool is_module, > > + unsigned long *feature_mask) > > { > > struct alt_instr *alt; > > __le32 *origptr, *updptr; > > @@ -190,17 +191,17 @@ static void __nocfi __apply_alternatives(struct alt_region *region, bool is_modu > > } > > } > > > > +static const struct alt_region kernel_alternatives = { > > + .begin = (struct alt_instr *)__alt_instructions, > > + .end = (struct alt_instr *)__alt_instructions_end, > > +}; > > + > > /* > > * We might be patching the stop_machine state machine, so implement a > > * really simple polling protocol here. > > */ > > static int __apply_alternatives_multi_stop(void *unused) > > { > > - struct alt_region region = { > > - .begin = (struct alt_instr *)__alt_instructions, > > - .end = (struct alt_instr *)__alt_instructions_end, > > - }; > > - > > /* We always have a CPU 0 at this point (__init) */ > > if (smp_processor_id()) { > > while (!all_alternatives_applied) > > @@ -213,7 +214,8 @@ static int __apply_alternatives_multi_stop(void *unused) > > ARM64_NPATCHABLE); > > > > BUG_ON(all_alternatives_applied); > > - __apply_alternatives(®ion, false, remaining_capabilities); > > + __apply_alternatives(&kernel_alternatives, false, > > + remaining_capabilities); > > /* Barriers provided by the cache flushing */ > > all_alternatives_applied = 1; > > } > > @@ -236,17 +238,13 @@ void __init apply_alternatives_all(void) > > */ > > void __init apply_boot_alternatives(void) > > { > > - struct alt_region region = { > > - .begin = (struct alt_instr *)__alt_instructions, > > - .end = (struct alt_instr *)__alt_instructions_end, > > - }; > > - > > /* If called on non-boot cpu things could go wrong */ > > WARN_ON(smp_processor_id() != 0); > > > > pr_info("applying boot alternatives\n"); > > > > - __apply_alternatives(®ion, false, &boot_capabilities[0]); > > + __apply_alternatives(&kernel_alternatives, false, > > + &boot_capabilities[0]); > > } > > > > #ifdef CONFIG_MODULES > > -- > > 2.30.2 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel