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 228D5C43334 for ; Fri, 24 Jun 2022 12:37:21 +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=GbF4kqBnR3XP5Z1DDcB3S37RJYslJpGaZMH5B8T/SA4=; b=0E0hpESjcNS1N9 5hwxsM1IWoD1epnpCF1j165zlQd3Q6RHklrX0DrhT/m1EfILNt1BIu+MbMraOwE4cW3PZl/f3BjVZ WVeLsfZhrTLBbVfkosYJ1aNj/wRJh4YMMrn60vaxxnF+84cF0LTEYOdhxEpJ+bhKC9x1EcbAg+rN5 JM2fPEtVBd/AYtP9E7spZ3F6QNKkmEe3FhyW0YZx2FBIsI5pQ2JXMVPbDoF4QhfwxkSgb8c//VO3e raY1Fj3+sqYg7b3WFG7jkS0X9aC5jAcs+s/OUJ5jo1EkfC2NZelIF29sCwbOM0HLtz4pEOqVFJgrg lpFMOhnR63rMGO+4cV+g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o4iXo-002DAe-NC; Fri, 24 Jun 2022 12:36:16 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1o4iXl-002D9c-Hx for linux-arm-kernel@lists.infradead.org; Fri, 24 Jun 2022 12:36:15 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A65F161B48; Fri, 24 Jun 2022 12:36:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59B1FC34114; Fri, 24 Jun 2022 12:36:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656074169; bh=qS0WvydUMGkzxUfEfVLbi+q0Czzas7ZoRxwNwstvl2c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Vz2hrivxRLtV5aOLeMf7nLWH9z5Ory1F2dGbA+WErCEe/9rIkqhxA4DFW+8RBC+Ej 786B0J4v4yXPifTTp8P0bWBY2704+x6WmLy1ZDhx2OjlW9cCrtNv6I/xwL8fOiY3j8 sors15SBdgFgx2b3bfOZ/yCXz8kYh5bq4ofy0/dAhKbPeAj8kkZN+eYkoZiqhJoHZA l0VcknsX8tupA52F+X3Kz0p6hRp0b1T8SE4yjOJNh1YXi+Lh3biovEiTywI8Clkp4E FZJlWk0XRGIROGmpRwl5VQoNASn8w2wVaKNyl9te0ZzKYDZ81SrjWZQfsTUCCf93CB Cm4tZURApJ7vQ== Date: Fri, 24 Jun 2022 13:36:03 +0100 From: Will Deacon To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, linux-hardening@vger.kernel.org, Marc Zyngier , Mark Rutland , Kees Cook , Catalin Marinas , Mark Brown , Anshuman Khandual Subject: Re: [PATCH v4 03/26] arm64: head: move assignment of idmap_t0sz to C code Message-ID: <20220624123602.GC18561@willie-the-truck> References: <20220613144550.3760857-1-ardb@kernel.org> <20220613144550.3760857-4-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220613144550.3760857-4-ardb@kernel.org> 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-20220624_053613_714903_F8258137 X-CRM114-Status: GOOD ( 29.86 ) 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 Mon, Jun 13, 2022 at 04:45:27PM +0200, Ard Biesheuvel wrote: > Setting idmap_t0sz involves fiddling with the caches if done with the > MMU off. Since we will be creating an initial ID map with the MMU and > caches off, and the permanent ID map with the MMU and caches on, let's > move this assignment of idmap_t0sz out of the startup code, and replace > it with a macro that simply issues the three instructions needed to > calculate the value wherever it is needed before the MMU is turned on. > > Signed-off-by: Ard Biesheuvel > --- > arch/arm64/include/asm/assembler.h | 14 ++++++++++++++ > arch/arm64/include/asm/mmu_context.h | 2 +- > arch/arm64/kernel/head.S | 13 +------------ > arch/arm64/mm/mmu.c | 5 ++++- > arch/arm64/mm/proc.S | 2 +- > 5 files changed, 21 insertions(+), 15 deletions(-) > > diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h > index 8c5a61aeaf8e..9468f45c07a6 100644 > --- a/arch/arm64/include/asm/assembler.h > +++ b/arch/arm64/include/asm/assembler.h > @@ -359,6 +359,20 @@ alternative_cb_end > bfi \valreg, \t1sz, #TCR_T1SZ_OFFSET, #TCR_TxSZ_WIDTH > .endm > > +/* > + * idmap_get_t0sz - get the T0SZ value needed to cover the ID map > + * > + * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the > + * entire ID map region can be mapped. As T0SZ == (64 - #bits used), > + * this number conveniently equals the number of leading zeroes in > + * the physical address of _end. > + */ > + .macro idmap_get_t0sz, reg > + adrp \reg, _end > + orr \reg, \reg, #(1 << VA_BITS_MIN) - 1 > + clz \reg, \reg > + .endm > + > /* > * tcr_compute_pa_size - set TCR.(I)PS to the highest supported > * ID_AA64MMFR0_EL1.PARange value > diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h > index 6770667b34a3..6ac0086ebb1a 100644 > --- a/arch/arm64/include/asm/mmu_context.h > +++ b/arch/arm64/include/asm/mmu_context.h > @@ -60,7 +60,7 @@ static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm) > * TCR_T0SZ(VA_BITS), unless system RAM is positioned very high in > * physical memory, in which case it will be smaller. > */ > -extern u64 idmap_t0sz; > +extern int idmap_t0sz; > extern u64 idmap_ptrs_per_pgd; > > /* > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index dc07858eb673..7f361bc72d12 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -299,22 +299,11 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > * physical address space. So for the ID map, use an extended virtual > * range in that case, and configure an additional translation level > * if needed. > - * > - * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the > - * entire ID map region can be mapped. As T0SZ == (64 - #bits used), > - * this number conveniently equals the number of leading zeroes in > - * the physical address of __idmap_text_end. > */ > - adrp x5, __idmap_text_end > - clz x5, x5 > + idmap_get_t0sz x5 > cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough? > b.ge 1f // .. then skip VA range extension > > - adr_l x6, idmap_t0sz > - str x5, [x6] > - dmb sy > - dc ivac, x6 // Invalidate potentially stale cache line > - > #if (VA_BITS < 48) > #define EXTRA_SHIFT (PGDIR_SHIFT + PAGE_SHIFT - 3) > #define EXTRA_PTRS (1 << (PHYS_MASK_SHIFT - EXTRA_SHIFT)) > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 17b339c1a326..103bf4ae408d 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -43,7 +43,7 @@ > #define NO_CONT_MAPPINGS BIT(1) > #define NO_EXEC_MAPPINGS BIT(2) /* assumes FEAT_HPDS is not used */ > > -u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); > +int idmap_t0sz __ro_after_init; > u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; > > #if VA_BITS > 48 > @@ -785,6 +785,9 @@ void __init paging_init(void) > (u64)&vabits_actual + sizeof(vabits_actual)); > #endif > > + idmap_t0sz = min(63UL - __fls(__pa_symbol(_end)), > + TCR_T0SZ(VA_BITS_MIN)); nit: TCR_T0SZ shifts by TCR_T0SZ_OFFSET, so this is a bit confusing and works out because the register offset happens to be zero. Maybe it would be clearer to calculate the maximum of fls(__pa_symbol(_end)) and VA_BITS_MIN, then subtract that from 64? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel