From patchwork Mon Jan 4 17:56:36 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 59146 Delivered-To: patch@linaro.org Received: by 10.112.130.2 with SMTP id oa2csp5503343lbb; Mon, 4 Jan 2016 09:59:28 -0800 (PST) X-Received: by 10.66.236.69 with SMTP id us5mr11579060pac.93.1451930368134; Mon, 04 Jan 2016 09:59:28 -0800 (PST) Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id o65si66366880pfa.179.2016.01.04.09.59.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Jan 2016 09:59:28 -0800 (PST) Received-SPF: pass (google.com: domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) client-ip=2001:1868:205::9; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) smtp.mailfrom=linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aG9On-0002CE-5J; Mon, 04 Jan 2016 17:58:29 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aG9Ob-00020D-QL for linux-arm-kernel@lists.infradead.org; Mon, 04 Jan 2016 17:58:20 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6C9EB49; Mon, 4 Jan 2016 09:57:28 -0800 (PST) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B64A93F246; Mon, 4 Jan 2016 09:57:58 -0800 (PST) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Subject: [PATCHv2 03/18] arm64: mm: place empty_zero_page in bss Date: Mon, 4 Jan 2016 17:56:36 +0000 Message-Id: <1451930211-22460-4-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1451930211-22460-1-git-send-email-mark.rutland@arm.com> References: <1451930211-22460-1-git-send-email-mark.rutland@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160104_095818_065079_0818FF2A X-CRM114-Status: GOOD ( 15.36 ) X-Spam-Score: -6.9 (------) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-6.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [217.140.101.70 listed in list.dnswl.org] -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, lorenzo.pieralisi@arm.com, arnd@arndb.de, ard.biesheuvel@linaro.org, catalin.marinas@arm.com, will.deacon@arm.com, jeremy.linton@arm.com, ryabinin.a.a@gmail.com, labbott@fedoraproject.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Currently the zero page is set up in paging_init, and thus we cannot use the zero page earlier. We use the zero page as a reserved TTBR value from which no TLB entries may be allocated (e.g. when uninstalling the idmap). To enable such usage earlier (as may be required for invasive changes to the kernel page tables), and to minimise the time that the idmap is active, we need to be able to use the zero page before paging_init. This patch follows the example set by x86, by allocating the zero page at compile time, in .bss. This means that the zero page itself is available immediately upon entry to start_kernel (as we zero .bss before this), and also means that the zero page takes up no space in the raw Image binary. The associated struct page is allocated in bootmem_init, and remains unavailable until this time. Outside of arch code, the only users of empty_zero_page assume that the empty_zero_page symbol refers to the zeroed memory itself, and that ZERO_PAGE(x) must be used to acquire the associated struct page, following the example of x86. This patch also brings arm64 inline with these assumptions. Signed-off-by: Mark Rutland Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Jeremy Linton Cc: Laura Abbott Cc: Will Deacon --- arch/arm64/include/asm/mmu_context.h | 2 +- arch/arm64/include/asm/pgtable.h | 4 ++-- arch/arm64/kernel/head.S | 1 + arch/arm64/mm/mmu.c | 9 +-------- 4 files changed, 5 insertions(+), 11 deletions(-) -- 1.9.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index 2416578..600eacb 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -48,7 +48,7 @@ static inline void contextidr_thread_switch(struct task_struct *next) */ static inline void cpu_set_reserved_ttbr0(void) { - unsigned long ttbr = page_to_phys(empty_zero_page); + unsigned long ttbr = virt_to_phys(empty_zero_page); asm( " msr ttbr0_el1, %0 // set TTBR0\n" diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 35a318c..382d627 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -121,8 +121,8 @@ extern void __pgd_error(const char *file, int line, unsigned long val); * ZERO_PAGE is a global shared page that is always zero: used * for zero-mapped memory areas etc.. */ -extern struct page *empty_zero_page; -#define ZERO_PAGE(vaddr) (empty_zero_page) +extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; +#define ZERO_PAGE(vaddr) virt_to_page(empty_zero_page) #define pte_ERROR(pte) __pte_error(__FILE__, __LINE__, pte_val(pte)) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index b363f34..9da5d0c 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -423,6 +423,7 @@ __mmap_switched: str xzr, [x6], #8 // Clear BSS b 1b 2: + dsb ishst // Make zero page visible to PTW adr_l sp, initial_sp, x4 mov x4, sp and x4, x4, #~(THREAD_SIZE - 1) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index b25d5cb..cdbf055 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -49,7 +49,7 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS); * Empty_zero_page is a special page that is used for zero-initialized data * and COW. */ -struct page *empty_zero_page; +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; EXPORT_SYMBOL(empty_zero_page); pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, @@ -459,18 +459,11 @@ void fixup_init(void) */ void __init paging_init(void) { - void *zero_page; - map_mem(); fixup_executable(); - /* allocate the zero page. */ - zero_page = early_pgtable_alloc(); - bootmem_init(); - empty_zero_page = virt_to_page(zero_page); - /* * TTBR0 is only used for the identity mapping at this stage. Make it * point to zero page to avoid speculatively fetching new entries.