Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753798AbaKQDa6 (ORCPT ); Sun, 16 Nov 2014 22:30:58 -0500 Received: from mail-ie0-f173.google.com ([209.85.223.173]:54299 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753776AbaKQDa5 (ORCPT ); Sun, 16 Nov 2014 22:30:57 -0500 MIME-Version: 1.0 In-Reply-To: References: <20141114204517.GA24402@www.outflux.net> Date: Sun, 16 Nov 2014 19:30:56 -0800 X-Google-Sender-Auth: V0ee7MeIEInPHrxYV3tcteu0NfE Message-ID: Subject: Re: [PATCH v2] x86, mm: set NX across entire PMD at boot From: Yinghai Lu To: Thomas Gleixner Cc: Kees Cook , Linux Kernel Mailing List , Ingo Molnar , "H. Peter Anvin" , "the arch/x86 maintainers" , Andrew Morton , Andy Lutomirski , Yasuaki Ishimatsu , Wang Nan , David Vrabel Content-Type: multipart/mixed; boundary=047d7bdc9dae4896da0508059bbe Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --047d7bdc9dae4896da0508059bbe Content-Type: text/plain; charset=UTF-8 On Sun, Nov 16, 2014 at 1:26 PM, Thomas Gleixner wrote: > On Sat, 15 Nov 2014, Yinghai Lu wrote: >> +static pmd_t *last_pmd; >> /* >> * The head.S code sets up the kernel high mapping: >> * >> @@ -408,9 +409,26 @@ void __init cleanup_highmap(void) >> continue; >> if (vaddr < (unsigned long) _text || vaddr > end) >> set_pmd(pmd, __pmd(0)); >> + else >> + last_pmd = pmd; > > Why do you need to store this? You can compute this. I'm not quite sure about the xen path. > >> +static void __init cleanup_highmap_tail(unsigned long addr) > > Brilliant stuff. mark_rodata_ro() is called AFTER free_initmem() which > will free exactly that code. I missed that. Please check this one that address three problems that you pointed out. Subject: [PATCH v2] x86, 64bit: cleanup highmap tail near partial 2M range 1. should use _brk_end instead of &_end in mark_rodata_ro(). _brk_end can move up to &_end, i.e. to __brk_limit. It's safe to use _brk_end when mark_rodata_ro() is called because extend_brk() is gone already at that point. 2. [_brk_end, pm_end) page range is already converted mem. and is not wasted. 3. add cleanup_highmap_tail for [_brk_end, pm_end). Kernel Layout: [ 0.000000] .brk: [0x0437c000-0x043a1fff] Actually used brk: [ 0.272959] memblock_reserve: [0x0000000437c000-0x00000004382fff] flags 0x0 BRK Before patch: ---[ High Kernel Mapping ]--- ... 0xffffffff83400000-0xffffffff84200000 14M RW PSE GLB NX pmd 0xffffffff84200000-0xffffffff843a2000 1672K RW GLB NX pte 0xffffffff843a2000-0xffffffff84400000 376K RW GLB x pte 0xffffffff84400000-0xffffffffa0000000 444M pmd After patch: ---[ High Kernel Mapping ]--- ... 0xffffffff83400000-0xffffffff84200000 14M RW PSE GLB NX pmd 0xffffffff84200000-0xffffffff84383000 1548K RW GLB NX pte 0xffffffff84383000-0xffffffff84400000 500K pte 0xffffffff84400000-0xffffffffa0000000 444M pmd -v2: according to tglx caculate the pmd postion instead of passing last_pmd. cleanup_highmap_tail could not have __init, as it is called in mark_rodata_ro and mark_rodata_ro is called after free_initmem. highmap_end_pfn should keep PMD_SIZE alignment on !CONFIG_DEBUG_RODATA Signed-off-by: Yinghai Lu --- arch/x86/mm/init_64.c | 22 +++++++++++++++++++++- arch/x86/mm/pageattr.c | 4 ++++ 2 files changed, 25 insertions(+), 1 deletion(-) Index: linux-2.6/arch/x86/mm/init_64.c =================================================================== --- linux-2.6.orig/arch/x86/mm/init_64.c +++ linux-2.6/arch/x86/mm/init_64.c @@ -411,6 +411,23 @@ void __init cleanup_highmap(void) } } +static void cleanup_highmap_tail(unsigned long addr) +{ + int i; + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + + pgd = pgd_offset_k(addr); + pud = (pud_t *)pgd_page_vaddr(*pgd) + pud_index(addr); + pmd = (pmd_t *)pud_page_vaddr(*pud) + pmd_index(addr); + pte = (pte_t *)pmd_page_vaddr(*pmd) + pte_index(addr); + + for (i = pte_index(addr); i < PTRS_PER_PTE; i++, pte++) + set_pte(pte, __pte(0)); +} + static unsigned long __meminit phys_pte_init(pte_t *pte_page, unsigned long addr, unsigned long end, pgprot_t prot) @@ -1124,7 +1141,8 @@ void mark_rodata_ro(void) unsigned long end = (unsigned long) &__end_rodata_hpage_align; unsigned long text_end = PFN_ALIGN(&__stop___ex_table); unsigned long rodata_end = PFN_ALIGN(&__end_rodata); - unsigned long all_end = PFN_ALIGN(&_end); + unsigned long all_end = PFN_ALIGN(_brk_end); + unsigned long pmd_end = roundup(all_end, PMD_SIZE); printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n", (end - start) >> 10); @@ -1137,6 +1155,8 @@ void mark_rodata_ro(void) * should also be not-executable. */ set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT); + if (all_end < pmd_end) + cleanup_highmap_tail(all_end); rodata_test(); Index: linux-2.6/arch/x86/mm/pageattr.c =================================================================== --- linux-2.6.orig/arch/x86/mm/pageattr.c +++ linux-2.6/arch/x86/mm/pageattr.c @@ -100,7 +100,11 @@ static inline unsigned long highmap_star static inline unsigned long highmap_end_pfn(void) { +#ifdef CONFIG_DEBUG_RODATA + return __pa_symbol(PFN_ALIGN(_brk_end)) >> PAGE_SHIFT; +#else return 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