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Mon, 3 Feb 2020 08:06:59 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id GwpP5yhDHf9J; Mon, 3 Feb 2020 08:06:59 +0100 (CET) Received: from [172.25.230.102] (po15451.idsi0.si.c-s.fr [172.25.230.102]) by messagerie.si.c-s.fr (Postfix) with ESMTP id DAE178B752; Mon, 3 Feb 2020 08:06:58 +0100 (CET) Subject: Re: [PATCH v6 1/5] powerpc/mm: Implement set_memory() routines To: Russell Currey , linuxppc-dev@lists.ozlabs.org References: <20191224055545.178462-1-ruscur@russell.cc> <20191224055545.178462-2-ruscur@russell.cc> <8f8940e2-c6ab-fca2-ab8a-61b80b2edd22@c-s.fr> <8675c11631ac027a78e00d4fe2c20736496b1e97.camel@russell.cc> From: Christophe Leroy Message-ID: <59c7ce33-b61b-e008-f3fc-730ae1dd2ba7@c-s.fr> Date: Mon, 3 Feb 2020 08:06:58 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <8675c11631ac027a78e00d4fe2c20736496b1e97.camel@russell.cc> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ajd@linux.ibm.com, kernel-hardening@lists.openwall.com, npiggin@gmail.com, joel@jms.id.au, dja@axtens.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 03/02/2020 à 01:46, Russell Currey a écrit : > On Wed, 2020-01-08 at 13:52 +0100, Christophe Leroy wrote: >> >> Le 24/12/2019 à 06:55, Russell Currey a écrit : >>> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile >>> index 5e147986400d..d0a0bcbc9289 100644 >>> --- a/arch/powerpc/mm/Makefile >>> +++ b/arch/powerpc/mm/Makefile >>> @@ -20,3 +20,4 @@ obj-$(CONFIG_HIGHMEM) += highmem.o >>> obj-$(CONFIG_PPC_COPRO_BASE) += copro_fault.o >>> obj-$(CONFIG_PPC_PTDUMP) += ptdump/ >>> obj-$(CONFIG_KASAN) += kasan/ >>> +obj-$(CONFIG_ARCH_HAS_SET_MEMORY) += pageattr.o >> >> CONFIG_ARCH_HAS_SET_MEMORY is set inconditionnally, I think you >> should >> add pageattr.o to obj-y instead. CONFIG_ARCH_HAS_XXX are almost >> never >> used in Makefiles > > Fair enough, will keep that in mind I forgot I commented that. I'll do it in v3. >>> + pte_t pte_val; >>> + >>> + // invalidate the PTE so it's safe to modify >>> + pte_val = ptep_get_and_clear(&init_mm, addr, ptep); >>> + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); >> >> Why flush a range for a single page ? On most targets this will do a >> tlbia which is heavy, while a tlbie would suffice. >> >> I think flush_tlb_kernel_range() should be replaced by something >> flushing only a single page. > > You might be able to help me out here, I wanted to do that but the only > functions I could find that flushed single pages needed a > vm_area_struct, which I can't get. I sent out two patches for that, one for book3s/32 and one for nohash: https://patchwork.ozlabs.org/patch/1231983/ https://patchwork.ozlabs.org/patch/1232223/ Maybe one for book3s/64 would be needed as well ? Can you do it if needed ? > >> >>> + >>> + // modify the PTE bits as desired, then apply >>> + switch (action) { >>> + case SET_MEMORY_RO: >>> + pte_val = pte_wrprotect(pte_val); >>> + break; >>> + case SET_MEMORY_RW: >>> + pte_val = pte_mkwrite(pte_val); >>> + break; >>> + case SET_MEMORY_NX: >>> + pte_val = pte_exprotect(pte_val); >>> + break; >>> + case SET_MEMORY_X: >>> + pte_val = pte_mkexec(pte_val); >>> + break; >>> + default: >>> + WARN_ON(true); >>> + return -EINVAL; >> >> Is it worth checking that the action is valid for each page ? I >> think >> validity of action should be checked in change_memory_attr(). All >> other >> functions are static so you know they won't be called from outside. >> >> Once done, you can squash __change_page_attr() into >> change_page_attr(), >> remove the ret var and return 0 all the time. > > Makes sense to fold things into a single function, but in terms of > performance it shouldn't make a difference, right? I still have to > check the action to determine what to change (unless I replace passing > SET_MEMORY_RO into apply_to_page_range() with a function pointer to > pte_wrprotect() for example). pte_wrprotect() is a static inline. > >> >>> + } >>> + >>> + set_pte_at(&init_mm, addr, ptep, pte_val); >>> + >>> + return 0; >>> +} >>> + >>> +static int change_page_attr(pte_t *ptep, unsigned long addr, void >>> *data) >>> +{ >>> + int ret; >>> + >>> + spin_lock(&init_mm.page_table_lock); >>> + ret = __change_page_attr(ptep, addr, data); >>> + spin_unlock(&init_mm.page_table_lock); >>> + >>> + return ret; >>> +} >>> + >>> +int change_memory_attr(unsigned long addr, int numpages, int >>> action) >>> +{ >>> + unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); >>> + unsigned long size = numpages * PAGE_SIZE; >>> + >>> + if (!numpages) >>> + return 0; >>> + >>> + return apply_to_page_range(&init_mm, start, size, >>> change_page_attr, &action); >> >> Use (void*)action instead of &action (see upper comment) > > To get this to work I had to use (void *)(size_t)action to stop the > compiler from complaining about casting an int to a void*, is there a > better way to go about it? Works fine, just looks gross. Yes, use long instead (see my v3) Christophe 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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F4F6C33C9E for ; Mon, 3 Feb 2020 07:07:19 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id A240B20661 for ; Mon, 3 Feb 2020 07:07:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="IqgNPnJz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A240B20661 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17652-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 3398 invoked by uid 550); 3 Feb 2020 07:07:11 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 3359 invoked from network); 3 Feb 2020 07:07:11 -0000 Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=IqgNPnJz; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1580713614; bh=smrKpIHjFvgNU1nY+YX2OWlGMfhRIgdamHvzNUhVLVg=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=IqgNPnJzQokcayKUyec8eVwm/PCXeJ9wuAZ3C027ZMmxzRzPJudSm2cGpYnowyuC2 q7/KV4/7w7wzKa4FrQinYFr+MgOysUneExIAp9Jq/VZ5P/g/6VhhgsnR/FI5+hN9h5 WsXbN4D7oe/tUwwjQyyoyeRsIAwQEvIUutUOjooE= X-Virus-Scanned: amavisd-new at c-s.fr Subject: Re: [PATCH v6 1/5] powerpc/mm: Implement set_memory() routines To: Russell Currey , linuxppc-dev@lists.ozlabs.org Cc: joel@jms.id.au, mpe@ellerman.id.au, ajd@linux.ibm.com, dja@axtens.net, npiggin@gmail.com, kernel-hardening@lists.openwall.com References: <20191224055545.178462-1-ruscur@russell.cc> <20191224055545.178462-2-ruscur@russell.cc> <8f8940e2-c6ab-fca2-ab8a-61b80b2edd22@c-s.fr> <8675c11631ac027a78e00d4fe2c20736496b1e97.camel@russell.cc> From: Christophe Leroy Message-ID: <59c7ce33-b61b-e008-f3fc-730ae1dd2ba7@c-s.fr> Date: Mon, 3 Feb 2020 08:06:58 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <8675c11631ac027a78e00d4fe2c20736496b1e97.camel@russell.cc> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Le 03/02/2020 à 01:46, Russell Currey a écrit : > On Wed, 2020-01-08 at 13:52 +0100, Christophe Leroy wrote: >> >> Le 24/12/2019 à 06:55, Russell Currey a écrit : >>> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile >>> index 5e147986400d..d0a0bcbc9289 100644 >>> --- a/arch/powerpc/mm/Makefile >>> +++ b/arch/powerpc/mm/Makefile >>> @@ -20,3 +20,4 @@ obj-$(CONFIG_HIGHMEM) += highmem.o >>> obj-$(CONFIG_PPC_COPRO_BASE) += copro_fault.o >>> obj-$(CONFIG_PPC_PTDUMP) += ptdump/ >>> obj-$(CONFIG_KASAN) += kasan/ >>> +obj-$(CONFIG_ARCH_HAS_SET_MEMORY) += pageattr.o >> >> CONFIG_ARCH_HAS_SET_MEMORY is set inconditionnally, I think you >> should >> add pageattr.o to obj-y instead. CONFIG_ARCH_HAS_XXX are almost >> never >> used in Makefiles > > Fair enough, will keep that in mind I forgot I commented that. I'll do it in v3. >>> + pte_t pte_val; >>> + >>> + // invalidate the PTE so it's safe to modify >>> + pte_val = ptep_get_and_clear(&init_mm, addr, ptep); >>> + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); >> >> Why flush a range for a single page ? On most targets this will do a >> tlbia which is heavy, while a tlbie would suffice. >> >> I think flush_tlb_kernel_range() should be replaced by something >> flushing only a single page. > > You might be able to help me out here, I wanted to do that but the only > functions I could find that flushed single pages needed a > vm_area_struct, which I can't get. I sent out two patches for that, one for book3s/32 and one for nohash: https://patchwork.ozlabs.org/patch/1231983/ https://patchwork.ozlabs.org/patch/1232223/ Maybe one for book3s/64 would be needed as well ? Can you do it if needed ? > >> >>> + >>> + // modify the PTE bits as desired, then apply >>> + switch (action) { >>> + case SET_MEMORY_RO: >>> + pte_val = pte_wrprotect(pte_val); >>> + break; >>> + case SET_MEMORY_RW: >>> + pte_val = pte_mkwrite(pte_val); >>> + break; >>> + case SET_MEMORY_NX: >>> + pte_val = pte_exprotect(pte_val); >>> + break; >>> + case SET_MEMORY_X: >>> + pte_val = pte_mkexec(pte_val); >>> + break; >>> + default: >>> + WARN_ON(true); >>> + return -EINVAL; >> >> Is it worth checking that the action is valid for each page ? I >> think >> validity of action should be checked in change_memory_attr(). All >> other >> functions are static so you know they won't be called from outside. >> >> Once done, you can squash __change_page_attr() into >> change_page_attr(), >> remove the ret var and return 0 all the time. > > Makes sense to fold things into a single function, but in terms of > performance it shouldn't make a difference, right? I still have to > check the action to determine what to change (unless I replace passing > SET_MEMORY_RO into apply_to_page_range() with a function pointer to > pte_wrprotect() for example). pte_wrprotect() is a static inline. > >> >>> + } >>> + >>> + set_pte_at(&init_mm, addr, ptep, pte_val); >>> + >>> + return 0; >>> +} >>> + >>> +static int change_page_attr(pte_t *ptep, unsigned long addr, void >>> *data) >>> +{ >>> + int ret; >>> + >>> + spin_lock(&init_mm.page_table_lock); >>> + ret = __change_page_attr(ptep, addr, data); >>> + spin_unlock(&init_mm.page_table_lock); >>> + >>> + return ret; >>> +} >>> + >>> +int change_memory_attr(unsigned long addr, int numpages, int >>> action) >>> +{ >>> + unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); >>> + unsigned long size = numpages * PAGE_SIZE; >>> + >>> + if (!numpages) >>> + return 0; >>> + >>> + return apply_to_page_range(&init_mm, start, size, >>> change_page_attr, &action); >> >> Use (void*)action instead of &action (see upper comment) > > To get this to work I had to use (void *)(size_t)action to stop the > compiler from complaining about casting an int to a void*, is there a > better way to go about it? Works fine, just looks gross. Yes, use long instead (see my v3) Christophe