Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752115AbcLHISC (ORCPT ); Thu, 8 Dec 2016 03:18:02 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36336 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751567AbcLHISB (ORCPT ); Thu, 8 Dec 2016 03:18:01 -0500 Date: Thu, 8 Dec 2016 14:17:50 +0600 From: Alexnader Kuleshov To: Baoquan He Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, hpa@zytor.com, mingo@redhat.com, x86@kernel.org, keescook@chromium.org, yinghai@kernel.org, bp@suse.de, thgarnie@google.com, kuleshovmail@gmail.com, luto@kernel.org, anderson@redhat.com, dyoung@redhat.com, xlpang@redhat.com Subject: Re: [PATCH 2/2] x86/KASLR/64: Determine kernel text mapping size at runtime Message-ID: <20161208081750.GA3998@localhost.localdomain> References: <1481183765-4166-1-git-send-email-bhe@redhat.com> <1481183765-4166-3-git-send-email-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1481183765-4166-3-git-send-email-bhe@redhat.com> X-Operating-System: Linux X-Date: Thu Dec 8 13:52:43 +06 2016 User-Agent: Mutt/1.6.0-rc0 ((null)) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8214 Lines: 179 Hello, On 12-08-16, Baoquan He wrote: > X86 64 kernel takes KERNEL_IMAGE_SIZE as the kernel text mapping size, > and it's fixed as compiling time, changing from 512M to 1G as long as > CONFIG_RANDOMIZE_BASE is enabled, though people specify kernel option > "nokaslr" explicitly. > > This could be a wrong behaviour. CONFIG_RANDOMIZE_BASE should only decide > if the KASLR code need be compiled in. If user specify "nokaslr", the > kernel should behave as no KASLR code compiled in at all. > > So in this patch, define a new MACRO KERNEL_MAPPING_SIZE to represent the > size of kernel text mapping area, and let KERNEL_IMAGE_SIZE limit the size > of kernel runtime space. And change to determine the size of kernel text > mapping area at runtime. Though KASLR code compiled in, if "nokaslr" specified, > still set kernel mapping size to be 512M. > > Signed-off-by: Baoquan He > --- > arch/x86/boot/compressed/kaslr.c | 15 ++++++++++----- > arch/x86/include/asm/kaslr.h | 1 + > arch/x86/include/asm/page_64_types.h | 19 +++++++++++-------- > arch/x86/include/asm/pgtable_64_types.h | 2 +- > arch/x86/kernel/head64.c | 11 ++++++----- > arch/x86/kernel/head_64.S | 3 ++- > arch/x86/mm/dump_pagetables.c | 3 ++- > arch/x86/mm/physaddr.c | 6 +++--- > 8 files changed, 36 insertions(+), 24 deletions(-) > > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c > index a66854d..3b73c76 100644 > --- a/arch/x86/boot/compressed/kaslr.c > +++ b/arch/x86/boot/compressed/kaslr.c > @@ -22,6 +22,8 @@ > static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@" > LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION; > > +unsigned long kernel_mapping_size = KERNEL_IMAGE_SIZE; > + > static unsigned long rotate_xor(unsigned long hash, const void *area, > size_t size) > { > @@ -311,7 +313,7 @@ static void process_e820_entry(struct e820entry *entry, > return; > > /* On 32-bit, ignore entries entirely above our maximum. */ > - if (IS_ENABLED(CONFIG_X86_32) && entry->addr >= KERNEL_IMAGE_SIZE) > + if (IS_ENABLED(CONFIG_X86_32) && entry->addr >= kernel_mapping_size) > return; > > /* Ignore entries entirely below our minimum. */ > @@ -341,8 +343,8 @@ static void process_e820_entry(struct e820entry *entry, > > /* On 32-bit, reduce region size to fit within max size. */ > if (IS_ENABLED(CONFIG_X86_32) && > - region.start + region.size > KERNEL_IMAGE_SIZE) > - region.size = KERNEL_IMAGE_SIZE - region.start; > + region.start + region.size > kernel_mapping_size) > + region.size = kernel_mapping_size - region.start; > > /* Return if region can't contain decompressed kernel */ > if (region.size < image_size) > @@ -408,9 +410,9 @@ static unsigned long find_random_virt_addr(unsigned long minimum, > /* > * There are how many CONFIG_PHYSICAL_ALIGN-sized slots > * that can hold image_size within the range of minimum to > - * KERNEL_IMAGE_SIZE? > + * kernel_mapping_size? > */ > - slots = (KERNEL_IMAGE_SIZE - minimum - image_size) / > + slots = (kernel_mapping_size - minimum - image_size) / > CONFIG_PHYSICAL_ALIGN + 1; > > random_addr = kaslr_get_random_long("Virtual") % slots; > @@ -438,6 +440,9 @@ void choose_random_location(unsigned long input, > return; > } > > + if (IS_ENABLED(CONFIG_X86_64)) > + kernel_mapping_size = KERNEL_MAPPING_SIZE_EXT; > + > boot_params->hdr.loadflags |= KASLR_FLAG; > > /* Prepare to add new identity pagetables on demand. */ > diff --git a/arch/x86/include/asm/kaslr.h b/arch/x86/include/asm/kaslr.h > index 1052a79..c4f5728 100644 > --- a/arch/x86/include/asm/kaslr.h > +++ b/arch/x86/include/asm/kaslr.h > @@ -7,6 +7,7 @@ unsigned long kaslr_get_random_long(const char *purpose); > extern unsigned long page_offset_base; > extern unsigned long vmalloc_base; > extern unsigned long vmemmap_base; > +extern unsigned long kernel_mapping_size; > > void kernel_randomize_memory(void); > #else > diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h > index 62a20ea..b8e79d7 100644 > --- a/arch/x86/include/asm/page_64_types.h > +++ b/arch/x86/include/asm/page_64_types.h > @@ -49,18 +49,21 @@ > #define __PHYSICAL_MASK_SHIFT 46 > #define __VIRTUAL_MASK_SHIFT 47 > > + > +/* > + * Kernel image size is limited to 512 MB. The kernel code+data+bss > + * must not be bigger than that. > + */ > +#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024) > + > /* > - * Kernel image size is limited to 1GiB due to the fixmap living in the > - * next 1GiB (see level2_kernel_pgt in arch/x86/kernel/head_64.S). Use > - * 512MiB by default, leaving 1.5GiB for modules once the page tables > + * Kernel mapping size is limited to 1GiB due to the fixmap living in > + * the next 1GiB (see level2_kernel_pgt in arch/x86/kernel/head_64.S). > + * Use 512MiB by default, leaving 1.5GiB for modules once the page tables > * are fully set up. If kernel ASLR is configured, it can extend the > * kernel page table mapping, reducing the size of the modules area. > */ > #define KERNEL_MAPPING_SIZE_EXT (1024 * 1024 * 1024) > -#if defined(CONFIG_RANDOMIZE_BASE) > -#define KERNEL_IMAGE_SIZE KERNEL_MAPPING_SIZE_EXT > -#else > -#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024) > -#endif > +#define KERNEL_MAPPING_SIZE kernel_mapping_size After applying these patches I'm getting: CC arch/x86/kernel/setup.o In file included from ./arch/x86/include/asm/page_types.h:47:0, from ./arch/x86/include/asm/page.h:8, from ./arch/x86/include/asm/thread_info.h:11, from ./include/linux/thread_info.h:58, from ./arch/x86/include/asm/preempt.h:6, from ./include/linux/preempt.h:59, from ./include/linux/spinlock.h:50, from ./include/linux/seqlock.h:35, from ./include/linux/time.h:5, from ./include/uapi/linux/timex.h:56, from ./include/linux/timex.h:56, from ./include/linux/sched.h:19, from arch/x86/kernel/setup.c:24: arch/x86/kernel/setup.c: In function ‘dump_kernel_offset’: ./arch/x86/include/asm/page_64_types.h:67:29: error: ‘kernel_mapping_size’ undeclared (first use in this function) #define KERNEL_MAPPING_SIZE kernel_mapping_size ^ ./arch/x86/include/asm/pgtable_64_types.h:69:48: note: in expansion of macro ‘KERNEL_MAPPING_SIZE’ #define MODULES_VADDR (__START_KERNEL_map + KERNEL_MAPPING_SIZE) ^~~~~~~~~~~~~~~~~~~ ./include/linux/printk.h:271:35: note: in expansion of macro ‘MODULES_VADDR’ printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) ^~~~~~~~~~~ arch/x86/kernel/setup.c:826:3: note: in expansion of macro ‘pr_emerg’ pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n", ^~~~~~~~ ./arch/x86/include/asm/page_64_types.h:67:29: note: each undeclared identifier is reported only once for each function it appears in #define KERNEL_MAPPING_SIZE kernel_mapping_size ^ ./arch/x86/include/asm/pgtable_64_types.h:69:48: note: in expansion of macro ‘KERNEL_MAPPING_SIZE’ #define MODULES_VADDR (__START_KERNEL_map + KERNEL_MAPPING_SIZE) ^~~~~~~~~~~~~~~~~~~ ./include/linux/printk.h:271:35: note: in expansion of macro ‘MODULES_VADDR’ printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) ^~~~~~~~~~~ arch/x86/kernel/setup.c:826:3: note: in expansion of macro ‘pr_emerg’ pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n", ^~~~~~~~ scripts/Makefile.build:293: recipe for target 'arch/x86/kernel/setup.o' failed make[2]: *** [arch/x86/kernel/setup.o] Error 1 scripts/Makefile.build:544: recipe for target 'arch/x86/kernel' failed make[1]: *** [arch/x86/kernel] Error 2 Makefile:988: recipe for target 'arch/x86' failed make: *** [arch/x86] Error 2 here with disabled CONFIG_RANDOMIZE_MEMORY.