From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965125AbXIGInp (ORCPT ); Fri, 7 Sep 2007 04:43:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964986AbXIGIng (ORCPT ); Fri, 7 Sep 2007 04:43:36 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:43856 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964985AbXIGIne (ORCPT ); Fri, 7 Sep 2007 04:43:34 -0400 Date: Fri, 7 Sep 2007 14:13:15 +0530 From: Ananth N Mavinakayanahalli To: Mathieu Desnoyers Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Andi Kleen , pageexec@freemail.hu Subject: Re: [patch 05/10] Text Edit Lock - Alternative code for i386 and x86_64 Message-ID: <20070907084315.GA28915@in.ibm.com> Reply-To: ananth@in.ibm.com References: <20070906200124.595238505@polymtl.ca> <20070906200212.080849869@polymtl.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070906200212.080849869@polymtl.ca> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2007 at 04:01:29PM -0400, Mathieu Desnoyers wrote: > Index: linux-2.6-lttng/arch/i386/kernel/alternative.c > =================================================================== > --- linux-2.6-lttng.orig/arch/i386/kernel/alternative.c 2007-09-06 14:32:11.000000000 -0400 > +++ linux-2.6-lttng/arch/i386/kernel/alternative.c 2007-09-06 14:59:19.000000000 -0400 > @@ -16,6 +16,99 @@ > #ifdef CONFIG_HOTPLUG_CPU > static int smp_alt_once; > > +/* > + * Warning: > + * When you use this code to patch more than one byte of an instruction > + * you need to make sure that other CPUs cannot execute this code in parallel. > + * Also no thread must be currently preempted in the middle of these > + * instructions. And on the local CPU you need to be protected again NMI or MCE > + * handlers seeing an inconsistent instruction while you patch. > + * Warning: read_cr0 is modified by paravirt, this is why we have _early > + * versions. They are not in the __init section because they can be used at > + * module load time. > + */ > +static inline void text_sync(void *addr, size_t len) > +{ > + void *faddr; > + > + sync_core(); > + /* Not strictly needed, but can speed CPU recovery up. */ > + if (cpu_has_clflush) > + for (faddr = addr; faddr < addr + len; > + faddr += boot_cpu_data.x86_clflush_size) > + asm("clflush (%0) " :: "r" (faddr) : "memory"); > +} > + > +void * text_poke_early(void *addr, const void *opcode, > + size_t len) > +{ > + memcpy(addr, opcode, len); > + text_sync(addr, len); > + return addr; > +} > + > +void * text_set_early(void *addr, int c, size_t len) > +{ > + memset(addr, c, len); > + text_sync(addr, len); > + return addr; > +} > + > +/* > + * Only atomic text poke/set should be allowed when not doing early patching. > + * It means the size must be writable atomically and the address must be aligned > + * in a way that permits an atomic write. > + */ > +void * __kprobes text_poke(void *addr, const void *opcode, size_t len) > +{ > + unsigned long cr0; > + int unaligned; > + > + if (len > sizeof(long)) { > + printk(KERN_ERR "text_poke of len %zu too big (max %lu)\n", > + len, sizeof(long)); > + BUG_ON(1); > + } > + unaligned = (((long)addr + len - 1) & ~(sizeof(long) - 1)) > + - ((long)addr & ~(sizeof(long) - 1)); > + if (unlikely(unaligned)) { > + printk(KERN_ERR "text_poke of at addr %p of len %zu is " > + "unaligned (%d)\n", > + addr, len, unaligned); > + BUG_ON(1); > + } > + kernel_wp_save(cr0); > + memcpy(addr, opcode, len); > + kernel_wp_restore(cr0); > + text_sync(addr, len); > + return addr; > +} > + > +void * __kprobes text_set(void *addr, int c, size_t len) > +{ > + unsigned long cr0; > + int unaligned; > + > + if (len > sizeof(long)) { > + printk(KERN_ERR "text_set of len %zu too big (max %lu)\n", > + len, sizeof(long)); > + BUG_ON(1); > + } > + unaligned = (((long)addr + len - 1) & ~(sizeof(long) - 1)) > + - ((long)addr & ~(sizeof(long) - 1)); > + if (unlikely(unaligned)) { > + printk(KERN_ERR "text_set of at addr %p of len %zu is " > + "unaligned (%d)\n", > + addr, len, unaligned); > + BUG_ON(1); > + } > + kernel_wp_save(cr0); > + memset(addr, c, len); > + kernel_wp_restore(cr0); > + text_sync(addr, len); > + return addr; > +} > + The above chunk is within ifdef CONFIG_HOTPLUG_CPU. This breaks a CONFIG_SMP=n build: CHK include/linux/compile.h UPD include/linux/compile.h arch/i386/kernel/built-in.o: In function `apply_alternatives': /home/ananth/kprobes/marker/linux-2.6.23-rc4/arch/i386/kernel/alternative.c:293: undefined reference to `text_poke_early' arch/i386/kernel/built-in.o: In function `arch_disarm_kprobe': /home/ananth/kprobes/marker/linux-2.6.23-rc4/arch/i386/kernel/kprobes.c:185: undefined reference to `text_set' arch/i386/kernel/built-in.o: In function `arch_arm_kprobe': /home/ananth/kprobes/marker/linux-2.6.23-rc4/arch/i386/kernel/kprobes.c:180: undefined reference to `text_set' make: *** [.tmp_vmlinux1] Error 1 Ananth