Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756490AbZCFSpi (ORCPT ); Fri, 6 Mar 2009 13:45:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756725AbZCFSpN (ORCPT ); Fri, 6 Mar 2009 13:45:13 -0500 Received: from tomts5-srv.bellnexxia.net ([209.226.175.25]:61997 "EHLO tomts5-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756365AbZCFSpL (ORCPT ); Fri, 6 Mar 2009 13:45:11 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ah0FAIT9sElMQW1W/2dsb2JhbACBTtURhAgG Date: Fri, 6 Mar 2009 13:45:06 -0500 From: Mathieu Desnoyers To: Masami Hiramatsu Cc: Ingo Molnar , Andrew Morton , Nick Piggin , Steven Rostedt , Andi Kleen , Linux Kernel Mailing List , Thomas Gleixner , Peter Zijlstra , Frederic Weisbecker , Linus Torvalds , Arjan van de Ven , Rusty Russell , "H. Peter Anvin" Subject: Re: [PATCH -tip 4/4] Atomic text_poke() with fixmap take2 Message-ID: <20090306184506.GA16067@Krystal> References: <49B1428A.9050500@redhat.com> <49B14352.2040705@redhat.com> <20090306181356.GD14236@Krystal> <49B16C69.6060203@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <49B16C69.6060203@redhat.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 13:44:06 up 6 days, 15:10, 2 users, load average: 1.89, 1.39, 1.08 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4428 Lines: 131 * Masami Hiramatsu (mhiramat@redhat.com) wrote: > Mathieu Desnoyers wrote: > >> @@ -523,14 +526,17 @@ void *__kprobes text_poke(void *addr, co > >> pages[1] = virt_to_page(addr + PAGE_SIZE); > >> } > >> BUG_ON(!pages[0]); > >> - if (!pages[1]) > >> - nr_pages = 1; > >> - vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL); > >> - BUG_ON(!vaddr); > >> - local_irq_disable(); > >> + set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0])); > > > > Can the set_fixmap/clear_fixmap/local_flush_tlb be called within > > local_irq_save ? If yes, that would be better, especially for the SMP > > alternatives code, which would rely on interrupt disabling in text_poke > > for consistency (the mutex is not needed there). > > Yes, that just changes pte. > > --- > Use fixmaps instead of vmap/vunmap in text_poke() for avoiding page allocation > and delayed unmapping. > > At the result of above change, text_poke() becomes atomic and can be called > from stop_machine() etc. > > Signed-off-by: Masami Hiramatsu > Acked-by: Mathieu Desnoyers > Cc: Ingo Molnar > --- > arch/x86/include/asm/fixmap.h | 2 ++ > arch/x86/kernel/alternative.c | 24 +++++++++++++++--------- > 2 files changed, 17 insertions(+), 9 deletions(-) > > Index: linux-2.6-tip/arch/x86/kernel/alternative.c > =================================================================== > --- linux-2.6-tip.orig/arch/x86/kernel/alternative.c > +++ linux-2.6-tip/arch/x86/kernel/alternative.c > @@ -13,7 +13,9 @@ > #include > #include > #include > +#include > #include > +#include > > #define MAX_PATCH_LEN (255-1) > > @@ -505,15 +507,16 @@ void *text_poke_early(void *addr, const > * It means the size must be writable atomically and the address must be aligned > * in a way that permits an atomic write. It also makes sure we fit on a single > * page. > + * > + * Note: Must be called under text_mutex. Maybe you could add "or in specific cases ensuring UP behavior". The rest looks fine. Acked-by: Mathieu Desnoyers > */ > void *__kprobes text_poke(void *addr, const void *opcode, size_t len) > { > + unsigned long flags; > char *vaddr; > - int nr_pages = 2; > struct page *pages[2]; > int i; > > - might_sleep(); > if (!core_kernel_text((unsigned long)addr)) { > pages[0] = vmalloc_to_page(addr); > pages[1] = vmalloc_to_page(addr + PAGE_SIZE); > @@ -523,14 +526,17 @@ void *__kprobes text_poke(void *addr, co > pages[1] = virt_to_page(addr + PAGE_SIZE); > } > BUG_ON(!pages[0]); > - if (!pages[1]) > - nr_pages = 1; > - vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL); > - BUG_ON(!vaddr); > - local_irq_disable(); > + local_irq_save(flags); > + set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0])); > + if (pages[1]) > + set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1])); > + vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0); > memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len); > - local_irq_enable(); > - vunmap(vaddr); > + clear_fixmap(FIX_TEXT_POKE0); > + if (pages[1]) > + clear_fixmap(FIX_TEXT_POKE1); > + local_flush_tlb(); > + local_irq_restore(flags); > sync_core(); > /* Could also do a CLFLUSH here to speed up CPU recovery; but > that causes hangs on some VIA CPUs. */ > Index: linux-2.6-tip/arch/x86/include/asm/fixmap.h > =================================================================== > --- linux-2.6-tip.orig/arch/x86/include/asm/fixmap.h > +++ linux-2.6-tip/arch/x86/include/asm/fixmap.h > @@ -111,6 +111,8 @@ enum fixed_addresses { > #ifdef CONFIG_PARAVIRT > FIX_PARAVIRT_BOOTMAP, > #endif > + FIX_TEXT_POKE0, /* reserve 2 pages for text_poke() */ > + FIX_TEXT_POKE1, > __end_of_permanent_fixed_addresses, > #ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT > FIX_OHCI1394_BASE, > -- > Masami Hiramatsu > > Software Engineer > Hitachi Computer Products (America) Inc. > Software Solutions Division > > e-mail: mhiramat@redhat.com > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/