Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756510AbZCFScz (ORCPT ); Fri, 6 Mar 2009 13:32:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752983AbZCFScq (ORCPT ); Fri, 6 Mar 2009 13:32:46 -0500 Received: from mx2.redhat.com ([66.187.237.31]:47776 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751719AbZCFScp (ORCPT ); Fri, 6 Mar 2009 13:32:45 -0500 Message-ID: <49B16C69.6060203@redhat.com> Date: Fri, 06 Mar 2009 13:33:13 -0500 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Mathieu Desnoyers 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: [PATCH -tip 4/4] Atomic text_poke() with fixmap take2 References: <49B1428A.9050500@redhat.com> <49B14352.2040705@redhat.com> <20090306181356.GD14236@Krystal> In-Reply-To: <20090306181356.GD14236@Krystal> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3904 Lines: 119 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. */ 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 -- 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/