From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757403AbZCAOMS (ORCPT ); Sun, 1 Mar 2009 09:12:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754489AbZCAOMG (ORCPT ); Sun, 1 Mar 2009 09:12:06 -0500 Received: from mail-ew0-f177.google.com ([209.85.219.177]:38374 "EHLO mail-ew0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754390AbZCAOMF convert rfc822-to-8bit (ORCPT ); Sun, 1 Mar 2009 09:12:05 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:in-reply-to:references :x-mailer:mime-version:content-type:content-transfer-encoding; b=vWy2xCjxz0YRk2DiA4VKGUHnRGbeq8ge2kmuz23t0329Vd73w1BZszvfCeQB6HB5Fn CpelIWtgNqm9croRKPPNB4C7BLGdx/tnkuuRkPd4rQzwuXzoQaATrrm0S7eLfjtvxzUh LzvR96VgUmQI88Cjko/y5M8gpAVLLVtTp8jAE= Date: Sun, 1 Mar 2009 16:11:58 +0200 From: Pekka Paalanen To: Steven Rostedt , Ingo Molnar Cc: Pekka Paalanen , Stuart Bennett , "linux-kernel@vger.kernel.org" Subject: [PATCH 4/7] x86 mmiotrace: fix save/restore page table state Message-ID: <20090301161158.2c4b130d@daedalus.pq.iki.fi> In-Reply-To: <20090301160643.05a2219b@daedalus.pq.iki.fi> References: <20090301160643.05a2219b@daedalus.pq.iki.fi> X-Mailer: Claws Mail 3.7.0 (GTK+ 2.12.11; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From baa99e2b32449ec7bf147c234adfa444caecac8a Mon Sep 17 00:00:00 2001 From: Pekka Paalanen Date: Sun, 22 Feb 2009 20:02:43 +0200 Subject: [PATCH] x86 mmiotrace: fix save/restore page table state Blindly setting _PAGE_PRESENT in disarm_kmmio_fault_page() overlooks the possibility, that the page was not present when it was armed. Make arm_kmmio_fault_page() store the previous page presence in struct kmmio_fault_page and use it on disarm. This patch was originally written by Stuart Bennett, but Pekka Paalanen rewrote it a little different. Cc: Stuart Bennett Signed-off-by: Pekka Paalanen --- arch/x86/mm/kmmio.c | 66 ++++++++++++++++++++++++++++++++++----------------- 1 files changed, 44 insertions(+), 22 deletions(-) diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c index fb1f115..be361eb 100644 --- a/arch/x86/mm/kmmio.c +++ b/arch/x86/mm/kmmio.c @@ -32,6 +32,8 @@ struct kmmio_fault_page { struct list_head list; struct kmmio_fault_page *release_next; unsigned long page; /* location of the fault page */ + bool old_presence; /* page presence prior to arming */ + bool armed; /* * Number of times this page has been registered as a part @@ -105,8 +107,7 @@ static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long page) return NULL; } -static int set_page_present(unsigned long addr, bool present, - unsigned int *pglevel) +static int set_page_presence(unsigned long addr, bool present, bool *old) { pteval_t pteval; pmdval_t pmdval; @@ -119,20 +120,21 @@ static int set_page_present(unsigned long addr, bool present, return -1; } - if (pglevel) - *pglevel = level; - switch (level) { case PG_LEVEL_2M: pmd = (pmd_t *)pte; - pmdval = pmd_val(*pmd) & ~_PAGE_PRESENT; + pmdval = pmd_val(*pmd); + *old = !!(pmdval & _PAGE_PRESENT); + pmdval &= ~_PAGE_PRESENT; if (present) pmdval |= _PAGE_PRESENT; set_pmd(pmd, __pmd(pmdval)); break; case PG_LEVEL_4K: - pteval = pte_val(*pte) & ~_PAGE_PRESENT; + pteval = pte_val(*pte); + *old = !!(pteval & _PAGE_PRESENT); + pteval &= ~_PAGE_PRESENT; if (present) pteval |= _PAGE_PRESENT; set_pte_atomic(pte, __pte(pteval)); @@ -148,19 +150,39 @@ static int set_page_present(unsigned long addr, bool present, return 0; } -/** Mark the given page as not present. Access to it will trigger a fault. */ -static int arm_kmmio_fault_page(unsigned long page, unsigned int *pglevel) +/* + * Mark the given page as not present. Access to it will trigger a fault. + * + * Struct kmmio_fault_page is protected by RCU and kmmio_lock, but the + * protection is ignored here. RCU read lock is assumed held, so the struct + * will not disappear unexpectedly. Furthermore, the caller must guarantee, + * that double arming the same virtual address (page) cannot occur. + * + * Double disarming on the other hand is allowed, and may occur when a fault + * and mmiotrace shutdown happen simultaneously. + */ +static int arm_kmmio_fault_page(struct kmmio_fault_page *f) { - int ret = set_page_present(page & PAGE_MASK, false, pglevel); - WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", page); + int ret; + WARN_ONCE(f->armed, KERN_ERR "kmmio page already armed.\n"); + if (f->armed) { + pr_warning("kmmio double-arm: page 0x%08lx, ref %d, old %d\n", + f->page, f->count, f->old_presence); + } + ret = set_page_presence(f->page, false, &f->old_presence); + WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", f->page); + f->armed = true; return ret; } -/** Mark the given page as present. */ -static void disarm_kmmio_fault_page(unsigned long page, unsigned int *pglevel) +/** Restore the given page to saved presence state. */ +static void disarm_kmmio_fault_page(struct kmmio_fault_page *f) { - int ret = set_page_present(page & PAGE_MASK, true, pglevel); - WARN_ONCE(ret < 0, KERN_ERR "kmmio disarming 0x%08lx failed.\n", page); + bool tmp; + int ret = set_page_presence(f->page, f->old_presence, &tmp); + WARN_ONCE(ret < 0, + KERN_ERR "kmmio disarming 0x%08lx failed.\n", f->page); + f->armed = false; } /* @@ -207,7 +229,7 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr) ctx = &get_cpu_var(kmmio_ctx); if (ctx->active) { - disarm_kmmio_fault_page(faultpage->page, NULL); + disarm_kmmio_fault_page(faultpage); if (addr == ctx->addr) { /* * On SMP we sometimes get recursive probe hits on the @@ -249,7 +271,7 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr) regs->flags &= ~X86_EFLAGS_IF; /* Now we set present bit in PTE and single step. */ - disarm_kmmio_fault_page(ctx->fpage->page, NULL); + disarm_kmmio_fault_page(ctx->fpage); /* * If another cpu accesses the same page while we are stepping, @@ -288,7 +310,7 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs) if (ctx->probe && ctx->probe->post_handler) ctx->probe->post_handler(ctx->probe, condition, regs); - arm_kmmio_fault_page(ctx->fpage->page, NULL); + arm_kmmio_fault_page(ctx->fpage); regs->flags &= ~X86_EFLAGS_TF; regs->flags |= ctx->saved_flags; @@ -320,19 +342,19 @@ static int add_kmmio_fault_page(unsigned long page) f = get_kmmio_fault_page(page); if (f) { if (!f->count) - arm_kmmio_fault_page(f->page, NULL); + arm_kmmio_fault_page(f); f->count++; return 0; } - f = kmalloc(sizeof(*f), GFP_ATOMIC); + f = kzalloc(sizeof(*f), GFP_ATOMIC); if (!f) return -1; f->count = 1; f->page = page; - if (arm_kmmio_fault_page(f->page, NULL)) { + if (arm_kmmio_fault_page(f)) { kfree(f); return -1; } @@ -356,7 +378,7 @@ static void release_kmmio_fault_page(unsigned long page, f->count--; BUG_ON(f->count < 0); if (!f->count) { - disarm_kmmio_fault_page(f->page, NULL); + disarm_kmmio_fault_page(f); f->release_next = *release_list; *release_list = f; } -- 1.6.0.6