From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEBE5C433FE for ; Fri, 11 Dec 2020 02:24:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AA9A23E51 for ; Fri, 11 Dec 2020 02:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387840AbgLKCX2 (ORCPT ); Thu, 10 Dec 2020 21:23:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732286AbgLKCW7 (ORCPT ); Thu, 10 Dec 2020 21:22:59 -0500 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7CA3DC0613CF; Thu, 10 Dec 2020 18:22:19 -0800 (PST) Received: by mail-pj1-x1044.google.com with SMTP id hk16so1533745pjb.4; Thu, 10 Dec 2020 18:22:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=1UCYlEZsL7Xd8eqLfGV/OrwzMVa1p0uuWjkGcite2p0=; b=W80hiWeEYGrPdIjcZETnr/yd71a4RCCEoXESffDicVazZU8A+NGnzXfJKSEH993r2O 4VIwKrqAErU/dugzWimfBGsQF8jlbCS/tgqVdhSYCvV3qxIiHv9bU/5KLtB7PD8KRT3v v6nQp4KA4fEMI2P5a2kxx8WBXXmiEGLQe1jFCkzckUm0rv1O4YFQ3dnZmBKY9lgH7CWi JoR4FHLEvEBTBKC6+SWrmwMk4GedWyyFnpw5VHaQwdkCvHrCoX41YhPtPRLb5xlOBSTh +9KV2sm9SYReslFOG4NsKIq2j1hPr1muj9uBKQKxbiLoD9IQnNIK/A5L+YC5RfIhEuWR fo6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=1UCYlEZsL7Xd8eqLfGV/OrwzMVa1p0uuWjkGcite2p0=; b=nJJclsH/kvx42BEve2t4R/r7GSTA20HdotSomFOR+p/BC9SSPkprYSm7Vf5EYp+790 XWQdoGu4VPZwj+xeGgFFN0rbrfD4tay4zC8K30CoPRgvFG1GldgapdnbgvHYjT3Z5s0/ pfO2nIjszqtZRnYk9HsMuq2ssBulpbz2zlPtMqAaDalo7DWS3hkhTUoUsDj2NGJFQj5B 3k4jwbPJKGy90rWg9ooz2icqS10a/uEi2wK5YqWrH83E6hi40zHX4XHA7aind8b+Crxj tF9/JDwZ3YykcAo6MID5IB1sZv0fk0y8WQgcW1wEIyycuACOTP+Mpnq5AYMdHPWhK0nk bf0A== X-Gm-Message-State: AOAM530xpGKT8wSmzXP8FJ3nz672so/qPX7XP4kyug0of+CrEQYynJj0 Nvp+eDfhdp2ZkGB+KaJRCfs= X-Google-Smtp-Source: ABdhPJw7+qTu0l80JJ50DFA5MpKioH+K1qmRAX8DyhEsaFe0xlAFszg7nbWa2N7TvAHPBXzTlzDlhw== X-Received: by 2002:a17:90a:902:: with SMTP id n2mr10811937pjn.126.1607653338956; Thu, 10 Dec 2020 18:22:18 -0800 (PST) Received: from js1304-desktop ([114.206.198.176]) by smtp.gmail.com with ESMTPSA id 77sm8025802pfv.16.2020.12.10.18.22.14 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 10 Dec 2020 18:22:18 -0800 (PST) Date: Fri, 11 Dec 2020 11:22:10 +0900 From: Joonsoo Kim To: paulmck@kernel.org Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, andrii@kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , linux-mm@kvack.org Subject: Re: [PATCH v3 sl-b 1/6] mm: Add mem_dump_obj() to print source of memory block Message-ID: <20201211022205.GA11631@js1304-desktop> References: <20201211011907.GA16110@paulmck-ThinkPad-P72> <20201211012003.16473-1-paulmck@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201211012003.16473-1-paulmck@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Thu, Dec 10, 2020 at 05:19:58PM -0800, paulmck@kernel.org wrote: > From: "Paul E. McKenney" > > There are kernel facilities such as per-CPU reference counts that give > error messages in generic handlers or callbacks, whose messages are > unenlightening. In the case of per-CPU reference-count underflow, this > is not a problem when creating a new use of this facility because in that > case the bug is almost certainly in the code implementing that new use. > However, trouble arises when deploying across many systems, which might > exercise corner cases that were not seen during development and testing. > Here, it would be really nice to get some kind of hint as to which of > several uses the underflow was caused by. > > This commit therefore exposes a mem_dump_obj() function that takes > a pointer to memory (which must still be allocated if it has been > dynamically allocated) and prints available information on where that > memory came from. This pointer can reference the middle of the block as > well as the beginning of the block, as needed by things like RCU callback > functions and timer handlers that might not know where the beginning of > the memory block is. These functions and handlers can use mem_dump_obj() > to print out better hints as to where the problem might lie. > > The information printed can depend on kernel configuration. For example, > the allocation return address can be printed only for slab and slub, > and even then only when the necessary debug has been enabled. For slab, > build with CONFIG_DEBUG_SLAB=y, and either use sizes with ample space > to the next power of two or use the SLAB_STORE_USER when creating the > kmem_cache structure. For slub, build with CONFIG_SLUB_DEBUG=y and > boot with slub_debug=U, or pass SLAB_STORE_USER to kmem_cache_create() > if more focused use is desired. Also for slub, use CONFIG_STACKTRACE > to enable printing of the allocation-time stack trace. > > Cc: Christoph Lameter > Cc: Pekka Enberg > Cc: David Rientjes > Cc: Joonsoo Kim > Cc: Andrew Morton > Cc: > Reported-by: Andrii Nakryiko > [ paulmck: Convert to printing and change names per Joonsoo Kim. ] > [ paulmck: Move slab definition per Stephen Rothwell and kbuild test robot. ] > [ paulmck: Handle CONFIG_MMU=n case where vmalloc() is kmalloc(). ] > [ paulmck: Apply Vlastimil Babka feedback on slab.c kmem_provenance(). ] > Signed-off-by: Paul E. McKenney > --- > include/linux/mm.h | 2 ++ > include/linux/slab.h | 2 ++ > mm/slab.c | 20 ++++++++++++++ > mm/slab.h | 12 +++++++++ > mm/slab_common.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > mm/slob.c | 6 +++++ > mm/slub.c | 36 +++++++++++++++++++++++++ > mm/util.c | 24 +++++++++++++++++ > 8 files changed, 176 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index ef360fe..1eea266 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3153,5 +3153,7 @@ unsigned long wp_shared_mapping_range(struct address_space *mapping, > > extern int sysctl_nr_trim_pages; > > +void mem_dump_obj(void *object); > + > #endif /* __KERNEL__ */ > #endif /* _LINUX_MM_H */ > diff --git a/include/linux/slab.h b/include/linux/slab.h > index dd6897f..169b511 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -186,6 +186,8 @@ void kfree(const void *); > void kfree_sensitive(const void *); > size_t __ksize(const void *); > size_t ksize(const void *); > +bool kmem_valid_obj(void *object); > +void kmem_dump_obj(void *object); > > #ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR > void __check_heap_object(const void *ptr, unsigned long n, struct page *page, > diff --git a/mm/slab.c b/mm/slab.c > index b111356..66f00ad 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -3633,6 +3633,26 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t flags, > EXPORT_SYMBOL(__kmalloc_node_track_caller); > #endif /* CONFIG_NUMA */ > > +void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) > +{ > + struct kmem_cache *cachep; > + unsigned int objnr; > + void *objp; > + > + kpp->kp_ptr = object; > + kpp->kp_page = page; > + cachep = page->slab_cache; > + kpp->kp_slab_cache = cachep; > + objp = object - obj_offset(cachep); > + kpp->kp_data_offset = obj_offset(cachep); > + page = virt_to_head_page(objp); > + objnr = obj_to_index(cachep, page, objp); > + objp = index_to_obj(cachep, page, objnr); > + kpp->kp_objp = objp; > + if (DEBUG && cachep->flags & SLAB_STORE_USER) > + kpp->kp_ret = *dbg_userword(cachep, objp); > +} > + > /** > * __do_kmalloc - allocate memory > * @size: how many bytes of memory are required. > diff --git a/mm/slab.h b/mm/slab.h > index 6d7c6a5..0dc705b 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -630,4 +630,16 @@ static inline bool slab_want_init_on_free(struct kmem_cache *c) > return false; > } > > +#define KS_ADDRS_COUNT 16 > +struct kmem_obj_info { > + void *kp_ptr; > + struct page *kp_page; > + void *kp_objp; > + unsigned long kp_data_offset; > + struct kmem_cache *kp_slab_cache; > + void *kp_ret; > + void *kp_stack[KS_ADDRS_COUNT]; > +}; > +void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page); > + > #endif /* MM_SLAB_H */ > diff --git a/mm/slab_common.c b/mm/slab_common.c > index f9ccd5d..df2e203 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -536,6 +536,80 @@ bool slab_is_available(void) > return slab_state >= UP; > } > > +/** > + * kmem_valid_obj - does the pointer reference a valid slab object? > + * @object: pointer to query. > + * > + * Return: %true if the pointer is to a not-yet-freed object from > + * kmalloc() or kmem_cache_alloc(), either %true or %false if the pointer > + * is to an already-freed object, and %false otherwise. > + */ > +bool kmem_valid_obj(void *object) > +{ > + struct page *page; > + > + if (!virt_addr_valid(object)) > + return false; > + page = virt_to_head_page(object); > + return PageSlab(page); > +} > + > +/** > + * kmem_dump_obj - Print available slab provenance information > + * @object: slab object for which to find provenance information. > + * > + * This function uses pr_cont(), so that the caller is expected to have > + * printed out whatever preamble is appropriate. The provenance information > + * depends on the type of object and on how much debugging is enabled. > + * For a slab-cache object, the fact that it is a slab object is printed, > + * and, if available, the slab name, return address, and stack trace from > + * the allocation of that object. > + * > + * This function will splat if passed a pointer to a non-slab object. > + * If you are not sure what type of object you have, you should instead > + * use mem_dump_obj(). > + */ > +void kmem_dump_obj(void *object) > +{ > + char *cp = IS_ENABLED(CONFIG_MMU) ? "" : "/vmalloc"; > + int i; > + struct page *page; > + unsigned long ptroffset; > + struct kmem_obj_info kp = { }; > + > + if (WARN_ON_ONCE(!virt_addr_valid(object))) > + return; > + page = virt_to_head_page(object); > + if (WARN_ON_ONCE(!PageSlab(page))) { > + pr_cont(" non-slab memory.\n"); > + return; > + } > + kmem_obj_info(&kp, object, page); > + if (kp.kp_slab_cache) > + pr_cont(" slab%s %s", cp, kp.kp_slab_cache->name); > + else > + pr_cont(" slab%s", cp); > + if (kp.kp_objp) > + pr_cont(" start %px", kp.kp_objp); > + if (kp.kp_data_offset) > + pr_cont(" data offset %lu", kp.kp_data_offset); I don't check the code deeply but kp_data_offset could be 0 in normal situation. Is it intentional not to print a message in this case? > + if (kp.kp_objp) { > + ptroffset = ((char *)object - (char *)kp.kp_objp) - kp.kp_data_offset; > + pr_cont(" pointer offset %lu", ptroffset); > + } > + if (kp.kp_slab_cache && kp.kp_slab_cache->usersize) > + pr_cont(" size %u", kp.kp_slab_cache->usersize); > + if (kp.kp_ret) > + pr_cont(" allocated at %pS\n", kp.kp_ret); > + else > + pr_cont("\n"); > + for (i = 0; i < ARRAY_SIZE(kp.kp_stack); i++) { > + if (!kp.kp_stack[i]) > + break; > + pr_info(" %pS\n", kp.kp_stack[i]); > + } > +} > + > #ifndef CONFIG_SLOB > /* Create a cache during boot when no slab services are available yet */ > void __init create_boot_cache(struct kmem_cache *s, const char *name, > diff --git a/mm/slob.c b/mm/slob.c > index 7cc9805..2ed1de2 100644 > --- a/mm/slob.c > +++ b/mm/slob.c > @@ -461,6 +461,12 @@ static void slob_free(void *block, int size) > spin_unlock_irqrestore(&slob_lock, flags); > } > > +void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) > +{ > + kpp->kp_ptr = object; > + kpp->kp_page = page; > +} > + > /* > * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend. > */ > diff --git a/mm/slub.c b/mm/slub.c > index b30be23..0459d2a 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3918,6 +3918,42 @@ int __kmem_cache_shutdown(struct kmem_cache *s) > return 0; > } > > +void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) > +{ > +#ifdef CONFIG_SLUB_DEBUG We can get some infos even if CONFIG_SLUB_DEBUG isn't defined. Please move them out. Thanks.