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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 7B70FC433ED for ; Thu, 13 May 2021 02:52:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E0C4061396 for ; Thu, 13 May 2021 02:52:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0C4061396 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 62AB06B0036; Wed, 12 May 2021 22:52:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 600236B006E; Wed, 12 May 2021 22:52:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4EFE56B0070; Wed, 12 May 2021 22:52:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0065.hostedemail.com [216.40.44.65]) by kanga.kvack.org (Postfix) with ESMTP id 1C0B86B0036 for ; Wed, 12 May 2021 22:52:32 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B245D8249980 for ; Thu, 13 May 2021 02:52:31 +0000 (UTC) X-FDA: 78134684502.17.D95FCA1 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf01.hostedemail.com (Postfix) with ESMTP id 92AE7500152D for ; Thu, 13 May 2021 02:52:27 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 3E13061417; Thu, 13 May 2021 02:52:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620874348; bh=SLbN/DBHHqmewlE8uQW14WObooHOO9whfbtyrGVG5b4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HHlAXi1swYbztV+Xl0lXmdlm3Z62D/XY9oFpu3fdX9TfOekyShsSj+vQncgpZW7KI V5ZGTTo5f+r8od0SCbHo+X9celx0dnl2PvXHYQlmLXs57CaHKYzEeJQnGtu53dn8us HSJMlHfMNx0AkWyONanHd9JPnE3WKYCBojTArl0Y= Date: Wed, 12 May 2021 19:52:27 -0700 From: Andrew Morton To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: vbabka@suse.cz, iamjoonsoo.kim@lge.com, rientjes@google.com, penberg@kernel.org, cl@linux.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Marco Elver Subject: Re: [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time Message-Id: <20210512195227.245000695c9014242e9a00e5@linux-foundation.org> In-Reply-To: <20210511173448.GA54466@hyeyoo> References: <20210511173448.GA54466@hyeyoo> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 92AE7500152D Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=HHlAXi1s; dmarc=none; spf=pass (imf01.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam03 X-Stat-Signature: 87qwshd8bwusqmfaigk3eu33gu4sqqd9 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf01; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620874347-861665 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 12 May 2021 02:34:48 +0900 Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote: > currently when size is not supported by kmalloc_index, compiler will > generate a run-time BUG() while compile-time error is also possible, > and better. so changed BUG to BUILD_BUG_ON_MSG to make compile-time > check possible. > > also removed code that allocates more than 32MB because current > implementation supports only up to 32MB. > This explodes in mysterious ways. The patch as I have it is appended, for reference. gcc-10.3.0 allmodconfig. mm/kfence/kfence_test.c: In function 'test_free_bulk': mm/kfence/kfence_test.c:519:16: warning: unused variable 'size' [-Wunused-variable] 519 | const size_t size = setup_test_cache(test, 8 + prandom_u32_max(300), 0, | ^~~~ In file included from : In function 'kmalloc_index', inlined from 'test_alloc' at mm/kfence/kfence_test.c:270:82: ././include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_922' declared with attribute error: unexpected size in kmalloc_index() 328 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^ ././include/linux/compiler_types.h:309:4: note: in definition of macro '__compiletime_assert' 309 | prefix ## suffix(); \ | ^~~~~~ ././include/linux/compiler_types.h:328:2: note: in expansion of macro '_compiletime_assert' 328 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^~~~~~~~~~~~~~~~~~~ ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) | ^~~~~~~~~~~~~~~~~~ ./include/linux/slab.h:389:2: note: in expansion of macro 'BUILD_BUG_ON_MSG' 389 | BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); | ^~~~~~~~~~~~~~~~ make[2]: *** [mm/kfence/kfence_test.o] Error 1 make[1]: *** [mm/kfence] Error 2 make: *** [mm] Error 2 This patch suppresses the error: --- a/mm/kfence/kfence_test.c~a +++ a/mm/kfence/kfence_test.c @@ -318,13 +318,13 @@ static void test_out_of_bounds_read(stru /* Test both sides. */ - buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_LEFT); + buf = test_alloc(test, 32, GFP_KERNEL, ALLOCATE_LEFT); expect.addr = buf - 1; READ_ONCE(*expect.addr); KUNIT_EXPECT_TRUE(test, report_matches(&expect)); test_free(buf); - buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT); + buf = test_alloc(test, 32, GFP_KERNEL, ALLOCATE_RIGHT); expect.addr = buf + size; READ_ONCE(*expect.addr); KUNIT_EXPECT_TRUE(test, report_matches(&expect)); @@ -519,11 +519,11 @@ static void test_free_bulk(struct kunit const size_t size = setup_test_cache(test, 8 + prandom_u32_max(300), 0, (iter & 1) ? ctor_set_x : NULL); void *objects[] = { - test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT), - test_alloc(test, size, GFP_KERNEL, ALLOCATE_NONE), - test_alloc(test, size, GFP_KERNEL, ALLOCATE_LEFT), - test_alloc(test, size, GFP_KERNEL, ALLOCATE_NONE), - test_alloc(test, size, GFP_KERNEL, ALLOCATE_NONE), + test_alloc(test, 32, GFP_KERNEL, ALLOCATE_RIGHT), + test_alloc(test, 32, GFP_KERNEL, ALLOCATE_NONE), + test_alloc(test, 32, GFP_KERNEL, ALLOCATE_LEFT), + test_alloc(test, 32, GFP_KERNEL, ALLOCATE_NONE), + test_alloc(test, 32, GFP_KERNEL, ALLOCATE_NONE), }; kmem_cache_free_bulk(test_cache, ARRAY_SIZE(objects), objects); Is gcc-10.3.0 simply confused? test_out_of_bounds_read() is clearly calling kmalloc_index(32) which is OK. Anyway, I'll drop this patch for now so I can compile a kernel! From: Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: mm, slub: change run-time assertion in kmalloc_index() to compile-time Currently when size is not supported by kmalloc_index, compiler will generate a run-time BUG() while compile-time error is also possible, and better. So change BUG to BUILD_BUG_ON_MSG to make compile-time check possible. Also remove code that allocates more than 32MB because current implementation supports only up to 32MB. Link: https://lkml.kernel.org/r/20210511173448.GA54466@hyeyoo Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Reviewed-by: Vlastimil Babka Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton --- include/linux/slab.h | 7 +++++-- mm/slab_common.c | 7 +++---- 2 files changed, 8 insertions(+), 6 deletions(-) --- a/include/linux/slab.h~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time +++ a/include/linux/slab.h @@ -346,6 +346,9 @@ static __always_inline enum kmalloc_cach * 1 = 65 .. 96 bytes * 2 = 129 .. 192 bytes * n = 2^(n-1)+1 .. 2^n + * + * Note: there's no need to optimize kmalloc_index because it's evaluated + * in compile-time. */ static __always_inline unsigned int kmalloc_index(size_t size) { @@ -382,8 +385,8 @@ static __always_inline unsigned int kmal if (size <= 8 * 1024 * 1024) return 23; if (size <= 16 * 1024 * 1024) return 24; if (size <= 32 * 1024 * 1024) return 25; - if (size <= 64 * 1024 * 1024) return 26; - BUG(); + + BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); /* Will never be reached. Needed because the compiler may complain */ return -1; --- a/mm/slab_common.c~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time +++ a/mm/slab_common.c @@ -755,8 +755,8 @@ struct kmem_cache *kmalloc_slab(size_t s /* * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time. - * kmalloc_index() supports up to 2^26=64MB, so the final entry of the table is - * kmalloc-67108864. + * kmalloc_index() supports up to 2^25=32MB, so the final entry of the table is + * kmalloc-32M. */ const struct kmalloc_info_struct kmalloc_info[] __initconst = { INIT_KMALLOC_INFO(0, 0), @@ -784,8 +784,7 @@ const struct kmalloc_info_struct kmalloc INIT_KMALLOC_INFO(4194304, 4M), INIT_KMALLOC_INFO(8388608, 8M), INIT_KMALLOC_INFO(16777216, 16M), - INIT_KMALLOC_INFO(33554432, 32M), - INIT_KMALLOC_INFO(67108864, 64M) + INIT_KMALLOC_INFO(33554432, 32M) }; /* _