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=-10.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 54371C4CECC for ; Sun, 15 Sep 2019 16:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25CAF214D8 for ; Sun, 15 Sep 2019 16:52:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Wv2SR5sO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726618AbfIOQwj (ORCPT ); Sun, 15 Sep 2019 12:52:39 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:45196 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726372AbfIOQwi (ORCPT ); Sun, 15 Sep 2019 12:52:38 -0400 Received: by mail-pf1-f193.google.com with SMTP id y72so21070613pfb.12 for ; Sun, 15 Sep 2019 09:52:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=nii43oMTaFtktKbnijjugyrLFfb5ZKvbiN8kMj3vNPE=; b=Wv2SR5sO7CBMS93mcNuzKaC33L131eKLxc2sWGOw4gZsA2mpeA6eOWAaQ/RIHpcvzE UYJ4XZ0cp7TvEj4HUH5RXcDkYGpi4w7RgV9JDzthjil/VX+OCBWBLiGeksGPio5nQ4W/ n+P7xO6d5cPH1Y2J1pefYxNd2a+8t/tYy1U5iv+qth1jnHJ5CU82f/XrNno5sG7w6YdU k8CQzOk8cSFIhkYRzTxSKtBvSH2vA3zRKAyWAPB3rtnYqJJ23EwyaBpsmIiHUeFdrX++ aRpLJJDVoVUYXcJKu5QRRIglkt97eQgVnqG/6gNYv3YgbZY8dd7gDsjlzpAuZyCQ/9hB GHpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=nii43oMTaFtktKbnijjugyrLFfb5ZKvbiN8kMj3vNPE=; b=cpx1ErHqU+zzORJhRR61JFFVO29xhvB9w8ggfprUinnzRIo5dCkKimEoCELqKKZAJS czIZn45mJ5Xw6xuPk4bNhBMR0ht8pUcikkdpbgPHCEazU00tlokAxBqW4HpEoL+Z5uRL q7cKCTgIVxysm4HksIyZX2T6L1yfl2/5ucBXwZXzpiXzEnZe54nyEtYuwEOGWVAVM/h/ 0G9bx/Txp7dmcqC+NUtfLc6h6Fghm+ytCjXyPtBNA4P0AEjae6AsFY1t2363TEj/fTbO lTGnA8FewO2VtsJy2Om/wIJhdv9e7KHuvwvV6cIQNX/TcuNCa0w787YOJIPEy2Han3H1 jtVA== X-Gm-Message-State: APjAAAUpyY/1NRKhTYWK4G6UL21N0rF9QrMKBwm8DfG8jTE0+kvHck23 VpE9LGXDXE1rRnjuydY42LI= X-Google-Smtp-Source: APXvYqxYf54cYNQWLvZP6JklEbGw44XbGka9yQDf7cpKtKvKEjKS+BbJ7rhYqAqRIGCfavv9PckRFQ== X-Received: by 2002:aa7:8f03:: with SMTP id x3mr66745495pfr.91.1568566358307; Sun, 15 Sep 2019 09:52:38 -0700 (PDT) Received: from localhost.localdomain.localdomain ([2408:823c:c11:160:b8c3:8577:bf2f:3]) by smtp.gmail.com with ESMTPSA id a4sm4383259pgq.6.2019.09.15.09.52.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Sep 2019 09:52:37 -0700 (PDT) From: Pengfei Li To: akpm@linux-foundation.org Cc: vbabka@suse.cz, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, guro@fb.com, Pengfei Li Subject: [PATCH v4 4/7] mm, slab: return ZERO_SIZE_ALLOC for zero sized kmalloc requests Date: Mon, 16 Sep 2019 00:51:14 +0800 Message-Id: <20190915165121.7237-6-lpf.vector@gmail.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190915165121.7237-1-lpf.vector@gmail.com> References: <20190915165121.7237-1-lpf.vector@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a preparation patch, just replace 0 with ZERO_SIZE_ALLOC as the return value of zero sized requests. Signed-off-by: Pengfei Li --- include/linux/slab.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index e773e5764b7b..1f05f68f2c3e 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -121,14 +121,20 @@ #define SLAB_DEACTIVATED ((slab_flags_t __force)0x10000000U) /* - * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests. + * ZERO_SIZE_ALLOC will be returned by kmalloc_index() if it was zero sized + * requests. * + * After that, ZERO_SIZE_PTR will be returned by the function that called + * kmalloc_index(). + * Dereferencing ZERO_SIZE_PTR will lead to a distinct access fault. * * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL can. * Both make kfree a no-op. */ -#define ZERO_SIZE_PTR ((void *)16) +#define ZERO_SIZE_ALLOC (UINT_MAX) + +#define ZERO_SIZE_PTR ((void *)16) #define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \ (unsigned long)ZERO_SIZE_PTR) @@ -350,7 +356,7 @@ static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags) static __always_inline unsigned int kmalloc_index(size_t size) { if (!size) - return 0; + return ZERO_SIZE_ALLOC; if (size <= KMALLOC_MIN_SIZE) return KMALLOC_SHIFT_LOW; @@ -546,7 +552,7 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags) #ifndef CONFIG_SLOB index = kmalloc_index(size); - if (!index) + if (index == ZERO_SIZE_ALLOC) return ZERO_SIZE_PTR; return kmem_cache_alloc_trace( @@ -564,7 +570,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node) size <= KMALLOC_MAX_CACHE_SIZE) { unsigned int i = kmalloc_index(size); - if (!i) + if (i == ZERO_SIZE_ALLOC) return ZERO_SIZE_PTR; return kmem_cache_alloc_node_trace( -- 2.21.0