From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id A2F596B0038 for ; Sun, 22 Jan 2017 17:25:38 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id 14so177463069pgg.4 for ; Sun, 22 Jan 2017 14:25:38 -0800 (PST) Received: from hqemgate15.nvidia.com (hqemgate15.nvidia.com. [216.228.121.64]) by mx.google.com with ESMTPS id h88si13654524pfk.4.2017.01.22.14.25.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 22 Jan 2017 14:25:37 -0800 (PST) Subject: Re: [PATCH] mm: do not export ioremap_page_range symbol for external module References: <1485089881-61531-1-git-send-email-zhongjiang@huawei.com> From: John Hubbard Message-ID: Date: Sun, 22 Jan 2017 14:25:36 -0800 MIME-Version: 1.0 In-Reply-To: <1485089881-61531-1-git-send-email-zhongjiang@huawei.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: zhongjiang , akpm@linux-foundation.org, minchan@kernel.org, mhocko@kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 01/22/2017 04:58 AM, zhongjiang wrote: > From: zhong jiang > > Recently, I find the ioremap_page_range had been abusing. The improper > address mapping is a issue. it will result in the crash. so, remove > the symbol. It can be replaced by the ioremap_cache or others symbol. Hi Zhong, After thinking about this for a bit, and looking through our own (out-of-tree) kernel modules, I think you have a good point. I just can't see any reason for a driver to call ioremap_page_range directly. So the code change looks good to me. For the commit description, here is a proposed re-wording, optional, that perhaps may be a little clearer. See if you like it? ------- Recently, I've found cases in which ioremap_page_range was used incorrectly, in external modules, leading to crashes. This can be partly attributed to the fact that ioremap_page_range is lower-level, with fewer protections, as compared to the other functions that an external module would typically call. Those include: ioremap_cache ioremap_nocache ioremap_prot ioremap_uc ioremap_wc ioremap_wt ...each of which wraps __ioremap_caller, which in turn provides a safer way to achieve the mapping. Therefore, stop EXPORT-ing ioremap_page_range. ------- I may get some heat for this if another out-of-tree driver needs that symbol, but if no one else pops up and shrieks, you can add: Reviewed-by: John Hubbard thanks, john h > > Signed-off-by: zhong jiang > --- > lib/ioremap.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/lib/ioremap.c b/lib/ioremap.c > index 86c8911..a3e14ce 100644 > --- a/lib/ioremap.c > +++ b/lib/ioremap.c > @@ -144,4 +144,3 @@ int ioremap_page_range(unsigned long addr, > > return err; > } > -EXPORT_SYMBOL_GPL(ioremap_page_range); > -- > 1.8.3.1 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org