Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Subject: Re: [PATCH] LoongArch: Add kernel address sanitizer support
To:     Andrey Konovalov <andreyknvl@gmail.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Huacai Chen <chenhuacai@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        WANG Xuerui <kernel@xen0n.name>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        kasan-dev@googlegroups.com, linux-doc@vger.kernel.org,
        linux-mm@kvack.org, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>
References: <20230328111714.2056-1-zhangqing@loongson.cn>
 <CA+fCnZevgYh7CzJ9gOWJ80SwY4Y9w8UO2ZiFAXEnAhQhFgrffA@mail.gmail.com>
 <dccfbff3-7bad-de33-4d96-248bdff44a8b@loongson.cn>
 <CA+fCnZddt50+10SZ+hZRKBudsmMF0W9XpsDG6=58p1ot62LjXQ@mail.gmail.com>
From:   Qing Zhang <zhangqing@loongson.cn>
Message-ID: <2360000f-7292-9da8-d6b5-94b125c5f2b0@loongson.cn>
Date:   Thu, 30 Mar 2023 12:32:53 +0800
User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:68.0) Gecko/20100101
 Thunderbird/68.7.0
MIME-Version: 1.0
In-Reply-To: <CA+fCnZddt50+10SZ+hZRKBudsmMF0W9XpsDG6=58p1ot62LjXQ@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk


On 2023/3/30 上午10:55, Andrey Konovalov wrote:
> On Thu, Mar 30, 2023 at 4:06 AM Qing Zhang <zhangqing@loongson.cn> wrote:
>>
>>> But I don't think you need this check here at all: addr_has_metadata
>>> already checks that shadow exists.
>>>
>> On LongArch, there's a lot of holes between different segments, so kasan
>> shadow area is some different type of memory that we concatenate, we
>> can't use if (unlikely((void *)addr <
>> kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) to determine the
>> validity, and in arch/loongarch/include/asm/kasan.h I construct invalid
>> NULL.
> 
> I get that, but you already added a special case for
> __HAVE_ARCH_SHADOW_MAP to addr_has_metadata, so you can just call it?
> 
ok, all the changes are going to be in v2.

Thanks,
-Qing
>> This is because in pagetable_init on loongarch/mips, we populate pmd/pud
>> with invalid_pmd_table/invalid_pud_table,
> 
> I see. Please add this into the patch description for v2.
> 
>> So pmd_init/pud_init(p) is required, perhaps we define them as __weak in
>> mm/kasan/init.c, like mm/sparse-vmemmap.c.
> 
> Yes, this makes sense to do, so that KASAN doesn't depend on
> definitions from sparse-vmemmap.c.
> 
> Thank you!
>