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[61.230.45.44]) by smtp.gmail.com with ESMTPSA id z2sm6382878pfa.121.2021.02.04.06.46.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Feb 2021 06:46:22 -0800 (PST) From: Lecopzer Chen To: will@kernel.org Cc: akpm@linux-foundation.org, andreyknvl@google.com, ardb@kernel.org, aryabinin@virtuozzo.com, broonie@kernel.org, catalin.marinas@arm.com, dan.j.williams@intel.com, dvyukov@google.com, glider@google.com, gustavoars@kernel.org, kasan-dev@googlegroups.com, lecopzer.chen@mediatek.com, lecopzer@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-mm@kvack.org, linux@roeck-us.net, robin.murphy@arm.com, rppt@kernel.org, tyhicks@linux.microsoft.com, vincenzo.frascino@arm.com, yj.chiang@mediatek.com Subject: Re: [PATCH v2 1/4] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC Date: Thu, 4 Feb 2021 22:46:12 +0800 Message-Id: <20210204144612.75582-1-lecopzer@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210204124543.GA20468@willie-the-truck> References: <20210204124543.GA20468@willie-the-truck> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Sat, Jan 09, 2021 at 06:32:49PM +0800, Lecopzer Chen wrote: > > Linux support KAsan for VMALLOC since commit 3c5c3cfb9ef4da9 > > ("kasan: support backing vmalloc space with real shadow memory") > > > > Like how the MODULES_VADDR does now, just not to early populate > > the VMALLOC_START between VMALLOC_END. > > similarly, the kernel code mapping is now in the VMALLOC area and > > should keep these area populated. > > > > Signed-off-by: Lecopzer Chen > > --- > > arch/arm64/mm/kasan_init.c | 23 ++++++++++++++++++----- > > 1 file changed, 18 insertions(+), 5 deletions(-) > > > > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c > > index d8e66c78440e..39b218a64279 100644 > > --- a/arch/arm64/mm/kasan_init.c > > +++ b/arch/arm64/mm/kasan_init.c > > @@ -214,6 +214,7 @@ static void __init kasan_init_shadow(void) > > { > > u64 kimg_shadow_start, kimg_shadow_end; > > u64 mod_shadow_start, mod_shadow_end; > > + u64 vmalloc_shadow_start, vmalloc_shadow_end; > > phys_addr_t pa_start, pa_end; > > u64 i; > > > > @@ -223,6 +224,9 @@ static void __init kasan_init_shadow(void) > > mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR); > > mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END); > > > > + vmalloc_shadow_start = (u64)kasan_mem_to_shadow((void *)VMALLOC_START); > > + vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END); > > + > > /* > > * We are going to perform proper setup of shadow memory. > > * At first we should unmap early shadow (clear_pgds() call below). > > @@ -241,12 +245,21 @@ static void __init kasan_init_shadow(void) > > > > kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END), > > (void *)mod_shadow_start); > > - kasan_populate_early_shadow((void *)kimg_shadow_end, > > - (void *)KASAN_SHADOW_END); > > + if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) { > > Do we really need yet another CONFIG option for KASAN? What's the use-case > for *not* enabling this if you're already enabling one of the KASAN > backends? As I know, KASAN_VMALLOC now only supports KASAN_GENERIC and also KASAN_VMALLOC uses more memory to map real shadow memory (1/8 of vmalloc va). There should be someone can enable KASAN_GENERIC but can't use VMALLOC due to memory issue. > > + kasan_populate_early_shadow((void *)vmalloc_shadow_end, > > + (void *)KASAN_SHADOW_END); > > + if (vmalloc_shadow_start > mod_shadow_end) > > To echo Ard's concern: when is the above 'if' condition true? After reviewing this code, since VMALLOC_STAR is a compiler defined macro of MODULES_END, this if-condition will never be true. I also test it with removing this and works fine. I'll remove this in the next version patch, thanks a lot for pointing out this. BRs, Lecopzer