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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=WZLU4c8CFtN82E3juz+QcV9FF1JDMzfdyAO1GFaD3hY=; b=MT8C8vZ5Dpd3uqMfi//3wu7dr/GxwgifUTOkW+cHaER1ZrYWl2jxVMiY1+FrpjJct9 f2E7XjGG7hbdmuCCPnG31xhx0DQuVbJddtvyg5eN30vJeJvAib7FhVMua53W6u3Jf+Mi Lhxb8ecVe1V0O4lJ9IufewNoXSbAovkPD6vrbciCWFQwHVZEkwZ0aq28kZnZ4bWc6aqs VH3/zTjdyT3ZSRquUiFF4pKudWdUUAkI3gagNdv6x6itlPJuYI90JdnDBrUMSC3Fzvw7 xJ0X2hDs5HosL2s4/+CRON9zve53pUl+d1gRb3abYi9deKHlw6hDEo7n7LhjBZCVC7wL aLLA== X-Gm-Message-State: AOAM530KeYyT49KyTcxaUfGV7GpoNyUvsKqxarjPEKtYuH+2hcWe5sMK dfKchoLGa+hGqmvc3L97BIRiem+Xmg68X+mnAZdwoA== X-Google-Smtp-Source: ABdhPJyapOvhRRqZ+bQIBXS8rWxLcpUPYbQDSO/D7VDIaq2PS0n8HmEJl5SVaOYTt6EAsXuZBRAOpQBkCOHcYirmJBs= X-Received: by 2002:a17:90b:3756:: with SMTP id ne22mr5531867pjb.41.1612558266710; Fri, 05 Feb 2021 12:51:06 -0800 (PST) MIME-Version: 1.0 References: <20210204150100.GE20815@willie-the-truck> <20210204163721.91295-1-lecopzer@gmail.com> <20210205171859.GE22665@willie-the-truck> <20210205174301.GF22665@willie-the-truck> In-Reply-To: <20210205174301.GF22665@willie-the-truck> From: Andrey Konovalov Date: Fri, 5 Feb 2021 21:50:55 +0100 Message-ID: Subject: Re: [PATCH v2 1/4] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC To: Will Deacon X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210205_155109_373765_30236DDC X-CRM114-Status: GOOD ( 43.81 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lecopzer Chen , Catalin Marinas , LKML , Linux Memory Management List , tyhicks@linux.microsoft.com, Alexander Potapenko , Vincenzo Frascino , Ard Biesheuvel , yj.chiang@mediatek.com, kasan-dev , Dmitry Vyukov , Andrey Ryabinin , Guenter Roeck , Lecopzer Chen , Mark Brown , "moderated list:ARM/Mediatek SoC..." , Dan Williams , Linux ARM , gustavoars@kernel.org, Andrew Morton , Robin Murphy , rppt@kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Feb 5, 2021 at 6:43 PM Will Deacon wrote: > > On Fri, Feb 05, 2021 at 06:30:44PM +0100, Andrey Konovalov wrote: > > On Fri, Feb 5, 2021 at 6:19 PM Will Deacon wrote: > > > > > > On Fri, Feb 05, 2021 at 12:37:21AM +0800, Lecopzer Chen wrote: > > > > > > > > > On Thu, Feb 04, 2021 at 10:46:12PM +0800, Lecopzer Chen wrote: > > > > > > > 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). > > > > > > > > > > The shadow is allocated dynamically though, isn't it? > > > > > > > > Yes, but It's still a cost. > > > > > > > > > > There should be someone can enable KASAN_GENERIC but can't use VMALLOC > > > > > > due to memory issue. > > > > > > > > > > That doesn't sound particularly realistic to me. The reason I'm pushing here > > > > > is because I would _really_ like to move to VMAP stack unconditionally, and > > > > > that would effectively force KASAN_VMALLOC to be set if KASAN is in use. > > > > > > > > > > So unless there's a really good reason not to do that, please can we make > > > > > this unconditional for arm64? Pretty please? > > > > > > > > I think it's fine since we have a good reason. > > > > Also if someone have memory issue in KASAN_VMALLOC, > > > > they can use SW_TAG, right? > > > > > > > > However the SW_TAG/HW_TAG is not supported VMALLOC yet. > > > > So the code would be like > > > > > > > > if (IS_ENABLED(CONFIG_KASAN_GENERIC)) > > > > > > Just make this CONFIG_KASAN_VMALLOC, since that depends on KASAN_GENERIC. > > > > > > > /* explain the relationship between > > > > * KASAN_GENERIC and KASAN_VMALLOC in arm64 > > > > * XXX: because we want VMAP stack.... > > > > */ > > > > > > I don't understand the relation with SW_TAGS. The VMAP_STACK dependency is: > > > > > > depends on !KASAN || KASAN_HW_TAGS || KASAN_VMALLOC > > > > This means that VMAP_STACK can be only enabled if KASAN_HW_TAGS=y or > > if KASAN_VMALLOC=y for other modes. > > > > > > > > which doesn't mention SW_TAGS at all. So that seems to imply that SW_TAGS > > > and VMAP_STACK are mutually exclusive :( > > > > SW_TAGS doesn't yet have vmalloc support, so it's not compatible with > > VMAP_STACK. Once vmalloc support is added to SW_TAGS, KASAN_VMALLOC > > should be allowed to be enabled with SW_TAGS. This series is a step > > towards having that support, but doesn't implement it. That will be a > > separate effort. > > Ok, thanks. Then I think we should try to invert the dependency here, if > possible, so that the KASAN backends depend on !VMAP_STACK if they don't > support it, rather than silently disabling VMAP_STACK when they are > selected. SGTM. Not sure if I will get to this in the nearest future, so I filed a bug: https://bugzilla.kernel.org/show_bug.cgi?id=211581 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel