From nobody Sun Dec 14 18:12:22 2025 Received: from mail-4316.protonmail.ch (mail-4316.protonmail.ch [185.70.43.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 002672DE200; Wed, 29 Oct 2025 20:08:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.70.43.16 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761768510; cv=none; b=UnF595ze7gK0D4C29Pu8FgA2E7Z+Jq4+IugtBdQX2L5yABysCu8mmQo3XEMeiqmz3XiwCcU144U/WBTluB5VltsI2GjP9bEfj0pMLp446Ey9gBlzLW2gRsKY6v4Bcgxib2Tz3mCZJR9JlGQ5xdVCr+Fl5uHSrcLtQgXws4j60mA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761768510; c=relaxed/simple; bh=bVzjv4HTOC1vQrn+XBZNIMKDdCF53/G6D7SEjdZ3RUs=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hcit+rYC99+bE8NiHAzuv7OEVhs4XYGCmtwpOIqjgXfYvIgsBPD9mfScUaCnT+3tyaWFUgfbVHIC/6lD8NAk4v4Q4ZGZgJr32ksf8N1nsMLJ8pqEUgiNqOZQA3xYFEfB22A01fLtMMOB8ABY6Ex72oBof9cY3tVE492o+6SRFQU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=pm.me; spf=pass smtp.mailfrom=pm.me; dkim=pass (2048-bit key) header.d=pm.me header.i=@pm.me header.b=f1ahGvJ8; arc=none smtp.client-ip=185.70.43.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=pm.me Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pm.me Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=pm.me header.i=@pm.me header.b="f1ahGvJ8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail3; t=1761768504; x=1762027704; bh=Ye8tYnzEiAyAJOizOqIrcZYSk2K1DbVUwkfvl955amo=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: Feedback-ID:From:To:Cc:Date:Subject:Reply-To:Feedback-ID: Message-ID:BIMI-Selector; b=f1ahGvJ8GYmWSAN4yQvaJJ8AMmaQXPPMzcKSaz6Xrvq0aoFjM/UK6qEVGIKRCoLqb 5LIptGgTqr85HdCtdsCnnkULneMU0vlAU6dQciyV6UUzUvyMy/kCVMmX+/4xr6YHW/ +oMozIC9BWSxBmEgcmmyjZZG3vnN+B3w2jxVYTdAYKkzhqe2taxX2Pl6kthj9hres/ YBb4kjMyUMhTGxyvSz8vda/30rOZZimxFRxQD0jyouhiV9xwy9nfBkUN6uEXRd/Z/X euFq5/cNqoY3dnXuBokf29Dwc8D5+0mx1I6WMSm4ouiysMLrt2mGdvalln0qeq9P+o sDufRjOTA1fvw== Date: Wed, 29 Oct 2025 20:08:18 +0000 To: xin@zytor.com, peterz@infradead.org, kaleshsingh@google.com, kbingham@kernel.org, akpm@linux-foundation.org, nathan@kernel.org, ryabinin.a.a@gmail.com, dave.hansen@linux.intel.com, bp@alien8.de, morbo@google.com, jeremy.linton@arm.com, smostafa@google.com, kees@kernel.org, baohua@kernel.org, vbabka@suse.cz, justinstitt@google.com, wangkefeng.wang@huawei.com, leitao@debian.org, jan.kiszka@siemens.com, fujita.tomonori@gmail.com, hpa@zytor.com, urezki@gmail.com, ubizjak@gmail.com, ada.coupriediaz@arm.com, nick.desaulniers+lkml@gmail.com, ojeda@kernel.org, brgerst@gmail.com, elver@google.com, pankaj.gupta@amd.com, glider@google.com, mark.rutland@arm.com, trintaeoitogc@gmail.com, jpoimboe@kernel.org, thuth@redhat.com, pasha.tatashin@soleen.com, dvyukov@google.com, jhubbard@nvidia.com, catalin.marinas@arm.com, yeoreum.yun@arm.com, mhocko@suse.com, lorenzo.stoakes@oracle.com, samuel.holland@sifive.com, vincenzo.frascino@arm.com, bigeasy@linutronix.de, surenb@google.com, ardb@kernel.org, Liam.Howlett@oracle.com, nicolas.schier@linux.dev, ziy@nvidia.com, kas@kernel.org, tglx@linutronix.de, mingo@redhat.com, broonie@kernel.org, corbet@lwn.net, andreyknvl@gmail.com, maciej.wieczor-retman@intel.com, david@redhat.com, maz@kernel.org, rppt@kernel.org, will@kernel.org, luto@kernel.org From: Maciej Wieczor-Retman Cc: kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, linux-kbuild@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-doc@vger.kernel.org, m.wieczorretman@pm.me Subject: [PATCH v6 12/18] x86/mm: LAM compatible non-canonical definition Message-ID: <56d9203b1fcb6281b0d29b44bc181530e5c72327.1761763681.git.m.wieczorretman@pm.me> In-Reply-To: References: Feedback-ID: 164464600:user:proton X-Pm-Message-ID: 015c7fdaea374a790951b755b565538ef4bdd04b Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Maciej Wieczor-Retman For an address to be canonical it has to have its top bits equal to each other. The number of bits depends on the paging level and whether they're supposed to be ones or zeroes depends on whether the address points to kernel or user space. With Linear Address Masking (LAM) enabled, the definition of linear address canonicality is modified. Not all of the previously required bits need to be equal, only the first and last from the previously equal bitmask. So for example a 5-level paging kernel address needs to have bits [63] and [56] set. Change the canonical checking function to use bit masks instead of bit shifts. Signed-off-by: Maciej Wieczor-Retman Acked-by: Alexander Potapenko --- Changelog v6: - Use bitmasks to check both kernel and userspace addresses (Dave Hansen and Samuel Holland). Changelog v4: - Add patch to the series. arch/x86/include/asm/page.h | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h index bcf5cad3da36..df2c93b90a6b 100644 --- a/arch/x86/include/asm/page.h +++ b/arch/x86/include/asm/page.h @@ -82,14 +82,37 @@ static __always_inline void *pfn_to_kaddr(unsigned long= pfn) return __va(pfn << PAGE_SHIFT); } =20 +/* + * CONFIG_KASAN_SW_TAGS requires LAM which changes the canonicality checks. + */ +#ifdef CONFIG_KASAN_SW_TAGS +static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) +{ + return (vaddr | BIT_ULL(63) | BIT_ULL(vaddr_bits - 1)); +} +#else static __always_inline u64 __canonical_address(u64 vaddr, u8 vaddr_bits) { return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits); } +#endif + +#ifdef CONFIG_KASAN_SW_TAGS +#define CANONICAL_MASK(vaddr_bits) (BIT_ULL(63) | BIT_ULL(vaddr_bits - 1)) +#else +#define CANONICAL_MASK(vaddr_bits) GENMASK_ULL(63, vaddr_bits) +#endif =20 static __always_inline u64 __is_canonical_address(u64 vaddr, u8 vaddr_bits) { - return __canonical_address(vaddr, vaddr_bits) =3D=3D vaddr; + unsigned long cmask =3D CANONICAL_MASK(vaddr_bits); + + /* + * Kernel canonical address & cmask will evaluate to cmask while + * userspace canonical address & cmask will evaluate to zero. + */ + u64 result =3D (vaddr & cmask) =3D=3D cmask || !(vaddr & cmask); + return result; } =20 #endif /* __ASSEMBLER__ */ --=20 2.51.0